ISSN:
0887-624X
Keywords:
thermal degradation mechanism
;
poly(styrene-co-methacrylonitrile)
;
pyrolysis gas chromatography
;
back-biting reaction
;
depolymerization
;
boundary effect
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The mechanism of thermal degradation of homopolymers of styrene (St) and methacrylonitrile (MAN) and their copolymers was investigated theoretically and experimentally by the pyrolysis gas chromatography using a Curie-point pyrolyzer. Poly(St-co-MAN)s generate dimers and trimers as well as monomers by flash pyrolysis. Parameter α was proposed to account for the competition between the back-biting reaction and depolymerization. The back-biting parameter α is defined as the ratio of rate constants, α = kbb/kdp, where kbb is the rate constant for the back-biting reaction and kdp is that for depolymerization. The back-biting process is followed by β-scission, where dimer and trimer are generated, and directly correlated with the C - H bond dissociation energies in the polymer chain. Using the back-biting parameter α, where 1/α is equal to the zip length n in depolymerization, the boundary effect for the difference of monomer yields from the homopolymers of St and MAN and their copolymers is well explained. The calculated values of boundary effect parameters, βSt and βMAN, agreed well with the experimental results. It was found that thermal degradation mechanisms of homo- and copolymers of vinyl compounds can be analyzed comprehensively using the back-biting parameter α and the boundary effect parameter β. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2315-2330, 1998
Additional Material:
10 Ill.
Type of Medium:
Electronic Resource
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