Thermoplastic elastomer from microwave-reclaimed shoe sole scrap and low density polyethylene

Abstract

Shoe sole scrap is a by-product from rubber shoe factory, which can cause an environmental problem. Therefore, the goal of this research was to reduce the amount and increase added values of rubber wastes by preparing thermoplastic elastomers (TPEs) from devulcanized shoe sole scrap and low density polyethylene (LDPE) at various ratios. Shoe sole scrap was devulanized by microwave energy at various microwave power and devulacanizing time (90, 180, 270, 360, and 450 watt and 30, 60, and 90 sec, respectively) and by using tetra methyl thiuram disulifde (TMT) as a reclaiming agent. The degree of crosslinking was evaluated by measurement of the gel fraction and swelling ratio of devulcanized shoe sole scrap as a function of microwave power and time to identify the optimum condition for devulcanizing shoe scrap. The effects of microwave energy and reclaiming agent on the mechanical, physical, and thermal properties as well as the morphology of the TPEs were studied. The results showed that the optimized condition to devulcanize shoe sole scrap by microwave energy was at 360 watt for 60 sec. The gel fraction and swelling ratio of devulcanized shoe sole scrap decreased with increasing microwave power. The mechanical and physical properties of TPEs. were increased with increasing LDPE content. In contrast, the mechanical and physical properties of TPEs increased when the microwave devulcanized shoe sole scrap and reclaiming agent were both added with the LDPE. The suitable ratio for preparing the TPE from this research was 80:20 for non-microwave devulcanized shoe sole scrap and LDPE, with the addition of 2.75 phr of TMTD.