双层包覆相变储能微胶囊的制备及性能研究
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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。
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.
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。
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.
引文
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[2]王永川,陈光明,张海峰,等.相变储能材料及其实际应用.热力发电. 2004,11:10-14
[3]宋德清,方利国,王聃.相变储能材料的研究进展及在建筑中的应用.节能. 2008,311:4-7
[4]张奕,张小松.有机相变储能材料储能的研究和进展.太阳能学报. 2006,27:725-730
[5] Mohammed M F, Amar M K, Siddique A R, et al. A review on phase change energy storage: materials and applications. Energy Conversion and Management, 2004, 45: 1597-1615
[6]李金辉,刘晓兰.新型相变储能材料研究进展.化工新型材料. 2006,35:18-21
[7]邢登清,迟广山.多元醇二元体系固-固相变贮热的研究.太阳能学报. 1995,16:131-137
[8]王小伍,吕恩荣,林文贤,等.多元醇NPG/PE和NPG/TAM二元体系贮热性能的实验研究.太阳能学报. 1999,20:44-48
[9]张建军,武克忠,张建玲,等.三羟甲基乙烷、新戊二醇及其二元体系相变动力学的DSC研究.太阳能学报. 2000,21:399-402
[10]徐瑞云.固-固相变储能材料的研究.化学世界. 2001,12:619-622
[11]陈爱英,汪学英,曹学增.相变储能材料的研究进展与应用.材料导报. 2003,17:42-45
[12]粟劲苍,刘鹏生.新型聚氨酯固-固相变储能材料的组成与热性能的关系.中国塑料. 2006,20:21-24
[13]郭元强,梁学海.中国专利:99116025. 8, 1999-01-21
[14]吕社辉,郭元强,陈鸣才,等.聚乙二醇-纤维素接枝物的合成与表征.高分子材料科学与工程. 2004,20:62-65
[15]郭元强,吕社辉,叶四化,等.聚乙二醇-纤维素接枝物固态相变材料的贮热性能.高分子材料科学与工程. 2005,21:176-179
[16] Frusteri F, Leonardi V, Maggio G. Numerical approach to describe the phase change of an inorganic PCM containing carbon fibre. Applied Thermal Engineering , 2006, 26: 1883-1892
[17]孙建强,张仁元.金属相变储能与技术的研究与发展.材料导报. 2005,19:99-102
[18] Birchenall C E, Riechman A F. Heat storage in eutectic alloys. Metall Trans A, 1980, 11A: 1415
[19] Bulychev V V, Chelnokov V S. Al-Si alloy base heat accumulators with phase transition. Izv Vyssh Uchebn Zaved Chern Metall, 1996, 7: 64
[20] Fan Y F, Zhang X X. Thermal Stability and Permeability of Microencapsulated n-Octadecane and Cyclohexane. Thermochimica Acta, 2005, 429: 25-29
[21] Kadir T, Ahmet S, Sefa T, et al. Lauric and Palmitic Acids Eutectic Mixture as Latent Heat Storage Material for Low Temperature Heating Applications. Energy, 2005, 30: 677-682
[22] Gülseren B, Ahmet S. Phase Change and Heat Transfer Characteristic of a Eutectic Mixture of Palmitic and Steric Acids as PCM in a Latent Heat Storage System. Energy Conversion and Management, 2003, 44: 3227-3246
[23] Ahmet S. Eutectic Mixtures of Some Fatty Acids for Latent Heat Storage: Thermal Properties and Thermal Reliability with Respect to Thermal Cycling. Energy Conversion and Management, 2006, 47: 1207-1221
[24] Feldman D, Banu D, Hawes D, et al. Obtaining an energy storing building material by direct incorporation of an organic phase change material in gypsum wallboard. Solar Energy Materials, 1991, 22: 231-242
[25] Schossig P, Henning H M, Gschwander S, et al. Micro-encapsulated phase-change materials integrated into construction materials. Solar Energy Materials & Solar Cells, 2005, 89: 297-306
[26] Zhang Y P, Zhou Z B, Lin K P, et al. Application of latent heat thermal energy storage in buildings: State-of-the-art and outlook. Building and Environment, 2007, 42: 2197–2209
[27]秦鹏华.定形相变材料的研制、热物性及应用研究.硕士学位论文,北京:清华大学,2003
[28] Peippo K, Kauranen P D. A multi-component PCM wall optimized for passive solar heating. Energy Builds, 1991, 17: 318-325
[29] Huang M J, Eames P C, Norton B. Phase change materials for limiting temperature rise in building integrated photovoltaics. Solar Energy, 2006, 80: 1121-1130
[30] Wang S X, Li Y, Hu J Y, et al. Effect of phase-change material on energy consumption of intelligent thermal-protective clothing. Polymer Testing , 2006, 25: 580-587
[31] Xiao M, Feng B, Gong K C. Preparation and performance of shape stabilized phase changethermal storage materials with high thermal conductivity. Energy Conversion and Management, 2002, 43: 103-108
[32] Sari A, Sari H, Onal A. Thermal properties and thermal reliability of eutectic mixtures of some fatty acids as latent heat storage materials. Energy Conversion and Management, 2004, 45: 365-376
[33] Zhang Z G, Fang X M. Study on parattin/expanded graphite composite phase change thermal energy storage material. Energy Conversion and Management, 2006, 47: 303-310
[34] Inaba H, Tu P. Evaluation of thermophysical characteristics on shape-stabilized paraffin as a solid-liquid phase change material. Heat and Mass Transfer, 1997, 32: 307-312
[35]林怡辉.硬脂酸-二氧化硅复合相变材料的制备.广州化工. 2002,1:18-21
[36]张仁元.无机盐/陶瓷基复合储能材料的制备和性能.材料研究学报. 2002,6:652-656
[37]蒋长龙. NPG-TAM/蒙脱土纳米复合贮能材料的研究.合肥工业大学学报(自然科学版) . 2004,10:1281-1283
[38]刘星,汪树军,刘红研.原位聚合制备三聚氰胺脲醛树脂石蜡微胶囊及性能.化工学报.2006,57:2991-2996
[39] Cho J S, Kwon A, Cho C G. Microencapsulation of octadecane as a phase-change material by interfacial polymerization in an emulsion system. Colloid and polymer science, 2002, 280: 260-266
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