Abstract
In this study, we examined the thermal characteristics of chlorobutyl rubber (CIIR) before and after press heat treatment. Differential scanning calorimetry (DSC) measurements revealed the appearance of a melting peak in the temperature range of 0 °C to 50 °C, indicating the formation of a microcrystalline structure as a result of heat treatment. The melting enthalpy of CIIR increased with longer heat treatment. In contrast, butyl rubber (IIR) did not exhibit any melting peak in the DSC test even after undergoing the same press heat treatment. Thus, it is suggested that the formation of the microcrystalline structure in CIIR is due to the existence of chlorinated isoprene molecules. X-ray diffraction (XRD) experiments also confirmed the exist of a microcrystalline structure. Upon gamma ray radiation, IIR showed approximately 100% degradation without any gel formation, whereas CIIR exhibited dominant cross-linking reactions and 80% gel formation at 30 kGy radiation. And the microcrystalline structure formed during heat treatment contributed to the increase in cross-linking density during gamma radiation, which is thought to be due to the changes of amorphous structure during the formation of microcrystals.
