Processing and mechanical properties of natural rubber/waste-derived nano filler composites compared to macro and micro filler composites

Nano-sized fillers produced from renewable materials can generate high performance natural rubber (NR) composites while reducing dependency on petroleum. We made NR composites, with both hevea and guayule NR, containing nano-scale waste-derived fillers as complete and partial replacements of carbon black. The effect of nano-filler type and loading on composite mechanical properties was analyzed and compared to previous results with micro and macro fillers. Also, processability of the compounds was investigated. Reinforcement of both NRs was achieved by nano-sized waste-derived fillers, even with complete replacement of carbon black. Increases of up to 2.4 and 1.8 times higher tensile and tear strength, respectively, were achieved in some of the composites compared to the unfilled compound. Better relative reinforcement was obtained in guayule than in hevea rubber due to different rubber macromolecular structure and the strength of the rubber-waste filler interactions. Composites containing waste-derived fillers as co-fillers with carbon black displayed uncommon combinations of properties not achieved with single conventional reinforcing fillers. Furthermore, significant reductions in power consumption during mixing, up to 10% in hevea and 19% in guayule composites, were obtained even by replacement of a small portion of carbon black in the composites. Despite increased interest in nano-sized particles, micro-sized fillers are effective reinforcing fillers when used as partial replacements of carbon black, and can be produced at a much lower cost than nano-sized particles.