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Polymer precursors of polyacetylene. Thermal degradation of poly(vinyl esters). Part 1-Molecular weight dependence of the autocatalytic thermal degradation of poly(vinyl acetate) (PVAc)

AutorBarrales-Rienda, J. M; Sánchez Chaves, M.; Mazón Arechederra, J. M.; Fernández Martín, Fernando
Fecha de publicación1988
CitaciónPolymer Degradation and Stability 21: 55- 72 (1988)
ResumenThis study is the first of a series on the pyrolyses of poly(vinyl esters) in which the kinetics of the isothermal degradation up to high conversions of five unfractionated heterotactic samples of poly(vinyl acetate) (PVAc) ranging in viscosity-average molecular weight Mv from 3·7 × 104 to 2·4 × 105 has been investigated by a static procedure in a nitrogen atmosphere over a wide temperature range. The experimental results can be explained by assuming the occurrence of a catalyzed deacetylation reaction which is first order with respect to CH3COOH simultaneously with an uncatalyzed reaction. This kinetic model, based on the stripping mechanism, has been shown to be in very good agreement with the experimental data not only for low, but also for moderately high, degrees of conversion. Rate constants k1 and k2, Arrhenius parameters E and A and ΔS≠ values have been determined for both the autocatalyzed and uncatalyzed elimination reactions. They are reasonable, since they compare quite favorably with those taking place by a unimolecular dissociation mechanism in homogeneous gas-phase reactions of simple ester molecules which we can consider as model substances for our stripping elimination reaction. The dependence of the kinetic parameters of the samples on molecular weight has been interpreted. © 1988.
DOI10.1016 / 0141-3910 (88) 90065-1
Identificadoresdoi: 10.1016 / 0141-3910 (88) 90065-1
issn: 0141-3910
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