以PNIPAm系凝胶为载体的复合相变材料的制备和研究

【作者】 于典；

【导师】 潘春跃；

【作者基本信息】 中南大学 ， 有机化学， 2007， 硕士

【摘要】 固-液相变蓄热材料因其具有较大的相变焓而成为目前研究的热点，但有固-液相变蓄热材料在相变过程中有固体变成液体体积变化大，盛装困难。针对这种缺点本文将固-液相变蓄热材料复合到高分子凝胶载体中，制备了一种不需要容器盛装的新型复合蓄热材料。首先，本文作者以N-异丙基丙烯酰胺（NIPAAm）系共聚凝胶为研究对象，通过引入亲水单体丙烯酰胺（AAm）和疏水单体甲基丙烯酸丁酯（BMA）制备了PNIPAAm、P（NIPAAm-co-AAm）和P（NIPAAm-co-BMA）三种具有不同亲水性的共聚凝胶。实验发现，NIPAAm系共聚凝胶呈现热缩温敏特性，在相转变温度LCST以下，随凝胶亲水性增强，凝胶的LCST升高。研究了三种凝胶在不同浓度的六种钠盐溶液中溶胀行为。结果表明，PNIPAAm系温敏凝胶在六种钠盐溶液中的仍具有热缩温敏特性，与在水中相比，温敏性减弱。20℃时，随着盐溶液浓度的增大，凝胶的溶胀速率减慢，平衡溶胀度减小。凝胶在盐溶液中达到溶胀平衡的时间比在水中达到溶胀平衡的时间长，且三种凝胶在盐溶液中的平衡溶胀度均小于相同温度下纯水中的平衡溶胀度。其次，本文采用自由基聚合法，合成了以PNIPAAm凝胶为载体，棕榈酸和月桂酸的混合物为相变材料有机复合相变蓄热材料；及P（NIPAAm-co-AAm）凝胶为载体，棕榈酸、月桂酸和Na₂HPO₄·12H₂O为相变材料的有机／无机复合相变蓄热材料，采用红外光谱（IR）、示差扫描量热法（DSC）、热重分析（TG）、扫描电镜（SEM）等手段对两种复合材料的结构及热性能进行了表征与分析，研究了有机酸和无机盐的百分含量对复合材料的相变温度和相变焓的影响。结果表明，两种复合材料都随有机酸含量的增加，相变温度升高，相变焓增大，相变材料和凝胶的相容性增强。在150℃之前，两种材料的失重率都只有1％左右。PNIPAAm凝胶与混合酸复合的相变材料，当混合酸的含量达到76％时，材料的相变焓为105 J·g^-1。添加Na₂HPO₄·12H₂O的复合材料，相变焓均大于100 J·g^-1，随着有机酸和无机盐的质量比例增大，复合材料的相变温度范围变窄。Na₂HPO₄·12H₂O在复合材料中依然保持原来的物性。更多还原

【Abstract】 Solid-liquid phase change materials for thermal storage become theresearch hotspot because of its big phase change enthalpy at the presenttime. However, Solid-liquid phase change materials has a so big volumethat it is difficult to load when materials change solid to liquid. Aim atthis phenomenon, solid-liquid phase change materials for thermal storagewas compounded to polymer gel carriers in this paper. A kind ofnew-style composite materials which needn’t container to fill wasprepared.Firstly, a serie of N-isopropylacrylamide （NIPAAm） copolymer gelswas investigated in this paper. Three homogeneous PNIPAm、P（NIPAm-co-BMA） and P（NIPAm-co-AAm） hydrogels with differenthydrophilicity were prepared from hydrophilic acrylamide （AAm） andhydrophobic butyl metha-crylate（BMA）. Copolymer gels show negativethermo-sensitivities. Lower critical solution temperature （LCST）、equilibrium swelling degree and the initial swelling rate increase as thehydrophilicity of gels increases. Swelling behavior in six different sodiumsalt solution were researched. Experimental results shows three gels shownegative thermo-sensitivities in salt solution , temperature responsiveperformance weakens compared with water. Swelling rate becomesslower and Equilibrium swelling ratios is small with increasing ofConcentration for salt under 20℃,Time for swelling equilibrium is longerin salt solution than that in water, furthermore, equilibrium swelling ratiosin sodium salt solution are all smaller than that in water when under thesame temperature.Secondly, organical composite thermal storage materials which takethe PNIPAAm gels as the carriers and the palmitic acid and the lauric acidmixture for phase change materials were Synthesized by radicalpolymerization ,and organical/inorganical composite materials which takeP（NIPAAm-co-AAm） gels as the carriers and the palmitic acid、thelauric acid and Na₂HPO₄·12H₂O mixture were also Synthesized byradical polymerization. Structure and thermal performance of twocomposite material were characterized and analyzed by infrared spectroscopy and differential scanning calorimetry, thermogravimetricand Scanning Electron Microscope. The influence of organic acid and theinorganic salt percentage on phase change enthalpy and transfertemperature studied. It finds out that phase change temperature andenthalpy for two composite material increase, Phase change material andgels are more compatible along with organic acid content increasing. Twokind of materials weightlessness rate all only have about 1%.For composite material of PNIPAAm gels and mixture acid, the phasechange enthalpy is 105 j.g^-1 when the mixed acid content achieved 76%the enthalpy is bigger than 100 J·g^-1when adding Na₂HPO₄.12H₂O,withthe quality proportion for organic acid and inorganic salt increasing, thephase change temperature scope changes narrowly. Na₂HPO₄·12H₂O stillmaintains the original nature in the compound materials.更多还原