Synthesis and characterization of UV curable polyurethane acrylate derived from α-Ketoglutaric acid and isosorbide

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A thermally stable coating of UV curable polyurethane acrylate (PUA) was prepared from bio-based PU and methyl 3-(4-hydroxy-3-methoxyphenyl)acrylate(MHPA). The presence of the aromatic ring in the backbone associated with MHPA imparts thermal stability in the structure. The bio-based PU was prepared through the condensation polymerization of hexamethylene diisocyanate(HDI) and a polyol prepared by the condensation reaction of α-ketoglutaric acid(KA) with isosorbide(IS). Isosorbide and α-ketoglutaric acid represent the replacement of the petroleum-based precursors used in polyol synthesis. Characterization of the new compound has been carried out using Fourier transform infrared spectroscopy(FT-IR) and nuclear magnetic resonance spectroscopy(NMR) and correlated with the quantitative analysis through hydroxyl and acid value. The UV curable PUA was added into the commercial polyurethane acrylate(CPUA) coating system and assessed based on their functional properties. The flexibility of the cured coating was determined by understanding the glass transition temperature through differential scanning calorimetry(DSC). Thermal gravimetric analysis was used to measure the thermal stability of the PUA and CPUA mixture. With an increase in the concentration of PUA, the thermal stability of the mixture improves. The structure of the prepared coating has been assessed using X-ray diffraction methods. The dynamic mechanical properties such as storage and loss modulus of the coating were determined from the rheological behavior. The mechanical properties and chemical/solvent resistance of the mixture were calculated and correlated with the gel content and moisture content. The nature of the fracture of the coating was observed through scanning electron microscopy(SEM).