Synthesis And Properties Study On Internal Crosslinking Waterborne Polyurethane

As environmental legislation that enacted by government becomes more and more rigid, as well as people continue to focus on their own health, people pay more and more attention to waterborne polyurethane(WPU) whose performance is equivalent to to solvent-based polyurethane. In this paper, the environment-friendly polyether-based waterborne polyurethane dispersion(WPUD), was synthesized by prepolymerization method and. The effect of hydrophilic chain extender, small molecule chain extender, HDI/IPDI ratio, the ratio of hard/soft segments and other factors on the performance and morphology of polyether-based WPUD was investigated. The preparation process, as well as the synthetic route was optimized in order to determine the optimal synthesis scheme. In addition, aiming at the problem of linear WPU with high water absorption and poor mechanical properties, a series of different internal cross-linking agents modified WPUs were prepared. Besides, the effect of the internal cross-linking agents on the performance of different internal cross-linking WPUs was discussed.During the polyether-based WPUD preparation, the infrared spectrum indicated that the polyether-based polyurethane with good hydrogenation degree was successfully synthesized. The tests confirmed that when soft/hard segment ratio is 2:1, the hydrophilic chain extender in an amount of 3.5wt.% DMPA, n(HDI) / n(IPDI) is 1/4, n(HDO) / n(HDA) is 2:1, WPUD showed moderate viscosity, dispersion stability, good water resistance, good mechanical properties, heat resistance, good crystallinity. By optimizing the preparation process of WPU, when the prepolymer reaction temperature is 80 ℃, prepolymerization time is 4 h, HDO chain time is 2 h, the chain extending reaction temperature is 80 ℃, TEA as neutralizer, neutralization degree is 90%, and the neutralization reaction temperature is 45 ℃, HDA chain extension was initiated after the completion of phase reversion, the preparation process exhibited preferable controllability and dispersion stability. SEM showed that the prepared polyether-based WPU exhibited high mechanical strength. DSC curves indicateed that with n(HDI) / n(IPDI) ratio increasing, the Tg of the prepared polyether-based WPU decreased firstly then rose, meanwhile, the crystalline melting peak area of hard segments gradually increased as well as the crystallinity of hard segments improved.On the basis of the preparation of polyether-based WPUD on, internal cross-linking WPUD was prepared by trimethylolpropane(TMP), pentaerythritol(PER), glycerol modified, respectively. The effect of three cross-linking agents on the performance of WPU was investigated. The FT-IR, the contact angle(CA), XRD, DSC, TGA, and other methods were applied to investigate the performance difference of three internal cross-linking WPUs. The results demonstrated that with 1.2wt.% TMP, 0.9wt.% Glycerol modified WPUD showed good stability, heat resistance, mechanical properties and water resistance, etc. From the above, 1.2wt.% TMP modified WPU exhibited slightly advantage than the 0.9wt.% Glycerol modified WPU.