MECHANICAL AND RHEOLOGICAL PROPERTIES OF STYRENE ACRYLIC GRADIENT POLYMERS/

A butyl acrylate monomer with a small amount of photosensitizer was di ffused into a slightly crosslinked polystyrene matrix. After a certain swelling time, the diffusion gradient was either fixed (by rapid phot opolymerization in situ) to form a gradient polymer or changed to form an interpenetrating polymer network (IPN), once thermodynamic equilib rium was achieved. Chemical compositions were determined by FTIR. Mech anical and theological measurements were performed using a universal t esting machine and dynamic rheometer, respectively. Impact properties were evaluated with a Falling Dart Impact Tester. Compared to the IPN materials, the gradient polymers exhibit higher moduli, considerable s train, and similar impact resistance. They are also able to retain pla stic properties at higher temperatures. Differences in chemical struct ure of equivalent layers for gradient and IPN polymers yield such diff erences in properties. (C) 1995 John Wiley & Sons, Inc.