Dynamic vulcanisation of poly(vinyl chloride)–epoxidised natural rubber thermoplastic elastomers

Abstract

Plasticised poly(vinyl chloride)–epoxidised natural rubber (PVC–ENR) thermoplastic elastomers (TPEs) were prepared by melt mixing in a Brabender Plasticorder at 150°C and a rotor speed of 50 rev min-1. Curative concen tration was progressively increased from 0 to 1 phr in order to study the effect of dynamic curing on the plasticised blend. The mechanical properties investigated include tensile strength, elongation at break, modulus at 100%; elongation, tear strength, hardness, and compression set. The effect of thermo- oxidative aging on the mechanical properties was investigated by exposing the PVC–ENR TPEs in an air oven at 80°C for 168 h. It was found that all physical and mechanical properties increased continuously with increasing sulphur concentration. A steady reduction in swelling index with increasing concentration of curatives is excellent evidence for a significant increase in crosslink density. The thermo-oxidative aging process resulted in a significant enhancement in mechanical properties with the exception of elongation at break. This observation seems to indicate that some microstructural changes, such as the formation of new crosslinks, have taken place in the thermo- oxidatively aged TPEs. This trend is supported by a further reduction in the swelling index of aged TPEs. Qualitative evidence from FTIR was used to support the trend observed in the mechanical and physical properties.