Polymer Degradation and Stability (v.91, #11)
Calendar of events (I).
Editorial board (CO2).
Comparison of different reactive organophosphorus flame retardant agents for cotton: Part I. The bonding of the flame retardant agents to cotton by Weidong Wu; Charles Q. Yang (2541-2548).
N-Methylol dimethylphosphonopropionamide (MDPA), known as “Pyrovatex CP” and “Pyrovatex CP New” commercially, has been one of the most commonly used durable flame retardant agents for cotton for many years. In our previous research, we developed a flame retardant finishing system for cotton based on a hydroxy-functional organophosphorus oligomer (HFPO) in combination with a bonding agent such as trimethylolmelamine (TMM) and dimethyloldihydroxyethyleneurea (DMDHEU). In this research, we investigated the bonding of these two flame retardant finishing agents to cotton. We found that the majority of MDPA is bound to cotton by its N-methylol group and that the use of TMM as a co-reactant modestly increases the fixation of MDPA onto cotton. For HFPO, however, the use of a bonding agent is necessary to form a covalent linkage between HFPO and cotton. Both the fixation of HFPO on cotton and its laundering durability are influenced by the effectiveness and concentration of the bonding agent. The commercial product of HFPO contains approximately 33% more phosphorus than that of MDPA and the percent fixation of HFPO on cotton is also moderately higher than that of MDPA. The bonding between MDPA and cotton is significantly more resistant to hydrolysis during multiple launderings than that between HFPO and cotton. The selection of catalyst also plays a significant role in influencing the bonding of the flame retardant agents to cotton.
Keywords: Cotton; Cellulose; Crosslinking; Flame retardant finishing; Organophosphorus chemical; Textile fibers;
Reheating decomposition process as chemical recycling for rigid polyurethane foam by Taro Fukaya; Hiroko Watando; Shinetsu Fujieda; Shioko Saya; Cao Minh Thai; Masaaki Yamamoto (2549-2553).
We have found that a reheating process for the products in the chemical recycling of rigid polyurethane foam by an extruder with diethanolamine as a decomposing agent is effective for improving the product stability. The product with stable viscosity was obtained by the reheating process at 175–200 °C for 2 h, regardless of the extruding condition. An amine adduct, which is an intermediate, was found to be the cause of instability of the discharged product from the extruder. At the initial stage of reheating, the intermediate decomposed, releasing toluenediamine, which promoted further decomposition of the discharged products. We have succeeded in controlling the quality of the recycled products.
Keywords: Rigid polyurethane; Chemical recycling; Reheating; Decomposition process; Extruder;
In vitro ageing and degradation of PEG–PLA diblock copolymer-based nanoparticles by Muriel Stefani; Jean Coudane; Michel Vert (2554-2559).
Diblock copolymers composed of poly(oxy-ethylene) (POE) and poly(dl-lactic acid) segments were synthesized by anionic polymerization of d,l-lactide using the oxyanion formed by reaction of the monohydroxyl monomethoxy-poly(ethylene glycol) on sodium hydride. For comparison, a similar copolymer was prepared by using tin octoate to catalyze the lactide polymerization. The copolymers were used to make nanoparticles, which were stored at 4 °C. After a few months under these storage conditions, a dramatic decrease of the poly(ethylene glycol) content was observed, however, the mean diameter of the nanoparticles was not affected. The degradation of the nanoparticles was investigated in vitro under conditions selected to mimic physiological conditions. Changes of characteristics were monitored by 1H NMR, SEC, DLLS and CZE on nanoparticles and/or on the degradation by-products dissolved in the ageing medium. According to their nanometric dimensions, the microparticles degraded very slowly and there was no difference in behaviour between the sodium hydride and the stannous octoate-derived copolymers.
Keywords: Block copolymers; Poly lactide; Poly ethylene glycol; Degradation; Nanoparticles;
IR laser-induced decomposition of poly(vinyl chloride-co-vinyl acetate): Control of products by irradiation conditions by Jaroslav Kupčík; Jadranka Blazevska-Gilev; Jan Šubrt; Vladimír Vorlíček; Josef Pola (2560-2566).
IR laser-induced, ablative decomposition of poly(vinyl chloride-co-vinyl acetate) was examined under different irradiation conditions and its volatile and solid products were characterized by mass spectroscopy, infrared spectroscopy, Raman spectroscopy and UV spectroscopy and EDX-measurements. The laser decomposition of the copolymer, compared with that of poly(vinyl acetate) and poly(vinyl chloride), is revealed to be a more efficient process leading to solid films with the proportion of Cl- and CH3C(O)O-groups controlled by irradiation conditions.
Keywords: Poly(vinyl chloride-co-vinyl acetate); Laser ablation; Laser decomposition; Laser-induced polymer films;
Comparative reactivity of glycols in PET glycolysis by Francis Pardal; Gilles Tersac (2567-2578).
The kinetics of poly(ethylene terephthalate) (PET) glycolysis by diethylene glycol (DEG), dipropylene glycol (DPG), glycerol (Gly) and mixtures of these glycols have been studied with two experimental procedures: uncatalysed at 220 °C and catalysed at 190 °C. An experimental device was set up allowing the isothermal kinetics to be monitored. A precise initial reaction time was obtained by separately warming the glycol and the polyester at the temperature of reaction before mixing them.The reactivity order of different glycols varies according to the conditions of temperature and catalysis. Schematically, the global reactivity does depend not only on the chemical reactivity of the glycol but also on its physico-chemical properties: ability to solvate the solid polyesters and polarity of the reaction mixture. Attempts to find synergic effects failed for almost all mixtures, except the mixture DPG + Gly in which the PET is digested more quickly than in pure DPG or Gly.
Keywords: Glycolysis; Alcoholysis; PET; Kinetics;
Two-step preparation and thermal characterization of cationic 2-hydroxypropyltrimethylammonium chloride hemicellulose polymers from sugarcane bagasse by J.L. Ren; R.C. Sun; C.F. Liu; Z.Y. Chao; W. Luo (2579-2587).
Cationic sugarcane bagasse hemicellulose derivatives with a relatively low degree of substitution (0.01–0.54) containing quaternary ammonium groups were prepared by etherification with 3-chloro-2-hydroxypropyltrimethylammonium chloride or preferably with 2,3-epoxypropyltrimethylammonium chloride using sodium hydroxide as a catalyst in aqueous solution. The extent of etherification was measured by yield percentage and degree of substitution (DS). The DS values of the products could be controlled by adjusting the molar ratio of etherifying agent to anhydroxylose units in hemicelluloses and the molar ratio of sodium hydroxide to etherifying reagent. In comparison, the etherified hemicellulose preparations were characterized by both degradative methods such as thermal analysis, and non-degradative techniques such as gel permeation chromatography (GPC), Fourier transform infrared (FT-IR), and 13C nuclear magnetic resonance (NMR) spectroscopy. It was found that a significant degradation of the hemicellulose polymers occurred during etherification under the alkaline conditions used. The thermal stability of the etherified hemicelluloses was lower than that of the unmodified hemicellulose polymers.
Keywords: Hemicellulose derivatives; Cationic polymers; Degradation; Thermal stability;
Silicon-containing flame retardant epoxy resins: Synthesis, characterization and properties by L.A. Mercado; M. Galià; J.A. Reina (2588-2594).
Epoxy resins with different silicon contents were prepared from silicon-containing epoxides or silicon-containing prepolymers by curing with 4,4′-diaminodiphenylmethane. The reactivity of the silicon-based compounds toward amine curing agents was higher than that of the conventional epoxy resins. The T g of the resulting thermosets was moderate and decreased when the silicon content increased. The onset decomposition temperatures decreased and the char yields increased when the silicon content increased. Epoxy resins had a high LOI value, according to the efficiency of silicon in improving flame retardance.
Keywords: Flame retardant polymers; Epoxy resins; Thermogravimetrical analysis; Limiting oxygen index;
The reciprocal influence between ion transport and degradation of PA66 in acid solution by Abastari; T. Sakai; H. Sembokuya; M. Kubouchi; K. Tsuda (2595-2604).
Transport behavior of acid solution through polyamide was studied by measuring element distribution in cross section, pH, and ion concentration. Degree of degradation that related to the decreasing of molecular weight and flexural strength was observed in order to study the influence of acid solution on the polyamide 66 (PA66) degradation. The permeation mechanism of acid solution can be explained: at first water penetrates into polyamide and it is followed by acid. In this process, water does not affect the molecular weight at 50 °C but only reduces the polyamide strength by plasticization. Moreover, proton (H+) has contributed to the anion transport and degradation of polyamide by the hydrolytic reaction. Proton attacks the polyamide chain, and scission of chain occurs, and reacts with anion to form other material substance. This process affects the decrease of molecular weight and the significant loss of polyamide strength. Analysis results from ion concentration measurement shows that the amount of proton and anion transport into deionized waterside was imbalance, which probably due to the different mobility between proton and anion or formation of other material substance by reaction of anion and PA66 bond. Such information is not only necessary for the investigation of hydrolytic degradation of polymer and prediction of lifetimes for a protective polymer lining/coating to chemical attack, but may also be helpful towards gaining a deeper insight into the processes of degradation of other polymer.
Keywords: Diffusion; Permeation; Ion transport; Polyamide; Proton; Degradation;
Characterization of thermo-oxidative stability of polymer optical fibers using chemiluminescence technique by Anilkumar Appajaiah; Volker Wachtendorf; Werner Daum (2605-2613).
The thermo-oxidative stability of commercially available polymer optical fibers (POFs) and their components (cores and claddings) was investigated. All the bare POFs (core and cladding only) studied here were based on poly(methyl methacrylate) (PMMA) core. The fibers were exposed to 100 °C/low humidity for about 4200 h. Chemiluminescence (CL) technique was applied to investigate the thermo-oxidative stability and for measuring the transmission loss during exposure a prototype device called multiplexer was used. POFs exhibited variation in thermo-oxidative stability although they possessed identical core material PMMA. This was due to difference in the chemical compositions of claddings. Claddings were more susceptible to the thermo-oxidative degradation compared to cores. The thermo-oxidative degradation of both the cladding and the core was found in POFs as a result of climatic exposure. POFs showed an early drop-off followed by a slow decline of transmission. The early drop-off of transmission was attributed to physical changes like thermal expansion and the slow decline of transmission to chemical changes like oxidative degradation of POFs. A good linear relationship between optical transmission stability and thermo-oxidative stability of POFs was established from these studies.
Keywords: Polymer optical fibers (POFs); Chemiluminescence (CL); Thermo-oxidative stability; Aging; Optical transmission stability;
Mechanical degradation of filter polymer materials: Polyphenylene sulfide by Winyu Tanthapanichakoon; Mitsuhiko Hata; Koh-hei Nitta; Masami Furuuchi; Yoshio Otani (2614-2621).
Polyphenylene sulfide (PPS) is known as a material resistant to high temperature and chemicals; however, there are arguments on the durability of PPS non-woven fabrics to chemicals, such as nitric acid (HNO3), sulfuric acid (H2SO4), and hydrochloric acid (HCl). Therefore, this work aims at investigating the degradation of PPS non-woven fabrics in HNO3, H2SO4 and HCl, and at confirming acid durability of PPS non-woven fabrics. In addition, this paper also studies the interaction among these three acids by measuring the retention of strength in binary or tertiary mixtures of these three acids. A discussion has been made on the acceleration/retardation of PPS degradation by the interactive effects, and also on the chemistry related to the degradation by these acids. Furthermore, there is a linear relationship between the nitric acid concentration and the proportion of carbon in the remaining PPS structures after 100 h of acid exposure. Also, this proportion of carbon is a good indicator of the retained strength in PPS fabrics.
Keywords: Polyphenylene sulfide; PPS; Fabric; Degradation; Chemistry; Interaction;
Comparison of one-step and two-step methods of polyimidization and substitution effect in the synthesis of new poly(ester-imide)s with bulky pendent group by Shahram Mehdipour-Ataei; Naeemeh Bahri-Laleh; Ahmad Amirshaghaghi (2622-2631).
New naphthalene-ring containing ester diamines, as new monomers for the preparation of polyimides were synthesized via two successive reactions. Nucleophilic reaction of 3,5-dinitrobenzoylchloride with 1-naphthol and 2-naphthol in the presence of sodium hydroxide led to the preparation of 1- and 2-(3,5-dinitrobenzoyloxy)naphthalene, respectively. Next step was reduction of them by hydrazine hydrate/Pd–C to produce 1- and 2-(3,5-diaminobenzoyloxy)naphthalene. All the prepared compounds were characterized by common spectroscopic methods. These ester containing aromatic diamines with pendent naphthalene group were used to prepare soluble polyimide copolymers via two different methods: catalyzed one-step high-temperature polycondensation in m-cresol, and two-step polycondensation in NMP and subsequent chemical dehydration. The obtained poly(ester-imide)s were characterized and their properties were studied. One-step and two-step methods for the preparation of five-membered ring polyimides were compared. Polymers prepared through one-step method showed higher yield and inherent viscosities and therefore better physical properties.
Keywords: Thermally stable; Polyimide; Ester; Structure–property relations; Pendent group;
Preparation of flame retardant polyamide 6 composite with melamine cyanurate nanoparticles in situ formed in extrusion process by Yinghong Chen; Qi Wang; Wei Yan; Hongmei Tang (2632-2643).
This paper is focused on in situ preparation of melamine cyanurate (MCA) nanoparticles from reaction of melamine (MEL) and cyanuric acid (CA) and their flame retardant polyamide 6 (PA6) composite in the extrusion process through a novel reactive processing method. Fourier transform infrared (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) were utilized to characterize the in situ formed MCA nanoparticles and their blends with PA6. Introduction of pentaerythritol (LTP) and water-bound plasticizer dioctyl phthalate (DPT) into the extrusion reaction system greatly inhibits the evaporation of water required for melamine and cyanuric acid reaction at high temperature (higher than 180 °C), laying a foundation for successful in situ preparation of MCA through reactive processing. XRD and FT-IR measurements indicate that under the effect of pentaerythritol, dioctyl phthalate and water, melamine really reacts with cyanuric acid to in situ form MCA in extrusion process. The reaction degree is close to 100%. A very important finding through SEM is that the in situ formed MCA particles, which were found to have aspect ratio of about 7.5, radial size in the range of 70–300 nm (mostly 70–90 nm) and crystallite size of less than 22 nm, are uniformly dispersed in the matrix PA6 at nanoscale. The in situ formed MCA nanoparticles greatly improve the flame retardancy and the mechanical properties of flame-retarded PA6 materials, and the introduced plasticizer dioctyl phthalate also ameliorates the related impact property. The obtained flame-retarded PA6 materials have good comprehensive performance with flame retardancy UL-94 V-0 rating at 1.6 and 3.2 mm thickness, tensile strength 48.0 MPa, elongation at break 106.3% and Izod notched impact strength 8.92 kJ/m2. Compared with flame-retarded PA6 material with in situ formed MCA, the one prepared through conventional blending of PA6 with commercial MCA product has improved tensile strength but deteriorated impact strength and flame retardancy.
Keywords: Polyamide 6; Flame retardant; Melamine cyanurate; Nanoparticles; In situ formation;
A study on the effects of ozone treatment on the properties of raw and degummed mulberry silk fabrics by D. Sargunamani; N. Selvakumar (2644-2653).
Ozone is a powerful oxidizing agent and is widely used in various applications, which includes bleaching of cotton. Its application on the processing of silk is non-existent. Research studies on degumming and bleaching of silk reveal that almost no work involving ozone has been carried out. Therefore a study was carried out to understand the effects of process parameters namely wet pickup, pH and time in the ozone treatment of raw and degummed mulberry and tassar silk fabrics on their properties. This paper reports on the effects of ozone treatment on the mulberry silk fabrics. The study was extended with a view to compare the ozone treatment with soap degumming and hydrogen peroxide treatment carried out on raw and degummed mulberry silk fabrics, respectively. The treatment results in increase in yellowness index and amino group content and decrease in breaking strength and elongation, weight and flexural rigidity. The results obtained are substantiated with tyrosine content, scanning electron micrographs and infrared spectroscopy of the treated materials. The effect of pH on the treatment is maximum up to pH 4 and then decreases. The treatment is more severe when the wet pickup used is 50% compared to that of 10 and 100%. With respect to treatment time, though the severity increases with time, it is maximum during the first 10 min of the treatment. Soap degumming of raw silk fabric results in lower yellowness index and flexural rigidity and lesser loss in breaking strength and elongation compared to that of ozone treated material. There is not much of difference between ozone and hydrogen peroxide treatments of degummed silk fabric except for the lower yellowness index obtained in the latter case.
Keywords: Ozone; Silk; Strength; Elongation; FTIR; Electron microscopy;
Hydrolytic degradation of carbohydrate-based aromatic homo- and co-polyesters analogous to PET and PEI by Francisca Zamora; Khalid Hakkou; Sebastián Muñoz-Guerra; Juan A. Galbis (2654-2659).
The hydrolytic degradation of a series of homo- and co-polyesters analogous to poly(ethylene terephthalate) (PET) and poly(ethylene isophthalate) (PEI), prepared from carbohydrate-based monomers, was studied. The degradation process was carried out at temperatures of approximately 10 °C above the T g of the polymers. All the studied polyesters were found to degrade at significant rates, and degradability showed a clear dependence on the configuration of the sugar units present in the polymer chain. No weight loss was detected upon degradation, apparently due to the non-solubility of the degraded products in the aqueous incubation medium. Hydrolysis of co-polyesters took place preferentially by cleavage of the ester groups of the sugar units.
Keywords: Carbohydrate-based polyesters; Poly(ethylene terephthalate) (PET) analogs; Poly(ethylene isophthalate) (PEI) analogs; Random co-polyesters; Hydrolytic degradation;
Thermal transition of electrochemically synthesized polyaniline by Kun Luo; Nanlin Shi; Chao Sun (2660-2664).
The thermal stability of polyaniline (PAni) is of great importance in commercial applications. PAni and its emeraldine base form (PAni-EB) were electrochemically synthesized and subjected to thermogravimetric analysis (TGA) in inert atmosphere, which illustrated that the dopant HClO4 could act as the oxidizing agent at elevated temperature and caused serious decomposition of PAni. Combined with differential scanning calorimetry (DSC), in-situ X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) analyses, the crosslinking reaction among PAni-EB molecules at about 250 °C was characterized, and the kinetic parameters were calculated by applying different heating rates in the DSC measurement.
Keywords: Polyaniline; Electrochemical synthesis; Thermal transition; Crosslinking reaction; Kinetic parameter;
Styrenic polymer nanocomposites based on an oligomerically-modified clay with high inorganic content by Jinguo Zhang; David D. Jiang; Dongyan Wang; Charles A. Wilkie (2665-2674).
Clay was modified with an oligomeric surfactant containing styrene and lauryl acrylate units along with a small amount of vinylbenzyl chloride to permit the formation of an ammonium salt so that this can be attached to a clay. The oligomerically-modified clay contains 50% inorganic clay, and styrenic polymer nanocomposites, including those of polystyrene (PS), high-impact polystyrene (HIPS), styrene–acrylonitrile copolymer (SAN) and acrylonitrile–butadiene–styrene (ABS), were prepared by melt blending. The morphologies of the nanocomposites were evaluated by X-ray diffraction and transmission electron microscopy. Mixed intercalated/delaminated nanocomposites were formed for SAN and ABS while largely immiscible nanocomposites were formed for PS and HIPS. The thermal stability and fire properties were evaluated using thermogravimetric analysis and cone calorimetry, respectively. The plasticization from the oligomeric surfactant was suppressed and the tensile strength and Young's modulus were improved, compared to similar oligomerically-modified clays with higher organic content.
Keywords: Nanocomposites; Oligomerically-modified clay; Styrenics; Fire retardancy;
The hydrolysis mechanism of bis(2,4-di-tert-butyl)pentaerythritol diphosphite (Alkanox P24): An atmospheric pressure photoionisation mass spectrometric study by M. Papanastasiou; A.W. McMahon; N.S. Allen; A.M. Doyle; B.J. Johnson; K. Keck-Antoine (2675-2682).
Alkanox P24 is a commercial phosphite antioxidant, well known in the literature for its excellent processing stability. As in the case of many processing phosphites, however, Alkanox P24 might undergo hydrolysis when exposed to small amounts of water. A number of products proposed recently in the hydrolytic pathway of the phosphite [Ortuoste N, Allen NS, Papanastasiou M, McMahon A, Edge M, Johnson B, et al. Polym Degrad Stab; 2006;91:195–211] are investigated in this study by atmospheric pressure ionisation-mass spectrometry (API-MS). The applicability of atmospheric pressure photoionisation (APPI) and atmospheric pressure chemical ionisation (APCI) ion sources is tested and the ion formation characteristics of Alkanox P24 are compared in both sources. In positive ion mode, ionisation of the parent phosphite occurred by protonation. In negative ion mode no pseudo-molecular ion peak was detected and the deprotonated species were more dominant in APPI. This source was employed further for the investigation of the hydrolysis products, since it exhibited lower limits of detection. High performance liquid chromatography (HPLC) with single ion monitoring (SIM) detection was used for the separation of the species formed. Hydrolysis of the phosphite proceeded via the scission of the two P–Ophenol bonds exclusively to give 2,4-di-tert-butyl phenol quantitatively as a final product.
Keywords: Polymer additives; Hydrolysis; APPI; APCI; HPLC–MS;
The flame-retardant material – 1. Studies on thermal characteristics and flame retardance behavior of phosphorus-containing copolymer of methyl methacrylate with 2-methacryloxyethyl phenyl phosphate by Guo-An Wang; Cheng-Chien Wang; Chuh-Yung Chen (2683-2690).
2-Methacryloxyethyl phenyl phosphate/methyl methacrylate (MEPP/MMA) copolymers were synthesized by the bulk polymerization of MMA in the presence of various amounts of MEPP. MEPP was prepared by the esterification of phenyl dichlorophosphate with 2-hydroxyethyl methacrylate, followed by hydrolysis. Structural and compositional details of MEPP were obtained by Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance, 13C nuclear magnetic resonance, 31P nuclear magnetic resonance, and mass spectrometer, as well as by elemental analysis. The monomer reactivity ratios of MEPP/MMA system were calculated by the methods of Fineman–Ross, Kelen–Tüdös, and Joshi–Joshi. The thermal degradation temperature of the MEPP/MMA copolymers was considerably enhanced by only a slight decrease in T g, as determined by differential scanning calorimetry and thermogravimetric analysis experiments. The fire-retardant properties of MEPP/MMA copolymers were also studied by LOI and UL-94 tests, indicating that an MEPP/MMA copolymer with only 2.17 wt% phosphorus can effectively inhibit burning.
Keywords: Poly(methyl methacrylate); 2-Methacryloxyethyl phenyl phosphate; LOI; UL-94;
Hydrolytic degradation of poly[(4,4′-oxydiphenylene)pyromellitic amido acid] in concentrated sulphuric acid and in dimethylformamide via hydrodynamic investigations by Peter N. Lavrenko; Olga V. Okatova; Darya M. Volokhova; Natalia N. Ulyanova (2691-2697).
Translational diffusion and viscosity measurements were performed for poly[(4,4′-oxydiphenylene)pyromellitic amido acid] in DMF, LiCl/DMF, and 96% H2SO4 solutions to characterise the rate of the polymer degradation in 96% H2SO4 in comparison with its relative stability in organic solutions. The hydrodynamic data were obtained in different stages of hydrolytic polymer degradation at various temperatures from 20 to 80 °C. The mechanism of the degradation is discussed as well as the possibility of molecular investigations of the polymer under conditions of quasi-stable solution.
Keywords: Poly[(4,4′-oxydiphenylene)pyromellitic amido acid]; Hydrodynamic properties; Hydrolytic degradation in DMF and sulphuric acid; Film degradation; Activation energy; The rate of degradation;
Physico-chemical aspects of polyethylene processing in an open mixer. Part 26: Formal kinetics of aldehyde and carboxylic acid formation at a constant rate by F. Gugumus (2698-2714).
Formation of carboxylic acids at a constant rate can be easily explained. It seems to result from the formation and decomposition of α,γ-keto-hydroperoxides. Formal kinetics based on formation and decomposition of these structural units is in agreement with the experimental findings. The activation energy deduced from the calculations is negligible, in agreement with the experimental data showing the constant rate to be practically temperature independent. Comparison of the acids with the hydroperoxides and ketones formed initially shows that the rate of oxygen addition to alkyl radicals is significantly smaller than in low molecular mass liquids. The same conclusion is reached on comparing directly the acids formed on decomposition of α,γ-keto-hydroperoxides in polyethylene melt and in hexadecane. The rate of oxygen addition in polyethylene melt is closer to 2 × 105 than to 6 × 105 (s−1) that is valid in hexadecane.It is possible to attribute the relatively small amount of aldehydes that might be formed at a constant rate to different reactions of alkoxy radicals that are not in a cage with other radicals. These alkoxy radicals result from the addition of peroxy radicals to unsaturated bonds. This addition is followed mainly by epoxide formation and simultaneous release of an alkoxy radical.
Keywords: Polyethylene; Processing; Oxidation products; Aldehydes; Acids; Kinetics;
Effect of stearate preheating on the thermal stability of plasticized PVC compounds by Luis J. González-Ortiz; Martin Arellano; M. Judith Sánchez-Peña; Eduardo Mendizábal; Carlos F. Jasso-Gastinel (2715-2722).
Effect of preheating of stearates on the processing and post-processing thermal stability of poly(vinyl chloride) compounds, plasticized with di(2-ethylhexyl) phthalate (DEHP) and epoxidized soybean oil (ESO), using several ratios of calcium/zinc stearates and DEHP/ESO is reported. The compounds were prepared as follows: (1) dry-blending the compound components, (2) pelletizing the dry-blend and (3) extruding the pellets to obtain a ribbon geometry. Processing stability was determined by: (a) mechanical characterization and (b) visual color comparison of extruded samples. Post-processing thermal stability was followed by: (a) measurement of HCl release from heated pellets and (b) color changes in heated ribbon samples. From a practical point of view, the preheating has a negligible effect on the initial color of formulations; except for the case of formulations without both ESO and CaSt2. However, the effect of the preheating on the post-processing thermal stability is strongly determined by the composition formulation.
Keywords: Preheating of stearates; Plasticized PVC; Thermal stability; Color stability; HCl release;
Characterization of irradiation-induced crosslink of epoxidised natural rubber/ethylene vinyl acetate (ENR-50/EVA) blend by M. Zurina; H. Ismail; C.T. Ratnam (2723-2730).
The effect of irradiation on tensile, dynamic mechanical properties, thermal properties and morphology of ENR-50, EVA and ENR-50/EVA blend was investigated. All the samples were irradiated using a 3.0 MeV electron beam (EB) machine with doses ranging from 20 to 100 kGy. Results indicate that the gel fraction of ENR-50, EVA and ENR-50/EVA blend increases with irradiation dose. Concerning tensile properties, it can be seen that EB radiation increases the tensile strength of all the samples, increases the elongation at break of ENR-50 and ENR-50/EVA blend, reduces the elongation at break of EVA, increases M200 (modulus at 200% strain) of ENR-50 and EVA, while decreases M200 of the ENR-50/EVA blend. For dynamic mechanical studies, it was found that EB radiation increases the T g of all the samples due to the effect of irradiation-induced crosslinking. The compatibility of ENR-50/EVA blend also found to be improving upon irradiation. In the case of thermal properties, it was detected that T m, T c and the degree of crystallinity of ENR-50/EVA blend increase with an increase in irradiation dose. This was due to the perfection in the crystal growth occurring upon radiation. Morphology changes play a major role in the changes of the properties of ENR-50/EVA blend. Finally, it can be concluded that ENR-50/EVA blend can be vulcanized by EB radiation.
Keywords: EB irradiation; ENR-50/EVA blend; Irradiation-induced crosslink; Blend characterization;
Effects of TriSilanolIsobutyl-POSS on thermal stability of methylsilicone resin by Y.R. Liu; Y.D. Huang; L. Liu (2731-2738).
Methylsilicone resin/polyhedral oligomeric silsesquioxane (POSS) composites with various proportions of POSS monomer were synthesized by the reaction of functionalized TriSilanolIsobutyl-POSS macromonomer with hydroxyl-terminated methylsilicone resin. The structures of the obtained hybrid polymers were characterized with Fourier-transformed infrared (FT-IR) and transmission electron microscopy (TEM). The FT-IR spectra suggested successful bonding of TriSilanolIsobutyl-POSS and methylsilicone resin. TEM analysis showed that POSS can dissolve in methylsilicone resin at the molecular level. The influences of TriSilanolIsobutyl-POSS on the thermal stability and degradation behavior of methylsilicone resin were studied by thermogravimetric analysis (TGA), solid-state 29Si NMR and X-ray photoelectron spectroscopy (XPS). All these techniques showed that TriSilanolIsobutyl-POSS incorporation results in increased decomposition temperatures and oxidation resistance, primarily by reducing the effect of silanol end groups on the thermolysis through condensation reaction of Si–OH groups and partial loss of isobutyl followed by the formation of an inorganic SiO2 layer to prevent methylsilicone from further degradation.
Keywords: TriSilanolIsobutyl-POSS; Methylsilicone resin; Thermal stability; Thermogravimetric analysis (TGA);
Oxo-biodegradable carbon backbone polymers – Oxidative degradation of polyethylene under accelerated test conditions by E. Chiellini; A. Corti; S. D'Antone; R. Baciu (2739-2747).
Oxo-biodegradation of carbon-only backbone polymers is receiving ever increasing attention for the practical implications that some re-engineered thermoplastic polymer formulations based on conventional biostable polymeric materials may satisfy in terms of environmental friendliness and acceptance by commodity plastic manufacturers.In this respect, as part of our continuing activity in the area of bioactive polymeric materials for biomedical and environmental applications, we report the results of an investigation of the effects of different degradation conditions on the oxidative degradation of polyethylene (PE) film samples containing pro-oxidant additives and formulated according to a proprietary technology. The effects of temperature and relative humidity have been evaluated by monitoring, with time, several parameters associated to oxidation and cleavage of the macromolecules, such as the weight variation due to oxygen uptake, film wettability, carbonyl index, molecular weight and the extractability with polar solvents of oxidized PE samples.
Keywords: Polyethylene; Thermal degradation; Carbonyl index; Oxidative cleavage; HT-GPC;
Natural and artificial photo-aging of non-stabilized and pigmented, hindered-amine stabilized propylene–ethylene copolymers by Olivier Haillant; Jacques Lemaire (2748-2760).
This paper describes the chemical evolution of two propylene–ethylene copolymer formulations, non-stabilized and carbon black filled – HALS stabilized, exposed to a range of natural and artificially accelerated weathering techniques, commonly used in the field of material testing. With the non-stabilized formulation, a fairly good representation of weathering in outdoor conditions was demonstrated with any of the accelerated exposures through the recognition of similar chemical changes at the molecular level. In contrast, the additives in the stabilized matrix induced very different chemical evolutions depending on the weathering techniques employed. This variability has been used to critically characterize those techniques on a scientific basis.
Keywords: Polypropylene; HALS; Photooxidation; Weathering; Artificial; Accelerated;
Effects of solar UV irradiation on the tensile properties and structure of PPTA fiber by Huapeng Zhang; Jianchun Zhang; Jianyong Chen; Xinmin Hao; Shanyuan Wang; Xinxing Feng; Yuhai Guo (2761-2767).
This paper comprehensively studied the effects of simulated solar ultraviolet irradiation on the mechanical and structural properties of the Twaron2000 para-aramid fiber by use of mechanical test, SEM, XRD, DSC, DMA and ATR-IR measurements. The results showed that after UV irradiation, the mechanical properties of the fiber were decreased obviously, and UV irradiation deteriorated the surface and defect areas of the fiber severely by photo-induced chain scission and end group oxidation in air with the crystalline structure remained almost unchanged although some local rearrangement of the crystalline area might occur. It was found that surface etching and shortening of the crystalline correlation length along the fiber axis were the main causes of the mechanical loss induced by UV irradiation.
Keywords: PPTA fiber; Mechanical properties; Structure; UV irradiation;
Effect of dissolution-based recycling on the degradation and the mechanical properties of acrylonitrile–butadiene–styrene copolymer by A. Arostegui; M. Sarrionandia; J. Aurrekoetxea; I. Urrutibeascoa (2768-2774).
A dissolution-based recycling technique for acrylonitrile–butadiene–styrene copolymer (ABS) is proposed, and the effects of repeated recycling cycles are studied measuring changes in chemical structure, melt viscosity, and tensile and impact properties. Acetone as solvent, 0.25 g/ml concentration, room temperature and 40 min for dissolution have been found to be the most reliable recycling parameters. FTIR, DSC and MFI results have shown that the dissolution-based recycling itself does not degrade the ABS. However, TGA analysis suggests that during the dissolution some stabilizers are probably eliminated, and consequently degradation takes place in the following injection moulding step. Darkening of recycled ABS is attributed to the butadiene degradation, pointed out by FTIR results. Otherwise, the chemical structure of the SAN matrix has not been modified, but its molecular weight has been reduced. The modulus of elasticity is not affected even after four recycling cycles. However, yield stress and impact strength decrease after the first recycling cycle, and remain constant in the following steps.
Keywords: Recycling; Dissolution; Acrylonitrile–butadiene–styrene; Degradation; Mechanical properties;
Multi-component analysis of low-density polyethylene oxidative degradation by Mario Salvalaggio; Roberto Bagatin; Marco Fornaroli; Sergio Fanutti; Stefano Palmery; Ezio Battistel (2775-2785).
The oxidative degradation of polyethylene in various conditions has been studied. In order to gain insight into the oxidation process, a method for the curve-fitting analysis of the IR carbonyl band between 1800 cm−1 and 1600 cm−1 in oxidized low-density polyethylene (LDPE) has been developed. Up to 10 components were needed to fit the band envelope, whose assignments and peak positions were based on the literature and on the synthesis of an appropriate model compound. The determination of the other band parameters, such as peak width and peak shape, necessary for reliable best fitting of the absorbance envelopes, was obtained by overall fitting optimization process. By using the available extinction coefficients, the quantitative determinations of the main oxidized species, i.e. ketones, carboxylic acids, esters, γ-lactones and ketoacids, were obtained with a reasonable confidence by rigorous parameter setting. The method was applied to the IR analysis of LDPE samples oxidized in different conditions (under thermal and irradiation stimulation), either as beads or films, as a function of time. Total hydroperoxide concentrations were also quantitatively estimated by a modified iodometric titration procedure. A good linear correlation between concentrations estimated by chemical titration and by intensity analysis of the free hydroperoxide IR band was observed.
Keywords: Low-density polyethylene; Polyethylene oxidation; Hydroperoxides titration; FT-IR; Carbonyl band curve-fitting; Deconvolution analysis;
Thermal and structural stability of composite systems based on polyaniline deposited on porous polyethylene films by Galina K. Elyashevich; Askold V. Sidorovich; Michail A. Smirnov; Ivan S. Kuryndin; Natalia V. Bobrova; Miroslava Trchová; Jaroslav Stejskal (2786-2792).
Conducting composite systems containing polyaniline layers produced on the surface and inside the pores of polyethylene support have been prepared. Microporous polyethylene films were obtained by melt extrusion with subsequent annealing, uniaxial extension, and thermal fixation. Polyaniline layers were formed by in-situ polymerization of aniline onto polyethylene porous support placed into the aqueous reaction mixture. Structural and chemical transformations upon heating of these systems in air in free state and in vacuum under load have been investigated by thermo-mechanical tests, IR spectrometry, and electron microscopy. Changes in mechanical properties of composites after heating have been analyzed. Composite systems have been found to demonstrate a considerably lower shrinkage upon heating than microporous polyethylene substrates. It has been discovered that the composites preserve mechanical integrity on heating up to temperatures much higher than the polyethylene melting point. It is concluded that thermo-mechanical behaviour of the composites is determined by the space-continuous phase of polyaniline on the surface and in the bulk of polyethylene support.
Keywords: Polyaniline; Polyethylene porous films; Composites; Thermal stability;
Some aspects of the ozone degradation of poly(vinyl alcohol) by Franco Cataldo; Giancarlo Angelini (2793-2800).
Poly(vinyl alcohol) (PVAL) forms a strong hydrogen-bond complex with ozone. The interaction energy is of the order of 47.3 kJ/mol as calculated from the blue shift undergone by the ozone absorption band in the UV after its complexation with PVAL. This fact may have many important practical implications in the application of PVAL in wastewater treatment both in terms of O3 dissolution and persistence in water. Furthermore, PVAL is easily biodegradable but it is also slowly degraded by ozone. It is shown by viscometry, electrical conductimetry and by pH measurements that PVAL is degraded by ozone attack with extensive chain breaking. By FT-IR spectroscopy it has been shown that the final product is a PVAL oligomer with numerous ketonic groups along the main oligomer backbone and with carboxylic end groups. A mechanism of ozone degradation of PVAL has been presented and discussed. The chain scission is based on the ozone oxidation of the alcoholic groups of PVAL with formation of ketonic groups which in turn are the source of a keto–enol tautomerism which leads to random chain scission by further O3 attack. Viscometric measurements show that the main viscosity drop of PVAL is achieved when a nominal stoichiometric ratio of O3/PVAL < 0.05 is reached which means one ozone molecule for every >20 PVAL monomeric units. For comparison PVAL has been oxidized also with paraperiodic acid.Ozonized PVAL has been studied by thermal analysis (TGA, DTG and DTA) in comparison to a reference untreated PVAL under N2. The oxidation of PVAL causes its complete amorphization since the crystalline melting point of PVAL at 235 °C is no longer detectable in the case of ozonized PVAL. In any case ozonized PVAL shows a better thermal stability which can be confirmed for instance by a higher maximum decomposition rate temperature as measured by DTG. This result is in agreement with theoretical calculations made by group increments according to Van Krevelen's method which predicts a higher decomposition temperature for a PVAL having ketonic groups in place of alcoholic moieties in the main polymer backbone.
Keywords: Poly(vinyl alcohol); Ozone; Hydrogen bond; Chain degradation; Ozonolysis mechanism; Wastewater treatment;
Mechanical properties decay and morphological behaviour of biodegradable films for agricultural mulching in real scale experiment by Giacomo Scarascia-Mugnozza; Evelia Schettini; Giuliano Vox; Mario Malinconico; Barbara Immirzi; Stefania Pagliara (2801-2808).
The use of plastic materials in agriculture causes the serious drawback of huge quantities of waste. The introduction of biodegradable materials, which can be disposed directly into the soil, can be one possible solution to this problem. Biodegradable materials are actually innovative materials; therefore, their physical properties must be evaluated in relation to their functionality during the use in field. In the present research results of experimental tests carried out on biodegradable films used in strawberries protected cultivation are presented. The decay of some relevant physical parameters of biodegradable films during the cultivation period was monitored by laboratory tests (SEM analysis, mechanical tensile tests and infrared reflectance spectroscopy). Infrared spectroscopy clearly indicated that the mechanical degradation starts from the starch component of the material. Tensile tests showed that the value of elongation at break of biodegradable materials decreased in some cases by 300% after 10 days of field application.
Keywords: Biodegradable material; Agriculture; Mulching film; Physical properties; Degradation; Solar radiation;
Reactivity of polyesters in glycolysis reactions: Unexpected effect of the chemical structure of the polyester glycolic unit by Francis Pardal; Gilles Tersac (2809-2812).
Kinetic studies of PET glycolysis by diethylene glycol (DEG), dipropylene glycol (DPG), glycerol (Gly) and mixtures of these glycols have shown, in a previous study, that the order of reactivity of the glycols differs according to the conditions of temperature and catalysis. Indeed, their global reactivity depends both on their chemical reactivity and physico-chemical properties.Glycolysis of model polyesters which are liquid at the reaction temperature, which allows us to overcome the problem of the polyesters' solubility, were studied to compare the chemical reactivity of these glycols. Three oligoesters were synthesized from dimethyl terephthalate and three different glycols namely triethylene glycol, ethylene glycol and hexanediol to form, respectively, PE3T, OET and PTHD.Results showed that the order of reactivity of the glycols is the same for PET, OET and PTHD but different for PE3T. Indeed, DPG without catalyst has a particular and unexpected behaviour: its reactivity seems to be strongly influenced by the presence of oxygen atoms in the chain.
Keywords: Glycolysis; Polyesters; Kinetics; Reactivity;
Epoxides in the thermal oxidation of polybutadiene by M. Guyader; L. Audouin; X. Colin; J. Verdu; S. Chevalier (2813-2815).
Polybutadiene films were aged under air or high oxygen pressure (3.1 MPa). In both cases, the amount of epoxide formed was titrated. The results show that the epoxide formation rate is a decreasing function of oxygen concentration that validates the mechanism proposed by Mayo. According to this mechanism, epoxides are generated from the decomposition of β-peroxy alkyl radicals resulting from the addition of peroxy radicals on double bonds.
Keywords: Epoxide; Polybutadiene; Thermal oxidation; Oxygen pressure; Ageing; Degradation;
Erratum to ‘‘Enzymatic and microbial biodegradability of poly(ethylene terephthalate) copolymers containing nitrated units’’[Polym Degrad Stab 91 (2006) 663–671] by M. Soledad Marqués-Calvo; Marta Cerdà-Cuéllar; Darwin P.R. Kint; Jordi J. Bou; Sebastián Muñoz-Guerra (2816-2817).