Rheological and physico-mechanical properties of hybrid carbon black/palm kernel shell biochar (CB/PKSBC) filled carboxylated nitrile butadiene rubber (XNBR) composites / Zafirah Zainal Abidin

Palm oil related industry has been developing and blooming very well nowadays which would lead to abundance of palm oil waste. These palm oil waste especially palm kernel shell (PKS) can be turned into palm kernel shell biochar (PKSBc) and used as a natural filler in rubber composites. PKSBc has the potential to be a co-filler to carbon black (CB). CB is a commercialized reinforcing filler and widely used in the rubber industry, however it is a potential carcinogen and a petroleum-based product which is non-renewable and less sustainable. Hence, in this study, PKSBc is utilized to hybridize with CB (N660) in the efforts of managing and benefiting palm oil waste and finding sustainable way to reduce usage of CB. This research aims to elucidate the effect of hybrid CB/PKSBc at varying loading on the rheological properties and physico-mechanical properties of carboxylated nitrilebutadiene rubber (XNBR). In this study, both CB and PKSBc are incorporated into XNBR and was then cured with sulphur. The compounds were prepared by using a two roll mill. Different compositions of hybrid CB/PKSBc were incorporated. The rheological properties, crosslink density and physico-mechanical properties such as tensile strength, elongation at break, modulus, morphological analysis, compression set, abrasion resistance, and hardness of the vulcanizates were investigated. Based on the results, as the loading ratio of PKSBc increases, the physico-mechanical properties of XNBR composite decreases except abrasion resistance and hardness where high loading of PKSBc maintains these two properties. Hybridization of CB and PKSBc at optimum ratio of 30/5 phr, the XNBR composite achieved high tensile strength, low elongation at break, high M100 and M300, high reinforcement index, high abrasion resistance (low volume loss), high hardness and low compression set. Therefore, this approach of using eco-friendly filler derived from palm oil agricultural waste (PKSBC) can reduce the abundance of palm oil waste, be a sustainable alternative to act as co-filler in hybrid CB/PKSBc to decrease usage of CB and helps to enhance quality of existing rubber-based products especially for shoe sole application in the footwear industry.