Synthesis And Properties Study On Polyethylene Glycol/Poly (Vinyl Alcohol) Polymeric Solid-Solid Phase Change Materials

In recent years, phase change materials (PCM) are becoming an activeresearch field in energy utilization and material science. When temperature ishigher than PCM's phase change point, it will absorb heat; on the contrary it willrelease heat when temperature is lower than PCM's phase change point, which isessential of phase change. According to its working style, PCM can be dividedinto solid-liquid, solid-solid, solid-gas and liquid-gas. Solid-solid phase changematerials can be also divided into inorganic salt, polyhydric alcohol and polymer. Polymeric solid-solid phase change materials(SSPCM) present reversiblephase change procession. Their main advantage is little variation volume and noliquid lick when phase change happen, thus can decrease the requirement ofvessel. SSPCMs even can be made structural materials directly and need novessel. They have feasible phase change temperature, long using life and steadyproperties, which is worthy of application in practice. SSPCMs are hotspot inphase change materials research. Exploitation and application in SSPCM overseas is more and more excellentin these years. This field was first set foot in in 1990 in our country, there are lotsof important theories have not been studied in our country. The PCM in temperature adaptable textile fibers is solid-liquid style, Outlastfibers which have been in market are made by microcapsule of solid-liquid phase 113聚乙二醇/聚乙烯醇高分子固－固相变材料的合成与性能研究change materials. Repeated shrinking and expanding during phase change processmade the volume of this solid-liquid PCM changed and its using life are alsodecreased, and the wearable properties will be effected to. In our research, new kinds of polymeric SSPCMs (PVA-g-PEG) wereprepared. In these materials, PVA worked as solid skeleton and PEG as workingsubstance, which can be used as short fibers or insulating padding directly or usedas functional factor in spinning. New kinds of polymeric SSPCMs (PVA-g-PEG) were prepared by means ofsolvent blend and graft copolymerization. Their phase change behaviors wasstudied by DSC method, they had reversible solid-solid phase change properties.The melting point(Tm) of blends kept invariable, the peak crystalline point (Tc)was related to the weight percentage of PEG. Tc was higher when the weightcontent of PEG/PVA was nearly and Tc was lower when the weight content ofPEG/PVA was six to one. The enthalpy of blends was declined with the weightcontent of PEG decreased; Graft ratio had no relation with phase changetemperature and normalized enthalpy in graft copolymers, but the phase changetemperature became higher when molecular weight of PEG hoisted. We canadjust phase change temperature by controlling molecular weight and enthalpy bycontrolling graft ratios. The crystallization structure and morphology of PEG/PVA SSPCMs wereanalyzed by WAXD, POM and SEM. Their melting and crystalline procedure wasaffected due to the addition of PVA, but their crystalline structure had not beenchanged. The crystalline degree of blends decreased gradually with the weightcontent of PEG decreased; the graft copolymers were lower than blends and thegraft ratio had no evidence relationship with crystalline degree disliking whatblends did. The effect of chemical bond was more notable than physicalmolecular interaction. 114吉林大学博士学位论文 In order to review how blend proportion and graft ratio effect crystallizationtime (t1/2) and speed (G), the crystallization kinetics of PEG/PVA SSPCMs werestudied by DSC method. In isothermal crystallization at the same temperature, Gof blend system and graft system were lower than pure PEG4000, and graftsystem was lower than blend system, too. G of graft system decreased as thedeclining of graft ratio.G of blend system became higher when the proportion ofPEG and PVA was nearly, and lower whe...