Effect of some curatives on the properties of ethylene propylene diene rubber/polyethylene blends

A series of ethylene propylene diene rubber/polyethylene (EPDM/PE) blends h as been prepared containing different weight fractions of PE up to 0.66. Th e blends were vulcanized with a sulphur system N -cyclohexyl-2-benzthiazol sulphenamide/sulphur (CBS/S), and a non-sulphur-system dicumyl peroxide (DC UP). The concentration of the latter has been changed from 1.5 phr up to 6p hr calculated on the total weight of the blend composition. It has been fou nd that the maximum torque obtained from rheographs for blends vulcanized w ith the CBS/S system decreases markedly with increasing PE concentration in comparison with those vulcanized with peroxide. The E modulus obtained fro m the stress-strain diagram at 110 degrees C showed the role played by the crosslinking of PE, the E modulus for blends vulcanized by peroxide being h igher than for samples vulcanized with CBS/S. In contrast, the values off m odulus of both samples are practically the same at room temperature and att ain more than 40MPa depending on the composition. The tensile strength at r oom temperature strongly increases with increasing the weight fraction of P E. It has also been confirmed that the melting point of the crystalline pha se of PE decreases with increasing crosslinking density of PE. The shear mo dulus obtained from dynamic mechanical measurements is in accordance with t hat obtained from static mechanical measurements. (C) 1999 Society of Chemi cal Industry.