【作者】 王海鸥；

【导师】 翁端；

【作者基本信息】 清华大学 ， 材料科学与工程， 2009， 硕士

【摘要】 随着能源和环境污染问题的日愈凸显,节能减排已成为各国的发展主题之一。相变储能技术利用材料的相变过程实现能量的吸收、存储和释放,从而解决能量供求在时间和空间匹配上的矛盾,提高能源的利用率。开发高效、长寿命的相变储能材料（phase change materials,PCMs）是目前节能技术研究的热点之一。PCMs应用过程中的泄露及与环境的相容性等问题直接制约了其应用。因此,PCMs的封装技术尤为重要,目前的主要封装方法有定形化和微囊化。本文选择化学稳定性好,来源广泛,价格低廉,绿色环保的明胶、阿拉伯胶作为原料,以两者聚合反应生成的聚合物作为微囊的首层壁材,以聚乙烯醇（PVA）为复层膜壁材,对多元醇等PCMs进行微囊化,并对所制备的PCMs微囊进行了性能研究。本文以Span-80+Tween-80为复合乳化剂,采用搅拌法制备稳定好的十二醇乳液。乳液中的十二醇微滴在静置一个月后其大小仍与新鲜样品保持一致,约为1-4μm。所制备的十二醇乳液具有黏度小（298 K,6.4 mPa·s）、储热密度高(20.0-40.0 J·g^-1)的特点。在制得稳定乳液的基础上,通过相分离法制备了明胶-阿拉伯胶聚合物/PCMs（十二醇、十六醇和BS）微囊,实现单层膜包覆,制得微囊的ΔHf分别为96.2 J·g^-1、96.3 J·g^-1、48.4 J·g^-1,芯材包覆效率为44.7 wt%、46.3 wt%、45.7 wt%。在此基础上,在喷雾干燥过程中加入聚乙烯醇（PVA）,得到PVA/明胶-阿拉伯胶聚合物/PCMs（十二醇、十六醇和BS）微囊,从而实现双层膜包覆,制得微囊的ΔHf分别为111.6 J·g^-1、109.7 J·g^-1、61.4 J·g^-1,芯材包覆效率为51.8 wt%、52.8 wt%、57.7 wt%。结果表明,相对于单层膜包覆,PVA的加入进一步提高了微囊的分散性,并有效阻止了芯材的流失,从而提高了PCMs的储热密度和使用寿命。更多还原

【Abstract】 Recently, energy and environmental crises become more and more serious. Therefore, energy saving becomes one of developing topics in most countries including China. Phase change materials （PCMs） can settle the contravention between energy supply and demand by heat absorbing, storing and releasing via the phase change of the materials. To develop high efficient and durable PCMs is one of important fields in energy saving.The application of PCMs is seriously restricted by the leakage and herby environmental pollution in service. Thus, encapsulation of PCMs is paid more and more attention to. Encapsulating is one of the major routes to achieve it. In this paper, glutin and acacia gum, which are chemically stable, abundant, inexpensive and environment friendly, were chosen as coating material to encapsulate the PCMs such as lauryl alcohol. The received PCMs microcapsules were characterized and analyzed.Span-80 and Tween-80 were used as mixed emulsifier for preparation of stable lauryl alcohol emulsion with simple stirrer. Emulsion were observed by microscope. The diameter of PCMs particles in emulsion keeps 1-4μm in one month observed by microscope. The viscosity of emulsion was 6.4 mPa·s at 298K. The heat enthalpy of emulsion was 20-40J/g, which was 3-10 times as that of water.On the basis of stable PCMs emulsion, spherical microcapsules with polymerization product of glutin and acacia gum （PGA） as shell and PCMs as core were prepared. During the spray drying process of the as-parepared PGA/PCMs monolayer microcapsules, PVA was added as the second shell material. Lauryl alcohol, cetyl alcohol and BS were encapsulated in this way, whose phase change enthalpy were 111.58 J·g^-1, 109.7 J·g^-1 and 61.36 J·g^-1, respectively. The corresponding contents of core material in the microcapsules were 51.8wt%, 52.8% and 57.7%, respectively. The SEM micrographs showed that the encapsulation of PVA improved the dispersion of the microcapsules and effectively prevented the leakage of the core material.更多还原