Synthesis And Properties Of UV-Oxygen Dual Curing Waterborne Polyurethane Acrylate

Along with the increasingly strict limits on the VOC emissions, various regulations were formulated, and VOC has been specified as the source of atmopheric haze. Therefore, energy-saving and environmental products get more and more attention. And it is urgent and important to develop high cost-performance and environmental waterborne resin with high solid content in the field of coating. UV-curing technology has become a research hotspot in recent years. Curing technology owns multiple advantages like fast curing speed, energy-saving, low VOC emissions, etc. However, the application of ordinary UV-curable waterborne polyurethane was restricted due to several defects, such as low solid content of product, slow film-forming, high cost, poor mechanical properties and disappointing performance of weather resistance and solvent resistance. In this paper, to improve the solid content, curing efficiency and product performace, sulfonate polyester polyol (BY3301), polyvinyl alcohol of (PVA), and polyvinyl butyral (PVB) have been introduced, respectively. And a series of UV curable waterborne polyurethanes with high performance were prepared based on molecular design. The preparation scheme and the relationship between structure and properties of composite emulsions and films were discussed.(1)A series of waterborne UV-oxygen curable sulphonate polyurethane were synthesized with isophorone diisocyanate as hard segment, poly(caprolactone glycol)(PCL1000) and sulfonate polyester polyol (BY33O1) as soft segment. Effects of m(PCL)/m(BY3301) on film morphology, mechanical property, water resistance and thermal stability were characterized by Fourier transform infrared spectroscopy(FTIR), dynamic light scattering(DLS), transmission electron microscope(TEM), atomic force microscope(AFM), thermal gravimetric analysis(TG), scanning electron microscope(SEM) and other methods. With increasing BY3301 content, the solid content of emulsion increased from 38% to 55%. Meantime, the particle size increased from 33.70 nm to 50.94 nm, and the distribution was also slightly increased. The tensile strength of emulsion film increased from 46.7 nm to 55.65 MPa; The water absorption decreased, and the surface roughness increased, as well as the thermal stability. However, the mechanical property and thermal stability decreased when BY3301 content was greater than 16.7%. The particle size and distribution index of emulsion reduced when BY3301 content was greater than 33.3%. Compared with separate UV and oxygen curing method, UV-O2 dual-curing method was beneficial to significantly improve the tensile strength and water resistance of emulsion films. The application performance tests revealed that the comprehensive properties reached optimum when the BY3301 content was 26.7%.(2)Sulphonate waterborne UV-curable polyurethane (UV-SWPU) was prepared by acetone method, using isophorone diisocyanate (IPDI), sulphonate type polyester polyol (BY3301) and pentaerythritol triacrylate (PETA) as main materials, and dimethylolbutyric acid as hydrophilic chain extender. Afterwards, the obtained UV-SWPU emulsion was mixed with polyvinyl alcohol (PVA) solution to prepare UV-SWPU/PVA blend emulsion. The structure and crystallization properties of blend films were characterized by FTIR and X-ray diffraction. In addition, the emulsion particle size and cross-sectional morphology were investigated by dynamic light scattering instrument and scanning electron microscopy. It was found that the particle size increasing as increasing PVA content. The particles size distribution curves and differential thermogravimetric curves displayed as unimodal distribution, and slight change take place in distribution index, indicating better compatibility between UV-SWPU and PVA.(3)UV-curable waterborne polyurethane (UV-WPUB) was prepared by acetone method using IPDI, PCL1000 and 2,2-dimethylol butanoic acid (DMBA), polyvinyl butyral (PVB), PETA, and maleic anhydride (MA) as main materials. First, grafted polyvinyl butyral material (PVB-M) was prepared by modification of polyvinyl butyral (PVB) with maleic anhydride via free radical polymerization. The structure and properties of polymer were characterized with FTIR, DLS, AFM, TQ SEM and other methods. The structure of UV-WPUB was demonstrated by FTIR. With increasing PVB-M content, the particle size of UV-WPUB emulsion increased from 29.87 nm to 79.95 nm. However, the stability of emulsion decreased and particle size increased abruptly to 428.9 nm when the PVB-M content was greater than 8.53%. In addition, the water absorption decreased from 51.34% to 11.93%, and contact angle increased from 92° to 103°, the water resistance was greatly enhaced by the incorporation of PVB-M. The tensile strength increased first and then decreased, and reached the maximum value of 41.31 MPa when the PVB-M content was 8.53%. Whereas the elongation at break decreased. The crystallization degree decreased from 23.17% to 0.70%, and the fracture mode transferred from brittle fracture to ductile fracture. Moreover, the storage modulus increased, as well as the intermolecular interaction, and the microphase separation was weakened. Thermal analysis indicated that the thermal stability increased with increasing PVB-M content. Furthermore, the UV-curing properies were also improved with certain amount of PVB-M.