Liquid guayule natural rubber, a renewable and crosslinkable processing aid in natural and synthetic rubber compounds

Abstract

Liquid guayule natural rubber (LGNR) was produced by thermal degradation of guayule natural rubber and tested as a renewable alternative to naphthenic oil (NO) processing aid in natural rubber (Hevea and guayule rubber) and synthetic (styrene-butadiene) rubber composites filled with carbon black (CB). Processing oils are rubber additives commonly used to improve the processability of a compound. Most processing oils, like NO, are petroleum-based, and negatively impact the carbon footprint of the rubber industry. Moreover, these aids act as diluents that lower the mechanical performance of the resultant rubber products.The energy consumption of rubber compounding, mechanical properties and crosslinking networks of natural and synthetic rubber composites made with LGNR were characterized. LGNR effectively helped the compounds mix as demonstrated by 13–21% lower energy consumption compared to compounds mixed without processing aids. Moreover, unlike NO, LGNR acted as an active additive in the vulcanization reaction. Tensile strength, elongation at break, modulus at 100% strain and hardness increased when NO was replaced with LGNR in the compounds. The higher mechanical properties may be explained by additional crosslinking networks formed between LGNR and the rubber matrices and strong LGNR-CB interactions. LGNR, as a renewable processing aid, can address rising performance goals, and reduce carbon footprint for rubber products. In conclusion, LGNR provides the same benefits as conventional diluent processing aids, enhances the properties of the final material, and is produced from a renewable plant source.