Studies On UV-Curable Aqueous Oil-Modified Polyurethane

Currently the development of UV cured aqueous technology is cared most,especially the study of UV cured aqueous polyurathane,which are synthesized with the introduction of the UV cured double bonds of acrylic acid,such as hydroxyethyl acrylate(HEA),hydroxyethyl methacrylate(HEMA),pentaerythritol triacrylate(PETA),etc.Each molecule only contains one OH group,which reacts with the NCO groups in both ends of PU chains for end capping reaction.Therefore the molecular weight of PU decreases with the increased content of acrylates or the number of double bonds.However,the number of introduced double bonds diminishes if the molecular weight of PU is increased.In a word,high molecular weight and large number of double bonds can’t be attained simultaneously to prepare ideal materials with the satisfied properties.Based on the current preparation methods of the UV curable aqueous polyurethane resin,in this paper polyether polyol,unsaturated polyol,dimethylol butyric acid(DMBA),hydroxyethyl acrylate(HEA)and isophorone diisocyanate(IPDI)were used as the main raw materials,to successfully synthesize UV curable waterborne polyurethane oil emulsion with high molecular weight and high content of double bonds,whose structures were characterized with the infrared spectroscopy(FI-IR)and nuclear magnetic resonance(1H-NMR).The influences of the unsaturated polyol and HEA on the performances of the emulsion were studied.The Soxhlet extractor,universal mechanical testing machine,pendulum hardness tester,thermal dynamic mechanical analyzer(DMA)and so on were respectively used to characterize the cross-linking degree,tensile properties,hardness and glass transition temperature of the UV curable waterborne polyurethane oil film.The results showed that:the double bonds of the unsaturated polyol and HEA were successfully introduced into the polyurethane oil molecular chain,and the storage stability of obtained UV curable waterborne polyurethane emulsion was more than half a year.When the amount of Light initiator Darocur 1173 was between 0.4wt%～0.7wt%and the illumination time was 60s,the light curing efficiency was high and the obtained film had excellent comprehensive performances.When the content of HEA was 8.12wt%,the tensile strength of the film was up to 12.5MPa and the glass transition temperature was 64.5 ℃.The Unsaturated polyol had great influences on the film glass transition temperature,which increased by about 17℃.When the content of unsaturated polyol was 35wt%,the ability of resistance to oxygen inhibition was enhanced,whose crosslinking degree of the film increased obviously,which was up to 90%,and the tensile strength was 11 MPa.