相变微胶囊悬浮液喷淋换热特性实验研究

根据相变微胶囊储存和释放潜热的特殊性质,分别使用相变微胶囊悬浮液（MPCMS）和纯水作为喷淋介质,搭建了一个小型喷淋塔装置,其中相变微胶囊的芯材为正二十二烷(C₂₂H₄₆)。实验设定了五个喷淋温度(35、40、44、47、51℃)、三个空气流量(0.011、0.018、0.025 m³/s)和两种直径(SMD=80、240 μm)的大、小液滴作为实验变量,探究了上述两种介质与空气之间的换热特性。实验结果表明：相变微胶囊的过冷会影响换热过程。常温常湿条件下,对于小液滴,当空气流量为0.018、0.025 m³/s时,喷淋温度为44、47℃的MPCMS比相同温度下的纯水更能促进换热;当空气流量为0.011 m³/s时,喷淋温度为44℃的MPCMS比相同温度下的纯水更能促进换热。对于大液滴,在三种空气流量下,喷淋温度为44℃的MPCMS比相同温度下的纯水作为喷淋介质时换热效果更好。     

Structural control of core/shell polystyrene microcapsule‐immobilized microbial cells and their application to polymeric microbioreactors

Polystyrene microcapsules possessing a large single core and highly microporous wall were prepared as immobilization supports for microbial cells by a new method based on phase separation of polystyrene within a mixed organic solvent system in an oil‐in‐water (o/w) emulsion. The structures of core and micropore were controlled by changing the concentration of isooctane in the organic phase and the temperature of solvent evaporation. The immobilization of baker's yeast into the polystyrene microcapsules was carried out by entrapping the yeast into calcium alginate beads before encapsulating in the microcapsules and followed by removing the beads with HCl solution. The morphology of the microcapsules was observed by means of SEM, and the activity of the immobilized yeast was evaluated by using the microcapsules in ethanol fermentation. It was found that the formation of the core and wall pore was remarkably influenced by the isooctane concentration, and the diameter of the core was affected by the temperature of solvent evaporation. The yeast was successfully immobilized into the polystyrene microcapsules at a high density and a high catalyst activity by the proposed immobilization method. Furthermore, the polystyrene microcapsules exhibited a high operational stability in the repeated batchwise fermentation test. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1966–1975, 2003     

微胶囊红磷阻燃剂在环氧树脂基电子电气封装材料中的应用研究

研究了微胶囊红磷对环氧树脂基电子电气封装材料的阻燃性能、力学性能及抑烟性能的影响。添加微胶囊红磷10份量即可使材料的阻燃性能达UL94V 0级,氧指数(LOI)从19 5上升到28 2;添加量在一定范围内对材料的力学性能影响很小,随添加量从0增加至14份,材料的拉伸强度略有下降,从48 84MPa下降至46 92MPa;冲击强度有所上升,从9 29kJ·m-2提高到10 28kJ·m-2;弯曲强度先略有上升然后有所降低,从130 2MPa变化至136 6MPa;微胶囊红磷与硼酸锌的复配体系具有很好抑烟性能。     

微胶囊相变材料及其应用

微胶囊相变材料是将微胶囊技术应用于相变材料而形成的新型复合相变材料。文中介绍了微胶囊相变材料及其特性,并就微胶囊相变材料的结构组成、制备方法和应用领域分别进行了综述。     

聚乙二醇改性相变微胶囊制备MicroPCMs-WF/HDPE复合材料物理力学性能

以正十二烷醇（DA）为芯材,密胺树脂（MF）和聚乙二醇改性密胺（PMF）树脂为壁材制备了相变微胶囊（MicroPCMs）,并分别添加到木粉/高密度聚乙烯（WF/HDPE）复合材料中,获得了具有相变蓄热能力的MicroPCMs-WF/HDPE复合材料。采用SEM、FTIR和纳米压痕等方法对MicroPCMs的表面形态、力学性能进行了分析与表征,同时对MicroPCMs-WF/HDPE复合材料的物理力学及热性能进行了测试。结果表明:经聚乙二醇改性后,改性微胶囊（PMF-MicroPCMs）的弹性模量和硬度较未改性微胶囊（MF-MicroPCMs）分别增加了13.9%和30.0%;MicroPCMs-WF/HDPE复合材料的熔融温度区间（22.2~28.7℃）满足人体舒适温度范围,较纯WF/HDPE复合材料温度变化速率明显减缓;相比纯WF/HDPE复合材料,MicroPCMs-WF/HDPE复合材料的吸湿性、冲击强度和表面硬度增加,弯曲和拉伸性能下降;PMF-MicroPCMs-WF/HDPE复合材料的性能均优于MF-MicroPCMs-WF/HDPE复合材料,且达到了木塑装饰板材的力学性能标准要求。      

丙烯酸树脂一正十二烷醇相变微胶囊制备及性能表征

微胶囊化相变材料具有储能密度高、相变温度近似恒定、便于储存和输运等特点,在热能储存、输运和利用领域具有广泛的应用前景。本工作采用悬浮聚合法辅以超声辐照手段合成了以正十二烷醇为芯材、丙烯酸树脂为壳材的新型高相变潜热相变微胶囊(MEPCM)颗粒。用扫描电子显微镜(SEM)、傅里叶红外光谱仪(FT-IR)、差式扫描量热仪(DSC)、热重分析仪(TGA)和激光粒度仪(LPSA)等设备对微胶囊性能进行了表征。结果表明,所制相变微胶囊呈较规则球体,粒径为638.14~1478.65 nm,中位径d50为933.91 nm。冷却过程中微胶囊芯呈两种不同的结晶过程,囊芯含量为43%,与设计值50%较接近,包覆率达86%,熔化相变潜热为93.31 kJ/kg;包覆后的相变材料融化温度为22.26℃,过冷度从4.61℃降至2.13℃。壳材不与芯材反应。MEPCM质量降低起始温度略高于纯正十二烷醇,封装可改善相变材料的热稳定性,该相变微胶囊具有良好的潜热储存能力和较快的温度变化响应速度。     

微胶囊相变乳状液在液冷服中的应用前景

介绍了一种能替代传统蓄冷介质的潜热型功能性热流体——微胶囊相变乳状液，它具有蓄冷密度大、传热性强、无过冷现象、价格低廉等优点。在传热量一定的条件下，微胶囊相变乳状液作为传热介质比水所需流量少，流动时摩擦阻力小，若用它作液冷服的冷却液可以大大减小换热管路的尺寸，降低循环泵的功耗。更重要的是，材料在发生相变前后其自身温度基本保持不变，解决了目前大多数液冷服穿着不舒适的问题。     

Importance of Both Imprinted Genes and Functional Heterogeneity in Pancreatic Beta Cells: Is There a Link?

Diabetes mellitus now affects more than 400 million individuals worldwide, with significant impacts on the lives of those affected and associated socio-economic costs. Although defects in insulin secretion underlie all forms of the disease, the molecular mechanisms which drive them are still poorly understood. Subsets of specialised beta cells have, in recent years, been suggested to play critical roles in “pacing” overall islet activity. The molecular nature of these cells, the means through which their identity is established and the changes which may contribute to their functional demise and “loss of influence” in both type 1 and type 2 diabetes are largely unknown. Genomic imprinting involves the selective silencing of one of the two parental alleles through DNA methylation and modified imprinted gene expression is involved in a number of diseases. Loss of expression, or loss of imprinting, can be shown in mouse models to lead to defects in beta cell function and abnormal insulin secretion. In the present review we survey the evidence that altered expression of imprinted genes contribute to loss of beta cell function, the importance of beta cell heterogeneity in normal and disease states, and hypothesise whether there is a direct link between the two.