Characterization Of Shape Memory Polyurethane And Investigation Of Its Application On Textiles

Solution-cast films made at different temperatures of shape memory polyurethane have been investigated. On the base of studies of microstructure and various properties of shape memory polyurethane membranes, the feasibility of its application to textile industry to develop the smart fabrics is discussed.Cast temperature influences the microstructure, the degree of phase separation and the crystalline of hard segment of the shape memory polyurethane membranes, and therefore influence on its properties, such as the thermal-mechanical property, water vapor permeability and shape memory behavior. With the increase of cast temperature, the degree of phase separation of soft/hard segment of the material is increased. The glass transition temperature Tg, the crystalline of hard segment and crystal perfectness are also increased with the increase of cast temperature. Experimental results show that the sample SMP-120 obtained in our laboratory, casted under 120C reveals the appropriate microstructure and degree of phase segment for better required properties.The solubility of water vapor in shape memory polyurethane membrane depends strongly on the interaction of the water molecules with the polymer containing polar groups. In addition, the solubility coefficient depends on the water vapor activity. According to the studies what we have done, the water sorption in the shape memory polyurethane membranes follows the dual-mode sorption model based on the Langmuir and Flory-Huggins equations. And appear clustering of water at high the water vapor activity. The diffusion coefficient for water in shape memory polyurethane membranes depend on the polymer fractional free volume, diffusion energy ED and the interaction of water-polymer.The changes in the water vapor permeability of SMP films with respect to the temperature follow an S-Shaped curve, and increases abruptly at Tg of the soft segment. The water vapor permeability increases with the difference of humid vapor partial pressure between the SMP films surfaces. The high casting temperature is favorable for the increase of water vapor permeability of shape memory polyurethane.The shape memory behavior of shape memory polyurethane depends on the mobility of soft segment of polymer; the response temperature of shape memory is dependent on the glass transition temperature Tg of the soft segment. The final recovery rate and the recovery speed are mainly related to the stability of the hard segment domains. In theory, the thermomechanical constitutive model based on the 4-element rheological model is developed.According to what we had studied on experiment and theory, the development of smart fabrics using the shape memory polyurethane is feasible.