Thermal properties and crystallization behavior of highly deproteinized natural rubber

摘要

Natural rubber was deproteinized with a proteolytic enzyme and surfactant to reduce nitrogen content less than 0.02%. The deproteinized rubber was further purified by acetone-extraction followed by transesterification with sodium methoxide. Thedensity of rubber decreased and the thermal expansion coefficient increased by deproteinization and transesterification. The glass transition temperature, T{sub}g, was slightly reduced after deproteinization and transesterification. These were explainedin relation to the decrease in gel content of the rubber. The equilibrium melting temperature, T{sub}m{sup}0, was practically unchanged by these treatments. The low-temperature crystallization between -30 and - 10℃ was significantly influenced by freefatty acids present as a mixture and fatty acid groups linked to the rubber chain. The crystallization behavior was independent of T{sub}g and T{sub}m{sup}0 values.