为了促进相变材料微胶囊的成核结晶,通过原位聚合法成功制备了芯材为正十八烷(其中包含微量正二十二酸作成核剂)、壁材为蜜胺树脂的相变材料微胶囊;采用傅里叶红外光谱仪(FT-IR)、X射线衍射仪(XRD)、冷场扫描电子显微镜(SEM)、差示扫描量热仪(DSC)、热重分析仪(TG)对微胶囊的化学结构、结晶性能、表面形貌、储热性能、热稳定性进行表征.结果表明:当微胶囊芯壁比为1:1时制得的微胶囊粒径均匀,表面光滑;随着正二十二酸含量的增加,微胶囊间的分散性变差;异相成核结晶峰(α峰)占比逐渐增大,当正二十二酸添加量为芯材含量的1.2％时,α峰占比为70.12％,包覆率可达63.74％;微胶囊壁材的分解温度升高了27℃,增强了壁材的热稳定性.

过冷度是相变材料及其微胶囊重要的热性能参数.为了获得这一数据,组装了一套用于精确测量相变材料及其微胶囊步冷曲线的装置.该装置采用廉价易得的T型热电偶、无纸记录仪测量温度数据,并通过USB转串口RS485采集数据到上位机,实现了温度数据的采集、储存和显示,进而得到温度随时间的变化曲线(步冷曲线).实验表明,测试管外围保温层厚度对步冷曲线的形状有显著影响.对正十八烷及其微胶囊的测试结果显示,当保温层厚度为0.5 mm时,可得到完整准确地步冷曲线.

为提高相变纳胶囊在静电纺纤维上的负载量,采用相反转温度(PIT)乳化和自由基聚合技术制备了交联聚甲基丙烯酸甲酯(PMMA)/正十八烷纳胶囊,将其添加到聚偏氟乙烯(PVDF)、聚丙烯腈(PAN)纺丝液中,通过静电纺丝技术分别制备了PVDF和PAN复合纳米纤维,并使用SEM、TEM、DSC和TG等方式对2种纳米纤维进行表征.结果表明:2种复合纤维均平直光滑,纺锤状较少;PVDF复合纤维平均直径在100～300 nm之间,PAN复合纤维平均直径在400～800 nm之间,纤维直径随胶囊加入量的增加而增大;PAN纤维负载相变纳胶囊的能力优于PVDF纤维,热性能更好;纳胶囊添加质量分数为9％的PAN相变纤维具有较为优良的热焓值和热稳定性,其结晶焓为22.55 J/g.

Calcium alginate hollow fibers have been used as bionic vascular channels in thick tissue and organ regeneration studies, whose permeability determines the transport efficiency of nutrients and oxygen. CaCl2 was dissolved in the solvent mixed with isopropyl alcohol (IPA) and deionized water to obtain a series of crosslinking agents with different polarities. Calcium alginate hollow fibers were fabricated by the coaxial flow, and the influence of interfacial polarity on its permeability was studied. The polarity evaluation results showed that the polarity index of the crosslinking agents decreased from 9.00 to 3.90 with the increase in IPA mass concentration. Scanning electron microscopy observations indicated that with the weakening of the interfacial polarity of the coaxial flow, the gel units tended to be shorter and denser along the flow direction. It was worth noting that the permeability did not change synchronously with the polarity, but first enhanced and then weakened with the decrease in the polarity. When the mass concentration of IPA exceeded 60%, the regulation ability of interfacial polarity on permeability was significantly improved. The research results will have a positive effect on the customization of physicochemical properties of alginate.

为了抑制正十八烷相变材料微胶囊的过冷行为,利用原位聚合法制备了添加十八酸的以正十八烷为芯材、氨基树脂为壁材的相变材料微胶囊,并利用傅里叶红外光谱仪(FTIR)、冷场扫描电镜(SEM)、差示扫描量热仪(DSC)、热重分析(TG)和X-射线衍射仪(XRD)等手段对微胶囊的结构、形貌、热性能及结晶性能等进行表征.结果表明:十八酸的添加使正十八烷微胶囊表面光洁度变差,过冷现象明显减弱;当十八酸的加入质量为芯材的4.2％时,过冷度从22.6 ℃降至10.0℃,异相成核结晶峰占比△H∞/△Hc.和包覆率分别达到75.2％和57.0％,且不影响微胶囊的耐热性能.这表明十八酸是正十八烷微胶囊较理想的过冷抑制剂.

为提高相变材料纳胶囊的使用频率和寿命,探究其合成的最佳条件,采用相反转乳化法(PIC),以Span-80、OP-10为复配乳化剂,以正十八烷为芯材,以正硅酸乙酯(TEOS)为硅源,制备{[正十八烷/TEOS](1)+[Span80(21)/OP-10(22)]+水(3)}的O/W型纳米乳液,在此基础上,利用氨水为催化剂制备正十八烷@SiO2相变材料纳胶囊;利用红外光谱仪(FTIR)、扫描显微镜(SEM)、透射电子显微镜(TEM)、差示扫描量热仪(DSC)、热重分析仪(TG)、X射线衍射仪以及热台等设备对所制备纳胶囊的性能进行表征.结果表明:随着芯壁比减小,纳胶囊的热稳定性增加,结晶性能降低;随着反应温度升高和pH值增大,纳胶囊的团聚现象加剧;当反应温度为45℃、pH值为11、芯壁比(正十八烷/TEOS)为1:1.5时,得到粒径为200～500 nm、分散性良好、核壳结构明显的球形纳米胶囊;芯壁比为1:1时,纳胶囊最大熔融热为95.5 J/g,凝固热为110.8 J/g,包覆率最大为51.6％,经400次冷热循环后其包覆率下降到39.8％.

School of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China 2 CRRC Nanjing Puzhen Co., Ltd, Nanjing 210031, China 3 CRRC Zhuzhou Locomotive Co., Ltd, Zhuzhou 412001, China *E-mail: zhangjx@just.edu.cn 1 1 1 1 1* 2 2 3 3 Shiyun Li, Ling Zhang, Shang Shang, Haijun Zhou, JiaoXia Zhang, Peixin Wei, Haifeng Xue, Xian Hu and Jianping Wang View Article Online

ABSTRACTIsocyanate and amine solution are microencapsulated, respectively, via in situ polymerization to realize the self‐healing function in epoxy matrix. First, the isophorone diisocyanate (IPDI) microcapsules prepared with different core/shell ratios, emulsifier dosages and emulsification rates are characterized by field emission scanning electron microscope (FE‐SEM). They exhibit integral spherical shape when the core/shell ratio is 3:1 and emulsifier concentration is 2.52 wt %, and the diameter of IPDI microcapsules ranged from 2.66 μm to 11.25 μm is manufactured by adjusting emulsification rate over the range of 3000–9000 rpm. Besides, during the microencapsulation of polyaspartic acid ester (PAE), urea, tung oil, as well as aqueous isocyanate are proposed to improve the stability of PAE emulsion. SEM and FTIR results reveal that aqueous isocyanate can react with partial PAE and form polyurea (PU) layer to take protection effectively. Further, IPDI‐PAE dual microcapsules are incorporated into epoxy coatings, the self‐healing and anticorrosion performance of coatings with various amounts of microcapsules are investigated systematically. It was found that the degree of repair and anticorrosion are increased with increasing microcapsules loading, and the appropriate amount of microcapsules addition is 15 wt %, which corresponding to 93% repair efficiency. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48478.

A novel reversible photo-responsive polyvinyl alcohol (PVA)/polyethylenimine (PEI) electrospinning nanofiber membrane (NFM), assembled with photochromic nanoparticles containing spiropyran, is herein presented and the water resistance, mechanical properties as well as photochromic properties are investigated systematically. Here, glutaraldehyde, which can undergo a cross-linking reaction with PVA/PEI, is selected as a cross-linker to enhance water resistance and mechanical behavior of the NFM. Photochromic polymer nanoparticles are prepared using octadecyl acrylate as polymer matrix monomer through miniemulsion polymerization. Effect factors of the whole preparation process such as the PVA/PEI mass ratio, the amount of emulsifier, and the amount of photochromic nanoparticles added are regulated to obtain the optimal experimental parameters. The surface morphology and microstructure, water resistance, and mechanical properties of NFMs are studied by thermal field emission scanning electron microscopy, static water contact angle tester, and tensile universal testing machine, respectively. Furthermore, UV-vis spectrophotometer is employed to investigate the photochromic performance and fatigue resistance of NFMs. Overall, analyses reveal that the reversible photo-responsive electrospinning NFM exhibit excellent photoresponsivity, photoreversibility, and fatigue resistance upon UV irradiation, thus showing promising application in the field of ultraviolet intensity indicator.

The polyurethane/polyurea microcapsules containing n-octadecane were prepared and modified by interfacial polymerization, where styrene maleic anhydride copolymer (SMA) was selected as emulsifier, polyurea based shell material was synthesized with isophorone diisocyanate (IPDI) and diethylenetriamine (DETA). Besides, polyethylene glycol 400 (PEG-400) was also added to form polyurethane shell and modify the microcapsules morphology. SEM images proved that with the modification of polyethylene glycol 400, the microcapsules morphology improved significantly. The microstructure of microcapsules under varying factors such as emulsification rates, DETA dropping rates and core/shell ratios were analyzed systematically. In particular, the equipments such as field emission scanning electron microscope (FE-SEM), different scanning calorimetry (DSC) and thermogravimetric (TG) were used to investigate the morphology, phase change properties and thermal stability of microcapsules. The DSC results verified the phase transition behavior of octadecane microcapsules, and microcapsules also displayed pretty thermal stability.

A series of facile flexible reversible thermochromic membranes containing micro/nanoencapsulated phase change materials were fabricated, which presented excellent thermochromic performance and striking latent heat storage property. In this composite membrane, the polyvinyl alcohol/water-soluble polyurethane composite was served as polymer matrix material, and the reversible thermochromic micro/nanoencapsulated phase change materials (TC-M/NPCMs) which energy storage efficiency reached 67.5%, were served as functional fillers. Moreover, trimesoyl chloride was used for modifying the water resistance of thermochromic membranes. The effects of TC-M/NPCMs contents on the morphology, thermochromic performance, thermal property, thermal stability and thermal cyclic durability of flexible thermochromic membranes were experimentally investigated using field-emission scanning electron microscope (FE-SEM), atomic force microscope (AFM), digital camera, differential scanning calorimeter (DSC) and thermogravimetric analyzer (TGA), et al. The results revealed that TC-M/NPCMs were distributed evenly in matrix membranes. The color of these obtained flexible thermochromic membranes could change in response to variation of external ambient temperature and thus presenting perfect thermochromic performance. As TC-M/NPCMs content increased, the mechanical property and thermal stability of membranes declined, while the enthalpy raised. In addition, the static water contact angles (WCAs) analysis indicated that the water resistance enhanced greatly after surface modification. Furthermore, thermochromic membranes still exhibited worth mentioning thermal cyclic durability undergoing 100 heating and cooling cycles. A facile temperature colorimeter was designed and fabricated, by using the flexible thermochromic membrane with heat storage and temperature regulation property, which could be served as a promising wearable temperature sensor. Hence, the application of the prepared thermochromic membrane in thermal regulation, energy storage and wearable temperature sensor has great potential in the future.

In order to improve the stability of pirimiphos-methyl(PM),PM microcapsules with melamine resin as wall material were fabricated successfully by in-situ polymerization.The effects of pH value and core/wall ratio on the properties of the microcapsules were investigated.The particle size,morphology,pesticide loading,encapsula-tion efficiency, thermal stability and sustained release property of the microcapsules were analyzed by Fourier transform infrared(FTIR)spectroscopy,scanning electron microscopy(SEM),laser particle size analysis (LPSA)and high performance liquid chromatography(HPLC).The results showed that the prepared microcap-sules had regular globular structure,excellent thermal stability and high encapsulation efficiency when pH value of the reaction system was 5.The thermal storage loss of the microcapsules was less than 5% when the core wall ratio was lower than 15:6.In addition,the slow-release rate of the active ingredients in microcapsules can be effectively controlled by adjusting the core/wall ratio.

In order to reduce environmental pollution during microencapsulating phase change materials and expand their applications as well, a novel eco-friendly microencapsulated/nanoencapsulated phase change materials (Micro/NanoPCMs) and the corresponding encapsulation method were proposed and discussed in this study, where the natural chitosan and side-chain crystallizable comb-like polymer were selected as shell material and core material, respectively. During the encapsulating process via coacervation, the effects of different core-shell ratios on the morphology and thermal storage properties of microcapsules were discussed. FE-SEM and TEM was employed to investigate the morphology and microstructure of the microcapsules. The thermodynamics performance of microcapsules was studied using TGA and DSC. The encapsulation efficiency of microcapsules ranged from 49.82% to 68.99%, and the thermal stability temperature of microcapsules was measured to be 243.2 degrees C. The fabrication process where natural raw materials were employed and showing promising applications in such fields as medical treatment.

To enhance the thermal and mechanical performance of macroencapsulated phase-change materials, we fabricated a series of organic-inorganic hybrid macrocapsules containing microcapsules with silicon dioxide shell synthesized by hydrolysis and condensation of tetraethoxysilane. These novel dual macroencapsulated phase-change materials with pomegranate-like structure were prepared through solution spray method and subsequent self-assembly technique. The morphology, cross-section and composite structure were investigated; furthermore, the phase-change properties, thermal stability and complexation structure of the macrocapsules were studied. The thermal analysis results indicated that the melting enthalpy of the macrocapsules could reach 140.6 J/g with a peak temperature of 33.0 degrees C for a weight ratio of n-octadecane to tetraethoxysilane of 1:2, more importantly, there was almost no enthalpy loss after heat-treatment and 10 thermal-cold cycles. In addition, the effects of organic-inorganic hybrid shell on thermal energy storage, thermal conductivity, encapsulation efficiency as well as the supercooling were investigated in detail.

Narrowly dispersed polyurethane (PU) nanocapsules containing lavender essential oil (LO) were fabricated by polyaddition of toluene diisocyanate (TDI) trimer with polyol using a phase inversion emulsification technique. The particle size distribution (PSD), surface morphology, structure, encapsulation parameters, release properties, and thermal stability of nanocapsules have been characterized using a laser particle size analyzer (LPSA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectrum (FTIR), and thermogravimetric analysis (TGA), respectively. Experimental results demonstrate that the nanocapsules have a smaller size (ca. 268 nm), regular sphericity, uniform particle size (polydispersity index, PDI = 0.078), clear core-shell structure, and smooth surface. When the ratio of LO to TDI trimer is 5:10, the yield, encapsulation efficiency, and loading capacity of the nanocapsules can reach a maximum of 70.7%, 98.6%, and 64.8%, respectively. Furthermore, the release experiments showed that the cumulative release of LO from nanocapsules was only about 17% at room temperature and about 32% at 50 degrees C even after 20 days.

In this work, polyurethane (PU) microcapsules containing pirimiphos-methyl (PM) were prepared by interfacial reaction between toluene diisocyanate (TDI) trimer and 1, 4-butanediol. The microcapsules with different core-wall ratios were structurally characterized by Fourier infrared spectroscopy (FTIR), scanning electron microscopy (SEM), laser particle size analysis (LPSA) and so on. The results showed that PM was successfully encapsulated in PU microcapsules and the microcapsules had regular spherical shapes and clean surface. The surface of the microcapsules became wrinkled and some small pores appeared when the core wall ratio was increased to 5:2. The microcapsules could effectively protect PM against degradation below 45 degrees C and showed sustainable release for 40-80 hours in alcohol aqueous solution (50:50, v/v). From the fitting parameters of the power exponent, the release of PM from PU microcapsules was controlled by mixing mechanism.

Abstract Hybrids of poly(3,4-ethylenedioxythiophene) (PEDOT):poly(4-styrene sulfonate) (PSS)/multi-walled carbon nanotube (MWCNT)/graphene (P/M/G), which have high electrical conductivity and low thermal conductivity, were successfully prepared in aqueous solution through in situ polymerization of 3,4-ethylenedioxythiophene (EDOT) monomers in the presence of poly(sodium 4-styrene sulfonate) (PSSNa). Meanwhile, the composites were characterized by Raman spectroscopy, infrared (IR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy. Thermoelectric properties of the samples were measured at room temperature and 50°C. Compared with pristine PEDOT:PSS (P), PEDOT:PSS/MWCNT (P/M) and PEDOT:PSS/graphene (P/G), the power factor of P/M/G composites was significantly improved, whatever the temperature. It increased from 0.061 μW/mK2 to 0.105 μW/mK2 at room temperature and from 0.070 μW/mK2 to 0.142 μW/mK2 at 50°C, meaning 72% and 103% enhancement, respectively. The increased power factor is attributed to the synergic effects of MWCNT and graphene, a hybrid structure with excellent electronic coupling and more electric channels.

To enhance the thermal stability and permeability resistance, a comb-like polymer with crystallizable side chains was fabricated as solid-solid phase change materials (PCMs) inside the cores of microcapsules and nanocapsules prepared via in-situ polymerization. In this study, the effects on the surface morphology and microstructure of micro/nanocapsules caused by microencapsulating different types of core materials (i.e., n-hexadecane, ethyl hexadecanoate, hexadecyl acrylate and poly(hexadecyl acrylate)) were systematically studied via field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). The confined crystallization behavior of comb-like polymer PCMs cores was investigated via differential scanning calorimeter (DSC). Comparing with low molecular organic PCMs cores, the thermal stability of PCMs microencapsulated comb-like polymer enhanced significantly, and the permeability resistance improved obviously as well. Based on these resultant analysis, the microencapsulated comb-like polymeric PCMs with excellent thermal stability and permeability resistance showed promising foreground in the field of organic solution spun, melt processing and organic coating.

In this study, a series of reversible thermochromic microencapsulated phase change materials (TC-MPCMs), exhibiting excellent latent heat storage-release performance, were designed and fabricated successfully. The characterization and microstructure regulation of TC-MPCMs were conducted systematically as well. The core of TC-MPCMs was comprised of crystal violet lactone employed as thermochromic colorant, bisphenol A employed as developer and 1-tetradecanol employed as co-solvent, respectively. These influencing factors of encapsulation process such as the amount of emulsifier, stirring rate, feeding weight of core/shell ratio, acid resistance and thermal cyclic durability were carried out to clarify the effect of various experimental conditions. The surface morphology, shell thickness and core-shell structure of TC-MPCMs were characterized via optical microscope (OM), thermal field emission scanning electronic microscope (TFE-SEM), transmission electron microscope (TEM), respectively. From different scanning calorimetry (DSC) analysis, the performance of temperature of fusion and crystallization and enthalpy of TC-MPCMs under various conditions were measured as well. The results of thermogravimetric (TG) analysis illustrated the influence on thermal stability of TC-MPCMs. In addition, Lab color space obtained by colorimeter is certainly intuitive to observe the colorimetric characteristics of TC-MPCMs as well. More importantly, the reversible thermochromic property associated with phase state of the 1-tetradecanol could also provide a visual evidence of energy storage or release performance of the TC-MPCMs. Furthermore, The TC-MPCMs exhibited excellent stability even after 100th thermal cycling test without any obvious performance degradation, including the morphology, phase change properties and thermal stability. In the end, the fire fighter protective clothing containing TC-MPCMs was designed and fabricated, which could provide adequate thermal protection in the various fire environments. Thus, TC-MPCMs developed in this work showed great potential applications in thermal protective clothing and other thermal regulation fields.

Microencapsulation of phase change materials (PCMs) could prevent the leakage of PCMs during solid–liquid phase change process. However, their applications are mainly limited by the compactness and thermal stability of the traditional polyurea shell microcapsules. To increase the thermal compactness and thermal stability of PCM microcapsules, tetraethylorthosilicate (TEOS) was employed to form polymer/SiO2 composite shells to enhance the mechanical performance of polyurea and polyurethane microcapsule via interfacial polymerization and in situ polymerization. The morphology and chemical components of the microcapsules were characterized by field-emission scanning electron microscope (FE-SEM) and Fourier transform infrared (FT-IR) spectroscopy, respectively. The thermal properties of the microcapsules were investigated by differential scanning calorimetry (DSC) and thermal gravity analysis (TGA). The results showed the smoothness and compactness of both polyurea–SiO2 and polyurethane–SiO2 microcapsules enhanced slightly, when compared with that without TEOS addition. Moreover, the SiO2 composite shell had good effect on thermal compactness, as the weight loss rate of polyurea–SiO2 microcapsules and polyurethane–SiO2 microcapsules decreased 3.5% and 4.1%, respectively.