THE MORPHOLOGY OF RUBBER PLASTIC BLENDS

This study considers the theological and interfacial effects on the ph ase morphology of the rubber/plastic blends during molten-state mixing , cold pressing, and compression molding. We utilized a specially desi gned tool to take a sample from the mixer and quickly cool it with lit tle chance for coalescence. The work of this report is mainly concerne d with soft rubbery compositions, which contain large concentrations o f elastomeric phases. The morphologies of rubber/plastic blends having low concentrations of plastic or rubber can be explained by the under standing gained from work previously reported by others. The viscosity -matched and polarity-matched rubber/plastic blend systems give the fi ner states of dispersion, especially during the early stages of mixing . At intermediate concentrations of rubber, (e.g., 60 vol. %) co-conti nuous and laminar structures are frequently formed. The determinants o f the concentration where the phase inversion occurs and the determina nts of phase-domain dimensions near this phase-inversion concentration (e.g., a thickness of a highly shaped structure) are complex and can only be rationalized qualitatively. However, we were able to quantitat ively relate phase-morphological dimensions to interfacial tension, th eology, and the observed type of morphology. When the hot batch is col d pressed, then a striated or laminar phase morphology is formed. Even very small particles deform greatly if the interfacial tension is low . Higher viscosities in the dispersed phase give rise to lesser deform ations during cold pressing. During compression molding, the laminar s tructure transforms itself into a random co-continuous structure of va stly increased textural dimensions. This coarsening is greatest when p olarities are most divergent and when the viscosities of the polymers are lowest.