Effects of functionalized carbon nanotubes in peroxide crosslinking of diene elastomers

The crosslinking reaction of ethylene–propylene–diene terpolymer (EPDM) peroxide vulcanization filled with pristine and functionalized carbon nanotubes (CNTs and S/CNTs) was evaluated by rheometric tests. The functionalization of CNTs was carried out by diazonium salt methodology in acid medium. S/CNTs were characterised by means of TGA, EDX, Raman and elemental analysis. Pristine CNTs were found to gradually increase the delta torque as a function of loading fraction. Nevertheless, the vulcanization time, scorch and optimum cure time hardly varied on addition of CNTs. However, S/CNTs noticeably affected the cure process, reducing the vulcanization time and delta torque. This effect was related to the presence of acid sites on the CNTs surface which reduced the peroxide efficiency. For this reason, triallyl cyanurate (TAC), highly reactive towards free radicals, was used as coagent to increase the crosslinking efficiency without affecting the cure rate or adding scorch.