Polyurethane–polyacrylate interpenetrating polymer networks. I

Two‐component topologically interpenetrating polymer networks (IPN) of the SIN type (simultaneous interpenetrating networks) composed of a melamine‐cured polyacrylate and five different polyether‐based polyurethanes were made. The linear polymers and prepolymers were combined in solution, together with the necessary crosslinking agents and catalysts; films were cast, chain‐extended, and crosslinked in situ . Infrared spectroscopy indicated that little or no reaction between the different networks occurred. In all cases, except for one IPN which was made from a very highly crosslinked polyurethane, maxima in tensile strength, significantly higher than the tensile strengths of the components, occurred. This was explained by an increase in crosslink density resulting from interpenetration. Some enhancement in other physical properties (impact strength and thermal resistance) was also noted.