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Polyurethane elastomers were prepared with hydroxytelechelic polybutadiene (HTPB) as polyol, modified 4,4′‐diphenylmethane diisocyanate (modified MDI) as liquid polyisocyanate, and phosphonate diols as chain extenders and flame retardant compounds. These phosphonate diols were synthesized by radical thiol–ene addition of allyl or vinyl dialkyl phosphonate to 3‐mercapto‐1,2‐propanediol. For various percentages of phosphorus (0 to 3%, w/w), polyurethane elastomers remain stable up to 250 °C. The percentage of residual char at 600 °C increases with increasing phosphorus content. For the soft segments, no variation in the glass transition temperature (Tg) is observed as the percentage of P increases, whereas the Tg of hard segments increases. Above 0.5% phosphorus content, the limiting oxygen index (LOI) becomes higher than the percentage of oxygen in the air. © 2003 Society of Chemical Industry

In this work, a new methacrylate phosphonate monomer synthesis was described according to two routes: firstly, by condensation of methacrylic acid with a phosphonate epoxide and secondly by an esterification between methacryloyl chloride and a phosphonate diol. The photoinduced polymerization of this new monomer was studied as a function of reaction temperature. The optimal conversion of the photopolymerization was 81% for temperatures below 60 °C. Above 60 °C, the existence of a thermal polymerization leads to a decrease in the apparent photochemical yield. This new monomer is less reactive than the commercial dimethacrylate polyether of Bisphenol A we have used for copolymerization. Mechanical and thermal properties of the final copolymers were studied as a function of methacrylate phosphonate monomer content. Tg of the copolymers reaches a maximum when the phosphorus content is about 2%. The addition of phosphorus leads to an improvement of the thermal and flame‐retardant properties. Thus, addition of 2% phosphorus allows us to decrease the degradation rate, to increase the amount of remaining residue after combustion up to 12%, and finally to increase the Limiting Oxygen Index (LOI) from 16.8 (0% P) to 21.4 (2% P).

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