Rheological properties of recycled chlorinated polyethylene/natural rubber blends vulcanized by sulfur

Abstract

Blends of elastomeric chlorinated polyethylene (CPE) and natural rubber (NR) with a blend composition ratio of 80/20 were prepared and recycled. Viscoelastic properties of the blends as a function of the recycling cycle were monitored. The results obtained revealed that, with an increase in the number of recycling cycles, a noticeable change in the viscoelastic properties of blends could be observed; that is, a decrease in the elastic contribution associated with a noticeable shift in the glasstransition temperature of the NR phase of the blends was observed, implying a molecular change in the NR phase via a thermal chain-scission mechanism. The influence of magnesium oxide (MgO) as an acid acceptor for CPE onthe viscoelasticity of the blends was also investigated. Through a reduction of the amount of MgO, the molecular change was found to be more pronounced in NR than in CPE phases in a manner similar to the increase in the recycling cycles. An explanation of the changes in. the viscoelastic properties of the blends with various MgO loadings and recycling cycles is proposed in terms of thermal degradation via a molecular chain-scission mechanism taking place mainly in the NR phase. © 2008 Wiley Periodicals, Inc.