Preparation and properties of castor oil/pentaerythritol triacrylate-based UV curable waterborne polyurethane acrylate

Castor oil (CO)/pentaerythritol triacrylate (PETA)-based UV curable waterborne polyurethane acrylate (UV-WPUA) was prepared by using isophorone diisocyanate (IPDI), poly(caprolactone diol) (PCL) and dimethylolbutyric acid (DMBA) as the main materials. A series of emulsions and films with different content of CO were obtained. The infrared spectra, together with the nuclear magnetic resonance spectroscopy, demonstrated the presence of CO and PETA in the UV-WPUA chains. The surface roughness of the curing film was measured by atomic force microscope. In addition, the effects of CO content on particle size, thermal properties, glass transition temperature and tensile performance of the emulsions and films were investigated. With the content of CO increasing from 1.72 to 8.58 wt%, the particle size of the UV-WPUA emulsion increased and the particle size distribution gradually widened. The appearance of the emulsions transformed from blue transparent into opaque and the stability decreased gradually. Water resistance, glass transition temperature for soft segment and thermal performance of the films were improved. The tensile strength of the films firstly increased and then decreased.