Study of the crosslinking process of waterborne UV curable polyurethane acrylates

• Synthesis of acrylic end capped UV curable waterborne polyurethane dispersions.
• UV curing process by Photo-DSC, Temperature Modulated DSC and FTIR-ATR.
• Conversion increases with curing temperature.
• Highest curing depth obtained using 0.3% of photoinitiator.
• Cp values enable to calculate crosslinking degree.

UV curable acrylic end capped polyurethane dispersions were obtained by the acetone process, using different molecular weight polyols. Photo Differential Scanning Calorimetry (Photo-DSC) was employed to study the effect of the photoinitiator concentration as well as the curing temperature in the curing reaction rate. The penetration capacity of UV radiation was determined by “in situ” Attenuated Total Reflectance Infrared Spectroscopy (ATR-FTIR). In addition, Temperature Modulated Differential Scanning Calorimetry (TM-DSC) was used to calculate the crosslinking degree through the measurement of the Heat Capacity (Cp). According to Photo-DSC data, the conversion of the curing reaction increased with temperature and no dependence with the photoinitiator concentration was found. Cp values of the cured samples enabled us to compare the crosslinking degree as a function of photoinitiator concentration, polyol molecular weight and curing temperature.