基于水凝胶的定形相变材料制备与性能研究

Preparation and Characterization of Form-stable Phase Change Materials with Hydrogel Skeleton as Supporting Material

在储冷控温用定形相变材料研究领域,水的相变储冷特性常被忽视.本研究以丙烯酸和聚乙烯醇为原料,通过交联聚合,辅以冻融循环和表面干燥制备了一类基于聚乙烯醇和聚丙烯酸的水凝胶定形相变材料.在氢键和冻融循环的作用下,聚乙烯醇和聚丙烯酸相互缠绕形成强大的氢键网络,赋予水凝胶极高的含水量和良好的塑形性能.将该水凝胶用作定形相变材料,通过其中水的相变实现相变储冷,储冷容量达237 J/g,且50℃以下水不会挥发.该水凝胶定形相变材料具有极好的抗泄漏性能和良好的循环稳定性,50次冻融循环后储冷性能无变化,且可塑成任意形状,可应用于储冷、冷链控温和冷敷等领域.此外,为充分利用水凝胶内部的孔隙,通过添加纳米石墨片增强水凝胶骨架的稳定性,并经冷冻干燥得到了一种高孔隙率支撑材料,然后以赤藓糖醇和PEG2000为相变材料,制备了2类定形相变材料.它们均具有极高的相变材料含量和相变储热容量,证明基于水凝胶的聚合物网络骨架是一类良好的支撑材料.本文所得结果对推进水凝胶材料在热能储存和温度控制领域的应用具有重要的价值.

Form-stable phase change materials(FSPCMs)are a kind of latent heat/cold energy storage materials and play key role in fields like new energy development,cold chain temperature control and healthcare.Lots of expensive chemicals have been investigated as phase change materials(PCMs)for FSPCMs,however,the application of water,a very cheap and abondance material in our planet,as a phase change cold energy storage material for FSPCMs is neglected.Herein,a kind of hydrogel based on poly(vinyl alcohol)and poly(acrylic acid)was prepared at first,and then novel FSPCMs with high latent cold energy storage capacity were obtained by solving the problem of water leakage in the hydrogel through simple surface freeze drying.The latent cold energy storage capacity of the obtained hydrogel-based FSPCMs attained 237 J/g,and the water in the FSPCMs would not volatilize when the temperature was not higher than 50℃.The FSPCMs also exhibited excellent anti-leakage performance even it was heavily pressed.Meanwhile,the FSPCMs possessed good long-term thermal reliability and its latent cold storage performance has not changed after 50 freeze-thaw cycles.The FSPCMs also had good temperature control and shaping properties,making it applicable to cold storage,cold chain temperature control,cold compress and other fields.In addition,in order to fully utilize the high porosity of dried hydrogel,exfoliated graphite nanoplatelets(xGnP)were applied to enhance the stability of the hydrogel skeleton with the largest water content,and a novel supporting material with high porosity was obtained by freeze-drying.Then,erythritol(ET)and PEG2000,two water-soluble PCMs,were selected as representatives,and two types of FSPCMs were prepared by melting impregnation.Both types of FSPCMs possessed very high content of PCMs and very high latent heat storage capacity,which proved that polymer network skeletons of hydrogels were perfect supporting materials for FSPCMs.Consequently,the results obtained in this study have important value for promoting the application of hydrogel itself and hydrogel materials in the fields of heat energy storage and temperature control.