Controlled chemical degradation of natural rubber using periodic acid: Application for recycling waste tyre rubber

Presently, the disposal of thousands of tons of waste tyres produced every year in the whole world is a major environmental problem. Since tyre rubbers do not decompose easily on account of crosslinking and stabilizers, the processing of the waste tyre rubber constitutes a significant technical challenge. This work describes the use of periodic acid for the controlled one-pot oxidative cleavage of carbonyl telechelic cis-1,4-oligoisoprenes (CTNR) and natural rubber (NR) as model compounds and the application of this method to the degradation of ground waste tyre rubber. Average molecular weight analysis of the degraded material indicates that the reaction time and the periodic acid quantity can be used to control the degree of breakdown; we obtained materials in the average molecular weight range of 700-5000 g mol−1. The processed material shows ketone and aldehyde groups at the chain ends. Degradation studies of waste tyre rubbers were also carried out using this oxidative cleavage by periodic acid, to achieve carbonyl telechelic oligomers. Well-defined structures were obtained with an average molecular weight from 3000 to 7000 g mol−1 according to the periodic acid/waste tyres rubber ratio used.