MORPHOLOGY DEVELOPMENT DURING REACTIVE AND NONREACTIVE BLENDING OF ANETHYLENE-PROPYLENE RUBBER WITH 2 THERMOPLASTIC MATRICES

The development of morphology from pellet-sized particles to submicrom etre droplets during the polymer-blending process is investigated for two pairs of polymer blends. The systems are blends of a rubbery phase in a glassy matrix, namely amorphous nylon/ethylene-propylene rubber and polystyrene/ethylene-propylene rubber blends. In each case the inv estigation is pursued for a non-reactive blend and a similar reactive blend where the phases may chemically react at the interface during th e blending process. The dispersed phase particle size distribution is determined as a function of mixing time for these systems. The behavio ur of the blends with matrices of nylon and polystyrene is qualitative ly similar. The major reduction in the dispersed phase sine is found t o occur at short mixing times, in conjunction with the softening proce ss. For example, in the case of a reactive nylon/ethylene-propylene ru bber blend, the volume average particle diameter of the dispersed phas e is reduced from similar to 4 mm (pellet size) to similar to 1 mu m w ithin the first 90 s of mixing. At intermediate mixing times, the morp hology consists of a large number of small dispersed phase particles ( which are about the same size as the particles observed in the final b lend) along with a small number of very large particles which constitu te most of the volume occupied by the rubber phase. The effect of subs equent mixing is primarily to reduce the size of the largest particles in the size distribution. The interfacial chemical reaction between t he phases reduces the dispersed phase size and narrows the size distri bution.