Synthesis, characterization, and application of polyurethane/2-hydoxyethyl methacrylate hybrids as additives to unsaturated polyester resins

Polyurethane/2-hydoxyethyl methacrylate (PU/2-HEMA) hybrids with the modifying properties of unsaturated polyester resin (UPR) were prepared through two steps of polymerization. In the first step, polyurethane prepolymers (PUA) were prepared with an NCO/OH ratio of 2.2 by a polyaddition reaction based on isophorone diisocyanate (IPDI), polyoxypropylene glycol (PPG 2000), and PPG 2700. In the second step, the hybrid was prepared by adding and mixing different contents of 2-hydroxyethyl methacrylate (2-HEMA) to prepolymer polyurethane (PUA). The effect of PUA and PUA/2-HEMA hybrid on the physicomechanical properties of UPR films was studied, including viscosity, compressive strength, hardness, thixotropy, and gamma radiation resistance. The addition of PUA/2-HEMA hybrids improved the physical and mechanical properties of UPR more than the addition of PUA owing to the existence of functional groups derived from PUA and PUA/2-HEMA, such as NCO, double bonds, and NH, which can establish cross-linking between UPR and PUA, as well as between UPR and PUA/2-HEMA. The findings demonstrate that the mechanical properties improve with dose, indicating cross-linking involving the double bonds of 2-HEMA, NH, C=O, as well as the ether group over oxidative degradation. However, an increase in 2-HEMA content in PUA hybrids increases the gamma radiation resistance, tensile, and compressive strengths demonstrating that cross-linking leads over oxidative degradation. This is attributed to the formation of the polymeric network as a result of cross-linking between PUA and 2-HEMA as indicated in the experimental results shown in Table 3 and Schemes 2 and 3 .