Synthesis and characterization of UV‐curable polyurethane acrylates derived from trimethylolpropane and hydroxyethyl methacrylate: Effect of 2‐hydroxyethyl methacrylate (HEMA) content on thermal stability, gloss properties, and microstructure

This study presents the synthesis of a series of ultraviolet (UV)‐curable polyurethane acrylates (PUAs) derived from trimethylolpropane (TMP) and 2‐hydroxyethyl methacrylate (HEMA) through a one‐step polymerization method. Fourier transform infrared (FTIR) reveals distinct vibration bands corresponding to different functional groups within the polyurethane structure and was used to explore microphase separation in these PUAs. Thermogravimetric analysis demonstrates two degradation steps in UV‐cured PUA films, revealing the influence of HEMA content on thermal stability. Gloss properties exhibit a complex relationship with HEMA content, with initial improvement followed by a decline. Hydrophilic/hydrophobic properties, measured by contact angle values, indicate increased cross‐linking and less polar surfaces with higher HEMA content. UV‐cured PUA films achieve effective chemical cross‐linking and a dense microstructure, contributing to enhanced film properties. Highlights HEMA's diluent effect increases the exposure of hydrophobic groups on the surface. FTIR with deconvolution techniques were used to analyze H‐bonding and microphase. Excessive HEMA led to phase separation and surface defects, reducing gloss. Formation of H‐bonds between N–H and C=O increased effective cross‐link density. PUA sample surface displays roughness with micropores and irregularities, indicative of lower cross‐linking density. UV60PUA surface appears homogeneous and smooth, suggesting enhanced uniformity and organized cross‐linking structure attributed to the branched structures of HEMA chains.