【作者】 辛长征；

【导师】 黄象安；

【作者基本信息】 东华大学 ， 材料科学与工程， 2013， 博士

【摘要】 随着传统能源的日趋紧张,提高能源的使用率和开发新能源是21世纪一个重要的研究课题。由于相变材料微胶囊在相变过程中能够储存和释放热量,并使温度保持相对恒定,将其应用到纤维和纺织品中,可以提高人体热平衡的自我调节,使人体处于一个较为舒适的环境温度中。将相变材料胶囊化,就是一种有效的蓄热储能手段。本文通过原位聚合法和界面聚合法,分别采用两种具有代表性的聚合物(脲醛树脂和聚脲)为壳材,以性价比较高的工业级石蜡为相变材料,从乳化机理和成囊机理上指导微胶囊的合成过程,制备了两种具有较小粒径且分布均匀、较大蓄热能力、较高耐温性的相变材料微胶囊。通过分析对比,将脲醛树脂(UF)/低熔点石蜡微胶囊与高熔指PP共混铸带,研究了共混体系的流变性能和熔喷纺丝工艺,尝试生产了克重为80g/m2的熔喷保暖棉。论文的研究内容和成果主要包括以下五点。(1)以工业级低熔点石蜡为相变材料,尿素和甲醛为反应单体,采用两步法原位聚合制备UF/低熔点石蜡相变材料微胶囊。利用DSC、TG、SEM、FTIR、激光粒度分布仪等表征手段,探索了脲醛树脂的聚合原理和成囊机理,重点研究了芯壁材投料比、单体摩尔配比、预聚温度、预聚体滴加时间、酸化时间、固化反应温度等因素对微胶囊蓄热能力、粒径大小及分布、外观形貌和耐温性等品质的影响。研究发现适当增加预聚体中二羟甲基脲的比例,利于提高微胶囊的成囊率和蓄热能力；而一味增加芯壁材投料比例,并不能同步增加微胶囊的相变潜热；酸化阶段主要影响初期树脂对低熔点石蜡的富集能力,固化阶段则影响树脂的交联度和微胶囊的成囊率。当芯壁材投料比为1.5：1～1.8：1,甲醛与尿素摩尔比为1.8：1,预聚温度为60℃,预聚体滴加时间为30min,酸化时间为60min,固化反应温度为60℃左右时,合成了相变潜热为76J/g,相转变温度为27.4℃,体积平均粒径为4.5μm左右,耐220℃高温,外观形貌为近圆球状的UF/低熔点石蜡微胶囊。(2)研究了非离子型乳化剂、阴离子型乳化剂在合成UF/低熔点石蜡微胶囊过程中的作用机理,并就单独采用乳化剂苯乙烯马来酸酐共聚物钾盐(SMA)或辛烷基酚聚氧乙烯醚(OP-10)的含量、乳化剪切速度对乳化效果、微胶囊的蓄热能力、粒径、形貌进行了分析和讨论。利用OP-10较高的空间位阻作用和SMA对初期树脂较大的富集作用,采用SMA/OP-10复合乳化剂制得了均匀稳定的O/W乳液和较高成囊率的UF/低熔点石蜡微胶囊。较佳的制备条件是乳液体系的pH值为9,SMA与OP-10质量配比为4：1,SMA/OP-10复合乳化剂含量为低熔点石蜡质量的9%。(3)以低熔点石蜡为包裹对象,以环己烷为油相溶剂,甲苯-2,4-二异氰酸酯(TDI)为油相单体,乙二胺(EDA)为水相单体,通过界面聚合法制备了聚脲/低熔点石蜡微胶囊。提出了壳材生成速率取决于EDA向反应微环境(油相乳滴)界面扩散速率的观点,重点讨论了乳化剂的种类、OP-10的用量、乳化剪切速度、芯壁材投料比、EDA和TDI的摩尔配比、油水相比、乙二胺滴加速度、聚合反应温度等因素对乳化液滴和相变材料微胶囊性能的影响。当采用占乳液质量1.8%的OP-10为乳化剂,乳化剪切速度7000r/min,芯壁材投料比3：1～3.5：1,TDI与EDA摩尔比1：3,相比1：8,EDA滴加速度为2mL/min左右时,能够合成相变潜热为85J/g,相转变温度为28.7℃,耐210℃高温,体积平均粒径为7.5μm左右,外观形貌为圆球状的聚脲/低熔点石蜡微胶囊。(4)以高熔指PP为基材,以UF/低熔点石蜡微胶囊为功能添加物,采用微型锥型双螺杆挤出机共混铸带制得MicroPCMs/PP切片,采用高熔指熔体流动速率仪和毛细管流变仪,研究了MicroPCMs的添加比例、熔体温度、剪切速率等因素对共混体系的流变性能、表观黏度、非牛顿指数、结构黏度指数和黏流活化能的影响。采用12wt.%MicroPCMs的MicroPCMs/PP切片为原料,尝试生产了克重为80g/m2的熔喷保暖棉,并就其热性能和物理机械性能进行了分析讨论。研究发现MicroPCMs/PP共混体系具有明显的非牛顿假塑性流体行为,当微胶囊含量为12%时,共混体系的可纺性较好,所制得的熔喷保暖棉相变潜热为8.52J/g,相转变温度为28.2℃,其物理机械性能与纯PP熔喷保暖棉基本相当。(5)通过熔喷扩大试验获得的结果表明,本研究成果具有产业化应用前景。更多还原

【Abstract】 With the traditional energy becoming more tense, it is very important to improve the energy efficiency and develop the new energy in the21st century. Phase change materials (PCMs) are the materials that can absorb, store and release large amount of thermal energy during the phase change process. And PCMs has been used to manufacture thermoregulated fibers and textiles to improve the thermal self-regulation of the wearer. Encapsulation is an effective means of energy storage. In this study, microencapsulated paraffin wax with urea-formaldehyde (UF) resins and polyurea shells were synthesized through in situ polymerization and interfacial polycondensation, respectively. The aim of this work was to guide the synthesis process from the emulsification mechanism and encysted mechanism in order to fabricate MicroPCMs with small particle size and uniform distribution, a large thermal storage capacity and heat resistance. Moreover, MicroPCMs and PP were blended using micro-twin-screw. The spinnability of this system was studied by capillary rheometer. At last, the melt-blown spinning process and produced80g/m2melt-blown warm cotton were investigated. The content and achievements of this thesis include the following five points.(1) MicroPCMs containing low melting point paraffin as phase change core were synthesized by two-step in situ polymerization which the urea and formaldehyde as a reactive monomer. The aggregation principle and encysted mechanism of UF resin were explored. We focused on the effects of the molar ratios of core and shell materials, the molar ratios of monomer, the prepolymerization temperature, the dropping speed of prepolymer, the acidification time and the curing temperatures on the heat storage capacity, the particle size and distribution, the morphology and heat resistance of MicroPCMs. It was found that increasing the proportion of dimethylol urea was helpful to improve the encysted rate and the heat storage capacity. The acidification stage mainly affected the enrichment capacity of UF resin to lowing melting point paraffin. It was also found that the curing stage mainly affected the crosslinking degree of UF resin and the encysted rate of MicroPCMs, respectively. The results showed that the formaldehyde and urea in the ratio of1.8:1, the prepolymerization temperature at60℃, the core and shell material in the ratio of1.5:1～1.8:1, the dropping time of prepolymer for30min, the acidification time for60min, the curing temperature at60℃were the chosen conditions for the synthesis of MicroPCMs. Under the conditions, the appearance of MicroPCMs was nearly spherical with the latent heat of76J/g, the phase transition temperature of27.4℃, the volume average particle diameter of4.5μm and with220℃heat resistance.(2) The action mechanism of non-ionic emulsifiers and anionic emulsifiers in the synthesis process of UF/low melting point paraffin MicroPCMs was researched. And along with the contents of emulsifier styrene-maleic anhydride copolymer (SMA) potassium salts or sim alkylphenol polyoxyethylene ether (OP-10), the effects of emulsifying,shearing velocity on the emulsification, microencapsulation heat storage capacity, particle size, morphology were analyzed and discussed. Uniform and stable O/W emulsion and higher encysted rate of UF/low melting point paraffin MicroPCMs were obtained using SMA/OP-10combined emulsifier, this was attributed to high steric hindrance of OP-10and great enrichment of SMA to the resin in the initial process. The results showed that the optimum conditions were pH9of emulsion system, SMA and OP-10in the mass ratio of4:1and SMA/OP-10content of9wt.%low melting point paraffin.(3) Cyclohexane as the oil phase solvent,2,4-diisocyanatotoluene (TDI) as the oil phase monomer, ethylene diamine (EDA) as the water phase monomer, MicroPCMs with low melting point paraffin as core materials were fabricated via interfacial polymerization. The generation rate of shell materials depended on the diffusion rate of EDA to microenvironment (oil phase droplet). The influences of the type of emulsifier, the amount of OP-10, emulsion shear rate, the ratio of core and shell materials, the molar ratio of EDA and TDI on the emulsion droplets and MicroPCMs performance were investigated, and the influences of the ratio of oil and water, the dropping rate of EDA, the polymerization temperature were also discussed. The results illustrated that the optimum conditions were OP-10accounted for1.8wt.%of the emulsion, emulsion shear rate was7000r/min, the ratio of core and shell was3:1-3.5:1, the ratio of TDI and EDA was1:3, the ratio of water and oil was1:8, the dropping rate was2mL/min. Under the optimized conditions, the appearance of MicroPCMs was nearly spherical and the properties of MicroPCMs were the latent heat of85J/g, the phase transition temperature of28.7℃, the volume average particle diameter of7.5μm and with210℃heat resistance.(4) MicroPCMs/PP blends were prepared with high melt index PP as the substrate, UF/low melting point paraffin as the functional additives using a miniature conical twin-screw extruder. The effects of the content of MicroPCMs, melt temperature, shear rate on the rheological properties, the apparent viscosity, non-Newtonian index, structural viscosity index and flow activation energy of MicroPCMs/PP melts were studied by using high melt index melt flow rate meter and capillary rheometer. The80g/m2melt blown warm cotton was produced with the content of12wt.%MicroPCMs. Moreover, the thermal and mechanical properties were analyzed and discussed. The MicroPCMs/PP blends showed non-Newtonian pseudoplastic fluid behavior. When the MicroPCMs content was12wt.%, the melt had a good spinnability. The latent heat of obtained melt-blown warm cotton was8.52J/g, and the phase transition temperature was28.2℃. The mechanical properties of melt blown warm cotton compared with pure PP had not changed.The melt-blown expanding test results obtained show that the research achievement has industrial application prospect.更多还原