Effect of Hot Air Aging on Structure and Properties of Raw Natural Rubber

Abstract

The molecular structure, molecular weight and its distribution, P0, PRI, Mooney viscosity, processibility of raw natural rubber, curing characteristics of compounds and mechanical properties of vulcanites were studied by hot air aging. The results show that for raw natural rubber after heating at 70°C for 20 days, C = C bond of molecular chains was broken, the numbers of the C = C bond decreased, methyl oxidized, and –OH and –COOH formed. The number-average molecular weight, weight-average molecular weight and viscosity-average molecular weight decreased, the molecular weight distribution became wide. P0, PRI, Mooney viscosity, rubber elastic torque S ', viscous torque S ", elastic modulus G', viscous modulus G" and complex viscosity η* decreased, loss factor tanδ increased. The curing rate of compound reduced and curing characteristics were inferior. The elongation at break and tensile strength decreased, and tensile stress at 300% modulus and 500% modulus did not change obvious. Anti-aging property became deteriorate.