Effect of Shea butter as plasticizer on natural rubber-carbon black reinforced composites

This paper presents the effect of eco-friendly plasticizer, Shea butter oil (SBO) in rubber compounding involving Carbon black (CB)-filled Natural rubber (NR). The SBO based compounds (SBC) was systematically investigated and the results were compared with compositions prepared with Petroleum-based oil (PO). Although, some of the measured properties were comparable between SBC and POC, however, the SBC generally exhibited better properties compared to the POC. For example, the SBC coded NS5: (NR-50 parts per hundred parts of rubber (phr) CB-5phr SBO) and NS40 (NR-50 phr CB-40 phr SBO) obtained 7 and 17% greater than NT5 (NR-50 phr CB-5phr PO) and NT40 (NR-50 phr CB-40 phr PO), respectively, based on 300 and 100% modulus ratio (M300/M100). In terms of reinforcement measured by bound rubber content, BR (%), NS5 and NS40 recorded higher BR (%) of 9 and 48% than NT5 and NT40, respectively. The NS5 > NT5 by 12 and 7% in terms of crosslinking density and rebound resilience, respectively. Also, the NS5 > NT5 and NS40 > NT40 by 40 and 75%, respectively, in terms of fatigue life behavior. Such enhancement has been linked to successful distribution of the CB particles assisted by SBO within the matrix of NR. While the SBO is economical and has high potential to substitute the PO which is already suspected to be carcinogenic and environmentally unfriendly, SBO has exhibited good plasticizing effect for rubber compounding, especially as curing activators for recipe intended for manufacturing rubber articles.