A novel strategy for preparation of solvent-free high-solid content water-based polyurethane

Eethylenediamine (EDA), isophorone diamine (IPDA), diethylenetriamine (DETA), N- β- (aminoethyl)- γ- aminopropylmethyl dimethoxysilane (KH602) and polyether amine (D-230) were used as post chain extenders, a series of solvent-free high-solid content water-based polyurethanes (WPU) were prepared. The reactivity of different post chain extenders and the effects of different R values (mole ratio of –NCO/-OH) on solid content as well as the effects of chain extension degree on properties of WPU were investigated in detail. Among of water, small molecule diamine and diol, diamine with higher activity is preferred to water to complete the post chain extension reaction and improves the mechanical properties of WPU. When the R value is higher than 1.7 and the post chain extension degree is controlled at 70%, the viscosity of the solvent-free prepolymer is small enough to be emulsified, and the as-prepared WPUs show more excellent thermodynamic properties. In comparison, the cyclic chain extender such as IPDA can improve the mechanical properties and heat resistance of WPU, crosslinking type chain extenders involving DETA and KH602 can improve the heat resistance and anti-sticking of WPU coating. Whilst the WPU prepared by the chain extender containing flexible space, such as D-230, has a very low modulus and is suitable for preparing soft–type WPU.