Investigation Of The Synthesis And Modification Of Waterborne Polyurethane

In recent years, It has been attentioned widely due to the excellent performance and environmental effects of waterborne polyurethane(WPU).WPU was synthesized from poly (propylene glycol) (PPG), dimethylol-propionic acid (DMPA), isophorone diisocyanate (IPDI) and ethylenediamine (EDA). And we studyed on the emulsion and films properties which inflected by n(NCO):n(OH), DMPA content, Degree of neutralization, molecular weight of soft segment, EDA content and feeding methods of EDA. The result indicated that tensile strength of WPU were significantly improved, elongation at break decreased with the increase of n(NCO):n(OH) and DMPA content. Solvent-resistance and micro-phase separation of WPU were increased as n(NCO):n(OH) increased, stable emulsion of WPU was obtain under the condition of n(NCO):n(OH) 1.5. As solvent-resistance of WPU was decreased with increased of DMPA content, therefore on condition that WPU emulsion was stable, DMPA content should be possibly lower. While it was strongly dependent DMPA content for 5.99～6.8%. Overall performance of WPU were the best under the conditions of degree of neutralization 80～100% and n(NH2):n(NCO) value 0.9; In the process of emulsifying, solvent-resistance of WPU was significantly enhanced, elongation at break decreased, particle size distribution narrowed and stable emulsion under the condition of EDA dissolving in water, solvent-resistance and tensile strength of film decreased, the elongation at break increased with the increase of soft segment molecular weight.The surface of nano-TiO₂ was modified by silane coupling agent, titanium coupling agent, stearic acid, and their complex agents. the results showed that, when the content of titanium coupling agent and stearic acid were 5% and 205 , reaction temperature 45℃and reaction time 90 min, the effect of surface modification was the best.Based on WPU preparation, WPU/nano-TiO₂ composite was prepared by means of in-situ and sol-gel preparation. The influence of nano-TiO₂ on performance of WPU/anno-TiO₂ were characterized by using FT-IR, UV spectrophotometry, TEM, SEM. The result showed that nano-TiO₂ dispersed homogeneously in the WPU matrix, played a toughening effect, and significantly UV absorption <650 nm was observered . Respectively, antibacterial of WPU/nano-TiO₂ composite was investigated. The results showed that WPU/namo-TiO₂ composite exhibited excellent inhibit against the growth of escherichia coli.In the process of sol-gel preparation , reasonable technology parameters for synthesis were determined, The result showed that hydrolysis condensation time 150 min, 5～10% of TNB content n(H2O):n(TNB)≥602, pH 9.5～10.5.