MORPHOLOGY AND AGING BEHAVIOR OF SILICONE-EPDM BLENDS

The silicone-EPDM system has been studied with blend ratios (silicone: EPDM) of 50:50, 40:60 and 30:70. The first set of blends was prepared by roll-mixing of the elastomers and curative whereas in the second set, DCP-cured powder of EPDM, prepared in a Brabender plasticorder, was mixed with silicone rubber and DCP in a roll mill. A comparison of blends show that the second set exhibits inferior properties as compared to the first set. Specimens were also aged at 150 and 175-degrees-C for various periods. The physical properties of the aged specimens show a reversal in trend, i.e. the second set of specimens shows better physical properties on ageing. The strengthening of the silicone phase by use of a different curative (Perkadox 14/40) in the 50:50 blend of the second set shows a beneficial action on ageing. Morphology studies with SEM confirm the two-phase structure for both sets of blends. In both cases phase separation occurs with ageing, but the continuous phase for the second set of blends maintains its continuity for a higher period than the corresponding specimens of the first set.