Thermal behaviour and flame retardancy of polyurethane high-solid coatings modified with hexakis(2,3-epoxypropyl)cyclotriphosphazene

Hexakis(2,3-epoxypropyl)cyclotriphosphazene was employed for preparation of high solid hybrid organic inorganic poly(urethane-cyclophosphazene) coatings based on epoxy-terminated urethane oligomer which were cured with ethylenediamine. The flame retardancy, thermal degradation behavior and some surface properties of the coatings were investigated. The results of thermogravimetric analysis suggested that thermal degradation of poly(urethane-cyclophosphazene) occurred in two main stages and the introduction of cyclophosphazene resulted in increase of thermal stability. The main gases released during thermal decomposition of the samples were carbon dioxide, ammonia, water and tetrahydrofuran. The microscale combustion calorimetry revealed that the maximum specific heat release rate and the heat release capacity of the hybrid materials decreased significantly with incorporation of cyclotriphosphazene. The water contact angle and gloss decreased while hardness increased with the increase of hexakis(2,3-epoxypropyl)cyclotriphosphazene contribution in the coating.