Unique Behavior of Hydrocarbon Resin Tackifier on Unaged and Aged Tack of Brominated Isobutylene-co-p-methylstyrene (BIMS) Rubber

The effect of hydrocarbon resin tackifier on autohesion of brominated isobutylene-co-p-methylstyrene (BIMS) rubber was investigated by a 180 degrees peel test. The tack strength increased with resin ( tackifier) loading up to 10 phr beyond which it dropped. At 10 phr resin concentration, the tackifier enhanced the self-bond formation by enhancing the chain mobility across the interface and, in turn, by providing greater separation resistance from the diffused chains. These conclusions were derived from measured maximum tensile stress, compression creep and viscoelastic properties of the rubber-resin mixtures. The tack strength of neat BIMS rubber showed t(1/2) dependence with respect to increasing contact time (t). On the other hand, the tack strength of the resin loaded sample showed t(1/4) time dependence on contact time. Although the results from dynamic mechanical analysis (DMA) studies suggested good compatibility between the blend components, morphological studies revealed migration of the tackifier to the rubber surface. Upon aging at 100 degrees C for 36 h, the values of tack strength of both the neat BIMS rubber and the BIMS/tackifier blends significantly decreased. The reduced tack strength of the aged samples was attributed to the changes in compression creep, maximum tensile stress and viscoelastic properties of the samples after aging. Upon aging, the resin loaded samples exhibited excessive blooming of the tackifier onto the rubber surface. (C) Koninklijke Brill NV, Leiden, 2008