Bio-inspired polydopamine-coated clay and its thermo-oxidative stabilization mechanism for styrene butadiene rubber

Abstract

Polydopamine (PDA) is labeled as one category of synthetic melanin because it mimics the intriguing radical-scavenging behaviors of its natural counterpart. In this study, PDA modified montmorillonite (PDA-MMT) is utilized as a thermo-oxidative stabilizer for styrene butadiene rubber (SBR). PDA-MMT is fabricated by an aqueous dip-coating, based on the spontaneous alkaline auto-oxidative polymerization of dopamine hydrochloride in an air atmosphere, and is then associated with the SBR matrix via latex compounding. The PDA coating plays an excellent role as a radical-scavenger, and the uniformly dispersed PDA-MMT significantly functions as a physical barrier, which collaboratively work to reduce thermo-induced radical production during the decomposition process of SBR. This mechanism was attested by an in situ thermo-oxidative ageing test along with electron spin resonance (ESR) analysis. Thermal kinetics calculations showing that the apparent activation energy (E_a) of the SBR compounds is augmented by a large margin in the presence of PDA-MMT also corroborate this trend. Above all, the bio-inspired PDA-coating combined with the homogeneous dispersion of MMT exerts a synergistic effect on the thermo-oxidative stabilization of SBR matrix.