Synthesis And Properties Of UV Curable Waterborne Polyurethane Acrylate

UV-curable materials were paid more attentions because of its fast curing speed, energy saving. However, the application of UV-curable waterborne polyurethane acrylate(UV-WPUA) system with free radical type was restricted due to oxygen polymerization inhibition, together with the negative impact of single curing and higher price. Biomolecules with low price and extensive sources, such as β-cyclodextrin(β-CD) and castor oil(CO), were used to modify the UV curing materials. Pentaerythritol triacrylate(PETA)/ pentaerythritol tetraacrylate(PETTA) composite curing system and UV-WPUA/ polyvinyl alcohol(PVA) were also prepared. And the relationship between the performance and structure was mainly studied. The main work was given as follows:(1) UV-WPUA was prepared by using isophorone diisocyanate(IPDI) and polycaprolactone diols(PCL), β-CD and PETA as the main materials. And 2,2-dimethylolbutyric acid(DMBA) was used as the hydrophilic chain-extending agent. The study showed that UV-WPUA dispersions belonged to Newtonian fluids and the viscosity was low. The amount of acetone was reduced with the increasing amount of β-CD in the synthesis process. The viscosity of the emulsion was decreased firstly and then increased. The appearance of the emulsion changed from transparent and blue to translucent. The elongation at break and tensile strength were decreased when w(β-CD) was 14.86 %. The introduction of β-CD contributed to the increase of gel content. But too much additive amount made the later curing incomplete and the increasing degree was limited. When w(β-CD) was higher than 9.48 %, too much β-CD could’t participate in the reaction and migrated to the surface of film, which resulted that the water resistance was declined.(2) A series of UV-WPUA were synthesized by changing the mass ratio between the PETA and PETTA, which was used as the active diluent. The research showed that the particle size was increased with the increasing PETTA. When the amount of PETTA was increased to 66.67 %, more polyurethane prepolymer couldn’t be capped, which led to the formation of polyurea and the obvious increasing degree of the particle size. The particle size distribution became wider and the contact angle increased. The tensile strength and elongation at break were improved. When the amount of PETTA was increased to 83.33 %, the phase separation became obvious, which led to the decreasing mechanical properties and the increasing viscosity of the emulsion. The contact angle decreased and the alcohol resistance together with the water resistance became worse. The thermal stability decreased with the introduction of PETTA. However, with the increasing amount of PETTA, the thermal stability of the film increased gradually. When the amount of PETTA was 83.33 %, the thermal stability was declined. The introduction of PETTA made the film produce larger curing shrinkage and the surface became rougher. The gel content, pencil hardness and other performances increased with the increase of PETTA content.(3) UV-WPUA/PVA blends were prepared by mixing the PVA with UV-WPUA, which was obtained by using PCL, IPDI and PETA as the main materials. The structure and the crystallization performance were characterized by FT-IR and X-ray diffraction, respectively. Particle size, water absorption, contact angle, thermogravimetric properties and other performances were also tested. Decomposition kinetics of the blend films were investigated by using the Flynn-Wall-Ozawa method. The results showed that strong intermolecular interactions were existed between UV-WPUA and PVA. The crystallization performance was between pure PVA and WPUA. There were compatibility problems between the two phases to a certain extent, which could be improved by UV curing. The water resistance of UV-WPUA/PVA decreased and the thermal stability increased with the increasing PVA content. The activation energy of the thermal decomposition was higher than 100 KJ?mol-1 and increased with the deepening of the thermal decomposition.(4) UV-WPUA was prepared by using IPDI, CO and PETA as the main materials. Its structure was confirmed by FT-IR and NMR and the various properties of UV-WPUA were investigated by varying the amount of CO. The particle size of the emulsion increased and the particle size distribution became wider with the increase of CO content. Water absorption rate decreased from 20.45 % to 9.24 % and the contact angle increased from 77.45° to 100.69°, which showed that the water resistance was improved. The initial decomposition temperature was increased by 35 ℃and the glass transition temperature increased with the increasing content of CO. The tensile strength of the film increased, while the elongation at break decreased. When the content of CO exceeded 6.86 %, the tensile strength decreased. The enhanced performances were mainly attributed to the UV/oxygen dual curing and the formation of the larger cross-linking structure with the introduction of CO.