Preparation and Application of a Zinc Oxide/Microcrystalline Cellulose Composite as a Cure Activator in Comparison with a Commercial Zinc Oxide Composite

This study aimed to synthesize a new grade of ZnO composite by depositing nanosized ZnO on microcrystalline cellulose (MCC), named MCC-ZnO, and compared its performance as a cure activator with an existing commercial ZnO composite using inorganic nanoparticles as a supporting core, named herein as In-ZnO. The results reveal that the synthesized MCC-ZnO consisted of approximately 50% wt. of nanosized ZnO, whereas the commercial one contained approximately 60% wt. When incorporated into styrene-butadiene rubber (SBR), both ZnO composites performed effectively as cure activators, resulting in decreases in scorch time and cure time in association with an increase in torque difference (state of cure). At a given content, MCC-ZnO showed superior cure activation efficacy to In-ZnO, as evidenced by the higher torque difference, which may be attributed to the smaller particle size of ZnO in MCC-ZnO. Regardless of the ZnO composite type, tensile strength, hardness, and modulus kept increasing as the ZnO composite content increased up to 5 phr. Tear strength also increased and reached its maximum at 3 phr for both ZnO composites. The results clearly reveal the potential of using MCC-ZnO to replace conventional ZnO in the production of more environmentally friendly rubber products.