Characterization and kinetics study of the photochlorination of polyethylene

Abstract

The radical chlorination of polyethylene was carried out in perchloroethylene solvent using chlorine gas and ultraviolet photoradiation to investigate a reaction kinetics model. The recurrent structure of chloromethylene (-CHCl-) and methylene (-CH 2 -) groups and the percentage of substituted chlorine were determined using hydrogen-nuclear magnetic resonance (H-NMR) (500 MHz) spectra. A kinetics model has been proposed for this reaction in which the conversion of methylene (-CH 2 -) units to chloromethylene (-CHCl-) units was considered to be the main reaction step. The simplified version of the obtained kinetics model indicates that the reaction is first order with respect to the chlorine gas concentration and zero order with respect to the methylene concentration up to 40% chlorination. At the first stage of the reaction, the concentration of γ-methylene sequences is high. Once the degree of chlorination exceeds 40%, the reaction order changes and becomes zero order with respect to the chlorine gas concentration and first order with respect to the methylene group concentration. At this stage of the reaction, the concentration of γ-methylene groups has decreased considerably. © 2012 The Society of Polymer Science, Japan (SPSJ) All rights reserved.