Cohesive Strength in Guayule Rubber and Its Improvement through Chemical Promotion

Abstract

Abstract Green (cohesive) strength of Guayule rubber (GR) was determined and compared to that of natural rubber (NR). In the case of GR gum compounds the green strength was shown to be inferior to that of NR gum compounds; however, in the case of black compounds GR green strength was similar to that of NR. Green strength was very much improved in both rubbers by the addition of MNNA (N-(2-methyl-2-nitropropyl)-4-nitroso aniline) for gum and black compounds. MNNA also acted as an accelerator and thus reduced the difference in vulcanization rate between NR and GR. When using MNNA, a reduction in energy consumption during mastication was also noted. Finally, MNNA notably increased the tensile modulus and decreased the elongation at break for GR vulcanizates, while maintaining an almost constant tensile strength.