Thermoplastic-Guayule Rubber Blends—Compositions and Mechanical Properties

Abstract

Abstract An experimental study of the mixing and final mechanical properties of blends of guayule rubber with polyolefins was carried out. It was found that (1) variation in total mixing time during blend preparation produced only minor differences in maximum tensile properties; (2) tensile properties of the blends approach those of the plastic at GR concentrations of 50% and lower, those of the rubber at GR concentrations of 70% and higher; (3) tensile properties of partially crosslinked blends improve if the addition of DCP is effected after partial mixing of the pure homopolymers; (4) the partial cross-linking of the blend exerts a strong beneficial influence on the mechanical properties; (5) the addition of carbon black exerts little influence on the mechanical properties of the blend. It can be suggested that, at 60% GR, both polymers (GR and HDPE) show the same tendency to form the continuous or dominant phase. Above 60%, the rubber tends to be the dominant phase, and below 60% the plastic tends to be the dominant phase. The mechanical properties of partially crosslinked GR-HDPE blends are comparable with those of similar commercially available products. This suggests a further alternative in the commercialization of natural guayule rubber, namely, thermoplastic rubbers.