Thermal decomposition of poly(butylene terephthalate)

Detailed results of the overall thermal degradation of poly(butylene terephthalate) are reported. Laser microprobe analysis and dynamic mass spectrometric techniques were used to identify the primary volatile degradation products and initial pyrolysis reactions that control polymer degradation. A complex multistage decomposition mechanism was observed which involves two major reaction pathways. Initial degradation occurs by an ionic decomposition process that results in the evolution of tetrahydrofuran. This is followed by concerted ester pyrolysis reactions that involve an intermediate cyclic transition state and yield 1,3-butadiene. Simultaneous decarboxylation reactions occur in both decomposition regimes. Finally, the latter stages of polymer decomposition were characterized by evolution of CO and complex aromatic species such as toluene, benzoic acid, and terephthalic acid. Activation energies of formation for the main pyrolysis products were determined from the dynamic measurements of the major ion species and indicate values of E = 27.9 kcal/mole for the production of tetrahydrofuran and E = 49.7 kcal/mole for the production of butadiene.     

Thermal decomposition of poly(sec-amyl methacrylate)

The thermal decomposition of poly(sec-amyl methacrylate) is studied by simultaneous thermogravimetry–gas chromatography–mass spectrometry and by pyrolysis–gas chromatography. The TG curve has four distinct breaks and a plateau. Results of the identification of the evolved gas at the individual breaks by GC–MS techniques lead to the conclusion that these breaks correspond to the individual processes in the decomposition mechanism like that of poly(tert-butyl methacrylate): the first break, the depolymerization initiated at the unsaturated chain ends; the second break, the depolymerization initiated at the saturated chain ends; the third break, the ester decomposition; the plateau, the inhibition of decomposition by the formation of poly(methacrylic anhydride); the fourth break, the decomposition of poly(methacrylic anhydride). The extent of ester decomposition is related to the substituent constants based on Hammett equation. The ester decomposition product is separated into three pentene isomers by pyrolysis–gas chromatography: trans-2-pentene, cis-2-pentene, and 1-pentene. As raising decomposition temperature, the composition ratio of trans-2-pentene decreases and becomes constant above 620 K, and the composition ratios of cis-2-pentene and 1-pentene increase and also become constant above 620 K. These results are accounted for by mobility of atoms included in the substituent at forming a ring transition state.     

Thermal decomposition products of poly(vinyl alcohol)

The thermal decomposition of poly(vinyl alcohol) is known to occur in two stages. In a study of first-stage decomposition, this polymer was pyrolyzed in vacuum at 240°C for 4 hr and the products were determined by using gas chromatography. The main products were water, aldehydes having the general formula and methyl ketones having the formula , where n = 0, 1, 2, 3, etc. Mechanisms for the formation of these carbonyl compounds are discussed.     

Thermal decomposition of poly(1,4-dioxan-2-one)

To evaluate the feasibility of poly(1,4-dioxan-2-one) (PPDO) as a feed stock recycling material, the pyrolysis kinetics of PPDO were investigated. The pyrolysis of PPDO exclusively resulted in the distillation of 1,4-dioxan-2-one (PDO). From thermogravimetric measurements conducted at different heating rates, the kinetic parameters of the pyrolysis: activation energy, E_a=127 kJ mol⁻¹; order of reaction, n=0; and pre-exponential factor, A=2.3×10⁹ s⁻¹, were estimated by plural analytical methods. The estimates show that the decomposition of PPDO proceeds by unzipping depolymerization as main reaction and random degradation process with lower E_a and A values. Equivalent isothermal degradation curves calculated from the thermogravimetric curves were supported by experimental isothermal degradation data. The calculation that PPDO is converted smoothly into PDO at 270°C agrees with the reported ceiling temperature of PPDO.     

Thermal decomposition of tert-butyl ester of triethylsilylperacetic acid

Conclusions A study was made of the decomposition products of the tert-butyl ester of triethylsilylperacetic acid in cumene, n-nonane and tetraethylstannane. In the latter case the processes of generating the free radicals (C₂H₅)₃SiCH₂COO and (CH₃)₃CO, and their subsequent decomposition, are markedly suppressed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1542–1544, July, 1971.     

Thermal decomposition behaviour of cobalt(II)-picolyl-terminated poly(dimethylsiloxane)

Thermal, chemical and rheological properties of ultraviolet aged asphalt binder were characterized by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) and dynamic shear rheometer (DSR), respectively. Asphalt binder samples were made with different film thickness (50, 100, 200 and 500 μm) and suffered different ageing time (0, 48, 96 and 144 h), at a certain UV radiant intensity of 20 w m^–2 in a self-made accelerated ageing oven. The results indicate that the UV light ageing would lead to the improvement of thermal behavior and the growth of the glass transition temperature of asphalt binder. This type of ageing can be also reflected from the FTIR spectra in terms of the characteristic peaks of the carbonyl groups and sulphoxides. The UV light ageing can change some rheological parameters of asphalt binder, such as complex modulus and phase angle. The ageing degrees of asphalt binder by this type of ageing test are mainly related to the ageing time and film thickness of the sample.     

Induced decomposition of di(tert-butyl)trioxide

Thermal decomposition of di(tert-butyl)trioxide (Bu^tOOOBu^t) in a wide range of concentrations was studied by visible and IR chemiluminescence. Induced decomposition of Bu^tOOOBu^t caused by its reaction with the peroxy radicals formed in the solvent (CH₂Cl₂) was found and investigated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 924–927, May, 1997.     

Thermal decomposition of solid state poly(β-L-malic acid)

Thermal decomposition process of solid state poly(β -L-malic acid) was traced by DSC combined with FT-IR. Melting temperature of this partially crystallized polymer was detected at 46-60°C. The thermal decomposition initiated at ca 185°C accompanied by an evolution of gaseous products. In contrast to the cleavage reaction in the aqueous polymer solutions which gives L-malic acid and corresponding dimer of L-malic acid, the solid state poly(β -L-malic acid) decomposed at above the decomposition temperature giving not the constituent L-malic acid but fumaric acid at the first stage of the reaction then, maleic and maleic anhydride. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal decomposition of microbial poly(γ-glutamic acid) and poly(γ-glutamate)s

The thermal decomposition of poly(γ-glutamic acid), poly(α-methyl γ-glutamate) and ionic complexes of the polyacid with alkyltrimethyl ammonium salts was studied by TGA, GPC, and FTIR and NMR spectroscopies. It was found that both poly(γ-glutamic acid) and poly(α-methyl γ-glutamate) depolymerised above 200 °C by unzipping mechanism with generation of pyroglutamic acid and methyl pyroglutamate, respectively. On the other hand, the ionic complexes degraded through a two-stage process, the first stage being cyclodepolymerisation of the poly(γ-glutamate) main chain along with decomposition of the ionic complex promoted by the adsorbed water. Decomposition of the previously generated alkyltrimethyl ammonium compound followed by unspecific cracking of the resulting nitrogenated compounds accounted for the second degradation step, at higher temperatures. Mechanisms explaining the decomposition of the three studied systems were proposed according to collected data.     

Thermal decomposition behavior of poly(propylene carbonate) in poly(propylene carbonate)/poly(vinyl alcohol) blend

Journal of Thermal Analysis and Calorimetry - To provide guidance for the practical thermal processing and applications of poly(propylene carbonate)/poly(vinyl alcohol) (PPC/PVA) blend, an...     

Kinetics of radical decomposition of di(tert-butyl) trioxide

The kinetics of radical decomposition of di(tert-butyl) trioxide was studied by spectrophotometry from the consumption of an acceptor of free radicals, 2,6-di(tert-butyl)-4-methylphenol, in CFCl₃ and CH₂Cl₂ (in the latter case, in the presence of 0.1M Bu^tOOH). The activation parameters of the reaction (log(A/s ⁻¹)=14.8±1.2 and 14.1±1.6,E _a=21.6±1.4 and 20.1±1.9 kcal mol⁻¹ in CFCl₃ and CH₂Cl₂, respectively) and the probability of radical escape to the bulk (e=0.9±0.1) were determined. The known experimental and calculated values of the O−OO bond strength in trioxides were analyzed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 61–65, January, 1999.     

Reactions of cationic living poly(tert-butyl aziridine)

The cationic polymerization of N-tert-butyl aziridine (TBA) can be conducted in such a way that the rate of termination is much slower than the rate of propagation, thus permitting preparation of a corresponding polymer which is “temporarily living”. Reactions of N-methyl-N-tert-butyl aziridinium triflate (which is the model for the active species of the living polymer) with different nucleophiles show that, at room temperature, the aziridinium ring reacts almost instantaneously with nucleophiles to form the corresponding ring-opened product. Analogous reactions with the aziridinium end group of living poly-TBA lead to polymers with varying end groups such as hydroxy, ester, primary, secondary or tertiary amino, halogen, and others. End group analysis by means of 360-MHz ¹H-NMR nuclear magnetic resonance spectroscopy showed that the concentration of the end groups was in all cases equal to the concentration of the methyl head group, originating form the initiation reaction, if the terminating nucleophile was added five minutes after initiation (at 15°C). Under these conditions the polymerization is quantitative for initiator concentrations down to 0.01 mol L^?1.     

Thermal decomposition of poly(vinylidene chloride) prepared in presence of oxygen

The thermal decomposition of poly(vinylidene chloride) was studied for samples prepared in the presence of oxygen. The products from both mass and aqueous suspension polymerizations show two modes of thermal decomposition. A rapid initial mode varies in rate and extent with the amount of oxygen present. A slower mode is unaffected by oxygen and in similar in rate to the polymer made in the absence of oxygen. The chief volatile products are phosgene and formaldehyde for the rapid decomposition and hydrogen chloride for the slow decomposition. The rapid decomposition is interpreted to be an unzipping reaction of a vinylidene chloride–oxygen alternating copolymer initiated by homolysis of a peroxide bond. The absence of significant amounts of hydrogen chloride during this stage of decomposition shows that none of the free radicals generated are capable of initiating a chain reaction that would unzip hydrogen chloride from the poly(vinylidene chloride) backbone. The presence of oxygen during the aqueous suspension polymerization correlates with the generation of hydrochloric acid in the aqueous phase. By analogy with the high temperature decomposition, the hydrochloric acid is believed to result primarily from the hydrolysis of phosgene produced by partial decomposition of the polyperoxide. Initiation of the decomposition is believed due to a reaction of the chain propagating radical.     

Thermal decomposition of glassy poly(di-t-butyl fumarate) as a topochemical reaction

Decomposition of t-butyl carboxylate (TBC) groups in a glassy poly(di-t-butyl fumarate) (PDTBF) at 140–170°C proceeds with a sharp acceleration caused by interchain interaction of TBC and carboxylic groups. According to selective dissolution data, at 70% degree of conversion the reaction system contains both unchanged PDTBF and a final product: poly(fumaric acid). For TBC groups decomposition in di-t-butyl fumarate (DTBF)–styrene copolymers above their T_g an apparent rate constant of autocatalysis increases with the increase of DTBF content in copolymer. Together with previously obtained x-ray data these results lead to conclusions about the topochemical character of the PDTBF decomposition. The mechanism suggested includes thermal decomposition of TBC groups (initiation), autocatalytic growth of spheric clusters up to a critical size (an appearance of primary germs of the new phase), and growth and branching of thread-like germs. A mathematical model based on these assumptions describes quantitatively the kinetic data. © 1993 John Wiley & Sons, Inc.     

Thermal decomposition of poly(vinyl chloride) and chlorinated poly(vinyl chloride). II. Organic analysis

A concerted study of poly(vinyl chloride), chlorinated poly(vinyl chloride), and poly(vinylidene chloride) polymers by spectroscopy, thermal analysis, and pyrolysis-gas chromatography resulted in a proposed mechanism for their thermal degradation. Polymer structure with respect to total chlorine content and position was determined, and the influence of these polymer units on certain of the decomposition parameters is presented. Distinguishing differences were obtained for the kinetics of decomposition, reactive macroradical intermediates, and pyrolysis product distributions for these systems. It was determined that chlorinated poly(vinyl chloride) systems with long-chain ? CHCI? units were more thermally stable than the unchlorinated precursor, exhibited increasing activation energy for the dehydrochlorination, and produced chlorine-containing macroradical intermediates and chlorinated aromatic pyrolysis products. The poly(vinyl chloride) polymer was relatively less thermally stable, exhibited decreasing activation energy during dehydrochlorination, and produced polyenyl macro-radical intermediates and aromatic pyrolysis products.     

Chemiluminescence in the thermal decomposition of di(tert-butyl) trioxide

Intense chemiluminescence (CL) in the visible and IR regions arising during the thermal decomposition of di(tert-butyl) trioxide has been observed. The decomposition rate constants have been determined. The emitter of CL in the IR region is singlet oxygen, that of CL in the visible region is triplet excited acetone. Kinetic and spectral data and thermochemical and MNDO calculations point to a homolytic mechanism of decomposition. The formation of the CL emitters occurs in the reactions of radicals that arise upon the decay of di(tert-butyl) trioxide.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2056–2059, December, 1993.     

Thermal decomposition and volatilization of poly(α-olefins)

The thermal decomposition of normal alkanes and linear poly(α-olefins) was found to occur predominately by random scissions, followed by volatilization into an open system. To show these processes the fragment distribution from high molecular weight linear polyethylene (fragments to C₅₅), n-alkanes, polypropylene, and polyisobutylene (fragments to C₆₀) are reported and discussed in depth. Based on the results, a mechanism of random scissions followed by volatilization is postulated for polyethylene and n-alkanes as well as for polyisobutylene and polypropylene. Polystyrene is shown not to follow the same mechanism, for little evidence for fragments above trimers was found. In addition, temperature rise–time measurements at the pyrolyzer probe are reported and explained.     

过氧化苯甲酸叔丁酯的热分解动力学研究及SADT推算

研究了过氧化苯甲酸叔丁酯的热分解动力学及不同包装规格下的自加速分解温度(SADT),利用C600微量热仪测试了过氧化苯甲酸叔丁酯的热分解特征,得到升温速率分别为0.1 K/min、0.2 K/min、0.5 K/min、1 K/min下热流随时间的变化曲线,并使用Friedman等转化率法对所得的实验数据进行分析处理,得到了过氧化苯甲酸叔丁酯的分解反应活化能、指前因子等热动力学参数,推算了不同包装规格的过氧化苯甲酸叔丁酯的SADT。结果表明TBPB分解活化能及指前因子随转化率变化而变化,活化能范围为42-135.5 kJ/mol,指前因子范围为0.25-33.5,在25L聚乙烯桶包装下的SADT为59℃,50L下为52℃,200L下为46℃。     

Thermal decomposition of poly(2-vinylpyridine): Effect of complexation with copper chloride

The thermal decomposition of complexes between poly(2-vinylpyridine) (P2VPy) and copper chloride was investigated by several techniques, including thermogravimetric analysis and mass spectrometry. P2VPy was selected as the host polymer for two reasons: its ability to form complexes with copper compounds which are soluble in high concentrations, and because it forms essentially no char upon pyrolysis. The decomposition mechanism of P2VPy changes significantly upon complexation with copper compounds. P2VPy was initially thought to be an ideal ligand for the pyrolytic formation of pure copper owing to its low carbon yield upon thermal decomposition. The presence of copper chloride during polymer decomposition alters the decomposition mechanism of the polymer and accounts for significant yields of carbonaceous char. The magnitude of this effect is dependent upon the quantity of copper present. Polymer char yields as high as 41 wt% have been obtained when each pyridine moiety is complexed by CuCl₂. Studies based on the model compound Cu(2-picoline)₂Cl₂ indicate that the diffusion length of released volatiles plays a significant role in the observed decomposition mechanisms.