Safety risk investigation of trace moisture on solvent-free polyurethane synthesis reaction

Polyurethane materials are widely used, yet their thermal hazards remain underexplored. This study investigates the solvent-free polyaddition of hexamethylene diisocyanate (HDI) and hydroxyethyl acrylate (HEA) under trace moisture conditions. Titration results showed that moisture significantly reduces the reaction rate, while Karl Fischer titration confirmed effective moisture removal using molecular sieves. NMR and FTIR revealed that dehydration enhances isocyanate electrophilicity and hydroxyl nucleophilicity, accelerating the reaction. DSC indicated that moisture induces additional exothermic peaks due to side reactions, and ARC testing showed elevated initial temperatures and reduced adiabatic temperature rise. A kinetic model revealed a consistent reaction order of 0.8, regardless of moisture. T D8 and T D24 were predicted, and a risk matrix assessed the thermal hazards. This study provides essential guidance for the safe and efficient development of novel eco-friendly polyurethane formulations and offers valuable insights for large-scale industrial safety.