In situ high-pressure vulcanization and thermal properties of polyisoprene

Abstract

Liquid cis-1,4-poly(isoprene) (PI) has been vulcanized under high pressures without using additives. Moreover, the thermal conductivity and heat capacity per unit volume of both unvulcanized (liquid state at room temperature) and vulcanized (rubbery state) PI have been measured, and found to be the same in both states. However, the relaxation behavior associated with the glass transition differs. The unvulcanized PI exhibits two clearly resolved relaxation processes near the glass transition whereas these tend to combine into one process in the vulcanized PI. Moreover, at the same pressure temperature co-ordinate, the relaxation time of the vulcanized sample (∼1 s at 220 K at atmospheric pressure) is longer than that of the unvulcanized sample.

Keywords:

• Pressure
• Vulcanization
• Thermal conductivity
• Heat capacity
• Glass transition