Polymer Degradation and Stability (v.84, #1)
Ultrasonic degradation studies of poly(ethylene oxide), poly(ethylene adipate) and poly(dimethylsiloxane) by Farah Kanwal; Richard A Pethrick (1-6).
Ultrasonic degradation studies on solutions of poly(ethylene adipate), poly(ethylene oxide) and poly(dimethylsiloxane) are reported. Measurements of the molar mass distribution using gel permeation chromatography indicate that there is little evidence for degradation in the shorter chain polymer materials. For the higher molar mass polymers, a progressive decrease in the number and weight average molar masses observed and the molar mass distribution was observed to progressively narrow with increase in the ultrasonic irradiation time. For the higher molecular weight polymers, a decrease in the viscosity of polymer solution was also observed with increasing irradiation time. Various mechanisms for the interpretation of the degradation process are considered and it is proposed that the degradation process is in part be connected with the changes that occur in the viscoelastic relaxation spectrum for the polymer solution with changes in the molecular weight distribution of the polymers being irradiated. The proposed mechanism is consistent with the observation of a lower limiting molar mass below which degradation does not occur.
Keywords: Ultrasonic; Degradation; Poly(dimethylsiloxane); Poly(ethylene oxide); Poly(ethylene adipate);
The effect of metals on thermal degradation of polyethylenes by L.M. Gorghiu; S. Jipa; T. Zaharescu; R. Setnescu; I. Mihalcea (7-11).
A chemiluminescence study on thermal degradation of some polyethylenes (LDPE, LLDPE, HDPE, UHMWPE) on seven metal trays in the presence of triazines as stabilisers was carried out. The kinetic effects of metals (Al, Zn, Ti, Mo, Mn, Fe and Cu) were assessed at 200 °C by the calculation of oxidation induction period, half-oxidation time, maximum oxidation time and rate in the propagation stage. Different sequences of catalytic effect provided by the studied metals in LDPE and HDPE are reported. A characteristic copper index for each metal was also calculated. Some considerations on the thermal stability of polyethylenes in intimate contact with metal surfaces are presented.
Keywords: Metals; Degradation; Polyethylenes; Chemiluminescence;
Thermal degradation of cellulose derivatives/starch blends and sisal fibre biocomposites by V.A. Alvarez; A. Vázquez (13-21).
Thermal analysis of cellulose derivatives/starch blends with different sisal short fibre content, were performed by TGA/DTGA under dynamic conditions. Apparent kinetic parameters were determined using a variety of conventional thermogravimetric methods. Two peaks were found: the first close to 334 °C and the second at 369 °C. The apparent activation energy value of the first peak slightly increased as well as the maximum temperature value. The apparent activation energy values for the second peak decreased as well as the maximum temperature value. The addition of the sisal fibres has not produced a high effect on the thermal degradation of the composites materials in comparison with the matrix alone.
Keywords: Thermal degradation; Thermal stability; Biodegradable polymer; Cellulose derivative/starch blend; Sisal fibre; Mathematical analysis;
Thermooxidative degradation of poly(vinyl chloride)/chlorinated polyethylene blends investigated by thermal analysis methods by Nataša Stipanelov Vrandečić; Ivka Klarić; Tonka Kovačić (23-30).
The thermooxidative degradation of poly(vinyl chloride)/chlorinated polyethylene (PVC/CPE) blends of various compositions was investigated by means of thermal analysis methods: differential scanning calorimetry (DSC) and thermogravimetry (TG). By using DSC it was found that all investigated PVC/CPE blends were heterogeneous. The main reaction of PVC degradation at moderate temperatures is dehydrochlorination, which is also a dominant reaction in CPE degradation. In spite of chemical similarity of the investigated polymers, thermooxidative stability and degradation mechanism are different. In order to evaluate the effect of CPE on the thermooxidative degradation of PVC in the blends, different criteria have been used. It was found that CPE had a stabilizing effect on thermooxidative degradation of PVC and interactions of blends components with their degradation products occurred.
Keywords: Differential scanning calorimetry; Polymeric modifiers; PVC/CPE blends; Thermogravimetry; Thermooxidative degradation;
Kinetics of thermooxidative degradation of poly(vinyl chloride)/chlorinated polyethylene blends by Nataša Stipanelov Vrandečić; Ivka Klarić; Tonka Kovačić (31-39).
The thermooxidative degradation of poly(vinyl chloride)/chlorinated polyethylene blends of different compositions was investigated by means of dynamic thermogravimetry in flowing atmosphere of synthetic air in temperature range 50–650 °C. Kinetic analysis was applied to the first basic degradation step (up to 400 °C) where the main degradation processes were the dehydrochlorination of PVC and CPE. For calculation of the apparent activation energy and apparent preexponential factor three kinetic methods were compared: integral Kissinger method, integral isoconversional Kissinger–Akahira–Sunose method and differential isoconversional Friedman method. The existence of the true or false compensation effect is discussed.
Keywords: Kinetic analysis; Polymeric modifiers; PVC/CPE blends; Thermogravimetry; Thermooxidative degradation;
Thermal and hydrolytic degradation behaviour of degradable poly(etheresteramide) copolymers based on ϵ-caprolactone, 11-aminoundecanoic acid, and poly(ethylene glycol) by ZhiYong Qian; Sai Li; Yi He; XiaoBo Liu (41-47).
A new kind of aliphatic polyetheresteramide copolymers (PEEAs) based on ϵ-caprolactone, 11-aminoundecanoic acid, and poly(ethylene glycol) (PEG) were synthesized by melt polycondensation. The thermal and hydrolytic degradation behaviour of these copolymers was studied using FTIR, 1H-NMR, and TGA. PEG content, thickness of the test sample, and pH of degradation medium have great effect on degradation rate. The degradation rate increased with PEG content and pH, but decreased with thickness of the test sample.
Keywords: Polyetheresteramide; Degradable polymer; Thermal degradation; Hydrolytic degradation; TG;
Influence of metals on the phenol–formaldehyde resin degradation in friction composites by Monika Křı́stková; Peter Filip; Zdeněk Weiss; Rudolf Peter (49-60).
Degradation process and influence of metal particles (Cu, Fe, CuZn) on the stability of acid catalyzed (novolak) phenolic resin during curing and friction process in friction composites have been studied. Using TGA, FTIR and Py-GC methods, the significant influence of copper and iron chips, in case of high metal concentrations, on degradation process during curing of novolac phenolic resin has been found. The same behavior was confirmed for friction process. It follows that copper and iron can act as catalysts and therefore the model mechanisms for metal catalysis were proposed. The key role in the phenolic resin degradation process belongs to the elimination of formaldehyde, as an important curing agent, caused by metal and metal oxide catalysis. Brass (CuZn) does not influence the stability regardless of concentration but the wear characteristics after friction process of brass containing samples were extremely high if compared to other ones. Brass influence is rather physical as chemical owing to formation of ZnO and consequent degradation of fiber/resin interface. This caused that CuZn particles were released from the matrix and a high porosity on the friction surface was observed.
Keywords: Phenol-formaldehyde resin; Friction composite; Thermal degradation;
Effect of joint action of high pressure and shear deformation on mechanical degradation of isotactic polypropylene by L.V Kompaniets; S.A Kuptsov; N.A Erina; I.L Dubnikova; A.A Zharov; E.V Prut (61-68).
The degradation of isotactic polypropylene (iPP) subjected to the joint action of high pressure of 1, 2, and 5 GPa and shear deformation on the Bridgman anvils was evaluated by following the changes in the molecular weight distribution curves obtained by gel-permeation chromatography. It was shown that Mw and Mn values decrease with shear deformation. The melting behavior of isotactic polypropylene samples treated under high pressure and shear deformation was studied by differential scanning calorimetry. The melting temperature was found to decrease linearly with number-average molecular weight decreasing. The changes in thermodynamic parameters for various iPP samples were accounted for differences in molecular weight. The tensile mechanical behavior of iPP samples subjected to the joint action of high pressure and shear deformation followed by repressing at 190 and 220 °C was investigated. It was found that the drawability of such samples is controlled by molecular weight and polymer morphology. It was shown that the lower is the repressing temperature, the lower the plastic deformability.
Keywords: Isotactic polypropylene degradation; Molecular weight distribution; Melting behavior; Tensile mechanical behavior;
The effect of different siloxane chain-extenders on the thermal degradation and stability of segmented polyurethanes by F.S Chuang; W.C Tsen; Y.C Shu (69-77).
The thermal degradation and stability of siloxane-containing segmented polyurethane and poly(urethane-urea) polymers (OH-SiPU and NH2-SiPU), both prepared from 4,4′-diphenylmethane diisocyanate (MDI), polytetramethylene ether glycol (PTMG) and silicon-containing chain-extenders, have been studied by thermogravimetric analysis (TGA) and Ozawa-Flynn kinetic analysis. The analyses identically revealed that OH-SiPU and NH2-SiPU polymers showed two stages of thermal degradation. The thermal stability and degradation depended on the kinds of hard and soft segment in the backbone of the polymers. The OH-SiPU polymers whose hard segment consists of siloxane-urethane displayed more thermal stability than the NH2-SiPU polymers, whose hard segment consist of siloxane-urea, in the initial degradation at the first stage of reaction (stage I). However, NH2-SiPU polymers were more thermally stable than OH-SiPU polymers and typical polyurethane as the weight loss went beyond about 5 wt.%. The length of the soft segment (PTMG molecular weight) affected the thermal stability of these polymers at various stage of degradation: polymers with a long soft segment had a high thermal stability in stage I, and those with a short soft segment had a higher thermal stability in the second stage of degradation (stage II). The Ozawa method was used to evaluate the activation the energies (Ea) of the whole process of degradation and the average activation energy (Ea,av) in each stage of degradation. The Ea and Ea,av values determined for the OH-SiPU and NH2-SiPU polymers according to the Ozawa method corresponds with the TG and DTG curve displaying the character of the degradation.
Keywords: Siloxane; Polyurethane; Thermal degradation; Stability;
Effects of pressure on the degradation of poly(vinyl chloride) by T. Kamo; Y. Kodera; Y. Sato; S. Kushiyama (79-85).
Poly(vinyl chloride) was decomposed for 0–90 min at 300–440 °C under 0–6.0 MPa of nitrogen pressure. Hydrogen chloride, liquid products, and residue were the main decomposition products. The yield of liquid products decreased with increasing reaction pressure, whereas the yield of residue increased, reaching maxima at 9.8 MPa (400 °C) and 22.4 MPa (440 °C). The pressure dependences of the product distribution and atomic ratio of hydrogen to carbon (H/C) imply that some of the liquid products were polycondensed with the dehydrochlorinated PVC and were retained in the residue under high-pressure. At atmospheric pressure, benzene was the predominant product. The yield of benzene decreased sharply with pressure, whereas the yield of linear paraffins increased significantly. The liquid product distribution suggests that polyene chains in the dehydrochlorinated PVC were converted to benzene and alkylbenzene under atmospheric pressure. However, some of the polyene chains underwent hydrogenation to form linear paraffins under high pressure.
Keywords: PVC; Pressure dependence; Reaction mechanism; Paraffin;
Enhancement of thermal stability of polystyrene and poly(methyl methacrylate) by cyclotriphosphazene derivatives by Takahito Muraki; Masahiro Ueta; Eiji Ihara; Kenzo Inoue (87-93).
The thermal stability and degradation behavior of polystyrene (PSt) and poly(methyl methacrylate) (PMMA) blended with organic cyclotriphosphazenes (N3P3(OR)6) were investigated by thermogravimetric analysis and gel permeation chromatography. The thermal degradation behaviors of polymers are strongly dependent on the organic groups attached to the phosphazene ring (R: S-4,-C6H3(-OCH2O-); S-5,-C6H4CH2OPO(OPh)2; S-6,-C6H4OPO(OPh)2; S-7,-C6H4OCH2OCH3). The onset temperature of decomposition (T 0) of PSt increased from 303 °C to 351 °C in air by the addition of 5 wt.% S-4, whereas S-6 has no ability to increase T 0 value of PSt. The GPC traces of PSt/S-4 film heated at 180 °C for 30 min in air showed no significant decrease of molecular weight of PSt. A similar enhancement of thermal stability was observed for the PMMA/S-4 system. From the reaction of radical initiators with S-4, it appears that –OCH2O– group in S-4 acts as an effective trapping site of peroxy radical. As expected, the physical loss of S-4 with molecular weight increased by using cyclotriphosphazene core from PSt film was significantly suppressed, i.e., the diffusion coefficient of S-4 was three orders of magnitude smaller than that of 3,4-methylenedioxyphenol (MOP). The enhancement of thermal stability of PSt and PMMA blended with cyclotriphosphazene derivatives were described.
Keywords: Cyclotriphosphazene; Thermal stabilizers; Polystyrene; Poly(methyl methacrylate);
Enzymatic degradation behavior of comonomer compositionally fractionated bacterial poly(3-hydroxybutyrate-co-3-hydroxyvalerate)s by poly(3-hydroxyalkanoate) depolymerases isolated from Ralstonia pickettii T1 and Acidovorax sp. TP4 by Lidan Feng; Yi Wang; Yasuhide Inagawa; Kenichi Kasuya; Terumi Saito; Yoshiharu Doi; Yoshio Inoue (95-104).
The enzymatic hydrolysis behavior of compositionally well-fractionated bacterial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] with 3HV-unit content from 8 to 98 mol% and bacterial poly(3-hydroxybutyrate) [P(3HB)] has been investigated in the presence of poly(3-hydroxyalkanoate) depolymerases isolated from Ralstonia pickettii T1 and Acidovorax sp. TP4. The water-soluble degradation products were characterized by HPLC and 1H NMR spectroscopy. P(3HB-co-3HV)s with the whole range of 3HV-unit content can be degraded by R. pickettii T1 depolymerase, while only P(3HB-co-3HV)s with 3HV-unit content less than 80 mol% can be degraded by Acidovorax sp. TP4 depolymerase. It was found that the enzymatic degradation behavior of fractionated P(3HB-co-3HV)s was affected not only by the comonomer unit composition and its distribution but also by the solid-state structure of P(3HB-co-3HV)s and further by the bacterial source of depolymerases. Based on the results, the mechanism of enzymatic degradation was discussed.
Keywords: Copolyester; Poly(hydroxyalkanoate); Biodegradation; PHA depolymerases;
Temperature dependence of the molecular motion in the crystalline region of biodegradable poly(butylene adipate), poly(ethylene succinate), and poly(butylene succinate) by Kazuhiro Kuwabara; Zhihua Gan; Takashi Nakamura; Hideki Abe; Yoshiharu Doi (105-114).
The information on molecular dynamics in solid-state polymers is of importance for controlling mechanical strength, processibility, and biodegradability. In our former article, molecular motion in the crystalline region of poly(butylene succinate) (PBS) and poly(butylene succinate-co-20 mol% butylene adipate) [P(BS-co-20 mol% BA)] at room temperature have been analyzed by 13C spin-lattice relaxation behavior (T 1C relaxation behavior). In the present study, at first, molecular motion at room temperature in the crystalline region of poly(butylene adipate) (PBA) and poly(ethylene succinate) (PES) have been investigated by the same T 1C method. As the result, it has been found that both the PBA and PES samples include two crystalline components with different molecular mobility. The rigid crystalline component is assignable to inner crystalline region (core of crystalline region) and the relatively mobile crystalline component is ascribed to interfacial crystalline region (crystalline region near amorphous area). To investigate the temperature dependence of molecular mobility, variable temperature T 1C measurements have been carried out for PBA, PES, and PBS samples. With increasing the temperature, remarkable change in molecular mobility has been seen in PBS sample. PES sample has also showed the increase in molecular mobility but the amount of the change has been smaller than that of PBS In PBA, the molecular mobility reflected in T 1C is almost independent of temperature. The significant molecular motion peculiar in PBS has been discussed.
Keywords: Poly(butylene adipate); Poly(ethylene succinate); Poly(butylene succinate); Biodegradable; Solid-state 13C NMR;
Degradation of poly(ethylene succinate) by mesophilic bacteria by Yoko Tezuka; Nariaki Ishii; Ken-ichi Kasuya; Hiroshi Mitomo (115-121).
We report for the first time the mesophilic poly(ethylene succinate)(PESu)-degrading microorganisms isolated from aquatic and soil environments. The degrading isolates were classified into two groups, Gram-positive bacterium and fungus. Phylogenetic analysis revealed that the degrading bacteria belong to the genera Bacillus and Paenibacillus. Thus, PESu may be degraded by very limited species in natural environments. Furthermore, strain KT 1012 which could degrade PESu film at the fastest rate among the degrading bacteria in this study was characterized in detail. The DNA G+C content was 40.4 mol% and iso-C15:0 was the major fatty acid. The temperature optima for growth was approximately 40–45 °C. The phenotypic properties and the phylogenetic inference indicate that strain KT1012 is a related species to Bacillus pumilus. Strain KT1012 did not hydrolyze poly(lactic acid), poly(butylene succinate), poly(3-hydoroxybutyrate) but hydrolyzed PESu, poly(ϵ-caprolactone) films and olive oil. Strain KT1012 exhibited a high PESu hydrolytic activity in liquid culture when it was cultivated on a nutrient rich medium such as LB medium, suggesting that the hydrolytic activity is not expressed inducibly but constitutively in strain KT1012.
Keywords: PESu; Mesophilic bacteria; Biodegradation; Bacillus; Phylogenetic analysis; Biodegradable polymer;
Liquid-phase catalytic degradation of mixtures of waste high-density polyethylene and polystyrene over spent FCC catalyst. Effect of mixing proportions of reactants by Kyong-Hwan Lee; Dae-Hyun Shin; Young-Hwa Seo (123-127).
The catalytic degradation of waste high-density polyethylene (HDPE) and polystyrene (PS) mixtures with a different mixing proportions over spent FCC catalyst has been studied using a stirred semi-batch reactor at 400 °C. The cumulative amount distribution, the degradation rate into liquid products, the carbon number distribution, and the paraffin, olefin, naphthene and aromatic (PONA) distribution in the liquid product were determined as a function of time or mixing proportion of reactants. The cumulative amount distribution of liquid product depended on the mixing proportion of both HDPE and PS. The degradation rate in the range of initial lapsed time (initial degradation rate) increased exponentially with PS content whereas that for the range of final lapsed time (final degradation rate) increased slowly with HDPE content. An increase of PS content in the reactants showed an increase of gasoline fraction, from about 85 wt.% (0 wt.% PS content) to about 98 wt.% (100 wt.% PS content). Liquid PONA product distributions revealed the interaction of the degraded intermediates from HDPE and PS degradation. The addition of PS to the catalytic degradation of HDPE accelerated the production of aromatic components with mono-cyclic species in liquid products and moreover showed the highest selectivity of above 60 wt.% for ethylbenzene and styrene (C2 benzene) in aromatic products
Keywords: Mixture (HDPE, PS); Catalytic degradation; Spent FCC catalyst; Liquid product composition;
Effects of culture conditions on the composition of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) synthesized by Comamonas acidovorans by Wing-Hin Lee; Mohd N.M. Azizan; Kumar Sudesh (129-134).
Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] copolymers containing 0–96 mol% 4HB monomers were produced by Comamonas acidovorans when cultivated on a mixture of glucose and 1,4-butanediol. In addition up to 53 wt.% of the dry cell weight (DCW) poly(3-hydroxybutyrate) [P(3HB)] was accumulated from two-stage cultures using glucose as the sole carbon source. This large accumulation of P(3HB) was achieved because glucose was also added to the first-stage of cell biomass production. Glucose addition to the first-stage did not result in significant accumulation of P(3HB) in the first-stage (<2 wt.% of the DCW) but is probably important in the induction of enzymes involved in glucose uptake and metabolism. By employing this strategy of glucose induction it is shown that C. acidovorans can produce more than 40 wt.% of the DCW P(3HB-co-4HB) from a mixture of glucose and 1,4-butanediol in two-stage cultivation. The copolymer composition can further be controlled by changing the concentrations of the carbon sources. In addition, factors such as pH, inoculum concentration and aeration significantly affected the composition of P(3HB-co-4HB).
Keywords: Polyhydroxyalkanoates; 4-Hydroxybutyrate; Comamonas acidovorans; 1,4-Butanediol;
Molecular mobility and crystalline phase structure of biodegradable poly[(R)-3-hydroxybutylic acid-co-(R)-3-hydroxyhexanoic acid] by Kazuhiro Kuwabara; Zhihua Gan; Takashi Nakamura; Hideki Abe; Yoshiharu Doi (135-141).
Solid-state 13C NMR analyses have been carried out on the temperature dependence of the molecular mobility and phase structure of biodegradable poly[(R)-3-hydroxybutyric acid-co-(R)-3-hydroxyhexanoic acid] [P(3HB-co-3HH)] copolyesters. 13C spin-lattice relaxation time (T 1C) experiments for the main chain CH and CH2 carbons have shown the existence of two components with different T 1C values for each carbon. This T 1C result is in accord with the previous T 1C results for poly[(R)-3-hydroxybutyric acid] [P(3HB)] homopolymer and other P(3HB)-type random copolyesters. In previous papers, however, the assignment of the two components with different T 1C values have been remained unsolved. In this study, by performing variable-temperature experiments and by comparing with the results of other partially crystalline polymers, we have investigated the assignment of the two components in detail. As the results, it has been concluded that both the two components are crystalline components. The crystalline component with longer T 1C value is assignable to the internal region of crystalline lamellae and the shorter T 1C component is ascribed to the interfacial crystalline region near amorphous phase. T 1C analyses have also detected the gradual increase in molecular mobility with an increase of temperature. When compared with the previous T 1C results for poly(butylene adipate) (PBA), poly(ethylene succinate) (PES), and poly(butylene succinate) (PBS), the tendency of the temperature change observed for P(3HB-co-3HH) has been close to that for PES.
Keywords: Poly[(R)-3-hydroxybutylic acid-co-(R)-3-hydroxyhexanoic acid]; Biodegradable; Solid-state 13C NMR; Phase structure; Crystal;
Thermal stability of poly (l-lactide): influence of end protection by acetyl group by Yujiang Fan; Haruo Nishida; Yoshihito Shirai; Takeshi Endo (143-149).
Thermal stability of end-protected poly (l-lactide) (PLLA) was studied by dynamic thermal degradation and pyrolyzate analyses. The treatment of PLLA by acetic anhydride resulted in the acetylation of end hydroxyl groups, and at the same time a decrease in the residual Sn content in the polymer. The thermal degradation of the acetylated PLLA-Ac showed a shift to a 40–50 °C higher degradation temperature range than that of untreated, high Sn content PLLA, but exhibited nearly the same degradation behavior as the untreated PLLA with a comparable Sn content. Purified metal-free PLLA-H showed good thermal stability, having the highest degradation temperature range. Interestingly, despite the end-protection, the acetylated metal-free PLLA-H/Ac decomposed at almost the same temperature as that of PLLA-H. From pyrolyzate and kinetic analyses, it was found that the contribution of the hydroxyl-end acetylation to the stability of PLLA was negligible, except for the stabilization effect due to the elimination of residual Sn during the acetylation process.
Keywords: Poly (l-lactide); Poly (l-lactic acid); PLLA; Thermal degradation; Thermal stability; Pyrolysis; End-protection; Acetylation; Kinetics;
Determination of end-group structures and by-products of synthesis of poly(α,β-malic acid) by direct polycondensation by Tetsuto Kajiyama; Hisatoshi Kobayashi; Kazuko Morisaku; Tetsushi Taguchi; Kazunori Kataoka; Junzo Tanaka (151-157).
We studied the synthesis of high molecular weight α,β-PMA derivatives by direct polycondensation to fabricate α,β-PMA for medical use. The terminal group of the polyester is important because it significantly influences hydrolysis of the main polymer chain. The molecular weight of about 4000 compounds at a variety of temperatures showed that the terminal olefinic group ratio changed from 0.23 at 110 °C to 0.30 at 120 °C and 0.60 at 130 °C. The highest α,β-PMA molecular weight, 5300, synthesized by direct polycondensation had a terminal hydroxy group ratio of 0.57. The main by-product of these reactions was unreacted l-malic acid at 110 °C and fumaric acid at 130 °C. The fumaric acid ratio of by-products increased with reaction time. We clearly determined the reaction mechanism for l-malic acid at 110–130 °C.
Keywords: Poly(α,β-malic acid); Direct polycondensation; l-malic acid; Fumaric acid; Terminal group; By-product;
Thermal degradation and flame retardancy of hexaacrylated/hexaethoxyl cyclophosphazene and their blends with epoxy acrylate by Jun Ding; Wenfang Shi (159-165).
Two kinds of cyclophosphazenes, bearing UV-reactive acrylic groups (HACP) and non-reactive ethyl groups (HECP), respectively, were synthesized, and characterized by FTIR, 1H-, and 13C-NMR. These compounds were used as flame retardants to blend with commercial UV-curable epoxy acrylate EB600. The thermal behavior and degradation mechanism were monitored by TGA, in-situ FTIR and apparent activation energy calculation. The UV cured blends showed better thermal stability at elevated temperature with higher char yields compared with pure EB600 sample. The flame retardancy of the blends was examined by LOI measurements, and has shown that the blends with HACP or HACP powder have higher LOI than that with HECP.
Keywords: Cyclophosphazene; Thermal degradation; Flame retardancy; UV curing;
Thermal degradation of photo-polymerized BisGMA/TEGDMA-based dental resins by Wataru Teshima; Yuji Nomura; Atsuharu Ikeda; Toshiya Kawahara; Masayuki Okazaki; Yukinori Nahara (167-172).
The thermal behavior of BisGMA/TEGDMA-based dental resins of various degrees of conversion was examined using differential scanning calorimetry (DSC), thermogravimetric-gas chromatography mass spectrometry (TG-GC/MS), and thermogravimetric-mass spectrometry (TG-MS). This study identified pyrolysates of BisGMA/TEGDMA copolymers from mass spectra. Three phases (initial, second, and final phases) of thermal degradation appeared in the TGA and derivative TGA (dTGA) curves. The thermal degradation mechanism in each phase was explained by the thermal behavior of four pyrolysates: methacrylic acid, 2-hydroxyethel methacrylate, propionic acid, and phenol. The thermal characteristics of copolymers of various degrees of conversion were determined from the temperatures at the intersections of the curves of the second and final phase separated from dTGA curves. Regression analysis revealed a very strong correlation (R 2=0.942) between the degree of copolymer conversion and the temperature at the intersection.
Keywords: BisGMA/TEGDMA; Copolymers; Degree of conversion; TG-GC/MS; TG-MS;
Thermal degradation kinetics of vinyl polyperoxide copolymers by G Sivalingam; Priyadarsi De; R Karthik; Giridhar Madras (173-179).
The thermal degradation of various vinyl polyperoxides (poly(styrene peroxide) [PSP], poly(methyl methacrylate peroxide) [PMMAP], poly(α-methyl styrene peroxide) [PAMSP]) and their binary copolyperoxides (PSP-PAMSP [SA], PSP-PMMAP [SM], PAMSP-PMMAP [AM]) were studied in a Thermogravimetric Analyzer (TGA). The thermal stability of the polyperoxides is in the order of PMMAP>SM>AM>SA>PSP>PAMSP. The addition of PAMSP to PSP showed a synergistic effect with higher thermal stability of the copolymer while the addition of PAMSP or PSP to PMMAP did not affect the thermal degradation of the copolymers. A method based on regression was proposed to determine the degradation parameters. The activation energies of degradation for the homopolyperoxides and copolyperoxides were determined by various methods and found in agreement with each other.
Keywords: Vinyl polyperoxides; Copolyperoxides; Activation energies; Rate coefficients; Linear regression method; Thermal degradation;
Calendar of events (181-182).