Accelerated Ageing of Styrene-Butadiene Rubber Nanocomposites Stabilized by Phenolic Antioxidant

摘要

Organoclay-reinforced styrene butadiene rubber (SBR) was subjected to accelerated thermo-oxidative ageing and its physical properties were compared to the virgin material. The oxidative degradation was studied in absence and in presence of a phenolic antioxidant. Ageing test was conducted at 70℃ for 7, 14, and 28 days. Then, mechanical and dynamomechanical properties were measured and related to chemical and morphological changes. The elongation at break of samples without antioxidant was found to decrease whereas the modulus and hardness of SBR and its nanocomposite increased with ageing time. Also, the storage modulus and the glass transition temperature increased monotonously with time. These results were attributed to main chain scission and crosslinks formation. The ageing mechanism, determined by infrared spectroscopy, was independent on the nanoclay presence. When the antioxidant was added, thermo-oxidative stability markedly increased. The retention in the physical properties upon ageing 28 days suggests that the addition of 0.5-1 phr antioxidant was sufficient to provide stability of SBR nanocomposite with minimum loss in physical properties. Also, SEM images showed no signs of degradation; this demonstrates that the antioxidant protects the surface from oxidative degradation. Moreover, infrared spectroscopy suggests that nanoclay could protect the elastomer surface from deterioration.