Thermally curable polyurethanes containing naphthoxazine groups in the main chain

A new methodology has been developed for the modification of polyurethanes with reactive naphthoxazine moieties in order to expand their industrial applicability as electrical insulators. Thermoplastic and organosoluble poly(urethane‐co‐naphthoxazine)s were prepared by the reaction of NCO‐terminated urethane prepolymers made from various soft segments with a naphthoxazine‐containing diol chain extender. The prepared polymers were easily processed into thin films using either solution casting or compression moulding techniques. Heat treatment of these films under optimized conditions (200 °C for 30 min) led to the thermally activated ring‐opening polymerization of naphthoxazine moieties, and consequently crosslinked networks were obtained. All of the starting materials and the final polymeric compounds were fully characterized using spectroscopic methods and their physical and chemical properties evaluated and then correlated with their chemical structures. Due to their good elongation property (up to 70% elongation at break) in comparison to polynaphthoxazines, significant enhancement in decomposition temperature as well as high value of dielectric breakdown strength (up to 30 kV mm^?1) in comparison to polyurethanes, these materials are potentially applicable as electrical insulators with service temperatures higher than those for related unmodified polyurethanes. Copyright © 2010 Society of Chemical Industry