Liquid phase decomposition of vulcanized isoprene rubber

Abstract

Recycling of waste tires has attracted great interest regarding the environment and finite natural resources. In this study vulcanized isoprene rubber was prepared as the model of waste tire, and treated in organic solvent at 200 °C to 430 °C to make clear the role of solvent on the devulcanization. With thermal treatment of vulcanized isoprene rubber at 300 °C, the polymer recovery reached to 27–90%, however, the weight-average molecular weight (Mw) of the recovered polymer decreased from 1.7 × 106 to 3.3 × 104 − 7.1 × 104. We have found that even with thermal treatment at 200 °C devulcanization was achieved, and a high polymer recovery exceeding 75% was achieved in an argon atmosphere in cyclohexane and m-xylene whose solubility parameters are 8.6 and 9.1. They are close to the solubility parameter of isoprene, 7.9–8.4. In liquid phase treatment optimum dispersion of the vulcanized isoprene rubber might be attained physically and excess decomposition and carbonization were prevented. The high ability of n-aliphatic alcohol as a thermal treatment solvent for vulcanized rubber was confirmed. In an argon atmosphere the polymer recovery ranged from 23.7% to 43.5%, and Mw of about 2.0 × 105 were obtained. 1-heptanol was the optimum solvent with which to obtain high polymer recovery with a relatively high Mw value.