A Solventless Waterborne Polyurethane Emulsifying Investigation

A solventless waterborne polyurethane emulsion is synthesized by prepolymerization. The effecting factors including the ratio of isocyanate content to hydroxyl group's (-NCO/-OH), the reaction temperature and the carboxyl group content (- COOH %) on target prepared emulsion's viscosity; particle diameter and the water absorption are experimentally investigated during the reaction processes. The results show that: (1) the emulsion viscosity and water absorption decrease when the -NCO/-OH ratio (the ratio of isocyanate content to hydroxyl groups) increases, but the particle diameter increases. (2) the reaction rate increases when the temperature is higher, but the side reaction is more easily arisen. (3) both the emulsion viscosity and water absorption increase but the particle diameter decrease if the carboxyl content (-COOH %) is bigger. (4) the properties of emulsion and film after coating are finer if glycol as the chain extender.