Synthesis And Properties Of Multifunctional Waterborne Polyurethane Acrylate

Ultraviolet (UV) curing polyurethane acrylate (PUA) resin has received increasing attention due to its high efficiency, energy saving, excellent wear resistance, chemical corrosion resistance and excellent gloss. However, common PUA was limited due to low crosslinking degree and slow curing rate resulted from its low number and density of photosensitive groups. And most of them were solvent-based, so the resin was limitations in the application process. In order to improve the performance of PUA, the multifunctional active monomers were added in the application process. Unfortunately, the active monomers show somewhat toxicity, irritation and insolubility. So it is necessary to modify the structure of the PUA to reduce the damage to human body and environment and improve the usability. In order to solve the above problems and expand its application areas, the multifunctional UV-curing waterborne PUA was synthesized by introducing water soluble groups and multifunctional end capping agent to replace the active monomer. This PUA used as adhesive in textile printing was able to be cured under UV light, which can significantly reduce the energy consuming. Specific research contents and results are as follows:Isophorone diisocyanate, polyethylene glycol 400 (PEG400) and 2,2-dimethylol propionic acid (DMPA) were selected as raw materials to synthesize isocyanate terminated polyurethane. And two functional polyurethane acrylate (PUA2) and six functional polyurethane acrylate (PUA6) were all synthesized using 2-hydroxyethyl acrylate and pentaerythritol triacrylate as the end capping agents. Then the PUA2 and PUA6 were dispersed in the water to make the corresponding emulsion. The synthesis temperature and time of PUA6 was confirmed through titration with dibutylamine-methylbenzene. The confirmed optimal parameters of the prepolymer stage, chain extender stage and polyurethane sealing end stage were 60℃/40min,70℃/1h and 70℃/4h, respectively. The PUA2 and PUA6 was proved successful synthesis by FTIR and GPC. The particle sizes of PUA2 and PUA6 emulsion were 124.1 nm and 307.9 nm, respectively, The particle size distribution index was 0.20 and 0.33 respectively. In order to study the effects of water soluble groups on viscosity and particle size, the reaction ratio of DMPA and PEG400 was changed. When PEG400:DMPA=1:1, the particle sizes of PUA2 and PUA6 were 91 nm and 208 nm, respectively. When the ratio of PEG400 and DMPA was 1:2, the emulsion viscosity reached the minimum value. When the solid content was beyond 20%, the emulsion viscosity increased sharply. There was no delamination after 60℃ heat treatment 48h.PUA6 and PUA2 oligomers, trimethylolpropane tris-acrylate and light initiator 1173 were added to obtain UV curable film of PUA. When the addition amount of monomer was 0, the gel content of PUA6 UV curable films was increased by nearly 20%, the water absorption rate was reduced 4.1%, the cure time was reduced by 10 s, the hardness was increased 13HC. The decomposition temperature increased by 82℃ at 10% thermal decomposition and the decomposition temperature increased by 45℃ at 90% thermal decomposition. While adding 30% monomer, the gel content of PUA2 UV curable films improved 20%, the water absorption rate reduced 4.3%, the curing time reduced by 12 s, the hardness increased 32 HC. The decomposition temperature increased 82℃ at 10% thermal decomposition and the decomposition temperature increased 74℃ at 90% thermal decomposition. The obtained polyurethane acrylate UV curable film flexibility decreased while tensile strength increased, the elongation at break decreased when monomer was added or the functional degree of oligomer increased which could improve the curing speed and efficiency of the PUA curing film.According to the study of PUA cured film properties including curing speed, high efficiency, PUA6 was select as pigment printing binder. Influences of the paste content and UV curing time on the properties of printing fabrics were investigated. The printed fabric testing results showed that the clarity was 91.7%, the K/S value was 8.9 under the condition of 25% PUA6 adhesive,6% active monomer and 5% photo initiator with 60s UV radiation. Furthermore, the washing fastness was 5, dry rubbing fastness was 4-5, wet rubbing fastness was 3, which were significantly enhanced.