Sustainable Use of Chloroprene Rubber Waste as Blend Component with Natural Rubber, Epoxidized Natural Rubber and Styrene Butadiene Rubber

Recycling of rubber waste and finding the effective methods to extend its use are one of major challenges nowadays. The potential approach to reduce rubber waste is to blend it with virgin rubber, perhaps with synergistic advantages. In this study, chloroprene rubber waste (CRw) is used as blend component in binary blends with natural rubber (NR), epoxidized natural rubber with 50 mol% epoxidation level (ENR50), and styrene butadiene rubber (SBR). The effects of blend ratio [95/5, 85/15, 75/25, 65/35 and 50/50 (phr/phr)] on the properties were studied. The results indicate that CRw prolongs scorch and curing times, due to the differences in unsaturation contents and cure incompatibility. The maximum torque (MH), minimum torque (ML), and torque difference (MH–ML) in all cases increased with CRw content in the blend. Because CRw has a crosslink precursor, crosslink density also increased with CRw content. This is clearly confirmed by the combination of swelling resistance, crosslink density and dynamic mechanical properties observed. SEM micrographs showed mostly rough surface and tearing areas for low CRw contents in the blends. The blends also showed less crack paths with increasing CRw content over 50 phr. Further increase in CRw content obviously enhanced the thermal stability of the blends, with elevated decomposition temperatures in TGA results.