Accelerated natural rubber ageing: An effect of storage temperature on molecular structure and properties

Abstract

The effect of storage temperature on the storage hardening of natural rubber (NR) and the evolution of molecular structure of natural rubber was investigated. Accelerated storage hardening number (ΔP) increased linearly and plasticity intention index (PRI) increased exponentially with the increment in storage temperature. Ester content and protein content results indicated that variation trend of ΔP is neither identical to the changing of α termini nor to that of ω termini. The gel content changing is related the changing of accelerated storage hardening number. NMR showed that with the increase of storage temperature from 40 °C to 80 °C, the crosslinking density would slightly increase firstly and then decrease. GPC measurement indicated that when the storage temperature rose, the molecular weight began to decrease and the corresponding molecular weight distribution also became wider. when the storage temperature beyond the 50 °C the molecular weight of the raw material rubber increased until the storage temperature reached the 70 °C and the corresponding molecular weight distribution generally became wider.