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Abstract

The addition of gelled or crosslinked material to an essentially linear elastomer often decreases “nerve,” mill shrinkage, or die swell. In the present work, poly(ethyl acrylate) systems previously characterized in steady flow, were studied in transient flow. Die swell in capillary flow and shear creep recovery in a biconical rheometer were examined and correlated with the amount, crosslink density, and particle size of the gel phase. In general, the addition of gel reduces deformation of extrudates by reducing the amount of elastic strain energy which can be imparted to the material in a stress field. Concurrently, by increasing the viscosity more at low than at high stresses, gel addition also provides an increased resistance to deformation in the low-stress regions outside of the equipment without exacting a comparable toll in increased power requirements.