脲醛树脂包覆异丙苯过氧化氢微胶囊的制备及热稳定性

针对可预涂厌氧胶贮存稳定性差的问题,从过氧化物微胶囊颗粒控制和热稳定性出发,以异丙苯过氧化氢(CHP)为芯材,脲醛树脂(PUF)为壁材,制备脲醛树脂包覆CHP微胶囊。研究了稳定剂用量、反应时间、搅拌速率和升温速率等工艺条件对微胶囊颗粒形态的影响。结果表明:稳定剂用量和反应时间需要大于一临界值后才能得到形貌规整的微胶囊;升温速率越快,颗粒越早稳定;只要反应速率合适,搅拌速率对颗粒大小的影响较小。在相同温度下,脲醛树脂包覆CHP微胶囊的热失重远低于CHP;制备的脲醛树脂包覆CHP微胶囊稳定性优于市售国外包覆CHP型微胶囊,大大提高了可预涂厌氧胶的贮存稳定性。     

稀释环氧树脂微胶囊的制备以及性能研究

通过二步法制备稀释环氧树脂脲醛树脂微胶囊并测试其性能。光学显微观测证实了微胶囊外壳理论形成过程；制得平均粒径在38μm的微胶囊，红外光谱（FTIR）分析及光学观测证实了环氧树脂的成功包覆；环境扫描电镜测试（ESEM）得到微胶囊的形貌同时验证了形成过程；热重分析表明微胶囊有良好的热稳定性，红246℃以下保持稳定；通过对比，证明微胶囊有很好的到温长期稳定性。     

啶虫脒/脲醛树脂微胶囊的制备及表征

以脲醛树脂为载体,采用原位聚合法制备了啶虫脒/脲醛树脂微胶囊,通过正交实验考察了单体摩尔比、乳化时间、酸化时间、固化时间等对微胶囊载药率、包封率的影响,并对微胶囊的形貌、释药性能和贮存性能进行了表征。结果表明,当尿素与甲醛摩尔比1.0∶1.8、乳化时间1 h、酸化时间1.0 h、固化时间2.0 h时,所得啶虫脒/脲醛树脂微胶囊形态光滑,粒径分布均匀,包封率高且具有良好的缓释效果和贮存稳定性。     

自修复聚脲甲醛微胶囊的制备及成囊机理研究

采用原位聚合法制备了自修复聚脲甲醛包覆环氧树脂微胶囊。考察了原料用量、反应温度、酸化值和固化时间等对微胶囊粒径分布和表面形态的影响,确定了微胶囊的最佳制备工艺。借助显微镜实时监测微胶囊化过程,探讨了微胶囊的成囊机理,并将微胶囊填充到脲醛树脂中。结果表明:采用最佳制备工艺制得的微胶囊包覆率较高、结构紧密、粒度均匀,室温下保存一周后没有出现团聚和破裂;将9%微胶囊添加到脲醛树脂中,微胶囊分散均匀,脲醛树脂复合材料的韧性得到提高。     

二步法制备亚麻油微胶囊及在自修复涂层中的应用

以亚麻油为芯材,脲醛树脂为壁材,采用二步法制备自修复微胶囊。通过探讨芯壁比、乳化剂用量、pH等对微胶囊形貌及性能的影响,确定了微胶囊的最佳合成工艺。将微胶囊应用到环氧树脂基体中制备自修复涂层,并考察了涂层的力学性能及自修复性能。结果表明,当芯壁比为3:5时,乳化剂用量为1.5wt%,脲醛树脂预聚温度为70℃,终点pH为3.0时,制备的微胶囊呈规则球形结构,平均粒径约为140μm,具有良好的热稳定性。当涂层中微胶囊质量分数为3%时,涂层的力学性能提升幅度较大。     

二步法制备脲醛树脂包覆环氧树脂溶液微胶囊

采用二步法制备了脲醛树脂为囊壳、环氧树脂的乙酸乙酯溶液为囊芯的微胶囊。研究了乳化剂类型及用量、搅拌速率、反应物浓度对微胶囊制备及性能的影响,通过光学显微镜和热重分析仪测试了微胶囊的形貌、粒径和热稳定性。结果表明:采用高分子乳化剂能够得到较好的微胶囊,随着其用量的增加或搅拌速率的提高,微胶囊平均粒径变小;随着反应物浓度的增加,微胶囊的产率提高,囊壳变得坚固而粗糙;采用二步法制备的微胶囊的热稳定性优于一步法,两者皆适用于制备自修复材料。     

原位聚合法制备脲醛树脂包覆环氧树脂微胶囊

以脲醛树脂为囊壁、环氧树脂E-51的乙酸乙酯溶液为囊芯,采用原位聚合法成功制备了脲醛树脂包覆环氧树脂溶液的微胶囊。通过改变尿素、甲醛、芯材用量等研究了脲醛树脂生成速率和沉积速率对微胶囊形貌和结构的影响。利用扫描电子显微镜、光学显微镜、傅里叶变换红外光谱仪和热重分析仪对微胶囊进行表征。结果表明:成功制备了外表面粗糙和光滑的两种微胶囊,且这两种微胶囊的芯材都具有良好的流动性;外表面粗糙的微胶囊力学性能较好,热稳定性优良。     

自修复微胶囊的制备及其影响因素研究

采用环氧树脂(E-51)和环氧小分子(SM80)为芯材、脲醛树脂为壁材,利用原位聚合法制备自修复微胶囊。采用光学显微镜(OM)观察了微胶囊的形成过程;采用扫描电子显微镜(SEM)考察了乳化剂种类对微胶囊微观形貌的影响;采用傅里叶红外光谱仪(FTIR)分析了微胶囊的化学成分;利用激光粒度仪分析了微胶囊的粒径分布;考察了不同乳化速度对微胶囊粒径分布的影响。试验结果表明:采用聚氧乙烯脱水山梨醇单油酸酯(吐温-80)作为乳化剂,其用量占芯材含量的3.0%,乳化转速为2000r/min时,制备的脲醛树脂微胶囊外形基本呈现球状,粒径分布较为均匀,红外分析表明已经成功制备了脲醛树脂微胶囊。     

助剂对微胶囊剂稳定性影响研究

以水为介质,脲醛树脂为壁材,用原位聚合法制备了氯氰菊酯微胶囊水悬浮液。为提高悬浮液的稳定性,在制备工艺过程中加入助剂,实验考察了各种助剂混配及其配比用量对悬浮液悬浮率的影响。结果表明,乳化过程中加入1.0%苯乙烯–马来酸酐共聚物、2.0%聚乙烯醇与3.0%阿拉伯树胶制备的微胶囊水悬浮液悬浮率达98.73%。     

海藻酸钠/脲醛树脂复合微胶囊的缓释动力学特性

采用两步法制备海藻酸钠/脲醛树脂复合微胶囊。在树脂化阶段引入海藻酸钠(SA)参与脲醛树脂(UF)的缩聚反应形成复合壳层,制备了阿维菌素复合微胶囊。通过FTIR、TG、SEM、粒度分析等表征微胶囊的结构特征、组成成分、表观形貌、粒度分布。结果表明,SA的引入可有效改善脲醛树脂微胶囊的团聚现象,提高药物的包覆率至60%以上。释放性能研究显示,复合微胶囊的缓释能力较脲醛树脂微胶囊提高,72 d累计释放率由27.5%增至44.5%,且释放速率受pH、温度的影响,25℃下酸性介质中27d累计释放率超过50%。释放行为均可用Korsmeyer-Pappas动力学模型进行描述。     

永固红F5R电泳液及其微胶囊的研究

采用十八胺对永固红FSR化学修饰,以Span-80为稳定剂,四氯乙烯为分散介质,使用正交设计方法优化电泳液组成和工艺条件,制备了分散性和稳定性良好的电泳液。使用红外光谱、紫外光谱、激光光散射和光学显微镜技术对永固红FSR电泳液进行了表征。以此电泳液为囊芯,脲甲醛树脂为壁材,制备一种红色电子墨水微胶囊,形貌规则球形,表面光滑,囊壁结构致密,包覆率达81％,囊芯含量为78％。永固红F5R电泳液及其微胶囊具有明显的电场响应行为,可以作为柔板显示器的功能材料。     

酵母细胞壁的盐酸氯丙嗪微囊的制备和稳定性考察

目的以酵母细胞壁为囊材,制备盐酸氯丙嗪微囊,并观察其稳定性。方法以载药量为评价指标,采用正交试验设计确定制备盐酸氯丙嗪微囊最佳处方和工艺,并对微囊含量的检测方法进行精密度、稳定性及准确性验证。光学显微镜观察微囊形态,考察其体外释放、高湿度和强光照射的稳定性。结果在40℃,盐酸氯丙嗪与酵母细胞壁质量比为1∶3,时间为6 h,微囊的平均载药量可达41.76%。改进的含量检测方法精密度、稳定性、准确性良好。光学显微镜下可见微囊囊壁完整,呈球形或椭球形,形态均一。盐酸氯丙嗪微囊500 min体外累积释放为94.89%。盐酸氯丙嗪微囊对湿度和光度稳定性显著增加。结论酵母细胞壁可作为囊材用于制备微囊,且能增加药物的稳定性。     

Thermal and morphological stability of polystyrene microcapsules containing phase‐change materials

Polystyrene microcapsules with paraffin wax as the active agent [phase‐change material (PCM)] were produced by a Shirasu porous glass emulsification technique and a subsequent suspension‐like polymerization process. The suitability of the obtained microcapsules for textile applications was studied. The thermal properties, surface morphology, and structural stability of the PCM microcapsules were investigated with differential scanning calorimetry, thermogravimetric analysis, and environmental scanning electron microscopy. The microcapsules could be used without any appreciable damage or irreversible changes in their integrity until 135°C. Furthermore, these microcapsules were heat‐resistant and could endure the curing conditions of textile coating up to 140°C for 30 min. In addition, the stability of the microcapsules under common laundering conditions was tested. It was confirmed that the microcapsules were durable enough and maintained their stability during stirring in hot water and alkaline solutions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of isocyanate microcapsules as functional crosslinking agent for wood adhesive

ABSTRACT

In this study, controlled-release isocyanate microcapsules were synthesized as functional crosslinking to slowdown the rate of cross-linking reactions. The isocyanate microcapsules were prepared by In-situ polymerization with polymethylene polyphenyl polyisocyanates (PAPI) as core and Urea formaldehyde resin as shell in oil-in-water emulsions. The particle size distribution, chemical structure, morphology, activity, and stability of the microcapsules were comprehensively characterized. Finally, the microcapsules were applied in a wood adhesive to prepare water-resistant plywood. The results showed that the size of the microcapsules was around 100 μm, the active content of NCO was about 23.5%, and the core content was approximately 80%. Compared with the stability of the bulk isocyanate, the stability of the isocyanate in microcapsules was significantly improved in the wood adhesive system. Furthermore, the isocyanate microcapsules showed highly efficient in plywood at different time, which indicated that isocyanate microcapsules could be controllable released in plywood applications.     

Effect of the microstructure on the stability of red onion microcapsules

The effect of microstructure on the stability of red onion encapsulated by two processes: (a) spray drying and (b) spray freezing into liquid cryogenic, was evaluated in this work. Water sorption isotherms and glass transition temperature of microcapsules conditioned at various water activities were determined and coupled to evaluate conditions of storage stability. The stability of red onion microcapsules was influenced not only by water activity increase but also by microstructural differences between the two types of microcapsules. Critical water content was a useful tool to establish adequate storage conditions for red onion microcapsules.     

Thermal stability of composite phase change material microcapsules incorporated with silver nano-particles

This paper reports a study on the thermal stability of phase change material microcapsules that are incorporated with silver nano-particles (Ag-NPs). The novel microcapsules were fabricated by the technique of in situ polymerization, with aminoplast as the wall and phase change material bromo-hexadecane (PCM BrC16) as the core. Thermal gravimetry (TG) analysis was applied to measure the thermal stability of these microcapsules and surface morphology of the microcapsules was observed by means of scanning electron microscopy (SEM) after an application of curing treatment at 130 °C. Comparing with conventional phase change material microcapsules (PCMMs), nano-composite phase change material microcapsules (NCPCMMs) have higher thermal stability. This can be attributed to nano-composite structure of the microcapsules, in which metal Ag-NPs distributed on the surface to increase wall toughness and strength. The possible reinforcement mechanisms of the nano-composite structure are explored.     

Development of thermoregulating textile materials with microencapsulated phase change materials (PCM). II. Preparation and application of PCM microcapsules

Melamine–formaldehyde microcapsules containing eicosane were prepared by in situ polymerization. The characterization of the microcapsules, including the particle size and size distribution, morphology, thermal properties, and stability, was carried out. The prepared microcapsules were added to polyester knit fabrics by a conventional pad–dry–cure process to develop thermoregulating textile materials. The morphology, thermal properties, and laundering properties of the treated fabrics were also investigated. The microcapsules were spherical and had melamine–formaldehyde shells containing eicosane. The microcapsules were strong enough to secure capsule stability under stirring in hot water and alkaline solutions. The heat storage capacity increased as the concentration of the microcapsules increased. The thermoregulating fabrics had heat storage capacities of 0.91–4.44 J/g, which depended on the concentration of the microcapsules. The treated fabrics retained 40% of their heat storage capacity after five launderings. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2005–2010, 2005     

棕榈酸/二氧化硅相变微胶囊的制备及性能研究

采用乳液模板自组装法通过界面缩聚制备了以棕榈酸(PA)相变材料为核、二氧化硅(SiO2)为壳的相变微胶囊,研究了不同核/壳质量比对PA/SiO2相变微胶囊的表面形貌、微观结构、相变储能性能、热稳定性和热循环性能的影响规律。结果表明,随着核/壳质量比的增加,PA/SiO2相变微胶囊呈现更完整的核/壳结构和更均匀的球形外观,其最佳核/壳质量比为60/40;所形成的微胶囊的最高相变储热能力可达98. 78%;致密SiO2包覆层的形成能够有效阻止相变芯材融化后的泄露和流失,同时也提升了相变微胶囊的热稳定性能,该相变微胶囊在快速热冲击下仍保持良好的形态稳定性,并展示了良好的相变可逆性和相变耐久性,该相变微胶囊可广泛应用于工业及民用各领域的潜热储存和热管理。     

Synthesis and characterization of chitosan/urea‐formaldehyde shell microcapsules containing dicyclopentadiene

Microcapsules containing healing agent have been used to develop the self‐healing composites. These microcapsules must possess special properties during the use of composites such as stability in surrounding, appropriate mechanical strength, and lower permeability. A new series of microcapsules containing dicyclopentadiene with chitosan/urea‐formaldehyde copolymer as shell materials were synthesized by in situ copolymerization technology. The microencapsulating mechanism was discussed and the process was explained. Also, the factors influencing the preparation of microcapsules were analyzed. The morphology and shell wall thickness of microcapsules were observed by using scanning electron microscopy. The size of microcapsules was measured using optical microscope and the size distribution was investigated based on data sets of at least 200 measurements. The chemical structure and thermal properties of microcapsules were characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis, respectively. The storage stability and isothermal aging experiment of microcapsules were also investigated. Results indicted that the chitosan/urea‐formaldehyde microcapsules containing dicyclopentadiene were synthesized successfully; the copolymerization occurred between chitosan and urea‐formaldehyde prepolymer. The microcapsule size is in the range of 10–160 μm with an average of 45 μm. The shell thickness of microcapsules is in the range of 1–7 μm and the core content of microcapsules is 67%. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011