Elastic properties in capillary and rotational viscosimetry have been examined for a series of styrene/acrylic terpolymers. Swelling ratio data confirm earlier contentions that melt flow behavior of these polymers is dominated by entanglement effects above an apparent critical temperature of about 180°C, and by a combination of specific interaction and entanglement factors at lower process temperatures. Maximum postextrusion swelling correlates well with zero‐shear melt viscosity, while a die‐swell reduction parameter has been introduced which appears to vary linearly with the recoverable shear component in capillary extrusion, and which also generates useful master curves over appreciable ranges of wall stress. It has been shown that some solid‐state properties of the polymers, including elastic modulus and bond strength of joints sealed by the polymers, vary with processing conditions, thereby also depending on the flow mechanisms operative during processing.