Synthesis And Properties Of Thermally Stimulated Shape Memory Waterborne Polyurethane

Three series of shape memory waterborne polyurethane, which were aromatic polyurethane, aliphatic polyurethane and low chemical cross-linked polyurethane, were respectively synthesized from polyester polyol, isophorne diisocyanate (IPDI) or4,4’-diphenylmethane diisocyanate (MDI), dimethylol propionic acid (DMPA), trimethylolpropane(TMP) and ethylenediamine(EDA) by self-emulsified method. The structure of these shape memory polyurethane was characterized by fourier transform infrared specroscope(FTIR). The effects of the molar ratio of NCO group to OH group, the amount of DMPA, the kind of chain extender and the hydrated temperature on the basic properties and shape memory effect of aromatic and aliphatic polyurethane were discussed.In the study of the basic properties of the polyurethane, the following research results were obtained. With the increase of the molar ratio of NCO group to OH group, the particle size of the polyurethane emulsion, the water absorption and the tensile strength of the polyurethane films enlarged, but the viscosity and the enlongation to break decreased. With the increase of the amount of DMPA, the viscosity, the water absorption and the tensile strength of the polyurethane films went up, but the particle size and the enlongation to break declined. The viscosity, the water absorption and the tensile strength of the polyurethane extended chains by EDA were much higher than the polyurethane extended chains by BDO When the polyurethane was emulsified in the relatively low temperature, the particle size and the water absorption were lower, but the tensile strength was higher. The water resistence and the mechanical properties of the aromatic polyurethane were superior to the aliphatic polyurethane, but the emulsion stability was inferior to the latter. With the addition of TMP, the water resistence and the tensile strength of the polyurethane had been improved because of chemical cross-linking, but the water vapor permeability(WVP) decreased.In the study of shape memory effect of the polyurethane, the following results were obtained. With the increase of the hard segment content, the shape fix ratio of SMPU decreased, but the shape recovery ratio went up. The shape recovery properties of the aromatic polyurethane were superior to the aliphatic polyurethane. The polyurethane extended chains by EDA showed better shape memory properties than the polyurethane extended chains by BDO. The shape memory properties of the low chemical cross-linked polyurethane was excellent because of the synergistic effect of physical cross-linking and chemical cross-linking. When TMP content was1%, the shape fixed ratio was more than80%, and the shape recovery ratio reached98.10%. The repeated draw-recovery promoted the shape recovery properties, and the recovery ratio was close to100%. The shape memory polyurethane was sensitive to the temperature. The recovery temperature at which the shape recovery ratio reached the best was little related to the hard segment structure.