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Oxidative degradation of poly (vinyl acetate) and poly ($\varepsilon$-caprolactone) and their mixtures in solution

Sivalingam, G and Madras, Giridhar (2004) Oxidative degradation of poly (vinyl acetate) and poly ($\varepsilon$-caprolactone) and their mixtures in solution. In: Chemical Engineering Science, 59 (7). pp. 1577-1587.

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Abstract

The oxidative degradation of the poly ($\varepsilon$-caprolactone) (PCL), poly (vinyl acetate) (PVAC) and their mixtures in dichlorobenzene has been investigated at various temperatures $(70 – - 130^oC)$ in the presence of benzoyl peroxide. The interaction between the polymers is quantified by monitoring the molecular weights of individual polymers using gel-permeation chromatography. The various physical mixtures employed in the present investigation are $\frac{20}{80}$ ,$\frac{50}{50}$ and $\frac{80}{20}$ wt%/wt% PCL/PVAC. Experimental data indicated that the degradation is random without cross-linking and repolymerization. An optimum in degradation temperature (corresponding to maximum degradation rate) of $105^oC$ was observed for the entire range of polymer compositions (0–100% PCL) investigated. This optimum temperature of degradation is characteristic mostly of the initiator and only to a small extent of the degrading polymer system. The experimental results of the mixtures indicated that the degradation rates of PVAC are significantly enhanced, while the degradation rates of PCL are decreased in the physical mixture. This can be attributed to the proton-accepting and proton-donating nature of PCL and PVAC, respectively. A radical mechanism for the oxidative degradation of pure polymers and their mixtures has been proposed and a model based on continuous distribution kinetics was developed considering the interaction of the polymers through hydrogen abstraction and the parameters were evaluated numerically. The activation energies for the peroxide attack for the PCL and PVAC are 10.5 and 10:6 kcal $mol^{-1},$ respectively. The activation energies for the random chain scission of PCL and PVAC are 10.6 and 14:5 kcal $mol^{-1},$ respectively.

Item Type: Journal Article
Additional Information: The copyright belongs to Elsevier.
Keywords: Polymer mixtures;Poly (E caprolactone); ;Poly (vinyl acetate);Continuous distribution kinetics;Hydrogen abstraction
Department/Centre: Division of Mechanical Sciences > Chemical Engineering
Date Deposited: 22 May 2006
Last Modified: 19 Sep 2010 04:26
URI: http://eprints.iisc.ernet.in/id/eprint/6755

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