Recycling of Individual Waste Rubbers

With the worldwide growing interest in the recycling of valuable materials, the need to find viable options for the re-use of vulcanized rubber articles is becoming more and more pressing. De-vulcanization needs to be discerned from reclaiming, where in the first case the aim is to primarily break crosslinks of the vulcanized rubber network, versus random scission of crosslinks and main polymer chains in the latter case. The first aims to obtain the best properties after renewed vulcanization. The present chapter starts with a description of an analytical technique to quantify the ratio between crosslink scission and main chain breakage, developed by Verbruggen et al. and based on the original work by Horikx. The de-vulcanization possibilities of various elastomers are further detailed including de-vulcanization of styrene-butadiene-(SBR)-based rubbers, polybutadiene (BR) rubbers, natural rubber (NR), chlorinated butyl rubber (CIIR) and ethylene-propylene-diene (EPDM) rubber. All elastomers require their own specific de-vulcanization additives and conditions, which need fine-tuning on a case-by-case basis for all the various products.