Synthesis and characterization of novel UV-Curable PU-Si hybrids: Influence of silica on thermal, mechanical, and water sorption properties of polyurethane acrylates

Abstract

Organic-inorganic hybrid membranes (HM1-HM4) were synthesized by incorporating 3 wt% (HM1), 5 wt% (HM2), 10 wt% (HM3), and 20 wt% (HM4) of silica precursors into UV-curable polyurethane acrylate (PU) matrix using sol-gel technique. PU, which was prepared by reacting polycaprolactone triol (PCLT) and isophorone diisocyanate (IPDI), was used as the starting organic polymer whereas tetraethoxysilane (TEOS) was used as a precursor for the development of the inorganic phase. The completion of the polymerization reaction of PU and the synthesis of hybrid membranes were confirmed by Fourier transform infrared spectroscopy (FTIR) whereas the morphology was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The thermal, mechanical, and anti-water sorption properties of the hybrid membranes were examined by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), nanoindentator and thin film diffusion analysis, which revealed that HM2 has the highest thermal, mechanical, and anti-water sorption properties. TGA demonstrated that the thermal decomposition temperature (T d10%) of HM2 increased significantly, being 30 °C higher than that of pure PU, whereas DSC indicated that the introduction of 5 wt% of TEOS increased the glass transition temperature from 93.8 to 103 °C. Accordingly, the mechanical and water sorption properties were also enhanced greatly as evidenced by nanoindentation analysis and anti-water sorption data, in which HM2 shows the highest elastic modulus (8.354 GPa), hardness (0.262 GPa), and lowest water sorption capacity. These thermal, mechanical, and anti-water sorption improvements are important for the practical process and applications of PU.