Preparation and properties of the waterborne polyurethane film modified with microcrystalline cellulose

摘要

Waterborne polyurethane (WPU) was synthesized by isophorone diisocyanate (IPDI), polyether polyol 220, dimethylol butanoic acid (DMBA). Then the prepolymer was neutralized by triethylamine (TEA) and the chains were extended by ethylenediamine (EDA). Microcrystalline cellulose (MCC) was used as modifier to prepare a series of modified WPU by changing the order of adding MCC and the hydrophilic cross-linking time in the synthetic process. It was found that the hydroxyl in MCC partly reacted with the isocyano (-NCO) on basis of the -NCO content test. The heat resistance of the WPU films which improved with the addition of MCC exhibited by Thermo Gravimetric Analysis (TGA). Differential Scanning Calorimetry (DSC) curves, which having two changes for glass transition temperature (Tg), showed that a certain degree of phase separation appeared with the addition of MCC. The mechanical properties of modified WPU films, examined by tensile tests, showed higher tensile strength and elongation at break than that of unmodified one. The water resistance of the film also enhanced greatly after modification.