Thermal aging properties of natural rubber-styrene butadiene rubber composites filled with modified starch from Dioscorea Hispida Denst extract prepared by latex compounding method

Carbon black has been used widely as reinforcing filler. However, due to its dependency on non renewable resources, new alternative filler such as chemically modified starch needs to developed. Poisonous starch from Dioscorea Hispida Denst extract which chemically modified using Resorcinol Formaldehyde (DRF) was applied as a novel reinforcing filler in Natural Rubber (NR) and Styrene Butadiene Rubber (SBR) composites. Latex Compounding Method (LCM) was applied in mixing of 50 phr NR and 50 phr SBR with different loading of DRF (0, 5, 10, 15, 20, 25) phr. The effect of thermal oxidative ageing at hot air circulation (70 °C) for 0, 12, 24, 48, and 72 hours towards physic, tear, and tensile properties were observed. The results showed that DRF could be used as a novel filler in NR/SBR composites due to its ability to improve hardness, tensile strength, and tear strength slightly. Based on curing characteristics, DRF loading could decrease the cure rate index and increase cross link density. To sum up, the duration of thermo-oxidative aging influences the changing of those properties. The longer duration aging time causes an increasing of hardness. In contrast, the tear strength and tensile properties such as elongation at break, tensile strength and modulus experienced decreasing value by the longer aging time. The eterioration of SBR/NR/DRF composites was possibly caused by a serious post curing effect, high cross linking density, cross link scission, stiffening effect, and severer oxidative degradation at higher temperature.