Polymer Degradation and Stability (v.120, #C)
Editorial Board (IFC).
Difference in polystyrene oxo-biodegradation behavior between copper phthalocyanine modified TiO2 and ZnO paint photocatalyst systems by Hisayuki Nakatani; Suguru Motokucho; Kensuke Miyazaki (1-9).
An oxo-biodegradation of polystyrene (PS) film was performed with copper phthalocyanine modified ZnO (CuPc-ZnO)/polyethylene oxide (PEO)/methyl linoleate (ML) and CuPc-TiO2/PEO/ML paint photocatalyst systems. Difference in the behavior between them was studied in the photodegradation and biodegradation stages, respectively. The CuPc modification brought about the improvement of the photodegradation activity. The smaller particle ZnO (50 nm) showed the less activity due to the ZnO dissolution process. The activity of the CuPc-ZnO/PEO/ML was higher than that with the CuPc-TiO2/PEO/ML. These systems highly contributed to the initial photodegradation stage. In the biodegradation stage, the dissolved CuPc-ZnO did not inhibit the fungus growth. The fungus was same species regardless of the kind of the photocatalyst system. The respirometric biodegradation profiles showed that the mineralization value reached at the same constant value around the 16 days. However, the initial biodegradation behavior was different.
Keywords: Oxo-biodegradation; Polystyrene; Photocatalyst; ZnO; TiO2;
Weathering properties of coextruded polypropylene-based composites containing inorganic pigments by Svetlana Butylina; Ossi Martikka; Timo Kärki (10-16).
This study concerns the weathering properties of coextruded polypropylene-based composites containing pigments. Three different pigments were incorporated in the shell layer of the composites: iron oxide, titanium dioxide and zinc oxide. The surface colour, surface gloss and tensile properties were tested. In addition, the weathered surfaces were studied by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The surfaces of the composites containing inorganic pigments were found to have fewer cracks after 500 h of weathering than the surface of the reference composite. The results revealed that the composites containing titanium oxide pigment exhibited better colour stability than the composites made with the other pigments. In spite of its high colour stability in weathering, the tensile properties (strength, Young's modulus and elongation at break) of the composite containing titanium oxide were reduced by weathering. The FTIR analysis revealed that the composite containing zinc oxide had a stabilising effect on polypropylene photo-degradation, which correlates well with the results of mechanical testing, showing that this composite retained its mechanical properties after weathering.
Keywords: Wood-polymer composite; Inorganic pigment; Coextrusion;
Controlled photooxidation of polymeric colloidal crystals for surface patterns tuning by Mun Ho Kim; Jae Hyun Jeong; Doo-Jin Byun (17-22).
Most polymers are not inherently stable to light, but this weakness of polymers can be exploited in a positive way. In this paper, we report a simple approach to modifying the surface patterns produced by polystyrene (PS) colloidal crystals by taking advantage of their instabilities under UV illumination. Colloidal crystals grown from PS colloidal suspension were prepared and exposed to the UV light. As a consequence of photochemical reactions, UV irradiation induced morphological changes in the film surface including changes in size and shape of PS particles. Specifically, the particle surface areas illuminated by the UV light in the colloidal crystal films could be controlled by tilting the films, to yield unique surface patterns, including complex and delicate surface patterns. The proposed approach provides a simple route to fabricating colloidal crystal masks with unique structures and without the need for special equipment.
Keywords: Colloidal crystal; Photooxidation; Micro/nanopatterning; Colloidal lithography; Surface characterization;
Ethylene-vinyl acetate copolymer/aluminium trihydroxide composites: A new method to predict the barrier effect during cone calorimeter tests by Florian Cavodeau; Rodolphe Sonnier; Belkacem Otazaghine; José-Marie Lopez-Cuesta; Christelle Delaite (23-31).
This study presents the use of oedometric compression test in order to evaluate the breakdown of a protective layer acting as a diffusion barrier (“barrier effect”) occurring during cone calorimeter tests for ethylene-vinyl acetate copolymer/aluminium trihydroxide (EVA/ATH) composites. The formation of an alumina layer at the sample surface during burning insulates thermally the underlying material and reduces the heat release rate. The efficiency of this barrier depends on the cohesion of the layer formed. This cohesion depends on the ability of the particles (ATH and synergistic mineral fillers) to self-arrange. During the test, the breakdown of this barrier can lead to an increase in HRR.The oedometric compression test allows assessing the ability of fillers to form a cohesive layer. Results obtained from compression modulus of filler powders are directly related to some aspects of the heat release rate curve of composites measured in cone calorimeter tests. Indeed, the appearance and the intensity of the second pHRR (related to the breakdown of the barrier layer) in cone calorimeter test are related to the slope of oedometric compression curve.
Keywords: Flame retardancy; Oedometric compression; Barrier effect; Aluminium trihydroxide; Ethylene-vinyl acetate;
The thermal degradation pathway studies of a phosphazene derivative on cotton fabric by Krystal R. Fontenot; Monique M. Nguyen; M. Sameer Al-Abdul-Wahid; Michael W. Easson; SeChin Chang; Gary A. Lorigan; Brian D. Condon (32-41).
Phosphazene derivatives have been recognized as promising flame retardants for numerous synthetic polymeric systems. However, limited studies are available for phosphazene derivatives on natural polymeric systems such as cotton fabric. The flammability and thermal stability of fabric treated with a phosphazene derivative 1,1,3,3-dihydroxybiphenyl-5,5-diaminoethanephosphazene (dBEP) indicated that only 9 wt% add-on of dBEP was required to achieve promising flame retardant properties on cotton fabric. To understand the mode of action of dBEP, the thermal degradation pathways of the control and cotton fabric treated with dBEP were investigated. Thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (TGA-FTIR) was used to follow the evolved gases produced by the control and treated fabrics during thermal degradation. Two techniques, attenuated total reflectance infrared spectroscopy (ATR-IR) and solid-state nuclear magnetic resonance (NMR) were employed to examine the degraded residues of the unburned fabrics, burned fabrics, and dBEP. The results show that dBEP undergoes decomposition to produce phosphoric acid and polymerization to form phospham-like derivative that are known to retard fire.
Keywords: Phosphazene derivative; ATR-IR; TGA-FTIR; Solid-state NMR; Thermal degradation pathway;
Gum ghatti and poly(acrylamide-co-acrylic acid) based biodegradable hydrogel-evaluation of the flocculation and adsorption properties by Hemant Mittal; Arjun Maity; Suprakas Sinha Ray (42-52).
The main aim of this study was to develop a biodegradable flocculent and adsorbent based on the graft co-polymer of the Gum ghatti (Gg) with the co-polymer mixture of acrylamide (AAM) and acrylic acid (AA) using the microwave assisted graft co-polymerization technique. The synthesized hydrogels were characterized using thermogravimetric analysis, Fourier transform infrared spectroscopy and scanning electron microscopy techniques. The swelling capacity of the synthesized hydrogel was studied in the double distilled water and it showed the maximum swelling capacity of 2547% at 50 °C. Moreover, the hydrogel polymer was employed for the selective removal of saline water from different petroleum fraction-saline emulsions. The flocculation characteristics of the synthesized hydrogel were investigated in clay suspension and the maximum flocculation efficiency was observed in the acidic clay suspension with 20 mg l−1 polymer dose. Furthermore, the synthesized hydrogel polymer was also employed for the successful removal of cationic dyes from the aqueous solutions and it was found to adsorb 96% of malachite green and 99% of methyl violet. Finally, the hydrogel polymer was subjected to biodegradation using the composting method and 91.77% degradation was achieved after 60 days. In summary, the biodegradable Gg-cl-P(AAM-co-AA) hydrogel have demonstrated potential for its use as flocculants and absorbents.
Keywords: Gum ghatti; Hydrogel polymer; Biodegradation; Adsorption; Flocculation;
The effect of common agrichemicals on the environmental stability of polyethylene films by Chung-Liang Yeh; Melissa A.L. Nikolić; Brunell Gomes; Emilie Gauthier; Bronwyn Laycock; Peter Halley; Steven E. Bottle; John M. Colwell (53-60).
The impact of commonly used agrichemicals (Paraquat, Mancozeb, Chlorpyrifos and Sulfur) on the environmental stability of polyethylene films has been evaluated under accelerated photo-oxidative conditions. Paraquat and Mancozeb when applied to unstabilized clear polyethylene film, followed by exposure to UV radiation, resulted in direct attack of the polymer, evident by faster rates of oxidation and shorter times to embrittlement compared to a polyethylene control. Reapplication of these chemicals during exposure, as often occurs in agricultural practice, resulted in even faster degradation. In contrast, Sulfur and Chlorpyrifos did not have a significant effect on the photodegradation of exposed unstabilized polyethylene film. When the polyethylene film was pigmented (white top layer containing rutile titanium dioxide and carbon black in the bottom layer) and stabilized with the addition of hindered amine stabilizers (HAS), differences in oxidation susceptibility were seen with repeated exposure to Paraquat showing the most dramatic effect. This was evident by an increased carbonyl index, decrease in elongation at break and an increase in tensile stress at yield compared to a control film and other agrichemical treatments. These studies enable degradation from accelerated consumption of stabilizers by the agrichemicals (and their degradation products) to be differentiated from enhanced photochemical initiation of the polyethylene degradation.
Keywords: Polyethylene; Mulch film; Paraquat; Hindered amine stabilizer; Agrichemical; Degradation;
Poly (butylene adipate-co-terephthalate)/hydroxyapatite composite structures for bone tissue recovery by Wilson A. Ribeiro Neto; Ana Claudia C. de Paula; Thaís M.M. Martins; Alfredo M. Goes; Luc Averous; Guy Schlatter; Rosario Elida Suman Bretas (61-69).
Tissue engineering is a multidisciplinary science that offers a strategy to circumvent the problems related with regenerative and therapeutic procedures. The development of biomaterials made of biodegradable polymers and hydroxyapatite (HA) has been extensively investigated to create biological substitutes to regenerate and repair bone tissue. In this research, a bionanocomposite scaffold based on poly (butylene adipate-co-terephthalate) (PBAT) and HA nanoparticles was prepared by electrospinning and spin coating techniques. The characterization of the composite structures was made by scanning and transmission electron microscopy (SEM and TEM), differential scanning calorimetry (DSC), Fourier Transform infrared (FTIR), wide angle X-rays diffraction (WAXD) and tensile mechanical properties, which were measured by dynamical mechanical analysis (DMA). Afterwards, human adipose stem cells (hASC) were seeded over the composite material and its differentiation in osteoblasts and in vivo biocompatibility were evaluated. This study showed that the composite material had a proper morphology, structure and mechanical properties which ensured the hASC attachment, proliferation and differentiation in bone cells. Finally, as implants, the composite material triggered only a mild inflammatory response.
Keywords: Biodegradable polymer; Hydroxyapatite; Composite; Scaffold; Bone tissue engineering;
Rheological study of the reaction kinetics in a poly(ethylene terephthalate) melt by M. Härth; J. Kaschta; D.W. Schubert (70-75).
Time dependent measurements of the zero shear viscosity are applied to study the thermal stability of a commercial poly(ethylene terephthalate). Firstly, the factors influencing the experimental results, like moisture content and type of atmosphere (air or nitrogen) are briefly reviewed. Secondly, the time dependent viscosity is studied on dry samples in nitrogen atmosphere at various temperatures, as these conditions are commonly used for the rheological material characterization. All viscosity curves show a characteristic maximum which strongly depends on time and temperature. This maximum reflects the changes in molar mass resulting from the various chemical reactions. A simplified kinetic model, based on one build-up and one degradation reaction, is derived and used to analyze the experimental data. This model enables to determine the activation energy of flow (65 kJ mol−1) and the activation energy resulting from the temperature dependence of the molar mass maximum (120 kJ mol−1). Kinetic constants and corresponding activation energies of the chemical reactions are determined as well. The comparison with literature shows that the activation energies are similar to those found for the polymerization process.
Keywords: Poly(ethylene terephthalate); Rheology; Reaction kinetics; Thermal degradation; Activation energy;
Molecular and macromolecular structure changes in polyamide 11 during thermal oxidation – Kinetic modeling by Octavie Okamba-Diogo; Emmanuel Richaud; Jacques Verdu; François Fernagut; Jean Guilment; Bruno Fayolle (76-87).
The oxidation kinetics of unstabilized polyamide 11 thin film under oxygen pressures up to 2.0 MPa was studied by means of ferrous ion method for hydroperoxides titration, size exclusion chromatography (SEC) for molar weight measurements and in situ FTIR monitoring for carbonyl build up. Oxidation was shown not to be limited by oxygen diffusion which militates in favor of the use of a simple kinetic model for simulating experimental data. The kinetic parameters of this model were estimated from literature for initiation and propagation, and from selective experiments such as aging under several oxygen pressures for the estimation of the termination rate constants, or exposures under inert atmosphere to investigate the solid state polymerization effects and tentatively check the boundary conditions of the model. The kinetic model simulates satisfyingly the overall experimental results using the minimal number of adjustable parameters (except for some reactions difficult to be experimentally isolated and studied).
Keywords: Polyamide; Kinetic modeling; Thermal oxidation; Solid state polymerization;
Flammability and thermal properties of polycarbonate /acrylonitrile-butadiene-styrene nanocomposites reinforced with multilayer graphene by Raheleh Heidar Pour; Mohammad Soheilmoghaddam; Azman Hassan; Serge Bourbigot (88-97).
A series of polycarbonate (PC)/acrylonitrile butadiene styrene (ABS) (70/30 wt.%) nanocomposites with varying concentrations (0–5 wt.%) of multilayer graphene particles (GNP) were fabricated using melt extrusion process. The flammability, thermal, mechanical and morphological properties of the nanocomposites was investigated. Cone calorimeter analysis, limiting oxygen index (LOI) and UL94 flame rating tests revealed that addition of GNP to PC/ABS significantly improved the flame retardancy of PC/ABS/GNP nanocomposites. As much as 30.4% reduction in peak heat release rate was observed for the 3 wt.% GNP loading. The maximum LOI value of 26% was observed for the nanocomposites with 3wt.% GNP content. UL-94 V-2 rating and less dripping was observed for the nanocomposites compared with the pure PC/ABS sample. TGA analysis showed that incorporation of GNP enhanced the thermal stability and char yield of the nanocomposites. Scanning electron microscopy revealed the GNP nanoplatelets were unidirectionally aligned in the PC/ABS parallel to the surface of the nanocomposites.
Keywords: Polycarbonate/acrylonitrile butadiene styrene (PC/ABS); Multilayer graphene; Nanocomposites; Flame retardancy; Thermal properties;
Influence of solid alkali application on corn stalk dissolution and degradation in solvent systems by Le Liu; Meiting Ju; Weizun Li; Yiliang Liu; Xueju Huang (98-106).
In our study, solid alkali were produced and characterized by a series of methods. Dissolution of corn stalk was achieved in solvent systems at 170 °C for 5 h by cooking with solid alkali. The components of ionic liquid and water in solvent systems showed synergistic effects on lignocellulosic dissolution and degradation. Alkaline molecular sieves were proven to be the most effective solid alkali for lignin degradation, which promoted the dissolution efficiency of the corn stalk in solvent systems. Under the combined action of solid alkali and the nucleophilic component in solvent systems, lignin and hemicellulose in corn stalk were degraded. It effectively enhanced cellulose solubilization in solvent systems. The regenerated cellulose was demonstrated to be similar to microcrystalline cellulose according to Fourier Transform infrared spectroscopy and Nuclear Magnetic Resonance analyses. X-ray diffraction curves showed that the crystallinity of the regenerated cellulose is lower than that of microcrystalline cellulose.
Keywords: Solid alkali; Corn stalk; Solvent system; Dissolution;
Thermal degradation of high molar mass hyaluronan in solution and in powder; comparison with BSA by Jakub Mondek; Michal Kalina; Vasile Simulescu; Miloslav Pekař (107-113).
The aim of the present work was to compare the thermal degradation of bovine serum albumin and hyaluronic acid of different molar masses by determining the loss in molecular weight by means of SEC-MALLS (size exclusion chromatography – multi angle laser light scattering). For all measured samples, the results obtained by this method were compared with the results for stability determined by electrophoretic light scattering. The degradation study was performed in solution and in powder.Bovine serum albumin (also known as BSA) is a protein derived from cows, which has many biochemical applications. Hyaluronic acid (hyaluronan or HA) is an anionic nonsulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues.The powder and solutions of BSA and HA were heated at different temperatures ranging from 37 °C to 120 °C for certain periods (the highest temperature was used only for the powder). The observed degradation increased with the duration of heating and with temperature for all hyaluronic acid samples analyzed in this work, in accord with Arrhenius law.At 37 °C and 60 °C, only moderate degradation was observed for hyaluronic acid solutions. For BSA at 37 °C no degradation was observed and at 60 °C significant aggregation occurred.
Keywords: Bovine serum albumin; Hyaluronic acid; Thermal degradation; SEC-MALLS; Electrophoretic light scattering;
Long-term accelerated weathering of HAS stabilized PE and PP plaques: Compliance of ESRI, IR, and microhardness data characterizing heterogeneity of photooxidation by J. Pilař; D. Michálková; M. Šlouf; T. Vacková (114-121).
Polymers in various applications are subjected to photooxidation processes resulting in loss of their material properties due to appearance of oxidation products and consequent degradation. Heterogeneous space distribution of concentration of oxidation products, crystallinity, stabilizer concentration and microhardness (MH) can be determined utilizing IR microspectroscopy and microhardness tester, respectively. We devoted this paper to direct determination of heterogeneity of the above mentioned parameters inside PE polymer plaques stabilized with secondary HAS Tinuvin® 770 and to the comparison of the data with nitroxide concentration profiles determined by ESRI that outline heterogeneity of the oxidation process inside the plaques. Data on heterogeneity of photooxidation processes in PP plaques stabilized with Tinuvin® 770 or binitroxide Prostab® 5415 are presented for comparison.
Keywords: Polyethylene; Polypropylene; Accelerated weathering; Hindered amine stabilizers; Electron spin resonance imaging; Infrared microspectroscopy; Microhardness; Heterogeneity of photooxidation;
Effect of carbon nanotubes on thermal pyrolysis of high density polyethylene and polypropylene by Omar Gutiérrez; Humberto Palza (122-134).
The goal of this work is to analyze the effect of carbon nanotubes (CNTs) on the pyrolysis of either high density polyethylene (PE) or polypropylene (PP) matrices by using both kinetic thermogravimetric analyses (TGA) under non-isothermal conditions and a fixed-bed reactor under isothermal conditions. Under non-isothermal conditions, CNTs increased the beginning of thermodegradation for both matrices with differences as high as 30 °C and 22 °C as compared with neat PP and PE, respectively. This enhanced thermal stability in PP based composites was associated with an increase in the apparent activation energy whereas in PE based composites lower pre-exponential factors associated with reduced conformational entropy, are responsible for the enhanced thermal stability. The thermodecomposition processes were studied by assuming geometrical contraction and nucleation models. The invariant pre-exponential factor and apparent activation energy obtained were quantified for each sample confirming that these values depended on the polymer matrix and concentration of CNTs. These invariant parameters were in good agreement with those obtained by isoconversional analyses allowing the prediction of the thermogravimetric behavior. Our findings clearly showed the strong effect of CNTs on the non-isothermal pyrolysis of polymer materials changing its kinetic and the activation energy. Results from isothermal pyrolysis (450 °C-40′) confirmed the thermal stability by the presence of CNTs as higher condensable (C9–C40) and lower gas (C1–C4) yields in PP-CNTs composites, and a higher amount of unreacted polymer and a lower both condensable and gas yields for PE-CNT, as compared with the pure matrix, were found.
Keywords: Polyolefin pyrolysis; Thermal degradation; Thermogravimetric kinetic analysis; Carbon nanotube-polyethylene nanocomposites; Carbon nanotube-polypropylene nanocomposites;
Influence of hybrid functionalized graphite nanoplatelets-tripolyphosphate on improvement in fire protection of intumescent fire resistive coating for steel structures by Somayeh Mohammadi; Homeira Shariatpanahi; Faramarz Afshar Taromi (135-148).
Functionalized graphite nanoplatelets (FGNP) were modified with tripolyphosphate (TPP) as a thermal oxidation inhibitor. The hybride nano-particles (FGNP-TPP) effects on improvement of fire retardant properties of a traditional intumescent fire retardant (IFR) formulation were investigated. FT-IR results showed that TPP was linked to FGNP nano-particle by hydrogen bondings. TEM image showed homogenous dispersion of FGNP-TPP nano-particles in epoxy. Thermogravimetric analysis (TGA) in air showed the oxidation onset temperature of FGNP was increased by approximately 125 °C in the presence of TPP. Incorporation of 2 wt.% of FGNP-TPP into the traditional IFR coating increased the LOI value from 27.1 to 32. Also, a crack free char with high adhesion to the metal substrate was observed in bunsen burner test which increased the time of failure from 43 to 94 min. The results showed the hybrid nano-particles can improve the thermal oxidation stability of the IFR coating at higher temperatures (900–1000 °C) leading to improved char strength, char adhesion, char morphology, residual weight and fire protection properties.
Keywords: Functionalized graphite nano-platelets; Tripolyphosphate; Thermal oxidation; Fire protection;
CO2-producing polymer micelles by Hoyoung Lee; Jaewon Lee; Jaeyoung Park; Taewook Kwon; Seunggweon Hong; You-Yeon Won (149-157).
Poly(propylene carbonate) (PPC) is a plastic material that can be mass produced from naturally abundant carbon dioxide. This polymer is also known to decompose back to CO2 when heated above about 200 °C. Here we report that the CO2-generation temperature of PPC can be reduced down to the 40–80 °C range in aqueous environment by using a photoacid generator (PAG) as the catalyst for activating the random scission reaction of PPC. We also investigated the thermal degradation of a PPC-based amphiphilic block copolymer, poly(poly(ethylene glycol) methyl ether methacrylate)-poly(propylene carbonate)-poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA-PPC-PPEGMA). These triblock copolymers form stable small-sized (<200 nm) micelles in water. We found evidence that with the aid of added PAG these micelles can degrade under mild heating conditions (<80 °C), similarly to what is expected from PPC homopolymer experiments. The combined results suggest that PPC-based amphiphilic block copolymers might be of interest for applications in ultrasound contrast.Display Omitted
Keywords: Poly(propylene carbonate); poly(poly(ethylene glycol) methyl ether methacrylate); Block copolymer; Photoacid generator; Carbon dioxide;
PET-based copolyesters with bisphenol A or bisphenol F structural units: Their distinct differences in pyrolysis behaviours and flame-retardant performances by De-Ming Guo; Xiang-Quan Chen; Liang Tang; Jia-Ning Wu; Teng Fu; Xiao-Lin Wang; Xiu-Li Wang; Li Chen; Yu-Zhong Wang (158-168).
In order to avoid potential environmental and safety problems caused by conventional flame retardants, we synthesized the flame-retardant-element-free copolyesters via chemically incorporating the structural units of bisphenol A and bisphenol F into the PET main chain via melt polymerization, respectively. The chemical structures of resulting copolyesters were confirmed by 1H NMR and 13C NMR spectroscopy. Interestingly, though there exists only a small structural difference between bisphenol A and bisphenol F, those two kinds of copolyesters show different thermal stabilities, pyrolysis behaviours and flame retardant performances. Pyrolysis-GC/MS tests were performed to investigate the pyrolysis mechanism of the copolyesters, and the results showed that the “Ar–CH2–Ar” structure units (bisphenol F) would lead to rearrangement reactions at high temperature, ultimately forming the phenanthrene ring structures; whereas “Ar–C(CH3)2−Ar” structure units (bisphenol A) could not. The corresponding specific pyrolysis processes are proposed. Thermogravimetric analysis (TGA) results indicated that these rearrangement reactions would most likely occur in the solid state of the copolyesters and made them have high residues. Cone calorimeter measurements, LOI and vertical UL-94 tests were used to characterize the flame-retardant properties of the copolyesters, and the results proved that the copolyesters containing bisphenol F had better flame retardancy, more char formation and less melt drippings than those containing bisphenol A due to the rearrangement reactions.
Keywords: PET copolyesters; Bisphenol F; Bisphenol A; Flame retardance; Pyrolysis; Rearrangement;
Changes in fibrolytic enzyme activity during vermicomposting of maize stover by an anecic earthworm Amynthas hupeiensis by Yuxiang Chen; Quanguo Zhang; Yufen Zhang; Jing Chen; Dongguang Zhang; Jin Tong (169-177).
In the present study, maize stover was treated with an anecic earthworm Amynthas hupeiensis. Fibrolytic enzyme activity was detected periodically during vermicomposting process. The presence of the earthworms increased the activity of carboxymethyl cellulase, avicelase, β-glucosidase, endo-β-1,4-xylanase, acetyl esterase, and manganese peroxidase significantly. The activity of ferulic acid esterase was also increased by the earthworm, although the extent was insignificant. The level of laccase activity was very low in the treatment with the earthworms and in the control group. Compared to the control group, the activity of the fibrolytic enzyme in the treatment with the earthworms reached its peak value rapidly and maintained the higher level of activity for about 30 days. The content of cellulose, hemicellulose, and lignin showed a decreasing trend in the treatment with the earthworms and in the control group. The decreasing extent was significant in the treatment with the earthworms (p < 0.01), and the highest decrease of cellulose, hemicellulose and lignin content was observed on day 15. In the treatment with the earthworms, the activity of carboxymethyl cellulase, avicelase, β-glucosidase, endo-β-1,4-xylanase, and manganese peroxidase on day 15 increased rapidly compared to the initial value. It was in accordance with the rapid decrease of cellulose, hemicellulose and lignin content. The dominant bacteria and fungi in the treatment with the earthworms were important decomposers of cellulose, hemicellulose and lignin. The higher activity of lignocellulolytic enzyme in the treatment with the earthworms can be attributed to the action of these microbial strains. Results indicated that earthworm treatment could accelerate maize stover stabilization by activating lignocellulose degrading microbes during vermicomposting process. Vermicomposting is an effective approach to manage crop residues such as maize stover.
Keywords: Vermicomposting; Amynthas hupeiensis; Maize stover; Fibrolytic enzyme;
The applicability of Impranil®DLN for gauging the biodegradation of polyurethanes by Justin C. Biffinger; Daniel E. Barlow; Allison L. Cockrell; Kathleen D. Cusick; William J. Hervey; Lisa A. Fitzgerald; Lloyd J. Nadeau; Chia S. Hung; Wendy J. Crookes-Goodson; John N. Russell (178-185).
Polyurethane-based polymers and their eventual degradation products pervade modern society. One common method for determining whether a microorganism or protein can degrade this class of polymer is to qualitatively assess its ability to “clear” a polyester-polyurethane colloid branded Impranil®DLN (Impranil), whose formulation is proprietary. However, its colloidal state has ultimately made Impranil a precarious choice for determining if an organism or enzyme can degrade polyurethanes. In this work, the chemical hydrolysis products from Impranil using 0.1 M HCl or 0.1 M NaOH were identified and compared to the concentration of hydrolysis products formed using three commercial enzymes by proton nuclear magnetic spectroscopy (1H NMR) and Fourier-transform infrared spectroscopy (FT-IR). The differences in the integrated signal intensities from key 1H NMR signals were used to calculate the amount of Impranil that was hydrolyzed. These data were then correlated with the change in optical density of colloid containing reaction mixtures (termed as “clearing”). The enzymes (a Pseudomonas fluorescens recombinant esterase, Pseudomonas sp. lipase, and Bacillus sp. protease) showed significant esterase activities and partially-cleared, completely-cleared, or aggregated Impranil, respectively. However, only the Pseudomonas sp. lipase significantly degraded Impranil based on NMR and IR data. This study illustrates how Impranil can be used to quantitatively assess biodegradation rather than just be a qualitative “clearing” indicator of biodegradation.
Keywords: Biodegradation; Polyurethane; Hydrolase; NMR; IR; Colloid;
Comparative assessment of degradation in aqueous medium of polypropylene films doped with transition metal free (experimental) and transition metal containing (commercial) pro-oxidant/pro-degradant additives after exposure to controlled UV radiation by Larissa Stieven Montagna; André Luis Catto; Maria Madalena de Camargo Forte; Emo Chiellini; Andrea Corti; Andrea Morelli; Ruth Marlene Campomanes Santana (186-192).
The comparative behaviour to degradation of polypropylene (PP) films with 1 and 3 wt.% of experimental (transition metal free) and commercial (transition metal containing) pro-oxidant/pro-degradant additive were investigated under accelerated environmental conditions. Specimens of 20 μm films, obtained by extrusion of the samples of PP containing the pro-oxidant/pro-degradant additives, were initially exposed to irradiation in a UV chamber for 270 h, and then submitted to a degradation test in aqueous medium for 100 days. The CO2 production in response of a microbial attack was monitored by back titration during all the experimented trials. The PP crystallinity was evaluated by differential scanning calorimetry (DSC) and the oxidation level was determined by the determination of carbonyl index by Fourier Transform Infrared analysis (FT-IR). The surface morphology of the PP samples was investigated by scanning electron microscopy. A degradation evidence of the additivated PP samples was attained in comparison with the behaviour of neat PP samples. The surface of the additivated PP films showed grooves and holes as a clear indication of the physical-chemical degradation. The PP samples with the experimental metal-free pro-oxidant/pro-degradant experienced a higher level of degradation with respect to the PP sample loaded with the commercial transition metal containing pro-oxidant/pro-degradant. Thus, the benzoin/potassium salt free of transition metal suggested in this work has showed be highly efficient degradant additive for PP degradation.
Keywords: Polypropylene; Pro-oxidant/pro-degradant additive; Degradation in aqueous medium; UV radiation;
Synthesis of a formaldehyde-free phosphorus–nitrogen flame retardant with multiple reactive groups and its application in cotton fabrics by Xinhang Li; Huiyu Chen; Wentao Wang; Yaqing Liu; Peihua Zhao (193-202).
A novel formaldehyde-free phosphorus–nitrogen flame retardant with multiple reactive groups, dioxo (3-triethylphosphite-5-chlorine−1−triazine) neopentyl glycol (DTCTNG), has been synthesized and was applied to cotton fabrics. The molecular structure of DTCTNG was characterized by FTIR, 1H NMR, and 31P NMR. The thermal degradation property of DTCTNG was assessed by thermogravimetric analysis (TGA), which revealed that it has good thermal stability on the high temperature condition. To achieve a covalent bond between DTCTNG and fiber matrix, the finishing conditions of cotton fabrics with different add-on's DTCTNG were investigated by using TGA, vertical flammability test, limiting oxygen index (LOI) and scanning electron microscope test (SEM). The water resistance of the treated cotton fabrics under optimal finishing condition was studied by LOI test. Furthermore, the mechanism of cross-linking reaction between DTCTNG and cotton fiber was discussed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). All the results showed that cotton fabrics treated with DTCTNG has good flame retardancy and steady water resistance.
Keywords: Flame retardant; Phosphorus–nitrogen; Multiple reactive groups; Synthesis; Cotton fabrics;
Chemisorption and thermally induced transformations of polydimethylsiloxane on the surface of nanoscale silica and ceria/silica by Kostiantyn Kulyk; Mykola Borysenko; Tetiana Kulik; Lyuba Mikhalovska; John D. Alexander; Borys Palianytsia (203-211).
Compositions of polydimethylsiloxane (PDMS) polymer with nanosized silica and ceria/silica were prepared. The influence of these nano-fillers on the thermal stability and degradation mechanism of silicone polymer was investigated using Thermogravimetric Analysis (TGA) and Temperature Programmed Desorption Mass Spectrometry (TPD MS). The results showed that thermal decomposition of pure and adsorbed PDMS differs significantly. The three main stages of the PDMS thermal transformations in the adsorbed state were determined to be: 1) chemisorption of PDMS chains involving the terminal trimethylsilyl groups of the polymer and silanol groups of the silica surface; 2) formation and desorption of cyclic oligomers; 3) high temperature radical degradation of the polymer accompanied by the formation of methane and ethylene. The kinetic parameters of the corresponding reactions were calculated from the TPD MS data. It was found that nanoparticles of cerium dioxide strongly influence the degradation pattern, lower the decomposition temperature and catalyze the formation of methane.
Keywords: Polydimethylsiloxane; Nanocomposite; Silica; Ceria; Pyrolysis; TPD MS;
Impact of biofibers and coupling agents on the weathering characteristics of composites by Dilpreet S. Bajwa; Sreekala G. Bajwa; Greg A. Holt (212-219).
This paper explores the ultraviolet (UV) weathering performance of high density polyethylene (HDPE) composites with different biofiber fillers and coupling agent. Biofiber polymer composite (BFPC) material samples were prepared using oak, cotton burr and stem (CBS) or guayule bagasse as fiber source HDPE as resin, and two different coupling agents. Weathering variables included exposure to UV radiation and moisture cycles for up to 2200 h. Each variable can degrade BFPC matrix independently or synergistically. The impact of weathering was measured through the changes in the surface matrix, mechanical properties and thermal stability of BFPC as a function of biofibers types and coupling agents. The coupling agent treated composites showed color shift (ΔE) and variable surface degradation. Water absorption of the weathered samples continued to increase after 10 days of immersion. Flexural stiffness, strength and impact properties of weathered samples decreased regardless of fiber type or coupling agent. Minimal linear thermal expansion was noted in weathered composites with coupling agents. Overall coupling agent helped to retain the mechanical properties of composites after exposure to UV weathering.
Keywords: Natural fiber composites; Coupling agents; Natural weathering; Polymer degradation; Mechanical properties;
Thermal and dynamic mechanical properties of beeswax-halloysite nanocomposites for consolidating waterlogged archaeological woods by Giuseppe Cavallaro; Giuseppe Lazzara; Stefana Milioto; Filippo Parisi; Veronica Sparacino (220-225).
Thermal and mechanical properties were determined for the halloysite nanotubes (HNT)/beeswax composites at various compositions. The beeswax degradation temperatures and time course, provided by thermogravimetry (TG), evidenced the improvement of the thermal properties operated by HNT. Differential scanning calorimetry (DSC) allowed us to determine the enthalpy of melting as well as the time course of the melting process for beeswax. A slight loss of beeswax crystallinity was observed upon HNT addition. The dynamical mechanical analysis (DMA) provided the loss and the storage modulus for the nanocomposites upon heating and it was shown that the nanoclays create an inorganic framework which enhances the mechanical properties keeping unaltered the beeswax shape even above the melting temperature. To the light of these insights, samples of waterlogged archaeological wood were consolidated with the HNT/beeswax nanomaterial. The amount of HNT entrapped into the pores as well as the shrinkage volume of wood samples were determined. The HNT/beeswax mixtures can be considered a promising consolidant material for archaeological wood.
Keywords: Halloysite; Beeswax; Thermogravimetry; Differential scanning calorimetry; Dynamic-mechanical analysis; Consolidant; Waterlogged archaeological wood;
PVC degradation by Fenton reaction and biological decomposition by Tomáš Mackuľak; Alžbeta Takáčová; Miroslav Gál; Marián Marton; Jozef Ryba (226-231).
The possibility of the degradation of the recalcitrant polymer polyvinylchloride (PVC) was the object of our study. For this purpose the Fenton reaction with subsequent biodecomposition step was successfully used. Molecular degradation fragments were determined by HPLC and GC-FID method. After the first step - degradation of PVC by the Fenton reaction, the formation of trans-1,2-dichloroethene, cis-1,2-dichloroethene, trichloroethene and tetrachloroethene was observed. Also more complex molecules such as benzene, ethylbenzene and o-xylene were identified. Probably these chemical compounds are the products of phthalates decomposition. The resulted mixture was in the second step used as a substrate for anaerobic biogas production. Biological degradation of used COD was α = 67.3% and F/I = 0.004 [gCOD g−1 VS]. The decomposition of other compounds such as trans-1,2-dichlorethylene (60%), cis-1,2-dichlorethylene (70%) was also observed. Moreover, benzene, ethylbenzene and o-xylene were completely removed during the biological decomposition step. It is possible to assume that Fenton pretreatment improves the degradation of PVC and, by this way the low molecular weight fragments are formed. Subsequently degradation products of PVC by GC-FID were identified. In next steps, the digestion of these fragments by anaerobic microorganisms was observed. It was also found that in anaerobic sludge the degradation of low molecular weight fragments is carried out. One can conclude that these small fragments are used by microorganisms as biological substrate.
Keywords: Fenton reaction; Polyvinylchloride; Biodegradation; Hydroxyl radicals; Biogas;
Alkali resistance of poly(ethylene terephthalate) (PET) and poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG) copolyesters: The role of composition by Tingting Chen; Weikai Zhang; Jun Zhang (232-243).
The alkali resistance of poly(ethylene terephthalate) (PET) and a series of poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG) copolyesters with different molar ratios of ethylene glycol (EG) to 1,4-cyclohexanedimethanol (CHDM) was systematically investigated. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) were used to probe the effect of the alkali treatment on the crystallization behavior and crystalline structure of the PET and PETG copolyesters. The surface groups and morphology changes were characterized by attenuated total reflectance Fourier transform-infrared spectroscopy (ATR-FTIR) and reflective polarized optical microscopy. The effects of temperature, duration, crystallinity and composition on the alkali resistance were examined. The incorporation of 1,4-cyclohexanedimethanol terephthalate (CT) in the PET chain, did not compromise the alkali resistance of the PETG copolyesters. On the contrary, the alkali resistance of the PETG copolyesters was enhanced when the CT content was increasing. The composition played an important role in the alkali resistance of the PET and PETG copolyesters, rather than the crystallinity. The ET component was more easily attacked by alkaline hydrolysis than the CT component, and the remaining polymer was enriched in the CT component. In addition, the amorphous regions on the surface of the PET and PETG copolyesters were more likely to be attacked by the hydroxyl anions compared to the crystalline regions. Moreover, the alkali treatment did not change the crystalline structure of the PET and PETG copolyesters, but the alkali treatment did result in corrosion to the crystals.
Keywords: PETG copolyesters; Alkali resistance; Composition; Hydrolysis; Crystallinity; Crystalline structure;
Formation and characterization of an inclusion complex of triphenyl phosphate and β-cyclodextrin and its use as a flame retardant for polyethylene terephthalate by Nanshan Zhang; Jialong Shen; Melissa A. Pasquinelli; David Hinks; Alan E. Tonelli (244-250).
Keywords: Flame retardant (FR); Triphenyl phosphate (TPP); β-cyclodextrin (β-CD); Inclusion complex (IC); Poly(ethylene terephthalate) (PET);
A novel efficient polymeric flame retardant for poly (lactic acid) (PLA): Synthesis and its effects on flame retardancy and crystallization of PLA by Fenghui Liao; Yaqing Ju; Xiu Dai; Yu Cao; Jiawei Li; Xinlong Wang (251-261).
A novel polymeric flame retardant (PNFR) containing phosphorus, ester groups and phenyl rings on the backbone was synthesized and analyzed by 1H NMR, FTIR, DSC, XRD and GPC. The crystallization of the poly (lactic acid) (PLA) composites with different content of PNFR was studied by DSC. The flame retardancy of the PLA composites with PNFR was investigated by limited oxygen index (LOI), cone calorimetry and vertical burning tests (UL-94). The results indicated that low loading of PNFR could significantly improve flame retardancy and crystallinity of PLA. The LOI was increased to 31.5 vol%O2 and UL-94 V-0 was attained for the PLA composites with loading of 3 wt% PNFR. Moreover, the crystallinity of this sample reached 46.03%. The char residues after the burning of the PLA composites with PNFR were analyzed by SEM, XRD, Raman and XPS.
Keywords: Poly (lactic acid); Condensation polymerization; Phosphorus-nitrogen; Flame retardancy; Crystallization; Char;
The study of air-plasma treatment on corn starch/poly(ε-caprolactone) films by G.A. Arolkar; M.J. Salgo; V. Kelkar-Mane; R.R. Deshmukh (262-272).
In spite of usefulness of synthetic polymers in every aspects of life, the environmental hazards limit their use. Starch based biodegradable polymers is one of the solutions to it. Packaging has a major share in use of synthetic polymers. For packaging application, it is necessary to have good surface and barrier properties of the material. Plasma surface modification of materials is a promising solution to enhance surface properties. In the present paper, cornstarch/poly(ε-caprolactone) (CSPCL) films were treated in air-plasma for different durations of time. The effect of air-plasma treatment on surface properties and biodegradation was studied. The extent of etching was evaluated from weight change (%) study. Changes in surface chemical composition were analyzed using ATR-FTIR and XPS. The contact angle and surface free energy (SFE) study indicate that air-plasma treatment leads to hydrophilization of CSPCL films. The changes in surface topography of plasma processed films were analyzed using AFM and SEM. The roughness caused by etching and increase in surface free energy facilitates the improvement in adhesive properties like printability and peel strength. Changes in barrier properties were studied using water vapor and oxygen transmission rate. Effect of air-plasma treatment on biodegradation of treated and untreated samples was studied by simulating natural biodegradation conditions in a controlled environment using indoor soil burial method and with a single bacterial system comprising of a commonly occurring soil bacterium, Bacillus subtilis MTCC 121. While the soil system is indicative of biodegradation due to macro as well as micro elements, a single microbial system will identify the interaction between the microorganisms and modified surface thus showing the effect of air-plasma treatment on the degradation process. Biodegradation by indoor soil burial method was assessed by measuring loss in tensile properties and growth of soil micro flora on surface by optical light microscopy (OLM). Biodegradation by B. subtilis was assessed by measuring increase in its number along with the changes it brought about in the sample surface by optical light microscopy and SEM. It was observed that such surface modifications enhanced the biodegradation rate along with finding application in packaging field, thus providing a green solution for the increasing packaging utilization and addressing environmental concerns.
Keywords: Corn starch/Poly(ε-caprolactone) (CSPCL); Air-plasma treatment; XPS; Surface free energy; Barrier properties; Biodegradation;
Injectable chitosan/dextran-polylactide/glycerophosphate hydrogels and their biodegradation by Jingjing Wu; Ting Zhou; Jiaoyan Liu; Ying Wan (273-282).
Dextran-polylactide (Dex-PLA) copolymers were synthesized and the selected Dex-PLA with water-soluble characteristics was used together with chitosan and glycerophosphate (GP) to produce injectable chitosan/Dex-PLA/GP hydrogels. Some chitosan/Dex-PLA/GP solutions with designated compositions were able to form into hydrogel in a temperature range between around 32 and 35 °C, and their pH values were found to alter between 7.0 and 7.2. Elastic modulus of the optimal chitosan/Dex-PLA/GP gel could reach about 1.0 kPa or higher, and meanwhile, it was much higher than their viscous modulus, revealing that these chitosan/Dex-PLA/GP gels behave like mechanically strong ones. Compression measurements indicated that the certain chitosan/Dex-PLA/GP gels had around 8-fold modulus and strength higher than the chitosan/GP gel, confirming that greatly enhanced compressive properties for chitosan/Dex-PLA/GP gels have been achieved. After 8-week subcutaneous degradation in rats, some chitosan/Dex-PLA/GP gels showed significantly extended degradation endurance compared to the chitosan/GP gel, and the PLA content in the chitosan/Dex-PLA/GP gels was able to regulate the degradation rate of the gels in a controllable manner. These results suggest that the presently developed chitosan/Dex-PLA/GP gels have promising potential for injectable gelling applications where the gel with mechanically strong features and degradation tolerance is needed.
Keywords: Chitosan; Dextran copolymer; Injectable hydrogel; Mechanical property; Degradation;
Structure effect of phosphite on the chain extension in PLA by Xin Meng; Guotao Shi; Weijie Chen; Chushi Wu; Zhong Xin; Ting Han; Yaoqi Shi (283-289).
PLA is synthesized from natural resource and can degrade easily, so it is a reasonable substituent of petroleum base plastic. Phosphites can increase the stability of PLA through the chain extension with PLA. In this paper, the molecular weights, complex viscosities and storage modulus of virgin PLA and PLA stabilized by different phosphites were characterized by gel permeation chromatography and rheometer. The results show that when there is a bigger substituent around the P–O bound in the phosphite molecule, the contact between the PLA and phosphite chain extender is inhibited and the chain extension becomes weak. In point of the three phosphite chain extenders of bis-2,2′-methyl-4,6-di-tert-butylphenyl phosphite (M46TBPP), tris(2,4-di-tert-butylphenyl) phosphite (Irgafos 168) and triphenylphosphite (TPP), the hindrance order around P–O bound is M46TBPP > Irgafos168 > TPP, and the hindrance of TPP is the smallest. So TPP takes the most effective chain extension in PLA. Furthermore, the by-product phenol formed due to chain extension of TPP has the weakest hydrogen donating ability, which makes PLA degrade weakest. So the average molecular weight values, complex viscosities and storage modulus of PLA stabilized by TPP are the biggest. In addition, the product, which was formed due to the chain extension of PLA and TPP, has some plasticization, so it makes PLA stabilized by TPP move free, crystallize easy. At last, compared to virgin PLA, PLA-TPP represents better mechanical properties.
Keywords: PLA; Chain extension; Phosphite; Melt stabilization;
Injection molding and characterization of polylactide stereocomplex by Yottha Srithep; Dutchanee Pholharn; Lih-Sheng Turng; Onpreeya Veang-in (290-299).
Poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) were hand mixed 50/50 which removed the need for melt mixing of PLLA with PDLA prior to injection molding to produce a stereocomplex. Various characterization techniques were employed to study the mechanical properties, rheological properties, and crystallization behavior of the materials. High stereocomplex content was obtained by molding PLLA and PDLA at a temperature between the melting temperature (Tm) of the homocrystal and the stereocomplex. However, PLLA and PDLA are easier to separate when being molded at below the Tm of the stereocomplex. The stereocomplex had a higher melting temperature (Tm) (more than 50 °C) and a higher crystallization temperature (Tc) (more than 25 °C) than the neat PLLA. Rheological measurements at 200 °C revealed that the PLLA50/PDLA50 showed a much higher mechanical strength (G′) than PLLA, which was attributed to stereocomplex formation by injection molding. Furthermore, PLLA50/PDLA50 greatly enhanced the elongation-at-break of PLLA. Finally, this novel process provided a unique processing route for preparing high degree stereocomplex crystallites that has not previously been reported.
Keywords: Stereocomplex; Injection molding; Polylactide;
Synthesis of biobased phosphorus-containing flame retardants for epoxy thermosets comparison of additive and reactive approaches by Raphaël Ménard; Claire Negrell; Laurent Ferry; Rodolphe Sonnier; Ghislain David (300-312).
This study presents a two-steps synthesis of novel additive or reactive phosphorus-and-sulfur-containing flame retardants (P-FR) for epoxy thermosets. The first step consists in totally epoxydizing the phloroglucinol. Then, the epoxy functions grafted are partially or totally open by a thiol bearing a phosphonate group to obtain a reactive P-FR and an additive P-FR respectively. The two synthesized P-FR are then incorporated into a DGEBA-IPDA matrix according to an appropriate approach. The impact of these P-FR on glass transition temperature (Tg) is assessed by DSC. Tg values exhibit the plasticizing effect of the additive P-FR and the loss of epoxy functionality due to the incorporation of the reactive P-FR. The thermal properties of the prepared thermosets are characterized by TGA, showing the more efficient action of the reactive P-FR in condensed phase (charring). TGA-FTIR coupling show the presence of phosphorus-containing gases released during the thermal degradation but these P-containing gases have no radical scavenging action in the gas phase. PCFC analyses prove the similar flame retardant properties of the two P-FR by reducing significantly the pHRR, the THR and the EHC. The cone calorimeter tests exhibit a strong intumescent effect of the residue brought by the two P-FR, leading to insulating expanded residue.Display Omitted
Keywords: Biophenol; Epoxy thermosets; Phosphorus-containing flame retardants; Reactive vs additive approaches; Intumescence;
Reprocessing of artificial UV-weathered wood flour reinforced polypropylene composites by L. Soccalingame; D. Perrin; J.-C. Bénézet; S. Mani; F. Coiffier; E. Richaud; A. Bergeret (313-327).
This work aims to determine and understand the influence of UV weathering on the reprocessing of a wood-plastic composite (WPC), i.e. of a wood flour reinforced polypropylene (PP) composites. Two wood flour contents (10% w/w and 30% w/w) were studied in comparison with neat PP. Compounds were produced by twin-screw extrusion. Then, ISO1A “dog bone” samples were obtained by injection molding and exposed to an artificial UV weathering using a xenon arc climatic chamber in order to simulate a long-term outdoor exposure. After this weathering stage, photo-degraded samples were submitted to grinding and injection cycles and characterized through different experimental technics. The visual evolution of the surface was followed by optical microscopy and scanning electron microscopy. In order to understand the material physical degradation, the mechanical behavior was measured thanks to tensile, Charpy impact and DMTA (Dynamic Mechanical Thermal Analysis) tests. The assessment of the microstructural evolution was performed by differential scanning calorimetry (crystallinity ratio), size exclusion chromatography (average molecular weights) tests and infrared spectroscopy (chemical structure). Additional rheological tests assessed assumptions on degradation mechanisms.
Keywords: Polypropylene; Wood flour; Biocomposites; Reprocessing; UV weathering; Microstructure; Mechanical properties; Degradation;
Degradation of different elastomeric polymers in simulated geothermal environments at 300 °C by Toshifumi Sugama; Tatiana Pyatina; Erica Redline; James McElhanon; Douglas Blankenship (328-339).
This study evaluates the degradation of six different elastomeric polymers used for O-rings: EPDM, FEPM, type I- and II-FKM, FFKM, and FSR, in five different simulated geothermal environments at 300 °C: 1) non-aerated steam/cooling cycles, 2) aerated steam/cooling cycles, 3) water-based drilling fluid, 4) CO2-rich geo-brine fluid, and, 5) heat–cool water quenching cycles. The factors assessed included the extent of oxidation, changes in thermal behavior, micro-defects, permeation of ionic species from the test environments into the O-rings, silicate-related scale-deposition, and changes in the O-rings' elastic modulus.The reliability of the O-rings to maintain their integrity depended on the elastomeric polymer composition and the exposure environment. FSR disintegrated while EPDM was oxidized only to some degree in all the environments, FKM withstood heat-water quenching but underwent chemical degradation, FEPM survived in all the environments with the exception of heat-water quenching where it underwent severe oxidation-induced degradation, and FFKM displayed outstanding compatibility with all the tested environments. This paper discusses the degradation mechanisms of the polymers under the aforementioned conditions.
Keywords: Elastomer; FKM; FFKM; EPDM; FEPM; Thermal degradation; Chemical degradation;
A new molecular understanding of the thermal degradation of PA 66 doped with metal oxides: Experiment and computation by E. Duemichen; U. Braun; H. Sturm; R. Kraemer; P. Deglmann; S. Gaan; R. Senz (340-356).
The thermal molecular degradation of polyamide 66 (PA 66) doped with (partially supported) metal oxide particles (Fe2O3, ZnO, Al2O3) was investigated qualitatively and quantitatively using common analysis techniques like thermogravimetry coupled with IR-spectroscopic evolved gas analysis (TGA-FTIR). Using pyrolysis coupled with gas chromatography mass spectrometry (Py-GC-MS), qualitative conclusions were drawn about the complex hydrocarbon products. However, the combination of TGA with solid-phase extraction, followed by thermal desorption gas chromatography mass spectrometry (TED-GC-MS), allows qualitative and even semi-quantitative conclusions about the decomposition pathway of PA 66 in the presence of various metal oxide particles.The investigations under inert conditions showed that the presence of metal particles increases the rate of decarboxylation and deamination reactions, as well as the formation rate of cyclopentanone and pyridine derivatives. These species are a consequence of various condensation reactions. The condensation reactions release a large amount of water, thus triggering the hydrolysis of PA 66. Molecular thermal degradation mechanisms were developed for the main decomposition as well as for the condensation reactions and supported by quantum chemical calculations. The catalytic effect of the metal oxides in PA 66 increases in the following order: PA 66 = PA 66 – Al2O3 < PA 66 – Fe2O3 < PA 66 – ZnO.
Keywords: PA 66; Metal oxide particles; Thermal degradation; Solid-phase extraction; Molecular modeling;
Fibroin degradation – Critical evaluation of conventional analytical methods by Monika A. Koperska; Dominika Pawcenis; Jakub M. Milczarek; Andrzej Blachecki; Tomasz Łojewski; Joanna Łojewska (357-367).
Due to their practical importance and widespread application in the studies of polymer degradation, the analytical methods: viscometry, colour and mass change, pH, mechanical strength were selected in this work so as to provide a macroscopic view of silk condition. The aim of the current work is to critically discuss the results obtained by these methods and confront them with the silk structure and degradation mechanism. They were differentiated with several criteria such as chemical (structural) information they bear, sensitivity to the changes induced by environment and their discriminative power. The results show that tensile strength before colour change and viscosity is the most sensitive method to measure silk degradation at various conditions. Significant colour change is typical of oxygen rich degradation atmosphere and was correlated with oxidation products of fibroin. Viscosity was shown to be hard to interpret in terms of mere changes of molecular mass as the most profound effects were observed in oxygen-rich conditions. Detailed research showed that oxygen plays an important role in silk degradation but it is only when combined with closed and humid conditions that results in catastrophic change.
Keywords: Fibroin; Artificial ageing; Viscosity; Tensile strength; Colour; CG-MS; pH; Degradation;
Hydrolytic and enzymatic degradation of flexible polymer networks comprising fatty acid derivatives by Jędrzej Skrobot; Wojciech Ignaczak; Miroslawa El Fray (368-376).
In this study a degradation process of flexible polymer networks fabricated from telechelic macromonomers comprising methacrylic functionalities and dimer fatty acid derivatives were discussed. Hydrolytic degradation in simulated body fluid (SBF) as well as enzymatic degradation with a lipase of six different systems comprising ester, anhydride and urethane bonds was investigated. In parallel, in order to make a comparison with other analogous polymeric systems, reference materials were also considered. The degradation process was monitored by determining the weight loss and water uptake, FT-IR analysis and changes in pH of degradation medium as a function of time. A rapid progress of degradation of the network containing anhydride bonds was observed. Furthermore, polymer networks showed low water absorption from 10 to 2 wt.%. Polymer networks did not release acidic degradation products in an amount that causes acidification of the medium except the anhydride network. The IR analysis of characteristic bands showed degradation of specific bonds leading to formation of possible hydrolysis products of these networks such as poly(methacrylic acid), macromonomer precursor molecules and derivatives of the macromonomers having terminal carboxylic and hydroxyl groups. We demonstrated that the referred polymeric networks undergo a controlled gradual degradation in the presence of lipase. This study provides an example of how the susceptibility of cross-linked polymers to degradation can be tailored by varying their molecular structure, depending on the needs.
Keywords: Polymer network; Cross-linked polymers; Fatty acid; Hydrolytic degradation; Enzymatic degradation;
Effects of lanthanum complex on the thermo-oxidative aging of natural rubber by Wei Zheng; Li Liu; Xiuying Zhao; Jingwei He; Ao Wang; Tung W. Chan; Sizhu Wu (377-383).
Novel mixed antioxidants composed of antioxidant IPPD and lanthanum (La) complex were added as a filler to form natural rubber (NR) composites. Mechanical testing was carried out before and after the thermo-oxidative aging of NR composites. Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) was performed to observe the variation of internal groups. The thermal and thermo-oxidative decomposition of NR were investigated by thermogravimetric (TG) curves, and the thermo-oxidative aging kinetic parameters were determined by the Flynn-Wall-Ozawa (FWO) method. The results showed that the thermo-oxidative degradation of NR composites was a two-stage reaction. Compared with the pure antioxidant IPPD, the same mass of mixed antioxidants had better effects to improve the mechanical properties of NR composites, reduce the formation of aging products, and increase the activation energies (E a ) of the thermo-oxidative degradation. Based on the autocatalytic, free radical chain reaction of the thermo-oxidative aging of NR, different function mechanisms of antioxidant IPPD and La complex were also compared. As a result of strong coordination abilities, large coordination numbers, and decomposition of the hydroperoxides, this new rare-earth antioxidant could indeed enhance the thermo-oxidative aging resistance of NR composites. This research has important significance for the exploitation of rubbers with high resistance to thermo-oxidative aging.
Keywords: Lanthanum (La); Rare earth complex; Thermo-oxidative aging; Antioxidant; Natural rubber (NR); Flynn-Wall-Ozawa (FWO) method;
Kinetics of the oxidative decomposition of potato-starch-g-poly(phenyl methacrylate) copolymers by Marta Worzakowska; Enelio Torres-Garcia; Marta Grochowicz (384-391).
The simultaneous TG-DSC-FTIR techniques were applied to study the thermo-oxidation of starch-g-poly(phenyl methacrylate) copolymers, using unmodified potato starch in order to compare the results. The study shows that the degradation of copolymers takes place in three large stages, between 150 and 600 °C. The main evolved volatile compounds were: H2O, CO2 and CO, in addition to a mixture of organic products. The kinetic analysis suggests that the initial degradation from all copolymers (between 245 and 250 °C) starts through a kinetic scheme of a reversible reaction, followed by an irreversible one, where the progressive decreasing of E(α) values, from ∼200 kJ mol−1 up to ∼150 kJ mol−1, reveals the auto-catalytic influence of an intermediary on the overall reaction rate. Subsequently, for α > 0.4 and temperatures higher than 300 °C, with E(α) values between 55 and 150 kJ mol−1, a complex set of competitive reactions linked to the secondary degradation of the graft suggests that both, the reaction mechanism and kinetic parameters are highly dependent on the conversion. For temperatures higher than 400 °C and α > 0.7, the direct gasification of carbonaceous residues occurs in at least two different energetic stages, with significant changes in the conversion dependence of the E(α) values, whose magnitudes and extents are highly dependent on the copolymer samples.
Keywords: Potato starch; Starch-g-copolymers; Oxidation; Kinetics; TG-FTIR;
Study of polypyrrole aging by XPS, FTIR and conductivity measurements by Jana Tabačiarová; Matej Mičušík; Pavol Fedorko; Mária Omastová (392-401).
Five different polypyrroles (PPys) with four different oxidants, namely, FeCl3, FeCl3·6H2O, Fe2(SO4)3, and (NH4)2S2O8, were prepared by chemical oxidative polymerization and studied during aging. In the case of FeCl3, the anionic surfactant dodecylbenzenesulfonic acid (DBSA) was used as a co-dopant to improve the stability. The prepared PPys were aged (>400 days) in ambient air at a temperature of 24 ± 2 °C in our laboratory, where they were not directly exposed to the sun. A clear increase in the oxygen content could be seen on the surface of all the prepared samples. There was no significant difference between PPy prepared using FeCl3 and FeCl3·6H2O as oxidants. The incorporation of the anionic surfactant dodecylbenzenesulfonic acid into the PPy structure did not lead to a longer effective conjugation length but did lead to the superior stability of the prepared PPy in ambient air. PPy prepared with Fe2(SO4)3 and (NH4)2S2O8 showed inferior stability of electrical conductivity among the samples studied. The samples were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared spectroscopy (FTIR), and elemental analysis (EA), and the chemical changes during aging were confronted with measurements of the electrical conductivity.
Keywords: Polypyrrole; Electrical conductivity; Degradation; Stability; XPS; FTIR; Chemical oxidative polymerization;
Annealing behavior and thermal stability of nanoporous polymer films based on high-performance Cyanate Ester Resins by Kristina Gusakova; Jean-Marc Saiter; Olga Grigoryeva; Fabrice Gouanve; Alexander Fainleib; Olga Starostenko; Daniel Grande (402-409).
The present study discloses the annealing behavior and thermal stability of nanoporous film materials based on Cyanate Ester Resins (CERs) obtained by the chemically induced phase separation technique through the use of porogenic molecules of different sizes and concentrations. Measurements were performed by means of thermogravimetric analysis in dynamic and isothermal modes as well as by Fourier Transform Infrared Spectroscopy. Isothermal annealing in the temperature range from 50 to 150 °C led to mass losses observed at temperatures far below the glass transition. Such mass losses were associated with desorption of moisture/water and residual porogen molecules trapped in the bulk. Therefore, these processes were described by diffusion laws, and the values of the basic kinetic parameters were determined. The results were correlated to the structure of the nanoporous CER-based networks derived from the extraction of different porogen molecules. Further, thermal-oxidative degradation occurred in the glass transition temperature domain (expected between 220 and 250 °C) during isothermal annealing at 250 °C.
Keywords: Cyanate Ester Resins; Polycyanurate; Nanoporous thermosets; Isothermal annealing; Thermal stability;
Nanoengineering of brucite@SiO2 for enhanced mechanical properties and flame retardant behaviors by Hongchang Pang; Xuesong Wang; Xingkun Zhu; Peng Tian; Guiling Ning (410-418).
An efficient halogen-free composite flame retardant (CFR) consisting of a brucite core and a thin SiO2 shell was synthesized via a facile nanoengineering route. The as-synthesized CFR was employed as a filler material to improve the mechanical performance and flame retardancy of EVA composite. In comparison with that of EVA/brucite and EVA/PM, the mechanical properties of EVA/CFR, especially the tensile strength (TS), presented a remarkable increase reaching at least a 25% increment. Meanwhile, with the same 50 wt% of fillers, the EVA/CFR formulation could achieve a limiting oxygen index (LOI) value of 34 (13% higher than that of EVA/PM blends) and UL-94 V-0 rating. Moreover, the heat release rate (HRR), peak heat release rate (PHRR), total heat released (THR), smoke production rate (SPR) and mass loss rate (MLR) were considerably reduced. Based on the results, the enhanced mechanism for the mechanical properties and flame resistance of CFR particles has been also proposed, which could be mainly ascribed to structural synergy between brucite core and SiO2 shell. Therefore, the nanoengineering of brucite@SiO2 might pave the way for the future development of a facile large-scale approach to brucite-based flame retardant materials.An efficient halogen-free composite flame retardant (CFR) consisting of a brucite core and a thin SiO2 shell was synthesized via a facile nanoengineering route. The as-synthesized CFR was employed as a filler material to improve the mechanical performance and flame retardancy of EVA composite, which could be mainly ascribed to structural synergy between brucite core and SiO2 shell.Display Omitted
Keywords: Brucite; SiO2; Mechanical properties; Flame retardant; Synergistic interaction; Nanoengineering;
Characterization of thermally aged polyetheretherketone fibres – mechanical, thermal, rheological and chemical property changes by Ville Mylläri; Tero-Petri Ruoko; Jyrki Vuorinen; Helge Lemmetyinen (419-426).
This paper investigates the effects of thermal degradation on polyetheretherketone (PEEK) fibres. PEEK samples were aged at a constant temperature of 250 °C for 1–128 days and characterized with mechanical tests, FTIR (Fourier Transform Infrared Spectroscopy), DSC (Differential Scanning Calorimetry), rheology, TGA (Thermogravimetric Analysis), SEM (Scanning Electron Microscopy), and UV–Vis diffuse reflectance spectroscopy. The short-term thermal annealing had a positive effect on the mechanical properties, due to the formation and growth of secondary crystals. Crosslinking in the material was verified by rheological inspections. The crosslinking increased the mechanical strength and modulus but reduced the elongation at break of the fibres. FTIR tests showed that carbonyl and hydroxyl groups were slowly formed on the surface of the fibres while ring opening reactions took place. The thermal ageing reduced the thermal stability of PEEK. The decreased stability was observed in the decomposition onset temperature after 8 d and in the melting point and the glass transition temperature after 32 d. The first signs of degradation, crosslinking, embrittlement, and reduced thermal stability, were visible roughly after 8 d of ageing, whereas the deterioration in general usability occurred after 64 d.
Keywords: PEEK; Fibre; Thermal degradation;
Effects of a novel phosphorus–nitrogen flame retardant on rosin-based rigid polyurethane foams by Meng Zhang; Zhenyang Luo; Jinwen Zhang; Shuigen Chen; Yonghong Zhou (427-434).
A novel phosphorus-nitrogen flame retardant (DOPO-BA) was synthesized from the condensation reaction of benzaldehyde, aniline and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). The structure of DOPO-BA was characterized by Fourier transform infrared spectrometry (FTIR), 1H NMR, 31P NMR, elemental analysis and thermogravimetric analysis (TGA). DOPO-BA was used as a flame retardant in the preparation of rosin-based rigid polyurethane foams (RPUFs). The effects of DOPO-BA addition on the mechanical, thermal, and flame-retardant properties of RPUF were investigated. The morphology of DOPO-BA filled RPUFs was characterized by scanning electron microscope (SEM). The results show that DOPO-BA rendered RPUF good physical, thermal stability and flame-retardant properties. Limiting oxygen index (LOI) value of RPUF containing 20 wt% DOPO-BA increased to 28.1% from 20.1% of the RPUF without DOPO-BA.
Keywords: Phosphorus–nitrogen flame retardant; DOPO; Rigid polyurethane foam; Rosin-derived polyol;
Selective degradation of biodegradable blends in simulated laboratory composting by Ramin Yousefzadeh Tabasi; Abdellah Ajji (435-442).
ATR-Fourier Transform infrared technique (ATR-FTIR) was used in combination with lab scale composting setup to investigate the selective composting of two-phase biodegradable blends based on Polylactic acid (PLA) or Polyhydroxybutyrate (PHB), toughened through melt blending with poly (butylene adipate-co-terephthalate) (PBAT), referred to as PLPT50 and PHPT50 respectively. All samples have been processed into films of 35 μm thickness by means of cast film process. The simulated lab scale composting setup with gas collection columns was used to measure cumulatively evolved CO2 gas as an indication of extent of biodegradation. The results from gas collection revealed a decrease in the rate of CO2 evolution as a consequence of blending. ATR-FTIR spectroscopy detected two distinctive C＝O ester bonds for PLPT50, PLA (1743 cm− 1)/PBAT (1710 cm− 1), and also PHPT50, PHB (1720 cm− 1)/PBAT (1710 cm− 1), indicating the phase separated morphology of blends. The absorption ratio of C＝O bond for PLA and PHB decreased gradually as a function of composting time leading to a decreased ratio of PLA/PBAT and PHB/PBAT ester bond absorption in the blends. SEM micrographs showed the formation of a porous three-dimensional (3D) network for both PLPT50 and PHPT50 through composting after 15 days. ATR-FTIR analysis shows that they are rich in PBAT content, thus indicating selective degradation of the PLA or PHB components in the blends. Investigation of the mechanical properties of the blends demonstrated a gradual loss of Young's modulus caused by the formation of defects through active microbial degradation and hydrolysis.
Keywords: Biodegradation; Polylactide; Poly(butylene adipate-co-terephthalate); Compost; Polyhydroxybutyrate; FTIR;