【作者】 樊耀峰；

【导师】 张兴祥；

【作者基本信息】 天津工业大学 ， 材料学， 2004， 硕士

【摘要】 相变材料胶囊是一种含有相变材料的微小容器。相变材料胶囊化技术在航空航天、机械制造、建筑材料、蓄热调温纺织品及电子设备等领域有广泛的应用前景。本项研究紧跟国际前沿，从探讨研制高性能的相变材料胶囊入手，研究提高其耐热温度和预防其过冷现象，所取得的研究结果有助于推动相变材料胶囊技术的应用。 本项研究以三聚氰胺树脂为囊壁，正十八烷为囊芯，通过原位聚合法制备相变材料微胶囊以及纳胶囊，并通过SEM、DSC、TG-DTA、XRD、FTIR、GC等分析测试手段对这些胶囊性能进行了系统研究和分析。首先，系统研究了乳化机转速和乳化剂浓度对胶囊性能的影响，并通过提高转速或乳化剂浓度获得相变材料纳胶囊；其次，系统研究了不同成核剂对微胶囊性能的影响，找到合适的成核剂抑制了相变材料微胶囊的过冷现象；再次，详细研究了环己烷对胶囊性能的影响，并通过添加适量环己烷提高了相变材料微胶囊及纳胶囊的耐热温度。研究结果表明： 1、当乳化机转速为9000rpm、TA浓度为1.2％时，合成重均粒径为0.9μm、数均粒径为0.8μm的纳胶囊。随着转速的增加，胶囊的平均粒径呈指数关系减小，分布变窄，多分散指数却增加。 2、乳化机转速对囊芯含量基本没有影响。在囊壁／囊芯比例固定的条件下，囊壁厚度与胶囊粒径呈线性关系，且随转速增加而减小。 3、对于平均粒径小于10μm的相变材料胶囊，胶囊的相变温度以及相变热基本不随粒径变化，而结晶峰变化较大，其过冷现象随着粒径的减小而加剧。 4、当乳化剂TA浓度为2.3％、乳化机转速为8000rpm时，合成重均粒径为1.0μm、数均粒径为0.9μm的纳胶囊。随着TA浓度的增加，胶囊粒径呈线性关系减小，分布变窄，多分散指数略有降低。 5、囊芯含量随TA浓度的增加而降低，囊壁厚度变化较小。 6、TA对胶囊的相变温度的影响很小，相变热随着TA浓度增加而减小；TA对胶囊的耐热性影响很小。 7、NaCl对微胶囊的相变热影响较小，但容易造成微胶囊粘结；乳液中的NaCI浓度超过为6%合成的微胶囊的过冷现象得到明显改善，然而，胶囊的机械强度与耐热性能均下降，微胶囊之间发生粘结。 8、1一十八醇对微胶囊的相变热影响也比较小，容易造成MF树脂为囊壁的相变材料微胶囊发生粘结;囊芯中1一十八醇含量约为9%的微胶囊的过冷现象得到有效抑制，然而，微胶囊之间发生粘结。 9、石蜡不会影响胶囊的表观形态以及分散性，超过30%的石蜡会降低微胶囊的有效蓄热调温效果;囊芯中20%左右的石蜡很好地抑制了微胶囊的过冷现象，然而，其用量要比NaCI和1一十八醇多一些。 10、NaCI、1一十八醇以及石蜡促进了微胶囊中正十八烷结晶，但三者均不会改变正十八烷的晶型。 11、加有环己烷的相变材料胶囊可以进行高温热处理，热处理温度应控制在160~180℃之间，热处理时间为30~60min为宜，此时，胶囊产生预留膨胀空间，囊壁发生交联。 12、环己烷使相变材料胶囊的粒径减小，粒径分布的均匀性增加。 13、热处理前，含有环己烷的胶囊的熔融峰加宽，结晶峰复杂化，160℃热处理30min除去胶囊中的环己烷，胶囊的相变性能得到恢复。 14、胶囊的预留膨胀空间随环己烷相对添加量的增加而增大，但并非线性关系，且受合成工艺的影响。 15、预留膨胀空间占胶囊体积(即刚合成的胶囊的囊芯中环己烷的含量)的百分比为14一18%时，经过160℃热处理30min的胶囊的耐热温度最高，微胶囊高于260℃，纳胶囊在 220℃左右。更多还原

【Abstract】 Microencapsulated phase change materials (MicroPCMs) and nanoencapsulated phase change materials (NanoPCMs) are tiny vessels with phase change materials (PCMs). MicroPCMs are widely applied in aviation, space flight, mechanical manufacture, architectural materials, heat-storage and thermo-regulated textiles, and electronic devices. There are still knowledge gaps between fabrication and properties of nano- and microencapsulated phase change materials. The present research has investigated improving their thermal stability and preventing them from super-cooling in order to fabricate MicroPCMs and NanoPCMs with higher performances.MicroPCMs and NanoPCMs were synthesized by encapsulating n-octadecane and the other components within the melamine-formaldehyde (abbr. MF) resin shell through in situ polymerization. Their properties have been investigated by using Scanning Electronic Microscopy (SEM), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), Thermogravimetry-Differential Thermal Analysis (TG-DTA), Infrared Spectroscopic Analysis (IR), and Gas Chromatography (GC), etc. The effects of the mulser’s stirring rate and the emulsifier concentration on the properties of encapsulated PCMs have been systematically studied, and NanoPCMs have been obtained by increasing the stirring rate or the emulsifier concentration. The influences of different nucleating agents on MicroPCM performances have also been investigated in detail to search for a suitable nucleating agent to prevent MicroPCMs from super-cooling. In addition, the impact of cyclohexane on MicroPCMs and NanoPCMs has been studied at length. Fortunately, their thermal stable temperature has been improved by feeding cyclohexane with an appropriate content to n-octadecane. The conclusions are showed as follows.1. Nanocapsules with 0.9 m in the weight-average diameter and 0.8 m in the number-average diameter have been obtained when the stirring rate of the mulser is 9000rpm and the TA concentration is 1.2%. As the stirring rate increasing, the average diameter of capsules decreases exponentially and its distribution turns narrow, but its polydispersity index increases.2. The mulser’s stirring rate has no effect on the core content of capsules. The shell thick is linear with the average diameter of capsules while the weight proportion of the shell to the core is constant. The shell thick decreases with the increase of the stirring rate.3. For encapsulated PCMs with less than 10 m in their average diameter, their temperature and heat of phase transition seldom change as their average diameter decreasing; however, their crystallization peaks vary dramatically and the super-cooling becomes worse.4. When the TA concentration is 2.3% and the mulser’s stirring rate is 8000rpm, nanocapsules with 1.0 m in the weight-average diameter and 0.9 m in the number-average diameter have been fabricated. As the TA concentration increases, the average diameter of capsules decreases exponentially. Simultaneously, its distribution gets narrow, and its polydispersity index decreases.5. The core content reduces as the TA concentration increasing; however, the shell thick changes slightly.6. Although the TA concentration hardly affects the phase change temperature, the heat of phase transition reduces as the TA concentration increasing. It scarcely influences the thermal stability of capsules.7. Sodium chloride has slight effect on the heat of MicroPCM phase transition, but it easily leads microcapsules to stick together. For the microcapsules feeding more than 6% sodium chloride in the emulsion, their super-cooling can be prevented availably; however, their mechanical intensity and their thermal stabilities turn worse and they cohere each other.8. 1-Octadecanol also affects slightly the heat of MicroPCM phase transition, but it easily induces microcapsules with MF resin as the shell to occur conglomeration. For the microcapsules with about 9% 1-octadecanol in the core, their super-cooling can al更多还原