Dynamic vulcanisation of poly(vinyl chloride)-epoxidised natural rubber thermoplastic elastomers - Part 2 - Thermo-oxidative aging

Plasticised poly(vinyl chloride)-epoxidised natural rubber (PVC-ENR) thermo plastic elastomers (TPEs) were prepared by melt mixing in a Brabender Plast icorder at 150 degrees C and a rotor speed of 50 rev min(-1). Curative conc entration was progressively increased from 0 to 1 phr in order to study the effect of dynamic curing on the plasticised blend. The mechanical properti es investigated include tensile strength, elongation at break, modulus at 1 00% elongation, tear strength, hardness, and compression set. The effect of thermooxidative aging on the mechanical properties was investigated by exp osing the PVC-ENR TPEs in an air oven at 80 degrees C for 168 h. It was fou nd 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 signific ant increase in crosslink density. The thermo-oxidative aging process resul ted in a significant enhancement in mechanical properties with the exceptio n of elongation at break. This observation seems to indicate that some micr ostructural changes, such as the formation of new crosslinks, have taken pl ace in the thermo-oxidatively aged TPEs. This trend is supported by a furth er 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. PRC/1428 (C) 1999 IoM Communications Ltd.