Polyurethane-Acrylic Copolymer Pseudo Interpenetrating Polymer Networks

Abstract

Previous investigations (1–6) have demonstrated that interpenetrating polymer networks (IPN’s) have exhibited better mechanical properties than those of their component networks. In addition, more complete phase mixing was observed for IPN’s than for blends of the corresponding linear polymers. These results were interpreted in terms of the permanent interlocking of the polymer chains of the composite structure. In this study, three different types of polymer blends, i.e., linear blends, pseudo-IPN’s and IPN’s, were prepared from a polyurethane and an acrylic copolymer. The polymers studied were similar to those used in an earlier study (7,8). However, the polyacrylate used in the present study cross-links by means of a free radical mechanism, while the polymer used previously was crosslinked with a melamine-formaldehyde resin via pendant hydroxyls. Therefore, in this study the possibility of grafting occurring between the component polymers is much less (i.e., reaction of the melamine with the hydroxyl-terminated chain extender for the polyurethane). The pseudo-IPN’s, made from a linear polymer and a crosslinked polymer, would theoretically result in temporary entanglements rather than permanent entanglements, which occur in the IPN’s.