Synthesisand Properties Of Polyurethane Solid-Solid Phase Change Materials

In this paper,a novel phase change heat storage polyurethane with MPEG-based soft segment and various MDI-NPG,MDI-BDO,MDI-PER,TDI-NPG-based hard segments was synthesized by two-step solution polymerization. FT-IR,DSC,TG,POM were used to study the structure characteristics,phase change behavior,heat storage characteristics and aggregation structure. Then the best process condition of polyurethane can be obtained.The results indicated that the best process condition of polyurethane with MPEG-based soft segment and MDI-NPG-based hard segments was as follows:reaction temperature was 70℃,reaction time is 12 hours, reation R([NCO]/[OH])is 1.01. In this condition, the phase-change temperature and enthalpy of phase change heat storage polyurethane were 43.92℃and 146.64J/g.Polarization Microscope(POM) and DSC investigation showed that the soft segments of Polyurethane phase change materials could crystallize and the crystal structure was spherulites,but the spherulites size was much smaller than that of MPEG because the soft segment MPEG's crystallization in polyurethane phase change materials was confined by the hard segment. The heat srorage is caused by the transition of the soft segments of polyurethane phase change materials from crystalline state to amorphous. The energy is mainly obtained from heat caused by entropy change between the crystal solid state and amorphous solid state. The hard segments acted as physical cross-linkers to restricted MPEG's segmental movement. when it is heated to the temperature above MPEG's melting point, polyurethane phase change materials still doesn't move freely and keep its solid - solid phase transition state.The polyurethane phase change materials made with MDI-BDO,MDI-PER-based hard segments have good thermal properties, great transition enthalpy, suitable phase transition temperature, good thermal stability, without liquid leakage during the phase transition process and reasonably good stability throughout the cycling process.BDO and PER have not phase transition temperature and transition enthalpy from room temperature to 100℃range. But NPG exists phase transition temperature and transition enthalpy and the transition temperature closes to MPEG's. To test the performance of MPEG-co-NPG,MPEG-co-BDO and MPEG-co-PER,the results show that the NPG has a synergetic effect on polyurethane phase change materials.The crystalline of polyurethane with MPEG-based soft segment and MDI-NPG-based hard segments was smaller than TDI-NPG's.