The study on the mechanical properties of PU/MF double shell selfhealing microcapsules

The self-healing microcapsules can be buried in the coating to improve the anticorrosive ability. In this paper,self-healing microcapsules of polyurea(PU)/melamine resin(MF) double shell were prepared by in-situ polymerization and interfacial polymerization with isocyanate as the core material. Scanning electron microscope was used to observe the microcapsule morphology. The structures of microcapsules prepared with different chain extenders were characterized by Fourier transform infrared spectroscopy. The micromanipulation system was used to loading–holding, loading–unloading and loading to rupture individual microcapsules, so as to explore the mechanical properties of microcapsules. The Young's modulus corresponding to microcapsules was calculated by mathematical model fitting. The self-healing properties of microcapsule coating were characterized by optical microscope. The experimental results showed that the microcapsule shell prepared under optimized conditions had a complete morphology and good mechanical properties. The microcapsule was in the elastic deformation stage under small deformation, and the plastic deformation stage under large deformation. The Young's modulus range of microcapsules was 9.29–14.51 MPa, and the corresponding Young's modulus could be prepared by adjusting the process. The surface crack of the coating containing microcapsule could heal itself after48 h in a humid environment.     

自修复聚合物材料用微胶囊

Microcapsules with dicyclopentadiene (DCPD) as core material and urea formaldehyde resin as wall material used for making self-healing polymer material were prepared with the in-situ polymerization method. The effect of microcapsules on the fracture toughness of epoxy resin was studied. The addition of microcapsules into epoxy resin results in the decrease of fracture toughness. When microcapsule content was kept constant, as the microcapsule size increased the fracture toughness of the epoxy resin decreased linearly and the percentage of decrease compared to the neat epoxy without microcapsules increased linearly. Moreover, the fracture toughness of the material decreases linearly with the increase of microcapsule content.     

Controlled release and enhanced antibacterial activity of salicylic acid by hydrogen bonding with chitosan☆

Microcapsules of salicylic acid(SA)with chitosan were prepared by spray drying method.Various analytical methods were used to characterize the nature of microcapsules.Fourier-transform infrared spectroscopy(FTIR)confirmed the presence of intermolecular interactions between chitosan and SA.Particle size analysis showed that the average size of microcapsules ranged from 2 to 20 μm.Scanning electron microscopy(SEM)studies indicated that the microspheres were spherical and had a relatively smooth surface.Microbiological assay of antibacterial activity for SA and its microcapsules was measured using different bacterial strains.It was found that the antibacterial activity of SA was improved after the formation of microcapsules.The in vitro release profile showed that the microcapsules could control SA release from 1 h to 4 h.Kinetic studies revealed that the release pattern follows Korsmeyer–Peppas mechanism.Enhanced antibacterial activity of the SA microcapsules was attributed to the synergistic effects of intermolecular hydrogen-bonding interactions N–H?O and O–H?O_C between SA and chitosan.It was also confirmed by quantum chemical calculation.     

Characterization of the Mechanical Properties of Urea-Formaldehyde Microcapsules

The mechanical properties of urea-formaldehyde (U-F) microcapsules were determined using a micromanipulation technique and a theoretical model. Loading-unloading, compressing and holding, and compressing to bursting tests at different speeds between two parallel plates for single microcapsules were carried out. It was found that the U-F microcapsules were visco-elastic (mainly elastic) at small compressive deformation, and plastic under large deformation. The transition point from elastic to plastic occurred at about (14±0.2)% compressive deformation. All the microcapsules would disrupt when compressed to about (17±0.2)% deformation, and the burst force increased linearly with their diameter. Compressing speed had no remarkable effect on both burst force and burst deformation. Liquid filled non-permeable and linear elastic spherical membrane model was used to simulate the uniaxial compression of single microcapsule, and its membrane modulus Eh was determined by fitting model prediction to experimental data. The average value of Eh was estimated to be (478±8) N/m.     

Development of barium@alginate adsorbents for sulfate removal in lithium refining

The demand for lithium has been steadily growing in recent years due to the boom of electric cars.High purity lithium is commonly used in the manufacture of battery grade lithium electrolyte.Sulfate residuals originating from acid leaching of lithium ores must be limited to below 20 mg·L^?1 during refining.There are methods to remove sulfate such as membrane processing and chemical precipitation using barium salts.However,membrane separation is unable to achieve the required purity while chemical precipitation often causes secondary contamination with barium and requires extra filtration processes that lead to increased processing costs.In this study,we developed a polymeric matrix entrapped with barium ions as a novel adsorbent to selectively adsorb sulfate in aqueous solutions.The adsorbent was prepared by dropwise injection method where alginate droplets were crosslinked with barium to form hydrogel microcapsules.In a typical scenario,the microcapsules had a diameter of 3 mm and contained 5 wt-%alginate.The microcapsules could successfully reduce sulfate concentration in a solution from 100 to 16 mg·L^?1,exceeding the removal target.However,the microcapsules were mechanically unstable in the presence of an excess amount of sulfate.Hence,calcium ions were added as a secondary crosslinking agent to improve the integrity of the microcapsules.The two-step Ca/Ba@alginate microcapsules showed an exceptional adsorption performance,reducing the sulfate concentration to as low as 0.02 mg·L^?1.Since the sulfate selective microcapsules can be easily removed from the aqueous system and do not result in secondary barium contamination,these Ca/Ba@alginate adsorbents will find applications in ultra-refining of lithium in industry.     

壳聚糖/乙基纤维素微胶囊的制备及特性

In this work a system which consists of chitosan microcores entrapped in ethylcellulose is presented.Vitamin D2 was eficiently entrapped in chitosan microcores with spray-drying method and was microencapsulated by coating of ethylcellulose.The average size of chitosan microspheres was 6.06μm.The morphology and release properties of microcapsules were tested.The results of release in vitro showed that the microcapsule could realize sustained release for 12h in artificial intestinal juice.     

甲基纤维素湿敏水凝胶中溶菌酶微球性质的体外评价

Long-terrn injectable microspheres have some inherent disadvantages such as migration of microspheres from the originalsite an.d the burst effect. In order to avoid these problems, microsphere-loaded thermosensitive, hydrogel system was designed and expected to achieve a zero-order release Of biomolecular drugs in relativehigh initial drug loadings. Lysozyme, an antibacterial protein usually used to reduce prosthetic valve endocarditis,was selected as the model drug. Poly （DL-lactide-co-glycolide） （PLGA） microspheres, prepared by solvent evaporation method, were employee to encapsulate lysozyme and dispersed into thermosensitive pre-gel solution containing methylcellulose （MC）, polyethylene glycol （PEG）, sodium citrate （SC）, and sodium alginate （SA）. The mixture could act asadrug reservoir by.performing sol-gel transition rapidly if the temperature was raised from roomtemperature to 37℃. The in vitro release results showed that the burst effect was avoided due to strengthening ofdiffusion resistance in the gel. The formulation was able.to deliver lysozy.me for over.30 daysin a nearly zero-order release profile with a rate of 32.8μg.d^-1 which exhibits its remarkable potential for effective aoolication in long-term drug delivery.     

Detailed kinetics of methylphenyldichlorosilane synthesis from methyldichlorosilane and chlorobenzene by gas phase condensation

Methylphenyldichlorosilane (MPDS, CH3C6H5SiCl2) is an important silicone monomer for the synthesis of high-performance polymethylphenylsiloxane polymers. In this work, the mechanism of the synthesis of MPDS from methyldichlorosilane and chlorobenzene by gas phase condensation was studied, and a kinetic model with 35 species and 58 elementary reactions was established. Experiments were carried out in a tubular reactor under a wide range of reaction conditions. The calculated mole fractions of the reactants and products were in a good agreement with the experimental results. A mechanism of the insertion of chloromethylsilylene into the C-Cl bond of chlorobenzene was proposed, which was proved to be the main pathway of MPDS production. The established kinetic model can be used in design and optimization of the industrial reactor for MPDS synthesis.     

甲基二乙醇胺水溶液在改进的湿壁塔上吸收二氧化碳的动力学模型

To get more accurate kinetic data of the absorption of CO2 into aqueous solution of N-methyldiethanolamine, a wetted wall column was modified to more uniformly distribute the liquid on the column surface and gas in the absorbing chamber and change the length of the column. The average liquid film thickness and the liquid-phase mass transfer coefficient were measured, and a correlation for the Sherwood number, Reynolds number and Schmidt number was obtained for the modified wetted wall column. The equilibrium concentrations in chemical reactions were calculated with a minor absolute error for calculating the rate constant more accurately. A mathematical model for the CO2 absorption was established based on the diffusional mass transfer accompanied with parallel reversible reactions, and the partial differential equation was solved by Laplace transform. An analytical expression for the concentration of carbon dioxide as a function of time and penetration depth in liquid film and the average interphase mass transfer rate was obtained. This model was also used to calculate the rate constant for a second-order reaction, which was in good agreement with reported data.     

低温可逆热敏示温微胶囊的粒径控制及结构

采用界面聚合法制备了以CoCl2为芯材、聚乙烯醇为壁材的可逆热敏示温微胶囊,系统研究了乳化剂用量、内水相与油相用量比、搅拌速度、内乳液加入方式对微胶囊粒径的影响,并对微胶囊的结构和形貌进行了表征. 结果表明,当Span-80/Tween-80含量为5%(w)、水油体积比为0.2、转速为1200 r/min、内乳液采用逐步滴加方式加入外水相中时,制备的微胶囊粒径均一,平均粒径为12 mm,分散性好.     

聚砜包覆双环戊二烯微胶囊的制备

采用简单易控的溶剂挥发法成功制备了聚砜包覆双环戊二烯微胶囊,讨论了反应温度、分散剂、芯壁比及搅拌速度对微胶囊性能的影响,并通过扫描电子显微镜、光学显微镜和热重分析仪对微胶囊的表面结构、形貌和热性能进行了研究。结果表明,选择明胶溶液作为分散剂,反应温度为30 ℃时,可制备出粒径和壁厚可控的具有规则球形的微胶囊;随着芯材比例的增大,微胶囊壁厚减小;粒径随着搅拌速度的加快而减小。     

癸酸相变微胶囊的制备及热性能

以尿素、甲醛及癸酸为原料,利用原位聚合法制备了脲醛树脂包覆癸酸的相变微胶囊。以芯壁质量比、乳化剂用量、乳化转速及固化剂含量为变量设计正交实验,采用ESEM、FTIR和DSC分别表征癸酸微胶囊的微观形貌、化学结构及热性能,利用渗漏率实验测试癸酸微胶囊的防渗性能。结果表明,m(OP-10)∶m(Span-80)=4∶1的复合乳化剂有利于改善癸酸微胶囊颗粒特性。癸酸微胶囊P(芯壁质量比3∶2、乳化剂用量占芯材质量5%、乳化转速1400 r/min、固化剂间苯二酚用量占尿素质量12%)在微观形貌上分散良好且大小均一,相变潜热为123.91 J/g,渗漏率和包覆率分别为6.95%和69.7%,与癸酸微胶囊S(芯壁质量比1∶1、乳化剂用量占芯材质量6%、乳化转速1100 r/min、固化剂用量占尿素质量10%)相比,癸酸微胶囊P的渗漏率降低了57.2%,包覆率反而提高了132.3%,具有良好的热性能。     

In situ polymerization of uniform poly(urea–formaldehyde) microcapsules containing paraffins under the high-speed agitation without emulsifier

In this paper, uniform spherical poly(urea–formaldehyde) (PUF) microcapsules containing paraffins, which can be used as phase change materials for energy storage, were prepared by in situ polymerization method under high-speed agitation (≥10,000?rpm) without emulsifier. The influence of high-speed agitation on particle size of as-prepared microcapsules and the tightness of microcapsules were also investigated. The results show that, all the microcapsules have <10?μm mean particles-size and narrow-size distribution, and the mean particle size decreases with the increase of agitation rate. Furthermore, when the agitation rate is >16,000?rpm, the effectiveness of reducing particle size by high-speed stirring is not as remarkable as that of lower speed agitation. In order to gain good tightness of PUF microcapsules under the high-speed agitation conditions, the final pH value of reaction solution should be lower down compared with that of conventional agitation. In our investigation, when the agitation rate was 10,000?rpm, microcapsules fabricated at pH value <2.0 were sealed and own good tightness, however, those fabricated at pH value >2.2 were not sealed.     

The effect of synthesis condition on physical properties of epoxy‐containing microcapsules

The physical properties of microcapsules are largely influenced by the synthesis conditions such as weight ratio of core/shell material, agitation rate, reaction time, and different emulsifier. Different synthesis condition would lead to different property. It is an important issue for application in composites that require self‐healing microcapsules possessing rough surface morphology, less adhesion, less core material permeability, appropriate diameter and core content, and adequate shell thickness. The properties of microcapsules influenced by the synthesis conditions were investigated systematically in this article. According to orthographic factorial design, the most influencing factor on microcapsule's yield, core material, average shell thickness and average diameter, are concluded, respectively. The synthesis parameters when the epoxy‐containing microcapsules exhibit the optimum properties are concluded: 1.4 : 1 for the weight ratio of core/shell material, 250 rpm for the agitation rate, 3 h for the reaction time and 1.5% content for the emulsifier DBS. The chemical structure of resultant microcapsules is confirmed by FT‐IR, and core material of microcapsule exhibits reactivity through DSC measurement. Subsequently, the microcapsules are characterized by SEM, OM, and contact angle experiment so as to provide parameters of microcapsule's physical properties for making binary self‐healing materials. As a result, the resultant microcapsules are suitable for fabricating self‐healing materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

用于自内冷溶液除湿的复配石蜡微胶囊的特性

以三聚氰胺?甲醛树脂为胶囊壁材、固液复配石蜡为胶囊芯材,采用原位聚合法制备了用于自内冷溶液除湿的相变材料微胶囊,研究了单一或不同类型乳化剂复配、乳化剂用量对相变材料微胶囊粒径、微观形貌及热性能的影响. 结果表明,非离子乳化剂NP-10与阴离子乳化剂SDBS复配所制微胶囊相变潜热较低,非离子乳化剂Span80和Tween80按质量比1:1复配、乳化剂占芯材质量的60%、乳化转速为1000 r/min时,所制微胶囊综合性能最佳,表面光滑致密,分散性良好,粒径均一,平均粒径为0.45 ?m,相变潜热为52.48 J/g,囊芯含量为58.44%,相变温度适用于以LiCl溶液为除湿剂的自内冷溶液除湿系统.     

Preparation and properties of phase‐change heat‐storage UV curable polyurethane acrylate coating

Phase‐change heat‐storage UV curable polyurethane acrylate (PUA) coating was prepared by applying microencapsulated phase change materials (microPCMs) to PUA coating. MicroPCMs containing paraffin core with melamine‐formaldehyde shell were synthesized by in situ polymerization. The effect of stirring speed, emulsification time, emulsifier amount, and core/shell mass ratio on particle size, morphology, and phase change properties of the microPCMs was studied by using laser particle size analyzer, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopic analysis, scanning electron microscopy, and differential scanning calorimetry. The results showed that the diameter of the microcapsules decreased with the increase of stirring speed, emulsification time, and emulsifier amount. When the mass ratio of emulsifier to paraffin is 6%, microcapsules fabricated with a core/shell ratio of 75/25 have a compact surface and a mean particle size of 30 μm. The sample made under the above conditions has a higher efficiency of microencapsulation than other samples and was applied to PUA coating. The dispersion of microPCMs in coating and heat‐storage properties of the coating were investigated. The results illustrated that the phase‐change heat‐storage UV curable PUA coating can store energy and insulate heat. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41266.     

环氧树脂微胶囊合成及其反应动力学

将环氧树脂E-51分散在水中形成稳定的乳液,使用三乙烯四胺固化剂,在环氧树脂液滴表面形成交联结构作为环氧树脂微胶囊囊壁,这种微胶囊为环氧树脂复合材料的科学研究和工程应用提供了无界面差异囊壁的研究模型。采用扫描电子显微镜（SEM）和光学显微镜（OM）分析了乳化剂种类及用量、反应温度和搅拌速率等工艺条件对这种微胶囊的形成过程、表面形貌、粒径大小及分布和壁厚的影响。采用红外光谱（FTIR）研究了环氧树脂微胶囊的化学结构。当合成条件为乳化剂Tween 80浓度为1%,固化剂三乙烯四胺浓度为2.5%,反应温度90℃,搅拌速度600～1000 r·min^-1,合成的环氧树脂微胶囊形状规整,表面光滑致密,平均粒径为103 μm,囊芯含量为44.65%,壁厚为5 μm。研究三乙烯四胺固化剂中伯胺和仲胺的反应速率常数和活化能等反应动力学参数,定量分析环氧树脂-三乙烯四胺的化学反应中伯胺和仲胺的反应活性差异。     

溶剂挥发法制备聚砜包覆桐油自修复微胶囊

以聚砜为壁材,桐油为芯材,采用溶剂挥发法制备了聚砜（PSF）包覆桐油自修复微胶囊。考查了不同种类的分散剂、搅拌速度、芯壁比（芯材与壁材的质量比）等工艺参数对微胶囊性能的影响,通过扫描电子显微镜、光学显微镜和热重分析仪等对微胶囊的表观形貌、粒径、壁厚、包覆率和热稳定性能等进行表征。采用所合成的微胶囊制备了环氧树脂基防腐蚀涂层,并对其防腐蚀性能进行了评价。结果表明,30 ℃时,以明胶/聚乙烯醇复配体系作为分散剂,芯材与壁材质量比为1.3:1,搅拌速度为700 r/min时制备出的微胶囊表面光滑致密,粒径在130 μm左右,热稳定温度为350 ℃;盐雾实验结果表明,所制备的微胶囊自修复涂层具有良好的防腐蚀性能。     

聚砜包覆环氧树脂微胶囊的制备

采用溶剂蒸发法制备了聚砜包覆双酚A型环氧树脂微胶囊,通过光学显微镜、激光粒度分布仪和微机差热天平对微胶囊的形貌、粒径分布及热性能进行了表征,讨论了分散剂种类及用量、搅拌速度、反应温度以及壁材与芯材投料质量比对微胶囊制备的影响。结果表明,反应温度过高时不能形成微胶囊;选择1.0 %（质量分数,下同）的聚乙烯醇分散剂、搅拌速度为750 r/min、反应温度为30 ℃、壁材与芯材投料质量比为2∶1时制得的微胶囊呈规则球形,产率较高,微胶囊分散较好,平均粒径在100 μm之内。