UV-Curable Polyurethane-Based, Halogen-Free, CaB4O7 Nanoparticles Decorated, Flexible Flame-Retardant Films

Abstract In this study, combinations of phosphorous silicone methacrylate monomer (PSiMA) and CaB 4 O 7 nanoparticles (CBO NPs) were prepared for formation of halogen-free, flame-retardant, UV-curable polyurethane acrylate (PUA) films. The addition of either PSiMA or CBO NPs to PUA increased the flame-retardancy as expected, but the PSiMA-only addition, unfortunately, had adverse effects on the physical properties. However, the combined addition of PSiMA and CBO NPs not only resulted in the best performance on flame retardancy but also recovered the polymer’s thermal and physical properties. With additives high initial decomposition temperatures were observed in the range of 175–216 °C. Among the combinations, PLU-60PSi-10NP (60 phr PSiMA + 10 phr CBO NPs) resulted in the best LOI performance of 27, which is 40% more than the PLU film (PUA-based film). In addition, the film had a remarkable char formation ability of 14.5% compared to PLU. The observed high LOI values could not be explained by the high percentages of P, Si, B, and N in the films, but the synergy among the additives was also considered. In this study, we have investigated the use of a promising technique, THz spectroscopy, on the characterization of these films as well. Very interestingly, the results showed a nice correlation between the dielectric responses measured by THz spectroscopy and the mechanical properties of the films. Observed great performances along with the simple preparation methods of these newly developed halogen-free , flame-retardant , PUA-based films are expected to significantly increase their potential use in many practical applications such as automobile, leather, printing, and coatings.