熱伝導率による加硫天然ゴムの熱酸化劣化評価

概要

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Thermal degradation effect on the thermal conductivity of vulcanized natural rubber (NR) was investigated. Thermal conductivity of NR sheet of 2 mm thickness measured by laser-flash method decreased with the progress of thermo-oxidative degradation regardless of the carbon black content. Therefore, thermal conductivity measurement can be used as a new evaluation method of thermo-oxidative degradation.Furthermore, thermal diffusivity of thin films of 200μm thickness taken out from NR sheet were measured by temperature wave analysis. It was revealed that pure NR sheet uniformly softened under the situation of thermo-oxidative degradation, whereas the surface of carbon black-filled NR sheet hardened and the inside of carbon black-filled NR sheet softened with thermo-oxidative degradation. Thus, the measurement of thermal conductivity of sheet NR and thermal diffusivity of thin film NR revealed that the carbon black influences the mechanism of thermo-oxidative degradation of vulcanized NR, and particularly on carbon filled NR, the process of thermo-oxidative degradation is different between the surface and the inside of sheet NR of thickness 2mm.