Polymer Degradation and Stability (v.91, #12)
Editorial board (CO2).
Standardization and certification in the area of environmentally degradable plastics by Andrej Krzan; Sarunya Hemjinda; Stanislav Miertus; Andrea Corti; Emo Chiellini (2819-2833).
Environmentally degradable polymers and plastics (EDPs) are a group of polymeric materials experiencing a rapid growth in number as well as in their applications and quantities used. The assessment of their key characteristic – degradability, including eventually biodegradability as the ultimate stage, is scientifically and technically a challenging issue and has led to differing interpretations in the past. In order to standardize techniques and criteria a number of standards were established by different standardization bodies which are also used as a basis for certification schemes. An up-to-date inventory of the rapidly growing standardization body is presented with basic interpretation to help guide the non-expert. A basic introduction to EDPs and polymer degradation is added for clarity.
Keywords: Environmentally degradable polymers and plastics; Biodegradation; Standardization; Certification;
IR laser ablative modification of poly(ethylene-co-acrylic acid) zinc salt by Jadranka Blazevska-Gilev; Jan Šubrt; Zdeněk Bastl; Josef Pola (2834-2839).
IR laser-induced ablative degradation of poly(ethylene-co-acrylic acid) zinc salt (PEAZn) leads to cleavage of both polyethylene backbone and CO2H group. It yields carbon oxides and volatile hydrocarbons (ethene as a major product) and affords ablative deposition of solid ionomeric films in which the initial ratio –CO2H/–CO2Zn is decreased due to higher thermal stability of the –CO2Zn group. The laser-induced process differs remarkably from conventional degradation of similar polyethylene chain-based metal methacrylate ionomers that are known to yield cold ring fraction containing only –CO2H group. The cleavage of the polyethylene backbone in the laser-induced degradation becomes more important at higher fluences. The presence of sodium metasilicate is shown to accelerate the decomposition of the CO2H group.
Keywords: Poly(ethylene-co-acrylic acid) zinc salt; Laser ablation; Laser degradation; Laser-induced polymer films;
Kinetics of poly(ethylene terephthalate) glycolysis by diethylene glycol. I. Evolution of liquid and solid phases by Francis Pardal; Gilles Tersac (2840-2847).
The kinetics of uncatalysed glycolysis, at 220 °C, of poly(ethylene terephthalate) (PET) by diethylene glycol (DEG) in high excess has been studied. An experimental device allowing good separation, at reaction temperature, of the solid and liquid phases was set up.The results suggest that PET is initially depolymerized in the slightly swollen solid phase, by glycolysis of the amorphous interlamellar chains. This mechanism continues until a solid phase of highly crystallized polyester is obtained.The internal tensions engendered by this chemical modification cause cracks, delamination and mechanical disintegration of the polymer. The transfer towards the liquid phase is then strongly accelerated and the solvolysis of the depolymerization products continues in the liquid phase, up to equilibrium.
Keywords: Glycolysis; PET; Diethylene glycol; Kinetics;
DFT study of the reaction sites of N,N′-substituted p-phenylenediamine antioxidants by M. Breza; I. Kortišová; Z. Cibulková (2848-2852).
The geometry of N,N′-diphenyl-p-phenylenediamine (DPPD), N-phenyl-N′-(1′-methylbenzyl)-p-phenylenediamine (SPPD), N-phenyl-N′-(1,3-dimethyl-butyl)-p-phenylenediamine (6PPD), N-phenyl-N′-isopropyl-p-phenylenediamine (IPPD), and N-(1-methyl-1-phenylethyl)-N′-phenyl-p-phenylenediamine (CPPD) as well as of their dehydrogenation products has been optimized at B3LYP/6-31G∗ level of theory. Our results support the idea of formation of stable ketimine Ph–N＝C structures (instead of quinonediimine structures) during consecutive dehydrogenation of SPPD, 6PPD, and IPPD antioxidants despite the formation of tertiary carbon-centered radicals in the first dehydrogenation step is energetically preferred for SPPD only.
Keywords: Antioxidants; N,N′-Substituted p-phenylenediamines; DFT method; Geometry optimization;
Effects of polymerization conditions on the in vitro hydrolytic degradation of plaques of poly(dl-lactic acid-block-ethylene glycol) diblock copolymers by Muriel Stefani; Jean Coudane; Michel Vert (2853-2859).
In the case of poly(lactic acid) stereocopolymers, it has been shown that the hydrolytic degradation of derived devices depends very much on whether zinc lactate or tin octoate was used to polymerize lactides. In contrast, no effect was found in the case of nanoparticles derived from poly(dl-lactic acid)-block-poly(ethylene glycol) copolymers obtained by anionic polymerization of dl-lactide initiated by the sodium salt of monomethoxypoly(ethylene glycol) or by coordination–insertion polymerization of dl-lactide initiated by monomethoxypoly(ethylene glycol) in the presence of tin octoate as catalyst. To understand the difference of behaviour, in vitro hydrolytic degradation of thick plates made of the same copolymers but under different conditions was investigated. Changes were monitored by 1H Nuclear Magnetic Resonance, Size Exclusion Chromatography, Electrospray Mass Spectrometry and Capillary Zone Electrophoresis. It is shown that chain cleavage occurred from the very beginning of degradation and that plates disintegrated after 13 weeks. In all cases, degradation proceeded faster inside than at the surface, in contrast to what was observed for nanoparticles. Tin-type copolymer plates degraded more slowly than sodium macroalcoholate-type ones and were sensitive to purification conditions, in contrast to the latter.
Keywords: Poly lactic acid; Poly ethylene glycol; Copolymer; Degradation;
Liquid-phase degradation of HDPE over alkali-treated MFI zeolites with mesopores by Dong Ho Choi; Ji Won Park; Jong-Ho Kim; Yoshihiro Sugi; Gon Seo (2860-2866).
The catalytic activities of MFI zeolites treated with NaOH solutions of various concentrations were investigated in the liquid-phase degradation of HDPE. The changes in the crystallinity, pore structure and acidity of MFI zeolites according to the alkali treatment were also examined. The parent MFI zeolite composed of large particles showed very poor activity, but the treatment with moderate NaOH solutions of 0.4–0.7 N enhanced considerably the catalytic activity of MFI zeolite by enlarging its external surface area due to the formation of mesopores. The activity of MFI zeolite was improved by about 20 times treated with 0.5 N NaOH solution. The formation of mesopores also contributed to the enhancement of the yield of liquid products by suppressing further cracking due to the rapid diffusion of products. The treatment with strong NaOH solution, however, lowered the catalytic activity because the treatment caused the loss of both crystalline structure and strong acid sites.
Keywords: Liquid-phase catalytic degradation; MFI zeolite; Alkali treatment; HDPE; Mesopore;
Preparation of the crosslinked polyethersulfone films by high-temperature electron-beam irradiation by Jingye Li; Akihiro Oshima; Takaharu Miura; Masakazu Washio (2867-2873).
The radiation-crosslinked polyethersulfone (RX-PES) films were prepared by means of electron-beam irradiation under nitrogen atmosphere at 230 °C, where the temperature is around the glass transition temperature of PES (222 °C). The gel formation of RX-PES films was observed when the absorbed doses exceeded 300 kGy, which indicated the crosslinking structure formation. The G(S) of 0.10 and G(X) of 0.23 were calculated according to the Y-crosslinking mechanism. The irradiation was also performed at ambient temperature for comparison. There was no gel formation of the irradiated films even for the absorbed doses as high as 2250 kGy. The thermal properties of the original and irradiated PES films were measured by means of DSC and TGA analyses. The chemical structure of the original and the irradiated films was analyzed by means of FT-IR ATR and UV–vis spectroscopies.
Keywords: Polyethersulfone films; High-temperature electron-beam irradiation; Crosslinking; Glass transition temperature;
Properties of poly(vinyl chloride)/wood flour/montmorillonite composites: Effects of coupling agents and layered silicate by Yongsheng Zhao; Kejian Wang; Fuhua Zhu; Ping Xue; Mingyin Jia (2874-2883).
Organomodified montmorillonite (OMMT) was prepared using cetylalkyl trimethyl amine bromide. OMMT and wood flour (WF) were surface-modified by silane coupling agent. They were melt-blended with polyvinyl chloride (PVC) and extruded into wood–plastic composite samples using one conical twin screw extruder. The effects of their contents on the composite mechanical properties were investigated. X-ray diffraction, transmission electron microscopy and scanning electron microscopy observed intercalation and dispersion of the OMMT. FTIR and X-ray photoelectron spectroscopy were used to analyze the silane-modification effects. The possible reaction mechanisms were proposed. After wood flour was modified by 1.5 phr silane, the impact strength and the tensile strength of wood flour–PVC composite were increased by 14.8% and 18.5%, respectively. Mechanical tests showed that the addition of OMMT did not enhance the untreated wood flour–PVC composites. However, adding 0.5% OMMT did improve the mechanical properties of the treated ones. The grafting improved the interfacial compatibility between components producing higher properties of the composites. Further addition of OMMT reinforced the composites. Too higher contents of silane and OMMT impaired some properties because of weak interfacial layer and higher concentrated stress. Cone calorimetry showed that the fire flame retardancy and smoke suppression of composites were strongly improved with the addition of OMMT.
Keywords: Wood–plastic composite; Poly(vinyl chloride) (PVC); Fire retardancy; Montmorillonite;
Talc-filled PP: A new concept to maintain long term heat stability by Bruno Rotzinger (2884-2887).
Talc as filler improves the mechanical properties of polypropylene. However, talc also reduces the efficiency of many stabilizers and so the life-time of a final product.In a study to find new modifiers to improve the heat stability of talc-filled PP formulations it was observed that selected blends of modifiers were more efficient than the single modifiers at the same total loading.
Keywords: Ageing; Amphiphiles; Fillers; Talc; Poly(propylene) (PP); Stabilization;
Study on the antioxidant activities of benzofuranones in melt processing of polypropylene by Xin Meng; Weiguang Gong; Zhong Xin; Zhi Cai (2888-2893).
The antioxidant activities of four benzofuranones in melt processing of polypropylene (PP) have been investigated using multiple extrusions. The antioxidant activities of those four benzofuranones with different substituent groups have been evaluated using melt flow index (MFI) and yellowness index (Y.I.) of multiple-extruded PP stabilized with those antioxidants. The change of MFI values indicates as follows: firstly, the position of substituent group has a very important effect on the antioxidant activity of benzofuranone in the melt processing of PP i.e. methyl group of 2′-position may prevent the hydrogen donation of benzofuranone toward PP radicals and make the antioxidant activity of benzofuranone in PP decrease; secondly, electronic property of substituent group of para position to 3-reactive hydrogen has little influence on the antioxidant activity. Furthermore, the theory that the formation of antioxidative products due to the dimerization and disproportionation of benzofuranyl radicals is the main reason that induces the discoloration of stabilized PP has been predicted for the first time.
Keywords: Benzofuranone; Antioxidant activity; MFI; Y.I; Processing; PP;
Enzyme catalysis of insoluble cornstarch granules: Impact on surface morphology, properties and biodegradability by S.H. Imam; S.H. Gordon; A. Mohamed; R. Harry-O'kuru; B.-S. Chiou; G.M. Glenn; W.J. Orts (2894-2900).
Granular cornstarch was treated with microbial glucoamylase (50 mM sodium acetate buffer at pH 5.5 at 30 °C, 150 rpm) for up to 8 h. Treated starch was recovered and evaluated for changes in granular morphology, chemical properties, thermal properties, crystallinity and impact on its biodegradability. As the enzyme treatment progressed, reducing sugars began to accumulate in the liquid culture media (total of 6% in 8 h) and the granule suffered roughly 6% weight loss within 8 h of incubation. While the granules appeared intact morphologically, numerous small pits developed throughout the surface of the granules as a result of the enzyme treatment. Even after 8 h of enzyme treatment, the pitted granules were not disrupted and remained intact. X-ray diffraction indicated no loss of crystallinity in the enzyme treated granules but rather an increase in relative crystallinity, suggesting that the enzyme preferentially catalyzed the anhydroglucose units in amorphous regions of the granule. These findings were further supported by FTIR data suggesting that granules become more resistant to enzyme attack as amorphous amylose is hydrolyzed faster than the crystalline amylopectin domains. These results also suggest that variations in the crystallinity of different types of starches have the potential to affect their rates of biodegradation. Enzyme treated starch granules exhibited resistance to biodegradation, and the degree of resistance was related to the length of enzyme treatment. Granules treated with enzyme for a total of 7 h and subjected to biodegradation in soil produced 40–50% less CO2 in a closed circuit respirometer compared to the untreated samples. Differential scanning calorimetry (DSC) thermograms showed an endothermic reaction with little change in the onset and peak temperatures indicating that glucoamylase started by degrading the starch granules from the surface.
Keywords: Biodegradation; Enzyme modification; Starch; Biocatalysis; Biopolymer; Glucoamylase;
Thermal stability of plasma deposited polysilanes by Ivo Kuřitka; Pavel Horváth; František Schauer; Josef Zemek (2901-2910).
A new method for studying thermal stability and concomitant chemical composition changes on thermal treatment of thin polymeric films is presented. It is applied to the study of thermal properties and modification of properties of polysilane-like materials with variable dimensionality prepared by radio frequency plasma enhanced chemical vapour deposition (CVD). Structure and microphysical properties of these materials, modified by progressive annealing, are examined by fluorimetry, FTIR absorption spectroscopy and XPS. In addition, the role, bonding conditions and structural environments of organic moieties as well as their influence on thermal degradation processes are examined. It is found that plasma polysilanes undergo three consecutive thermal degradation processes: Si–Si bond cleavage, elimination of side groups and final carbide formation. Presence of disorder and crosslinking stabilises the plasmatic material in comparison to classically prepared polysilanes. Nanostructural units in low dimensional polysilanes enable the peak of the luminescence to be adjusted in the spectral range from near UV (360 nm) to red (600 nm).
Keywords: Thermal desorption spectroscopy, TDS; Polysilane; Luminescence; Thin film; Plasma; Thermal degradation;
Physical, thermal, dielectric and chemical properties of a hyperbranched polyether and its linear analog by Jyotishmoy Borah; Sibdas Singha Mahapatra; Diganta Saikia; Niranjan Karak (2911-2916).
The hyperbranched and the linear polyethers were prepared by one-pot nucleophilic displacement polymerization technique using cyanuric chloride and aromatic diol as reported earlier. The physical, thermal, dielectric and chemical properties of the hyperbranched polyether and its linear analog have been studied. The amorphous character of both the polyethers was observed in XRD study. The solubility studies showed that the hyperbranched polyether has relatively higher solubility in different solvents compared to its linear analog. The thermal properties of both polymers have been studied by thermogravimetric (TG) and differential scanning calorimetric (DSC) analyses. The chemical resistance tests indicated that both polyethers are very good chemical resistances except in dilute aqueous alkali solution. The dielectric properties such as dielectric constant and loss factor for both polyethers have also been studied with respect to changes of frequency (50–500 kHz) and temperature (303–343 K).
Keywords: Hyperbranched polyether; Linear polyether; Physical property; Thermal behavior; Chemical resistance; Dielectric properties;
Synthesis and characterization of polydimethylsiloxane-cured organically modified silicate hybrid coatings by K.H. Wu; C.M. Chao; C.J. Yang; T.C. Chang (2917-2923).
Hybrid coatings based on polydimethylsiloxane-cured organically modified silicate were synthesized through a sol–gel technique. Amino-terminated siloxane, 3-glycidoxypropyltrimethoxysilane and tetraethoxysilane were used as precursors for the hybrid coatings. These hybrid films were deposited via spin coating onto an aluminum alloy to improve the corrosion protection. The effects induced by the different chain lengths of siloxane on the chain dynamics, thermal stability and corrosion performance of the coated samples were investigated. The rotating-frame spin–lattice relaxation times and scale of the spin-diffusion path length indicated that the configuration of the hybrid films was highly crosslinked, dense and adhered to the aluminum alloy substrates. The thermal stability and the apparent activation energy, evaluated by van Krevelen's method, of the hybrid coatings depended on the siloxane chain length. Potentiodynamic analysis revealed that the hybrid films provided exceptional barrier and corrosion protection in comparison with untreated aluminum alloy substrates.
Keywords: Coatings; Corrosion; Nuclear magnetic resonance (NMR); Relaxation; Thermal property;
Polyanhydride modified unsaturated polyesters as injectable drug carriers: Synthesis and antitumor efficacy in Sarcoma-180 mice bearing tumor by Wen-xun Guo; Zong-li Shi; Kui Liang; Xian-hong Chen; Wei Li (2924-2930).
New polyanhydride modified unsaturated polyesters, poly(dodecanedioic acid–tetradecanedioic acid) [P(DDDA–TA)] modified poly(fumaric acid–glycol) [P(FA–GLY)] copolymers, were prepared by melt polycondensation with corresponding polyanhydride and unsaturated polyester synthesized beforehand. The polyanhydride was characterized by FT-IR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), the liquid poly(fumaric acid–glycol) [P(FA–GLY)] and polyanhydride modified unsaturated polyesters were characterized by FT-IR, gel permeation chromatography (GPC) and viscosity of the polymers was measured with a Ubbelohde viscometer. In vitro studies showed that some of the copolymers are degradable in phosphate buffer at 37 °C and have properly drug release rate as drug carriers. The biocompatibility of P(DDDA–TA)–P(FA–GLY) copolymers under mice skin was also evaluated; macroscopic observation and microscopic analysis demonstrated that the copolymer is biocompatible and well tolerated in vivo. Antitumor efficacy of P(DDDA–TA) [molar ratio M DDDA:M TA = 1.0:1.0, 20% weight ratio in polyanhydride modified unsaturated polyester]–P(FA–GLY) [molar ratio M FA:M GLY = 1.0:1.1] containing 5% adriamycin hydrochloride (ADM) in Sarcoma-180 mice bearing tumor exhibited increased volume doubling time (VDT) (21 ± 1.5 days) compared to plain subcutaneous injection of adriamycin hydrochloride (ADM) (7 ± 1.0 days), and the antitumor efficacy of injected preparation of P(DDDA–TA)–P(FA–GLY)–ADM inside tumor twice intervene 16 days exhibited an especially increased cytotoxic effect as revealed by increased volume doubling time (VDT) (32 ± 2.5 days). The studies suggested that P(DDDA–TA)–P(FA–GLY) copolymers as an effective and injectable carrier of antineoplastic drug like adriamycin hydrochloride have a very good foreground in treatment of noumenon tumor.
Keywords: Unsaturated polyester; Polyanhydride; Drug release; Adriamycin hydrochloride; Antitumor efficacy;
Degradation of commercially important polyhydroxyalkanoates in tropical mangrove ecosystem by Nanthini Sridewi; Kesaven Bhubalan; Kumar Sudesh (2931-2940).
This paper presents the degradation trends of selected polyhydroxyalkanoate (PHA) films in a tropical mangrove environment. The biodegradability of homopolymer poly(3-hydroxybutyrate) [P(3HB)] and its co-polymers, poly(3-hydroxybutyrate-co-5 mol% 3-hydroxyvalerate) [P(3HB-co-5 mol% 3HV)] and poly(3-hydroxybutyrate-co-5 mol% 3-hydroxyhexanoate) [P(3HB-co-5 mol% 3HHx)], was investigated along with P(3HB) films containing 38 wt% titanium dioxide (TiO2) [P(3HB)–38 wt% TiO2]. The degradation of these formulations was monitored for 8 weeks at three different zones in an intermediate mangrove compartment along Sungai Pinang, adjacent to a famous fishing village on south of Penang Island. The degradation rate was observed both on the surface and in the sediment and was expressed in percentage of weight loss. The microbial enumeration done using sediment from the different zones indicated similar colony-forming unit (CFU) counts even though differences were noticed in the degradation profile of the various films in the respective zones. The results obtained revealed that co-polymers disintegrated at similar or higher rate than the homopolymer, P(3HB). However, the incorporation of TiO2 into PHB films caused the degradation rate of P(3HB)–38 wt% TiO2 composite film to be far slower than all the other PHA films. The overall rate of degradation of all PHA films placed on the sediment surface was slower than those buried in the sediment. Microscopic analyses showed that the surface morphology of P(3HB-co-5 mol% 3HHx) was more porous compared to P(3HB) and P(3HB-co-5 mol% 3HV) films, which may be an important factor for its rapid degradation.
Keywords: Polyhydroxyalkanoates (PHAs); Biodegradation; Mangrove; Titanium dioxide (TiO2); Photocatalytic degradation;
Characterization and enzymatic degradation of microbial copolyester P(3HB-co-3HV)s produced by metabolic reaction model-based system by Suchada Chanprateep; Hiroshi Shimizu; Suteaki Shioya (2941-2950).
The two types of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)s [P(3HB-co-3HV)s] were produced by Paracoccus denitrificans ATCC 17741 using two different feeding methods. The produced P(3HB-co-3HV)s were fractionated and the copolymer sequence distributions were analyzed by 1H and 13C NMR spectroscopy. It was found that the P(3HB-co-3HV) samples produced by conventional feeding method were statistically random copolymers. The sequence distributions of P(3HB-co-3HV) samples produced by optimization method were different from random P(3HB-co-3HV)s. The thermal properties and melting behaviors were analyzed by differential scanning calorimetry (DSC). These results demonstrated that P(3HB-co-3HV) samples produced by optimization method are close in nature to P(3HB-co-3HV)s rich in long-sequence of block 3HB units, but less in 3HV random regions. The enzymatic degradation profile of P(3HB-co-3HV) films was investigated in the presence of 3-hydroxybutyrate depolymerase from Pseudomonase lemoignei. The degradation process was observed by monitoring the time-dependent change in the weight loss of copolymer films. The surface erosion of copolymer films was qualitatively monitored by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The highest degradation rate of 2.6% per day was observed for random P(3HB-co-38%3HV) produced by conventional method. In comparison, the hydrolysis degradation rates of random P(3HB-co-3HV)s were about one time faster than those of P(3HB-co-3HV)s produced by optimization method.
Keywords: P(3HB-co-3HV); Characterization; DSC; SEM; AFM; Degradation;
Studies of ABS-graft-maleic anhydride/clay nanocomposites: Morphologies, thermal stability and flammability properties by Haiyun Ma; Zhongbin Xu; Lifang Tong; Aiguan Gu; Zhengping Fang (2951-2959).
ABS-g-MAH (maleic anhydride) with different grafting degree, ABS/OMT (organo montmorillonite) and ABS-g-MAH/OMT nanocomposites were prepared via melt blending. The grafting reaction, phase morphology, clay dispersion, thermal properties, dynamic mechanical properties and flammability properties were investigated. FTIR spectra results indicate that maleic anhydride was successfully grafted onto butadiene chains of the ABS backbone in the molten state using dicumyl peroxide as the initiator and styrene as the comonomer and the relative grafting degree increased with increasing loading of MAH. TEM images show the size of the dispersed rubber domains of ABS-g-MAH increased and the dispersion is more uniform than that of neat ABS resin. XRD and TEM results show that intercalated/exfoliated structure formed in ABS-g-MAH/OMT nanocomposites and the rubber phase intercalated into clay layers distributed in both SAN phase and rubber phase. TGA results reveal the intercalated/exfoliated structure of ABS-g-MAH/OMT nanocomposites has better barrier properties and thermal stability than intercalated ones of ABS/OMT nanocomposites. The T g of ABS-g-MAH/OMT nanocomposites was also higher than that of neat ABS/OMT nanocomposites. The results of cone measurements show that ABS-g-MAH/OMT nanocomposites exhibit significantly reduced flammability when compared to ABS/OMT nanocomposites even at the same clay content. The chars of ABS-g-MAH/OMT nanocomposites were tighter, denser, more integrated and fewer surface microcracks than ABS/OMT residues.
Keywords: ABS-g-MAH; Organo montmorillonite; Nanocomposites; Phase morphology; Thermal degradation; Flammability;
Thermal degradation of polycarbonate, poly(vinyl acetate) and their blends by Tamer Uyar; Alan E. Tonelli; Jale Hacaloğlu (2960-2967).
We have recently developed a novel approach for intimately mixing thermodynamically incompatible polymers, which utilizes the formation of inclusion compounds (ICs) formed with host cyclodextrins (CDs), followed by removal of CD and coalescence of the common guest polymers into a blend. In this paper direct insertion probe pyrolysis mass spectrometry (DIP-MS) analyses of polycarbonate (PC), poly(vinyl acetate) (PVAc) and PC/PVAc blends, obtained by coalescence from their inclusion compounds formed with host γ-CD (coalesced blend) and by co-precipitation (physical blend), have been performed. Variations in the thermal stabilities of the coalesced polymers were recorded both by TGA and DIP-MS and compared to the corresponding as-received polymers. It has been determined that for both coalesced and physical blends of PC/PVAc, CH3COOH formed by deacetylation of PVAc above 300 °C, reacts with PC chains decreasing their thermal stability. This process was more effective for the physical blend, most likely due to enhanced diffusion of CH3COOH, produced by deacetylation of PVAc, into the PC domains, where it can further react producing low molecular weight PC fragments bearing methyl carbonate chain ends.
Keywords: Polycarbonate; Poly(vinyl acetate); Blend; Cyclodextrin; Inclusion compound; Pyrolysis mass spectrometry;
Photochemical aging of in situ polymerized blends of polystyrene and poly[acrylonitrile-g-(ethylene-co-propylene-co-diene)-g-styrene] (AES) by Emerson Lourenço; Maria Isabel Felisberti (2968-2978).
The influence of photochemical aging of in situ polymerized PS/AES blends on their mechanical properties has been studied. The PS/AES blends were subjected to photochemical aging for 168 h and 720 h. Tensile properties and Izod impact resistance of aged and non-aged samples were evaluated. The mechanical properties of the PS/AES blends are influenced by the polymerization temperature and blend composition and represent a balance between the toughness of EPDM and the stiffness of SAN in the PS matrix. Even though the impact resistance and strain at break of HIPS are higher than those of the PS/AES blends, after the aging period all PS/AES blends showed higher strain at break than HIPS. PS/AES blends present higher photochemical stability than HIPS.
Keywords: In situ polymerized PS/AES blends; Photochemical aging; Mechanical properties; Impact resistance;
Mechanistic analysis and thermochemical kinetic simulation of the pathways for volatile product formation from pyrolysis of polystyrene, especially for the dimer by Marvin L. Poutsma (2979-3009).
Simulations of the initial distribution of volatiles from pyrolysis of polystyrene were based on propagation rate constants estimated by thermochemical kinetic procedures. The voluminous database exhibits a disturbing lack of consistency with respect to effects of conversion level, temperature, and reactor type. It therefore remains difficult to assign the true primary distribution of the major products, styrene, 2,4-diphenyl-1-butene (“dimer”), 2,4,6-triphenyl-1-hexene (“trimer”), 1,3-diphenylpropane, and toluene, and its dependence on conditions. Probable perturbations by secondary reactions and selective evaporation are considered. The rate constant for 1,3-hydrogen shift appears much too small to accommodate the commonly proposed “back-biting” mechanism for dimer formation. Dimer more likely arises by addition of benzyl radical to olefinic chain-ends, followed by β-scission, although ambiguities remain in assigning rate constants for the addition and β-scission steps. With this modification, the major products can be successfully associated with decay of the sec-benzylic chain-end radical. In contrast, the minimal formation of allylbenzene, 2,4-diphenyl-1-pentene, and 2,4,6-triphenyl-1-heptene suggests a minimal chain-propagating role for the prim chain-end radical. Compared with polyethylene, the much enhanced “unzipping” to form monomer from polystyrene and the more limited depth of “back-biting” into the chain arise from an enthalpy-driven acceleration of β-scission coupled with a kinetically driven deceleration of intramolecular hydrogen transfer. In contrast, the greater “unzipping” of poly(isobutylene) compared with polyethylene is proposed to result from relief of steric strain.
Keywords: Polystyrene; Pyrolysis; Computational modeling; Radical mechanisms; Hydrogen shift;
Influence of transition metal-doped titanium(IV) dioxide on the photodegradation of polystyrene by Terence J. Kemp; Robin A. McIntyre (3010-3019).
The effects of adding dispersed powders of various forms of titanium(IV) dioxide on the photodegradation of polystyrene have been examined using FT-IR spectroscopy from the following points of view: effect of crystal form, concentration of pigment, transition metal ion, dopant concentration, calcination temperature of pigment, and pigment coating.The rate of photodegradation of polystyrene is reduced by adding certain grades of TiO2 such as coated TiO2 particles or TiO2 doped with small percentages of Cr or Mn ions. The rate is increased on adding TiO2 doped with V and especially Mo or W ions. The anatase form of TiO2 is more photoactive than the rutile form, as is the effect of increasing the calcination temperature of the pigment. The concentration dependences of the degradation rates are complex, but can be directly related to the percentage of anatase achieved after calcination. Even the most aggressive of the metal-doped pigments are less photoactive than a Degussa P25 material, containing rutile and anatase.
Keywords: Anatase; Dopant; Photodegradation; Polystyrene; Titanium dioxide; Transition metal;
Influence of transition metal-doped titanium(IV) dioxide on the photodegradation of polyethylene by Terence J. Kemp; Robin A. McIntyre (3020-3025).
The effects of adding dispersed powders of various forms of titanium(IV) dioxide on the photodegradation of polyethylene have been examined from the following points of view: effect of crystal form, concentration of pigment, transition metal ion, dopant concentration, calcination temperature of pigment, and pigment coating.The rate of photodegradation of polyethylene is reduced by adding certain grades of TiO2 such as coated TiO2 particles or TiO2 doped with small percentages of Cr or Mn ions. The rate is increased on adding TiO2 doped with V and especially Mo or W ions. The anatase form of TiO2 is more photoactive than the rutile form, and the effect of increasing the calcination temperature of the pigment is to reduce photoactivity by boosting the rutile fraction. The concentration dependences of the degradation rates are complex, but can be directly related to the percentage of anatase achieved after calcination. Even the most aggressive of the metal-doped pigments are less photoactive than the Degussa P25 material, containing both rutile and anatase.
Keywords: Anatase; Dopant; Photodegradation; Polyethylene; Rutile; Titanium dioxide;
Thermal and mechanical properties of UV irradiated collagen/chitosan thin films by A. Sionkowska; M. Wisniewski; J. Skopinska; G.F. Poggi; E. Marsano; C.A. Maxwell; T.J. Wess (3026-3032).
The thermal and mechanical properties of collagen/chitosan blends before and after UV irradiation have been investigated using thermal analysis and mechanical (Instron) techniques. Comparisons were made with the thermal and mechanical properties of both collagen and chitosan films. Air-dried collagen, chitosan and collagen/chitosan films were exposed to UV irradiation (wavelength 254 nm) for different time intervals. Thermal properties of collagen/chitosan blends depend on the composition of the blend and are not significantly altered by UV irradiation.Mechanical properties such as ultimate tensile strength and ultimate percentage of elongation were much better for collagen films than for collagen/chitosan films. The results have shown that the mechanical properties of the blends were greatly affected by the duration of UV irradiation. Ultimate tensile strength and ultimate percentage elongation decreased after UV irradiation of the blend. Increasing UV irradiation leads to an increase in Young's modulus of the collagen/chitosan blend.
Keywords: Collagen/chitosan blend; Blend; UV irradiation; Thermal properties; Mechanical properties;
Photooxidation of vulcanized EPDM/montmorillonite nanocomposites by Sandrine Morlat-Therias; Elisabeth Fanton; Namrata S. Tomer; Sravendra Rana; R.P. Singh; Jean-Luc Gardette (3033-3039).
The photooxidation of a vulcanized ethylene–propylene–diene monomer (EPDM)/montmorillonite nanocomposite as well as EPDM/nanocomposite with stabilizers was studied under accelerated UV-light irradiation (λ ≥ 300 nm, 60 °C) for different times. The development of functional groups during oxidation was monitored by infrared spectroscopy. Photodegradation of the neat polymer and composites took place and the increases of absorbance in hydroxyl and carbonyl groups with irradiation times and also the decreases of the EPDM unsaturations were measured. The data indicated that the photooxidation products were not changed in the presence of the nanofiller. However, the presence of MMt was observed to dramatically enhance the rate of photooxidation of EPDM with a shortening of the oxidation induction time, leading to a decrease of the durability of the nanocomposites. On the other hand, it was observed that addition of stabilizers, either Tinuvin P or 2-mercaptobenzimidazole, was efficient in inhibiting the degradative effect of MMt.
Keywords: Nanocomposite; Photooxidation rate; EPDM; Stabilization;
Structural and thermal characterization of sugarcane bagasse cellulose succinates prepared in ionic liquid by C.F. Liu; R.C. Sun; A.P. Zhang; J.L. Ren; Z.C. Geng (3040-3047).
The chemical modification of SCB cellulose with succinic anhydride using 1-butyl-3-methylimidazolium chloride ionic liquid/DMSO system as reaction medium was studied. The parameters including the molar ratio of succinic anhydride/anhydroglucose units in cellulose from 1:1 to 12:1, reaction time 5–120 min, and reaction temperature 85–105 °C were investigated. The results showed that the degree substitution of succinylated cellulosic preparations ranged from 0.037 to 0.53. It was found that the treatment of the native cellulose in the ionic liquid/DMSO system under the conditions given significantly degraded the cellulose and completely destroyed the cellulose crystals. FT-IR and solid-state CP/MAS 13C NMR spectra produced evidence for succinoylation reaction and the results showed that succinoylation occurred at positions C-6, C-2 and C-3. The thermal stability of the succinylated cellulose decreased upon chemical modification.
Keywords: Cellulose; Ionic liquid; Succinic anhydride; Degradation; Thermal stability;
Influence of photostabilizers on wood flour–HDPE composites exposed to xenon-arc radiation with and without water spray by Nicole M. Stark; Laurent M. Matuana (3048-3056).
The weathering of wood–plastic composites changes their appearance and/or mechanical properties. These changes can be slowed through the addition of ultraviolet absorbers and pigments. The first phase of this study examined the effect of incorporating different concentrations of an ultraviolet absorber and/or pigment into wood-flour-filled high-density polyethylene (WF/HDPE) composites. Lightness and flexural properties of the composites were determined periodically during exposure to UV radiation and water spray in a xenon-arc type weathering apparatus. The influence of exposure type (UV radiation, with or without water spray) on the properties of photostabilized WF/HDPE composites was determined in the second phase of the study. The results showed that both ultraviolet absorbers and pigments provide protection against weathering of wood–plastic composites. The amount of protection can be influenced by both photostabilzer concentration and exposure variables.
Keywords: Wood--plastic composites; Weathering; Wood flour; High-density polyethylene (HDPE); Ultraviolet absorber; Pigment;
Oxidation behaviour in prosthetic UHMWPE components sterilised with high-energy radiation in the presence of oxygen by P. Bracco; V. Brunella; M.P. Luda; E.M. Brach del Prever; M. Zanetti; L. Costa (3057-3064).
UHMWPE orthopaedic components are commonly sterilised by high-energy radiation. In the last 10 years, many studies pointed out that irradiation in air can lead to an oxidative degradation of the polymer, but the correlation between the sterilisation conditions and the amount and distribution of the oxidation products in the prosthetic components is still unclear.In the present study, a large number of never implanted, gamma sterilised prosthetic components have been analysed by using FTIR micro-spectroscopy and derivatisation techniques. Based on the obtained oxidation profiles, the samples were divided into three groups and a correlation between the oxidation products and their distribution and some sterilisation parameters have been proposed. Presence of oxygen, dose rate and temperature were found to play a highly relevant role in determining the whole oxidation degree and its distribution in the UHMWPE components.
Keywords: UHMWPE; Gamma radiation; Oxidation; Hydroperoxides; FTIR;
Poly(l,l-lactide-co-glycolide)/tricalcium phosphate composite scaffold and its various changes during degradation in vitro by Fei Yang; Wenjin Cui; Zhuo Xiong; Li Liu; Jianzhong Bei; Shenguo Wang (3065-3073).
A poly(l,l-lactide-co-glycolide) (70/30)/(tricalcium phosphate) (PLGA/TCP) composite scaffold was fabricated by low-temperature deposition (LDM) and its degradation performed in vitro for 22 weeks. Various changes during degradation in vitro, which included changes in acidity of the degradation medium, morphology, weight, composition, molecular weight of the PLGA component and mechanical properties of the scaffold, were investigated. It was found that the acidity of degradation medium of the PLGA(70/30)/TCP composite scaffolds reduced and became much lower than that of TCP-free scaffold. With degradation, the volume and porosity of the PLGA(70/30)/TCP composite scaffold reduced at first then increased slowly, while the surface morphology of the scaffold changed from smooth to rough. The weight loss of the scaffold increased by dissolution of the degraded products and TCP component, but mainly by dissolution of the glycyl-rich degraded products of the PLGA component. The molecular weight of the PLGA component reduced with time, but the molecular weight distribution increased at first and then reduced. The compressive strength and modulus of the scaffold increased at first and then reduced with further degradation. The effect of degradation on modulus was much bigger than that on compressive strength. Based on excellent cell affinity of the PLGA(70/30)/TCP composite scaffold, a potentially useful bone tissue engineering scaffold is proposed.
Keywords: PLGA(70/30)/TCP composite; Scaffold; Manufacturing; Degradation; Mechanical property; Bone tissue engineering;
Study of hydromagnesite and magnesium hydroxide based fire retardant systems for ethylene–vinyl acetate containing organo-modified montmorillonite by F. Laoutid; P. Gaudon; J.-M. Taulemesse; J.M. Lopez Cuesta; J.I. Velasco; A. Piechaczyk (3074-3082).
A new flame retardant (FR) system for ethylene–vinyl acetate, mainly based on the combination of hydromagnesite (HM, obtained from an industrial by-product) and organo-modified montmorillonite (oMMT) has been compared with a magnesium hydroxide (MDH) and oMMT flame retardant system. The presence of oMMT in association with both hydrated minerals gave a strong decrease of heat release rate in cone calorimeter tests. Moreover, the HM/oMMT combination leads to a better improvement of resistance to ignition and self-extinguishability in comparison with the MDH/oMMT one. The study of residues formed during thermal decomposition revealed the formation of forsterite (Mg2SiO4) when either MDH or HM was used in combination with oMMT. SEM observations of residues showed sintering of the mineral particles at high temperature particularly in the case of HM/oMMT composition.
Keywords: Fire properties; Hydromagnesite; EVA; Char structuring;
Evaluation of polymers for conservation treatments of outdoor exposed stone monuments. Part I: Photo-oxidative weathering by M. Favaro; R. Mendichi; F. Ossola; U. Russo; S. Simon; P. Tomasin; P.A. Vigato (3083-3096).
The commercial acrylic polymers, Paraloid B72 and Paraloid B67, and a silicon-based product, Dri-Film 104, commonly used as water repellents/consolidants in the restoration of stone artefacts, have been tested to evaluate their performances when submitted to ageing, simulating the outdoor conditions of treated stone. After full characterization, the three polymers were applied as thin films on slides, as thick film on petri dishes and on marble by brush or by imbibition and the resulting samples were submitted to photo-oxidative weathering (λ = 340 nm). The weathering evolution was checked by ultrasonic and colorimetric measurements and by FT-IR, NMR and SEC determinations. Removability tests were also performed. All the polymers underwent irreversible modifications with reduction of their conservative properties, colour change and, above all, impossibility of their complete removal.
Keywords: Acrylic polymers; Silicones; Photo-oxidative ageing; Stone conservation; Polymer removability;
Properties and biodegradability of chitosan/nylon 11 blending films by Ping-Chung Kuo; Diptiranjan Sahu; Hsin Her Yu (3097-3102).
Different ratios of nylon 11/chitosan blending films were prepared by solution casting method. The strength of the hydrogen bond in the blending films is weakened after addition of chitosan and spherulite growth is restricted as the ratio of chitosan increases. Sea–island morphology could be observed once the concentration of chitosan in the blends was more than 50%. Blending films are characterized by FTIR (Fourier transform infrared spectroscopy), X-ray, and scanning electron microscopy (SEM) and the biodegradability is also investigated. The extent of biodegradability for nylon 11/chitosan blending films is strongly affected by the addition percentage of chitosan.
Keywords: Nylon 11; Solution casting method; Biodegradation; Sea–island configuration;
Melamine cyanurate-microencapsulated red phosphorus flame retardant unreinforced and glass fiber reinforced polyamide 66 by Yuan Liu; Qi Wang (3103-3109).
A novel microencapsulated red phosphorus (RP) was prepared through the molecular self-assembly of melamine cyanurate (MCA). Compared with the conventional encapsulated RP, MCA-encapsulated RP (MERP) shows simpler and more environment-friendly preparation process higher thermal stability and lower moisture absorption. With MERP filled in unreinforced polyamide 66 (PA66) and glass fiber (GF) reinforced PA66, flame retardant materials with satisfactory flame retardancy and mechanical performance can be obtained. The influence of the MCA/RP ratio on the flame retardancy as well as the condensed phase of MERP flame retardant PA66 was investigated to reveal the nitrogen–phosphorus (N–P) synergistic flame retarding effects between MCA and RP.
Keywords: Microencapsulated red phosphorus; Melamine cyanurate; Flame retardancy; Polyamide 66;
On the effectiveness of different additives and concentrations on the re-building of the molecular structure of degraded polyethylene by R. Scaffaro; N. Tzankova Dintcheva; F.P. La Mantia (3110-3116).
Mechanical recycling is an easy and economic way to re-use plastic waste as secondary materials, but, in general, their properties are worse with respect to the reclaimed materials and the virgin polymer. The aim of this work was to study the effect of concentration and reaction kinetics of two additives, an ethylene-co-glycidyl methacrylate (Lotader) and a hydroxylamine derivative (CGX), in the re-building of a degraded polyethylene. CGX is a nitroxyl radical generator able to form branching in polyolefins while the epoxy groups of Lotader can react with the functional groups present in the recycled polyethylene. The results indicate that the CGX has a higher reaction rate than Lotader, probably due to its lower molecular weight and the different reaction path. As for the effect of concentration, as expected, a higher amount of additive accelerates and increases re-building, especially when CGX is used. The melt strength increases with the additive content and the mechanical properties show a significant reduction at the highest concentrations of both additives due to excessive cross-linking.
Keywords: Recycling; Polyethylene; Re-building; Reactive processing; Elongational viscosity; Mechanical properties;
Study of electrochemical stability of conducting polymers by bidimensional spectroelectrochemistry: p- and n-doping of poly(4,4′-bis(butylthio)-2,2′-bithiophene) films by Virginia Ruiz; Álvaro Colina; Aránzazu Heras; Jesús López-Palacios (3117-3123).
UV–vis bidimensional spectroelectrochemistry has been applied to the study of the electrochemical stability of conducting polymer films during p- and n-doping processes. Specifically, poly(4,4′-bis(butylthio)-2,2′-bithiophene) has been chosen as example to prove the usefulness and suitability of this multi-response technique to characterize polymer stability during p- and n-doping. It was found that oxidative doping and corresponding de-doping alone did not result in noticeable polymer film degradation. However, in experiments involving both p- and n-doping of this conducting polymer, soluble species arising from the polymer film were detected in solution for the first time, indicating a lower electrochemical stability of the film under these experimental conditions. Moreover, bidimensional spectroelectrochemistry has enabled us not only to detect the soluble degradation products, but also the potential range in which the degradation takes place.
Keywords: Spectroelectrochemistry; Conducting polymers; Thiophenes; Doping; Electrochemical stability;
Influence of polycaprolactone-triol addition on thermal stability of soy protein isolate based films by V. Schmidt; V. Soldi (3124-3130).
The influence of polycaprolatone-triol (PCL-T) on the thermal degradation properties of soy protein isolate (SPI)-based films was studied by thermogravimetry and infrared spectroscopy under nitrogen atmosphere. The results showed that in the absence of PCL-T the thermal degradation began between 292 °C (pure SPI films) and ca. 264 °C (SPI/SDS films with more than 20% of SDS), and these values decreased further to the range 250–255 °C for SPI/SDS/PCL-T films. At the same time, the temperature of maximum degradation rate (T max) decreased from 331 °C (pure SPI film) to ca. 280 °C for SPI/SDS/PCL-T films with 39% PCL-T content. This behavior was also confirmed by the activation energy (E) values associated with the thermal degradation process. Apparently, the low thermal stability of PCL-T as compared to other film constituents, along with its plasticizer characteristics, is responsible for the decreased stability of SPI/SDS/PCL-T films. The FTIR spectra of gas products evolved during the thermal degradation indicated the formation of OH, CO2, NH3 and other saturated compounds, suggesting that the reaction mechanism involved simultaneous scission of the C(O)–O polyester bonds and C–N, C(O)–NH, C(O)–NH2 and –NH2 bonds of the protein.
Keywords: Soy protein isolate; Polycaprolactone-triol; Thermal stability; Activation energy;
Metallocene ethylene-1-octene copolymers: Influence of comonomer content on thermo-mechanical, rheological, and thermo-oxidative behaviours before and after melt processing in an internal mixer by S. Al-Malaika; X. Peng; H. Watson (3131-3148).
The influence of the comonomer content in a series of metallocene-based ethylene-1-octene copolymers (m-LLDPE) on thermo-mechanical, rheological, and thermo-oxidative behaviours during melt processing were examined using a range of characterisation techniques. The amount of branching was calculated from 13C NMR and studies using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were employed to determine the effect of short chain branching (SCB, comonomer content) on thermal and mechanical characteristics of the polymer. The effect of melt processing at different temperatures on the thermo-oxidative behaviour of the polymers was investigated by examining the changes in rheological properties, using both melt flow and capillary rheometry, and the evolution of oxidation products during processing using infrared spectroscopy.The results show that the comonomer content and catalyst type greatly affect thermal, mechanical and oxidative behaviour of the polymers. For the metallocene polymer series, it was shown from both DSC and DMA that (i) crystallinity and melting temperatures decreased linearly with comonomer content, (ii) the intensity of the β-transition increased, and (iii) the position of the tan δ max peak corresponding to the α-transition shifted to lower temperatures, with higher comonomer content. In contrast, a corresponding Ziegler polymer containing the same level of SCB as in one of the m-LLDPE polymers, showed different characteristics due to its more heterogeneous nature: higher elongational viscosity, and a double melting peak with broader intensity that occurred at higher temperature (from DSC endotherm) indicating a much broader short chain branch distribution.The thermo-oxidative behaviour of the polymers after melt processing was similarly influenced by the comonomer content. Rheological characteristics and changes in concentrations of carbonyl and the different unsaturated groups, particularly vinyl, vinylidene and trans-vinylene, during processing of m-LLDPE polymers, showed that polymers with lower levels of SCB gave rise to predominantly crosslinking reactions at all processing temperatures. By contrast, chain scission reactions at higher processing temperatures became more favoured in the higher comonomer-containing polymers. Compared to its metallocene analogue, the Ziegler polymer showed a much higher degree of crosslinking at all temperatures because of the high levels of vinyl unsaturation initially present.
Keywords: LLDPE; Olefin copolymers; Metallocene; Thermal oxidation; Short chain branching;
Rheology and thermal stability of polylactide/clay nanocomposites by Defeng Wu; Liang Wu; Lanfeng Wu; Ming Zhang (3149-3155).
Polylactide/clay nanocomposites (PLACNs) were prepared by melt intercalation. The intercalated structure of PLACNs was investigated using XRD and TEM. Both the linear and nonlinear rheological properties of PLACNs were measured by parallel plate rheometer. The results reveal that percolation threshold of the PLACNs is about 4 wt%, and the network structure is very sensitive to both the quiescent and the large amplitude oscillatory shear (LAOS) deformation. The stress overshoots in the reverse flow experiments were strongly dependent on the rest time and shear rate but shows a strain-scaling response to the startup of steady shear flow, indicating that the formation of the long-range structure in PLACNs may be the major driving force for the reorganization of the clay network. The thermal behavior of PLACNs was also characterized. However, the results show that with the addition of clay, the thermal stability of PLACNs decreases in contrast to that of pure PLA.
Keywords: Polylactide; Clay; Nanocomposites; Rheology; Thermal stability;
Degradation of sisal fibre/Mater Bi-Y biocomposites buried in soil by V.A. Alvarez; R.A. Ruseckaite; A. Vázquez (3156-3162).
Degradation of short sisal fibres/Mater Bi-Y™ biocomposites during indoor burial experiments was analysed. Within the first month, water sorption was the main event followed by weight loss. Water sorption results demonstrated that composites absorbed less water than the matrix. The lower sorption capacity of composites was related to the presence of fibre–fibre and fibre–matrix (both of carbohydrate nature) interactions which delay the water intake and enhances the material stability. In soil burial, all materials followed the same degradation pattern. The amorphous nature of the matrix favoured the preferential removal of starch, which was the most bio-susceptible material, as observed by thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Fibres seemed to play a secondary role in this process, as confirmed by the slight difference in weight loss between the matrix and composites (40 and 33 wt.%, respectively). The drop in mechanical properties as a function of the exposure time was associated with the preferential loss of matrix and fibre components and the detriment of the fibre/matrix interface.
Keywords: Biocomposites; Biofibre; Biodegradation; Soil burial; Mechanical properties;
Identification of polymer additives by liquid chromatography–mass spectrometry by C. Block; L. Wynants; M. Kelchtermans; R. De Boer; F. Compernolle (3163-3173).
LC–MS at different experimental conditions was used to construct a library of MS spectra of polymer additives. Combination of retention time information derived from the chromatogram with molecular mass and fragment ion information derived from MS and MS/MS was used for the identification of 20 additives. Mixtures of different additives and extracts of LDPE films were prepared and analyzed as unknowns. All 20 additives could be identified, 15 with 100% certainty.
Keywords: Polymer additives; Identification; LC–MS; Retention time; Molecular mass;
Unexplored capabilities of chemiluminescence and thermoanalytical methods in characterization of intact and degraded hyaluronans by J. Rychlý; L. Šoltés; M. Stankovská; I. Janigová; K. Csomorová; V. Sasinková; G. Kogan; P. Gemeiner (3174-3184).
Three intact and four degraded hyaluronans were investigated by using chemiluminometry, differential scanning calorimetry, and thermogravimetry. Degradation of hyaluronan was induced by a system containing H2O2 alone (882 mM); 55 mM H2O2 plus 1.25 μM CuCl2; NaOCl alone (10 mM); and NaOCl plus CuCl2 and ascorbic acid (10 mM, 0.1 μM, and 100 μM, respectively). The four different oxidative systems yielded biopolymer fragments represented by similar viscosity characteristics. The results obtained by using chemiluminescence and thermoanalytical methods indicate that hyaluronans of similar rheological properties could be distinguished from each other.
Keywords: Hyaluronan; Hyaluronan degradation; Chemiluminometry; Differential scanning calorimetry; Thermogravimetry; IR spectroscopy;
Effect of preparation conditions on the thermal stability of an epoxy-functional inorganic–organic hybrid material system with phenyl side group by Mehmet Çopuroğlu; Shane O'Brien; Gabriel M. Crean (3185-3190).
A hybrid material system consisting of (3-glycidyloxypropyl)trimethoxysilane and dimethyldimethoxysilane as matrix materials and diphenyldimethoxysilane (DPDMS) as both a matrix material and a potential thermal stabiliser by the sol–gel method. A detailed thermogravimetric analysis study of the influence of processing parameters, including DPDMS content, UV irradiation and sol ageing, on the thermal stability of the resultant thin films was presented. FT-IR spectroscopy was used to monitor the changes in the relative amount of epoxy rings in the system during processing. It was demonstrated that the crosslinking of epoxy groups in the structure is the primary reason for changes in the thermal stability of the system. It was also shown that the thermal stability, in terms of 10% mass loss, of the material system could be improved up to 280 °C, by adjusting the preparation conditions, compatible with several subsequent high temperature optoelectronic integration processes.
Keywords: Sol–gel method; Organically modified silane; Crosslinking; Thermal stability;
Effect of poly(hydroxybutyrate-co-hydroxyhexanoate) microparticles on growth of murine fibroblast L929 cells by Shan Cheng; Qiong Wu; Yan Zhao; Bing Zou; Guo-Qiang Chen (3191-3196).
Poly(hydroxybutyrate-co-hydroxyhexanoate) (PHBHHx) microparticles were successfully prepared and their proliferative effects on cultured fibroblasts were studied. PHBHHx microparticles (0.005–0.1 g/L) promoted cell proliferation in murine fibroblast L929 and elevated intracellular calcium concentrations ([Ca2+]i). EGTA (ethylene glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid) inhibited PHBHHx microparticle-induced cell proliferation by chelating the extracellular Ca2+ and blocking the PHBHHx particle-induced [Ca2+]i increase. Transwell experiments demonstrated that PHBHHx microparticles stimulated fibroblast proliferation when separated from cells by a 0.4 μm filter as effectively as when applied directly to cells. Since PHBHHx microparticles had a diameter of 75 μm, the stimulatory effect of PHBHHx particles on cell growth was attributed to degradation products smaller than 0.4 μm in diameter. The trophic effect of these microparticles is consistent with our previous reports demonstrating good biocompatibility for PHBHHx.
Keywords: PHB; PHBHHx microparticles; Fibroblast L929; Proliferation; Biodegradation;
Lifetime predictions of EPR materials using the Wear-out approach by K.T. Gillen; M. Celina; R. Bernstein; M. Shedd (3197-3207).
The Wear-out approach for lifetime prediction, based on cumulative damage concepts, is applied to several ethylene propylene rubber (EPR) cable insulation materials. EPR materials typically follow “induction-time” behavior in which their material properties change very slowly until just before failure, precluding the use of such time-dependent properties to predict failure. In the Wear-out approach, a material that has been aged at its ambient aging temperature T a or at a low accelerated aging temperature is subsequently aged at a higher “Wear-out” temperature T w in order to cause the material to reach its “failure” condition. In the simplest case, which involves the same chemical processes underlying degradation at T a and T w, a linear relationship is predicted between the time spent at T a and the time required at T w to complete the degradation. Data consistent with this expectation are presented for one of the EPR insulation materials. When the degradation chemistry at the two temperatures is different, a linear relationship between the time spent at T a and the time required at T w to complete the degradation is not generally expected. Even so, the Wear-out results for a second EPR material, which has evidence of changing chemistry, are reasonably linear and therefore useful from a predictive point-of-view. The Wear-out approach can therefore be used to transform non-predictive time-dependent material property results into predictive lifetime estimates. As a final example, the Wear-out approach is applied to an EPR insulation that had been aged in a nuclear power plant environment (∼51 °C) for times up to 23 years to show its likely viability for the hundreds of years predicted at this aging temperature from accelerated aging tests on EPR insulation materials.
Keywords: Lifetime prediction; EPR; Accelerated aging; Cable insulation;
Improvement of photo-stability of LLDPE-based nanocomposites by F.P. La Mantia; N. Tzankova Dintcheva; V. Malatesta; F. Pagani (3208-3213).
LLDPE-based nanocomposites undergo faster photo-oxidation than the unfilled matrix and the extent of their physical properties deterioration, namely elongation at break and tensile strength, is dependent on the organo-nanoclay loading. The observed acceleration is not due to faster photo-oxidation but rather due to a reduction of the oxidation induction time. The presence in the organoclays of trace amounts of metal ions may be promoting catalytic photodegradation. While UV absorbers provide useful protection, use of a metal deactivator has been found to greatly enhance the photo-stability of the LLDPE-based nanocomposites. Combinations of a metal deactivator and UV absorber yield synergistic effects.
Keywords: Photo-oxidation; Photo-stability; LLDPE-based nanocomposites; Metal deactivator; Mechanical properties;
Investigation of the thermal degradation of fully aromatic regular polyesters: Poly(oxy-1,4-phenyleneoxy-fumaroyl-bis-4-oxybenzoate) by Fabio Bertini; Vjacheslav V. Zuev (3214-3220).
The thermal behaviour and degradation mechanism of fully aromatic polyester, poly(oxy-1,4-phenyleneoxy-fumaroyl-bis-4-oxybenzoate), were studied by pyrolysis–gas chromatography and pyrolysis–gas chromatography/mass spectrometry at 500–700 °C, and by thermogravimetry. The influence of fullerene C60 additives on thermal behaviour and thermal degradation was investigated. On the basis of pyrolysis products determined, the origin of the main degradation products (maleic anhydride, phenol, hydroquinone, phenyl ether, p-hydroxybenzoate-p′-phenol, etc.) was estimated. The fullerene is a well-known efficient acceptor of radicals and its presence influences the thermal degradation process of polymers shifting the decomposition from a radical pathway to a non-radical mechanism. Thermal degradation mechanism of poly(oxy-1,4-phenyleneoxy-fumaroyl-bis-4-oxybenzoate) is discussed in detail.
Keywords: Poly(oxy-1,4-phenyleneoxy-fumaroyl-bis-4-oxybenzoate); Fullerene C60; Pyrolysis–gas chromatography; Thermal behaviour; Thermal degradation mechanism;
The thermal degradation of poly(diethyl fumarate) by Miloš Milovanović; Radomir Bošković; Tomica Tošić; Lynne Katsikas; Ivanka G. Popović (3221-3229).
The kinetics and mechanism of the thermal degradation of poly(diethyl fumarate) (PDEF) were studied by thermogravimetry, as well as by analysis of the thermolysis volatiles and polymer residue. The characteristic mass loss temperatures were determined, as were the overall thermal degradation activation energies of three PDEF samples of varying molar mass. Ethylene and ethanol were present in the thermolysis volatiles at degradation temperatures below 300 °C, while diethyl fumarate was also evidenced at higher degradation temperatures. The amount of monomer increased with increasing degradation temperature. The dependence of the molar mass of the residual polymer on the degradation time and temperature was established and the number of main-chain scissions per monomer unit, s/P 0, calculated. A thermal degradation mechanism including de-esterification and random main-chain scission is proposed. The thermal degradation of PDEF was compared to the thermolysis of poly(ethyl methacrylate) (PEMA), poly(diethyl itaconate) (PDEI) and poly(ethyl acrylate) (PEA).
Keywords: Poly(diethyl fumarate); Thermal degradation; Kinetics; Mechanism;
Thermal and rheological behaviours of some random aromatic amino-ended polyethersulfone/polyetherethersulfone copolymers by Lorenzo Abate; Ignazio Blanco; Gianluca Cicala; Antonino Recca; Carmelo Luca Restuccia (3230-3236).
The thermal and rheological characterizations of seven random, low molecular weight (M n ≅ 9500 g mol−1), H2N-ended polyethersulfone/polyetherethersulfone (PES/PEES) copolymers, at various PES/PEES ratios, were performed. The glass transition temperatures (T g) were determined by DSC. Degradations were carried out in a thermobalance, under flowing nitrogen, in dynamic heating conditions from 35 °C to 650 °C. The initial decomposition temperatures (T i) and the half decomposition temperatures (T 1/2) were directly determined by TG curves, while the apparent activation energies of degradation (E a) were obtained by the Kissinger method. In addition, the complex viscosities (η ∗) of the molten polymers were determined in experimental conditions of linear viscoelasticity. T g, E a and η ∗ values increased linearly with PES% content, while T i and T 1/2 values showed opposite behaviour. In every case both PES and PEES homopolymers felt outside linearity. The results obtained are discussed and interpreted, and compared with those of corresponding Cl-ended copolymers previously studied.
Keywords: Copolymers; Thermal stability; Kinetics of degradation; Rheological behaviour;
The effect of Zn, Al layered double hydroxide on thermal decomposition of poly(vinyl chloride) by Zhi Ping Xu; Susanta K. Saha; Paul S. Braterman; Nandika D'Souza (3237-3244).
Poly(vinyl chloride)/layered double hydroxide (LDH) composite was prepared by mixing 4 wt% Zn2Al–CO3–LDH with PVC and fluxing at 180 °C. The thermal decomposition behaviour of the LDH + PVC composite in air and nitrogen environments was systematically investigated. We found that mixing Zn2Al–CO3–LDH into PVC facilitates dehydrochlorination from ca. 300 to 270 °C but reduces the reaction extent to leave more chlorine on the polyene backbones both in air and N2. We have also found that at 400–550 °C, both in air and N2, LDH assists the formation of char-like materials and decreases the release of volatile hydrocarbons. From 550 to 800 °C, the char-like materials are mostly retained in N2 while they are almost completely thermo-oxidized (burned) in air. Thus, addition of Zn2Al–CO3–LDH to PVC does not increase the thermal stability, but does promote charring to retard the generation of flame. The influence of LDH on PVC thermal properties has been also addressed mechanically.
Keywords: Layered double hydroxide (LDH); Polymer composite; PVC additive; Thermal stability; Flame retardant;
Thermal stability and high glass transition temperature of 4-chloromethyl styrene polymers bearing carbazolyl moieties by Mirzaagha Babazadeh (3245-3251).
A new styrene derivative monomer, 4-(N-carbazolyl)methyl styrene (CzMS), was synthesized by reacting 4-chloromethyl styrene with carbazole in the presence of sodium hydride. Then, CzMS was homopolymerized and copolymerized with different monomers such as methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl acrylate (MA), ethyl acrylate (EA) and n-butyl acrylate (BA) by free radical polymerization method in N,N-di-methylformamide (DMF) solution at 70 ± 1 °C using azobisisobutyronitrile initiator to give the copolymers I–V in good yields. The structure of all the resulted polymers was characterized and confirmed by FT-IR, 1H NMR and 13C NMR spectroscopic techniques. The average molecular weight and glass transition temperature of polymers were determined using gel permeation chromatograph (GPC) and differential scanning calorimeter (DSC) instruments, respectively. It was found that these polymers with carbazole moieties have high thermal stability and the presence of bulk carbazole groups in polymer side chains leads to an increase in the rigidity and glass transition temperature of polymers.
Keywords: 4-Chloromethyl styrene; Carbazole; Acrylic monomers; Chemical modification; Thermal stability; Glass transition temperature;
Solvent effect on thermal degradation of plasticized para-substituted polystyrenes by Khalid E. Al Ani; Musa Al Barghouthi; Manal Al Buzour (3252-3258).
The thermal effect on stability of a series of para-substituted polystyrenes with methyl, methoxy and α-methyl substituents in various solvents was studied in the temperature range of 298–363 K. They gave a monomer fluorescence as a minor part and excimer fluorescence as a major part. Thermal heating of para-substituted polystyrenes shows a decrease in both monomer and excimer fluorescences in all used solvents. Thermal heating causes a small fluorescence quenching effect at lower temperatures in solution but becomes very dominant at higher temperatures. Added terephthalate and phthalate plasticizers to these para-substituted polystyrenes caused a quenching of both monomer and excimer fluorescences without the formation of exciplex emission. The thermal quenching processes of the plasticized polymers were accompanied by a change in the structure of the fluorescence spectra at high heating temperatures. This may indicate that thermodestruction of these polymers starts from a random chain scission. The change in solvent polarity has considerable effect on fluorescence quenching but it has a minor effect on the thermal degradation of these polymers. The binding energies for excimer formation were calculated in the used solvents.
Keywords: Thermal quenching; Fluorescence quenching; para-Substituted polystyrenes; Thermal degradation;
Kinetics of thermo-oxidative and thermal degradation of poly(d,l-lactide) (PDLLA) at processing temperature by Xiaobo Liu; Yaobang Zou; Wenting Li; Guoping Cao; Wenjin Chen (3259-3265).
Poly(d,l-lactide) (PDLLA) degraded at processing temperature under air and nitrogen. A random chain scission model was established and used to determine the activation energy E a, and FT-IR, 1H and 13C NMR were used to elucidate the degradation behavior under different atmospheres. Results showed that there were two to three stages. The 1st stage was dominated by the oligomers containing carboxylic acid groups and hydroxyl groups, during which oxygen and nitrogen had little effect on the degradation, thus they share similar E a. When the oligomers were consumed over or evaporated, the 2nd stage began, and oxygen had a promoting effect on the thermo-oxidation process, resulting in the great decrease in E a. The third stage of PDLLA was observed when it degraded under nitrogen over 200 °C, which was caused by the appearance of carboxylic acid substance.
Keywords: Thermo-oxidation; Thermal degradation; Kinetics; Poly(d,l-lactide);
Effects of polystyrene-encapsulated magnesium hydroxide on rheological and flame-retarding properties of HIPS composites by Suqin Chang; Tingxiu Xie; Guisheng Yang (3266-3273).
In this study, polystyrene (PS)-encapsulated magnesium hydroxide (Mg(OH)2) was successfully prepared by in situ polymerization of styrene on the surface of Mg(OH)2 in a high-speed mixer. A large amount of PS chemically bonded on Mg(OH)2 surface was confirmed by means of FT-IR, TGA and SEM. A series of composites of high impact polystyrene (HIPS) were prepared by melt blending in a co-rotating twin-screw extruder. The effects of PS-encapsulated filler on the properties of HIPS composites were studied by SEM, rheology and combustion tests (horizontal burning tests and cone calorimetry). The dispersion and adhesion patterns of PS-encapsulated Mg(OH)2 in HIPS matrix were investigated through FT-IR and SEM. The experimental results demonstrated that comparing to the composites containing untreated filler, the rheological and flame retardant properties of those containing PS-encapsulated filler were found to be significantly improved. This improvement is mostly attributed to a better dispersion of the encapsulated filler and a strong adhesion between the filler and matrix.
Keywords: In situ polymerization; High impact polystyrene; Magnesium hydroxide; Rheological properties; Flame-retarding properties;
Studies of the effects of copper, copper(II) oxide and copper(II) chloride on the thermal degradation of poly(vinyl chloride) by Susan M. Grimes; Huma Lateef; Ahmad J. Jafari; Lina Mehta (3274-3280).
Investigations of the pyrolysis of poly(vinyl chloride) (PVC) in the presence of copper metal (Cu), copper(II) oxide (CuO) and copper(II) chloride (CuCl2) are of potential importance because of the likelihood of the formation of these copper compounds during the thermal degradation of PVC-coated copper wires, a step in the recovery of copper from waste. The presence of Cu, CuO and CuCl2 (i) retards the thermal degradation of PVC in air and in nitrogen and (ii) decreases the percentages of volatile products produced at both stages of the decomposition. These effects are greatest for PVC–CuO. The presence of copper, CuO or CuCl2 in PVC has a major effect on the nature of the gaseous emissions of the thermal decomposition in air and in nitrogen. The concentrations of total chlorine, aliphatic hydrocarbons, aromatic hydrocarbons, chlorinated hydrocarbons and soot particulates are all affected relative to an equivalent amount of PVC. These changes are greatest for the PVC–CuO system for which total chlorine emissions in air and nitrogen are reduced by 40% in air and 20% in nitrogen, benzene emissions are reduced by greater than 90% in air and nitrogen, other aromatic and chloroaromatic emissions are reduced, and soot particulate emissions are reduced by more than 50% as the concentrations of aliphatic compounds are increased. These changes are consistent with the presence of copper or its compounds permitting more efficient combustion of the carbon content of the PVC and particularly in the case of PVC–CuO with the removal of chlorine during pyrolysis in the inorganic phase.
Keywords: PVC; PVC–CuO; PVC–Cu; PVC-coated cable; PVC degradation; Soot reduction;
Biodegradable liquid crystalline aromatic/aliphatic copolyesters. Part I: Synthesis, characterization, and hydrolytic degradation of poly(butylene succinate-co-butylene terephthaloyldioxy dibenzoates) by Jie Du; Yubin Zheng; Liang Xu (3281-3288).
To increase the thermal and mechanical properties of the aliphatic polyester poly(butylene succinate) (PBS), a series of potentially biodegradable liquid crystalline aromatic/aliphatic random copolyesters were prepared by melt polycondensation of new mesogenic monomers dimethyl 4,4′-(terephthaloyldioxy) dibenzoate (MTB), dimethyl succinate, and 1,4-butanediol. The synthesized copolyesters were characterized by means of proton nuclear magnetic resonance spectroscopy (1H NMR), gel permeation chromatography (GPC), viscosity measurements, differential scanning calorimetry (DSC), thermogravimetry (TG), X-ray diffraction (XRD), polarizing light microscopy (PLM) and mechanical property measurements. The MTB content was varied so that the effects of the mesogen content on the thermal and mechanical properties, degradable behaviours and mesophase were examined. It was found that introducing the rigid rod mesogens could increase the thermal stability and the mechanical properties, while it reduced the melting temperature (T m), the crystallization temperature (T c), the degree of relative crystallinity (X c) and the hydrolytic degradation rate. Only the homopolyester poly(butylenes terephthaloyldioxy dibenzoates) was able to show the schlieren texture characteristic of nematics.
Keywords: Liquid crystalline; PBS; Random copolyesters; Hydrolytic degradation;
In vitro degradation and swelling behaviour of rubbery thermoplastic starch in simulated body and simulated saliva fluid and effects of the degradation products on cells by Rui Shi; Tao Ding; Quanyong Liu; Yanming Han; Liqun Zhang; Dafu Chen; Wei Tian (3289-3300).
Degradation in vitro is of importance in implanted biological industry. This research investigated the swelling and degradation behaviours of glycerol plasticized thermoplastic starch (GTPS) in simulated body fluid (SBF) and simulated saliva fluid (SSF), respectively. The weight loss, swelling degree and linear extensibility as a function of time were measured. Changes in the morphology (SEM), chemical structure (FT-IR), crystal property (XRD) and thermogravimetic property (TG) during degradation were also investigated. Results show that the degradation in SSF was much quicker than that in SBF. About 1 h was needed for the swelling equilibrium in SBF, which was a little quicker than that in SSF. In alkaline solution the swelling speed and the swelling degree were larger than those in neutral and acidic solutions. The degradation in SBF was typical bulk degradation. In SSF the surface and bulk degradation took place synchronously, but the surface degradation played an important role in the first 2 h. Results from FT-IR and XRD suggest that the glycosidic linkages in starch chains were broken and the crystal structure in GTPS was destructed during degradation. Cytotoxicity test was used to investigate the effects of the short-term extracted dilutions and long-term degradation products on the cells, which illustrates that the degradation products not only had non-toxicity but also accelerated the cells' growth.
Keywords: Thermoplastic; Starch; Degradation; Swelling; Cytotoxicity test;
Influence of copper-phthalocyanine on the photodegradation of polycarbonate by Clodoaldo Saron; Fabio Zulli; Marco Giordano; Maria Isabel Felisberti (3301-3311).
Dyes and pigments are extensively used in polymer materials to confer colour-changing properties. However, these additives can significantly affect polymer stability against degradation. While the mechanism of stabilization of polymers by some pigments, such as carbon black, has been studied and is well known, the action of chromatic colorants, mainly in the sensitization of the degradation process, remains unclear. Cu-phthalocyanine dye can stabilize polymers against degradation as well as accelerate degradation in other situations. Cu-phthalocyanine incorporated into polycarbonate resulted in an acceleration of the degradation when the material was submitted to photochemical aging. The possible mechanism to explain the photodegradative behavior of PC containing Cu-phthalocyanine is based on the hypothesis that specific interactions among excited states of PC and Cu-phthalocyanine take place and enhance the formation of reactive species in polycarbonate. Excited states of Cu-phthalocyanine may abstract hydrogen atoms from methyl groups in polycarbonate, increasing the formation of free radicals P•, which are the starting points for the sequential photo-oxidation reactions that lead to the degradation of the polycarbonate. Electron transfer sensitization is also a possible mechanism: the excited state of Cu-Ph abstracts an electron from PC to form the Cu-Ph radical anion and the PC radical cation. These reactive species in the presence of oxygen can cause oxidation of the aromatic ring.
Keywords: Photodegradation; Colorant; Polycarbonate; Cu-phthalocyanine;
TGA/FTIR study on thermal degradation of polymethacrylates containing carboxylic groups by J.M. Cervantes-Uc; J.V. Cauich-Rodríguez; H. Vázquez-Torres; A. Licea-Claveríe (3312-3321).
In this work, the thermal degradation of polymethacrylates containing carboxylic groups namely poly(methacryloyloxy butanoic acid), PMBA; poly(methacryloyloxy hexanoic acid), PMHA; and poly(p-methacryloyloxy benzoic acid), PMBeA was investigated by TGA/FTIR. Moreover, in order to shed more light on the reaction pathways during the thermal decomposition of these polymers, an FTIR spectroscopic study of structural changes in the degrading material was performed. By TGA it was observed that PMBA exhibited two well-defined degradation stages at 327 and 450 °C; PMHA presents only one main weight loss at ca. 402 °C although from DTG curve it was noted that the single step degradation was composed by two overlapped peaks located at 414 and 449 °C and a small shoulder at 317 °C; finally PMBeA showed three weight loss regions at 265, 353 and 468 °C. From FTIR analysis of the partially degraded samples it was found that the thermal degradation of these polymers resembled that of polymethacrylic acid, i.e. anhydrides were initially formed and then the modified structure is broken to yield an aromatic structure with phenolic groups. In contrast, the analysis by FTIR of the volatile products from the studied polymers differs notably than those obtained for polymethacrylic acid: β-lactones and γ-lactones were released from PMBA and PMHA, respectively, during its thermal degradation, whereas an ester derivative from benzoic acid evolves from PMBeA probably through depolymerization.
Keywords: Thermal degradation; TGA/FTIR; Polymers with carboxylic groups; Thermal decomposition;
Poly(vinyl chloride)-paste/clay nanocomposites: Investigation of thermal and morphological characteristics by T. Peprnicek; A. Kalendova; E. Pavlova; J. Simonik; J. Duchet; J.F. Gerard (3322-3329).
The paper concentrates on poly(vinyl chloride) – PVC – from the point of nanocomposite characterisation through thermal degradation of samples, evolution of the changes caused by elevating temperature using TGA, FTIR and Congo Red methods combined with morphological characterisation by XRD and TEM analyses. A novel method of PVC-paste/nanocomposite preparation while processing was used. During preparation, PVC plasticizer was mixed with clay, both natural and organophilic, and the suspension was then compounded with the other components. Two factors were followed: effect of shearing alone, and in combination with temperature. As is presented, the type of nano-filler and its chemical modifier have obvious influence on final properties either thermal or morphological. Presented contribution follows previous part of investigation and brings further information from PVC-paste/nanocomposite field.
Keywords: Poly(vinyl chloride); Clay; Nanocomposite; Montmorillonite; Exfoliation; Delamination;
Catalytic degradation of high density polyethylene over nanocrystalline HZSM-5 zeolite by J.F. Mastral; C. Berrueco; M. Gea; J. Ceamanos (3330-3338).
High density polyethylene (HDPE) was catalytically degraded using a laboratory fluidised bed reactor in order to obtain high yield of gas fractions at mild temperatures, between 350 and 550 °C. The catalyst used was nanocrystalline HZSM-5 zeolite. High yields of butenes (25%) were found in the gas fractions, which were composed mainly of olefins. Waxes were wholly composed of linear and branched paraffins, with components between C10 and C20. The effects of both temperature and polymer to catalyst ratio on the product yield were studied. Gas conversion was dramatically decreased when the operation temperature was low (below 450 °C) or when the polymer to catalyst ratio was greatly increased (9.2). Gas and wax compositions significantly altered over 500 °C, showing that a part of the HDPE was degraded thermally, increasing the olefin concentration in the waxes. The same variation was observed in the experiments carried out at high polymer to catalyst ratios, obtaining a 50% olefinic concentration in the waxes. The differences observed in product distributions can be attributed to both thermal and catalytic degradations.
Keywords: High density polyethylene; Zeolite; Catalyst; Pyrolysis; Product distribution;
Flammability of wood–polypropylene composites by Slawomir Borysiak; Dominik Paukszta; Malgorzata Helwig (3339-3343).
Addition of wood particles to polymers can cause a change of properties of the composites which depends on features of lignocellulosic materials and those of polymers. It is also observed in the flammability characteristics of the composites.In this work, the flammability of polypropylene composites with pine wood particles obtained by extrusion and press moulding was analyzed. The amount of wood particles was 50%. Polymers with various melt flow index (MFI) were used (Malen F-401, PP HY-202 and Malen S-702).The samples were tested using Cone Calorimeter at heat flux of 35 kW/m2. Heat release rate (HRR) curves of composites show that thermal decomposition depends on the kind of polypropylene used. In the presence of PP HY-202 and Malen S-702, the flammability characteristic is similar to that of lignocellulosic materials, in contrast to composites with matrices prepared from Malen F-401. The observed phenomenon is interpreted in terms of the wettability of particles of pine wood by polymers of varying melt viscosity.
Keywords: Wood; Polypropylene; Composite; Flammability; Melt flow index;
Characterizations of a new flame-retardant polymer by Guo-An Wang; Wei-Ming Cheng; You-Liang Tu; Cheng-Chien Wang; Chuh-Yung Chen (3344-3353).
Poly(2-methacryloxyethyl phenyl phosphate) (PMEPP) was successfully obtained in a two-stage process by the bulk polymerization of 2-methacryloxyethyl phenyl phosphate (MEPP). The flame-retardant properties of PMEPP were studied with limiting oxygen index (LOI) and UL-94 tests, showing that PMEPP with a low flammability can effectively inhibit combustion. The result of energy dispersive spectrometer (EDS) reveals that the condensed-phase protection plays an important role for the flame retardance of PMEPP, because most portion of phosphorus was retained in the char residue. The thermal characteristics of PMEPP were investigated by differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The condensed-phase products at various temperatures during the thermal degradation of PMEPP were monitored by Fourier transform infrared (FT-IR) spectroscopy. The volatilized products formed on thermal degradation of PMEPP were characterized by TGA/FT-IR technique, indicating that the volatilized products are phenol, aldehyde RCHO, CO2, CO, water and alkane according to the temperature of onset formation. We propose the possible mechanisms for the thermal degradation of PMEPP in accordance with the analytical results of condensed phase and volatilized products.
Keywords: 2-Methacryloxyethyl phenyl phosphate; LOI; TGA/FT-IR technique; Thermal degradation;
Improving chemical recycling rate by reclaiming polyurethane elastomer from polyurethane foam by Hiroko Watando; Shioko Saya; Taro Fukaya; Shinetsu Fujieda; Masaaki Yamamoto (3354-3359).
Flexible polyurethane foam was decomposed into a polyol mixture by an extruder with diethanolamine (DEA) as a decomposing agent. The resulting decomposed product could be used as an alternative virgin polyol in reclaiming polyurethane. In the case of reclaiming elastomer by using the decomposed product without any purification, virgin polyol could be alternated by the decomposed product up to 80%. It is a great improvement compared with the reclamation to foam, whose percentage was maximum 5%. Furthermore, the percentage could be improved up to 100% by purifying the decomposed product. We have found that physical properties of reclaimed polyurethane elastomer, such as tensile strength, hardness, and elongation, can be regulated by the ratio of unrefined/refined polyol. Whereas the tensile strength and the hardness increased as the content increased, the elongation decreased.
Keywords: Polyurethane; Chemical recycling; Foam; Elastomer; Reclamation;
Effects of hydrolysis-induced molecular weight changes on the phase separation of a polyester polyurethane by Darla Graff Thompson; Jill C. Osborn; Edward M. Kober; Jon R. Schoonover (3360-3370).
A polyester polyurethane, was subjected to humid and dry aging conditions at 70 °C with 75% and 0% relative humidity, respectively. Differences in molecular weight and quasi-static tensile strength between humid- and dry-aged samples are attributed to hydrolysis of the humid-aged polymers. A phase-separation study was performed on selected samples from the aging matrix. Polymer samples were subjected to 110 °C for 10 min, by mixing the polyester (soft) and the polyurethane (hard) domains, then rapidly cooled to room temperature, initiating the phase-separation process. Uniaxial tension, dynamic shear and infrared spectra of these samples were measured as a function of time providing insight into the effects of hydrolytic degradation and the relationship of mechanical and molecular-level properties. An Avrami-type analysis shows two distinct processes whose characteristics vary as a function of increased hydrolysis. LA-UR 04-6447.
Keywords: Estane; Polyester polyurethane; Vibrational spectroscopy; Hydrolysis; Molecular weight;
Ionic liquids: New generation stable plasticizers for poly(vinyl chloride) by Mustafizur Rahman; Christopher S. Brazel (3371-3382).
Room temperature ionic liquids (ILs), based on ammonium, imidazolium and phosphonium cations, were studied as novel plasticizers for poly(vinyl chloride), PVC. All the ILs tested were able to produce flexible PVC. Upon 20 wt% plasticization, some of the ILs lowered the glass transition temperature (T g) of PVC more than that done by several traditional plasticizers. They showed good thermodynamic compatibility as well. Several ILs showed better leaching and migration resistance than the traditional plasticizers. This was, in particular, a significant observation considering the ongoing controversy regarding the leaching and migration issues of the commonly-used phthalate plasticizers. High temperature and ultraviolet (UV) ray stability of IL-plasticized PVC samples were also studied.
Keywords: Ionic liquid; Plasticizer; Poly(vinyl chloride); Leaching; High temperature stability; UV stability;
IR laser ablative decomposition and depolymerisation/repolymerisation of poly(ethylene succinate) by Dana Pokorná; Anna Galíková; Jan Šubrt; Vratislav Blechta; Josef Pola (3383-3389).
Pulsed IR laser ablation of poly(ethylene succinate) results in the formation of volatile products (mainly carbon oxides, hydrogen, C1–C4 hydrocarbons) and affords deposition of polymeric films. Composition, structure and molecular weight distribution of the latter products were examined by EDX–SEM, FTIR, UV and NMR spectroscopy and gel permeation chromatography and revealed to be virtually identical to the initial poly(ethylene succinate). The deposited films and poly(ethylene succinate) decompose in the same way, as proved by TGA analysis. The formation of the volatile products is accounted for by random cleavages of the polymer backbone. The deposition of the polymeric products is judged to be due to molecular ester group interchange and/or a sequence of the C–C bond homolysis and recombination of the produced radicals.
Keywords: Poly(ethylene succinate); Laser degradation; Laser ablation; Ablative deposition; Laser-induced polymer films;
Modelling light stabilizers as thermal antioxidants by Eldar B. Zeynalov; Norman S. Allen (3390-3396).
Light stabilizers often display some degree of antioxidant activity against thermal degradation of polymers both in the solid state and the melt. Although this capacity to date has been documented in some instances such features have not been kinetically modelled for many light stabilizers. An understanding of the mechanisms of this activity is crucial in polymer materials due to the close link between prior thermal behaviour and post stabilisation.This paper considers the potential antioxidant activity of three representative UV stabilizers using a model system initiated (2,2′-azo-bisisobutyronitrile, AIBN) cumene oxidation. Kinetic measurements of oxidation rates in the presence of the stabilizers showed that the antioxidant activity as well as the mechanism and mode of inhibition was different for each of the stabilizers. Thus, whilst a triazine UV absorber (Cyasorb UV 1164) did not display any antioxidant activity, a hindered phenol (Cyasorb UV 2908) operated as a peroxy radical acceptor, and a hindered amine (Cyasorb 3529) retarded the model reaction without an induction period like many HAS stabilizers.The Cyasorb 2908 revealed weak antioxidant activity with a rate constant for the addition of cumylperoxy RO2 • radicals to the functional group of the stabilizer k 7 = 106.2 ± 0.1 e−(3900 ± 600)/RT , however, the inhibition index f (80 °C) is significantly higher than that of the commercial phenolic antioxidant Irganox 1076. Oxidation rate profiles in the presence of Cyasorb 3529 displayed a strong retarding activity by the stabilizer under conditions of the model experiments. The rates were found to depend linearly on the reciprocal square root of the concentration of the stabilizer over a sufficiently wide range thereby fitting the mechanism for the addition of cumylalkyl R • radicals to the Cyasorb molecules. The rate constants for the addition of cumyl R • radicals to the Cyasorb were determined to be k (333–353 K) = (2.0 ± 0.8) × 108 M−1 s−1. This value surpasses even the rate constants for other related HAS Chimassorb [Zeynalov EB, Allen NS. Effect of micron and nano-grade titanium dioxides on the efficiency of hindered piperidine stabilizers in a model oxidative reaction. Polym Degrad Stab 2006;91(4):931–9.] stabilizers and it follows that Cyasorb 3529 is a powerful retarder of thermal oxidation.
Keywords: Model oxidation; Light stabilizers; Antioxidants; Rate constant; Induction period; Oxidation rate;
Oxo-biodegradable polymers – Effect of hydrolysis degree on biodegradation behaviour of poly(vinyl alcohol) by Emo Chiellini; Andrea Corti; Graziano Del Sarto; Salvatore D'Antone (3397-3406).
Poly(vinyl alcohol) (PVA) is considered to be one of the very few vinyl polymers soluble in water and susceptible to biodegradation in aqueous media by specific microorganisms, implying oxidation of the carbon backbone followed by a random endocleavage of the polymer chains. The overall process does not appear to be appreciably affected by either degree of polymerization (DPn) or degree of hydrolysis (HD) of PVA at least in the 100–1000 and 80–100% ranges, respectively.In order to assess the effect of HD on the biodegradation propensity of PVA, different PVA samples having similar DPn and noticeably different HD values were synthesized by controlled acetylation of commercial PVA (HD = 99%) and submitted to biodegradation tests in aqueous medium, mature compost and soil by using respirometric procedures. Re-acetylated PVA samples characterized by HD of between 25 and 75% underwent extensive mineralization when buried in solid media, whilst PVA (HD = 99%) showed recalcitrance to biodegradation under those conditions. An opposite trend was indeed observed in aqueous solution, thus suggesting that biodegradation is not an absolute attribute directly related to structural features of the substrate under investigation. Boundary conditions related to the framework under which the biodegradation assessment is undertaken have to be taken into account and specifically well defined.
Keywords: Poly(vinyl alcohol); Hydrolysis Degree; Oxo-biodegradation; Polymer reaction;
The effects of ageing by ultraviolet degradation of recycled polyolefin blends by J. Attwood; M. Philip; A. Hulme; G. Williams; P. Shipton (3407-3415).
Products manufactured from recycled polyolefin blends were subjected to accelerate weathering conditions and subsequent tests. Field-aged products were also tested.Samples were analysed for changes in mechanical, rheological and chemical properties. Data obtained in this study, by means of tensile, impact, and melt flow tests, GPC, gloss and colour analyses showed that the effect of UV exposure, whether in the field or artificial environments, was not significant as far as the mechanical properties of the materials were concerned. There was some change in the surface characteristics but such surface effects would not compromise the mechanical integrity of the product when recycled. During reprocessing of the materials, it is likely that stabilizer is redistributed at the surface of any new moulding, thus renewing the surface characteristics. Hence damaged or end-of-life products need not be discounted from recycling.
Keywords: Ultraviolet degradation; Recycled polyolefin; Accelerated weathering; Plastics;
Physico-chemical aspects of polyethylene processing in an open mixer. Part 25: Mechanisms of aldehyde and carboxylic acid formation by F. Gugumus (3416-3428).
Aldehydes and acids can be formed in numerous reactions in oxidizing polyethylene melts. Significant amounts of aldehydes result from β-scission of alkoxy radicals that are formed on bimolecular hydroperoxide decomposition. There are also large amounts of aldehydes expected from acid-catalyzed decomposition of allylic hydroperoxides as soon as enough acids have accumulated for efficient catalysis. There are difficulties in explaining the formation of aldehydes at a constant rate in sufficient amount for explaining the experimental data. There are much less difficulties with the constant rate of carboxylic acid formation. The α,γ-keto-hydroperoxides that are formed on chain propagation might account for the bulk of the acids formed at a constant rate.The foremost problems with the acids pertain to their formation at increasing rates in the initial as well as in the advanced stages. Formation and decomposition of α,β-di-hydroperoxides and α,γ-di-hydroperoxides is a possibility in this respect. Similarly, α,β-keto-hydroperoxides might be formed on peroxidation in the α-position to ketone groups in the advanced stages. There are considerable difficulties in elucidating the exact role of the aldehydes that are usually seen as the main precursors of the acids. Although there are many possibilities for transformation of aldehydes into acids, the free radical mechanisms envisaged usually have considerable disadvantages. These disadvantages result essentially from fast decarbonylation of acyl radicals and even faster decarboxylation of acyl-oxy radicals. Direct transformation of peracids into acids on reaction with double bonds is always a possibility. Moreover, in the low temperature range (150–160 °C) where hydroperoxides are accumulating, direct reaction of aldehydes with primary and/or secondary hydroperoxides will also yield acids.
Keywords: Polyethylene; Processing; Oxidation products; Aldehydes; Acids; Mechanisms;
Physico-chemical aspects of polyethylene processing in an open mixer by F. Gugumus (3429-3447).
There are many reactions susceptible to yield aldehydes and acids in polyethylene melts. It is β-scission of the alkoxy radicals formed on bimolecular hydroperoxide decomposition that is expected to be one of the main sources of the aldehydes that are formed at increasing rates in the early stages of polyethylene processing. Acid-catalyzed decomposition of allylic hydroperoxides is another source of substantial amounts of aldehydes. Formation and decomposition of α,γ- and α,β-di-hydroperoxides should yield acids. The activation energy estimated for these different processes is very large (about 57 kcal/mol) so that their contribution could be significant in the high temperature range only. This is different for the reaction of aldehydes with hydroperoxides to yield peroxy-hemiacetals. These intermediates can be expected mainly in the low temperature range where hydroperoxides are accumulating. Decomposition of the peroxy-hemiacetals gives acids as one of the main products. Free-radical induced oxidation of aldehydes is likely to yield peracids as far as oxygen addition is competitive with decarbonylation. The main problem is the transformation of the peracids into acids. The reaction with double bonds is expected to yield significantly more acids than thermal decomposition of peracids. If the last occurs, it will be followed mainly by decarboxylation. The overall activation energy for both processes of acid formation is negative (−18 to −20 kcal/mol). It is some combination of the various mechanisms examined that might account for the experimental activation energy for acid formation in the initial stages that is close to 18 kcal/mol.
Keywords: Polyethylene; Processing; Oxidation products; Aldehydes; Acids; Kinetics;
Mass deacidification of papers and books. IV – A study of papers treated with aminoalkylalkoxysilanes and their resistance to ageing by S. Ipert; A.-L. Dupont; B. Lavédrine; P. Bégin; E. Rousset; H. Cheradame (3448-3455).
In libraries and archives some of the time-acidified items are so brittle that they cannot be handled without risking loss of material. Currently used deacidification processes do not impart improved mechanical properties to the paper. The use of alcoholic solutions of three different types of aminoalkylalkoxysilanes was studied for the deacidification of paper-based items. It was shown that in addition to deacidifying and improving the stability of papers by providing an alkaline buffer the treatment also significantly improved their mechanical resistance, as measured by the folding endurance and tensile breaking resistance. Essential for the appraisal of the deacidification process, the behaviour upon ageing of the materials treated was investigated. Accelerated ageing methods involving heat/humidity and nitrogen dioxide atmosphere were used separately. It was shown that the reinforcement effect of the three aminosilane compounds tested persisted throughout the ageing, and in one case the mechanical properties even improved after ageing. Two of the aminosilanes tested were studied for their impact at the macromolecular level, on the molar masses of cellulose, using size-exclusion chromatography with multiangle light scattering detection. Their effectiveness in protecting paper from acid hydrolysis occurring during ageing was found significant.
Keywords: Aminosilane; Paper; Cellulose; Deacidification; Reinforcement; Ageing;
Dynamic vulcanization of reclaimed tire rubber and high density polyethylene blends by Panu Punnarak; Supawan Tantayanon; Varawut Tangpasuthadol (3456-3462).
Dynamic vulcanization of reclaimed tire rubber (RTR) and HDPE blends was reported. The effect of blend ratio, methods of vulcanization, i.e. sulphur, peroxide, and mixed system and the addition of compatibilizer on mechanical, thermal, and rheological properties were investigated. The blend with highest impact strength was obtained from 50/50 RTR/HDPE vulcanized by sulphur. Increasing the RTR content to more than 50% resulted in a decrease in the impact strength of blend, most likely due to the increasing carbon black content. For tensile strength, the presence of rubber and carbon black, however, unavoidably caused a drop in this property. Comparing among three methods of vulcanization, sulphur system seems to be the most effective method. Results from solvent swelling ratio, glass transition temperatures and viscosity indicated that the sulphur vulcanization created the highest degree of cross-link and filler–matrix interaction in the RTR/HDPE blend. Morphology of the blends was also assessed by scanning electron microscopy (SEM).
Keywords: Reclaimed tire rubber; High density polyethylene; Dynamic vulcanization; Morphology;
A study on the influence of anionic surfactants on electrochemical degradation of polyaniline by M.S. Rahmanifar; M.F. Mousavi; M. Shamsipur; S. Riahi (3463-3468).
The influence of anionic surfactants on the electrochemical degradation of polyaniline (PANI), deposited by electro-polymerization onto platinum electrodes, was investigated in an aqueous medium by means of cyclic voltammetry. The degradation rate was found to be greatly dependent on the pH of the solution. The electrochemical degradation of PANI/dodecylsulfate and PANI/dodecylbenzenesulfonate films was compared with that of a PANI/hydrochloride film. The degradation rate in the two former cases decreased by some 50% compared to the PANI/hydrochloride film in aqueous solution at pH = 2. The results were confirmed with theoretical calculations performed on the evaluation of head group charge of surfactants, the distance of anions from PANI positive sites and the shielding of anions on PANI positive sites.
Keywords: Polyaniline; Electrochemical degradation; Anion effect; Surfactant effect; Theoretical calculations;