Preparation of polyurethane membrane with dual switch temperature sensitivity and its moisture vapor permeability

Three types of thermal sensitive polyurethane(TSPU) were synthesized,and the switch temperatures(the phase transition temperature of soft segment defined as switch temperature) of TSPU blends were investigated,along with preparation of polyurethane membrane with dual switch temperature sensitivity.The study indicates that the blend(TSPU(a) and TSPU(b)) with the similarity of constitution and structure in soft segment,has just a new switch temperature.However,the blend(TSPU(b) and TSPU(c)) with different constitution and structure in soft segment shows two independent switch temperature.According to moisture vapor permeability(MVP) analysis,it is found that when the temperature exceeded the switch temperature,the MVP of all the blends of TSPU changed markedly.Moreover,the blend of TSPU(a) and TSPU(c) shows just one switch temperature characteristic for MVP,but the blend of TSPU(b) and TSPU(c),shows dual switch temperature characteristics for MVP.So,it is believed that it is an efficient approach to prepare TSPU membrane with dual different switch temperatures by means of blending two types of TSPUs with different soft segments.