Effect of palm oil as plasticizer for compounding polar and non-polar rubber matrix reinforced carbon black composites

The effect of palm oil (PO) on non-polar natural rubber (NR)-carbon black (CB) composites was investigated as a suitable plasticizer. The results were compared with NR-CB-aromatic oil (TDAE), NR-CB-Shea butter oil (SBO) and polar matrices of epoxidized natural rubber (ENR)-CB-PO and carboxylated acrylonitrile-butadiene rubber (XNBR)-CB-PO. The NR—S_x—CB-PO exhibited the best properties, mostly at lower PO content (5 phr). For example, the bound rubber content of PC5 was ⁓7 and ⁓17% higher than SBC5 (NR—S_x—CB—5phr SBO) and TDC5 (NR—S_x—CB—5phr TDAE oil), while PC40 (NR—S_x—CB—40 phr PO) led SB40 (NR—S_x—CB—40 phr SBO) and TDC40 (NR—S_x—CB—40 phr TDAE) by ⁓23 and 83% respectively. The improved dispersion of CB assisted by PO resulted in higher network density indices (∆M/dNm and N_c/molcm⁻³) and UTS (MPa) for PC5 than PC0 (NR—S_x—CB—0 phr PO), SBC5, TDC5 and XNBRPC5 (XNBR—S_x—CB—5 phr PO) by 3.9, 12.1, 3.4, 6.5, and 1.4% respectively. The PC5 obtained higher EBR (%) than PC0, SBC5, and TDC5 by 199.1, 174.9, and 170.5%, respectively. Therefore, edible PO has demonstrated properties that make it suitable softener capable of substituting petroleum oil plasticizers.