Designing of polyamidoamine-based polyurea microcapsules containing tung oil for anticorrosive coating applications

A novel method for the fabrication of robust polyurea microcapsules containing tung oil as a core material was developed for self-healing anticorrosive coating application. Well-distinct microcapsules with polyurea as a shell were prepared by reacting hexamethylene diisocyanate trimer with 0.0 G polyamidoamine (PAMAM) via interfacial polymerization technique. Fourier transform infrared spectroscopic analysis was performed to elucidate the chemical structure of microcapsules as well as to confirm successful encapsulation of core by the polyurea shell. Surface morphology, particle size, distribution of particle size, thermal, and mechanical properties of the prepared PAMAM-based polyurea microcapsules were compared with microcapsules that were prepared using diethylenetriamine (DETA) and triethylenetetramine (TETA). The prepared microcapsules were embedded with acrylic polyol-based polyurethane (PU) coatings to ensure anticorrosive performance. The immersion study of self-healing PU coatings loaded with 5% PAMAM-based polyurea microcapsules possesses satisfactory anticorrosive property under an accelerated corrosion process in 5% NaCl salt solution.     

Fabrication and thermal properties of microPCMs: Used melamine‐formaldehyde resin as shell material

An in‐situ polymerization process prepared a series of melamine formaldehyde (MF) microcapsules containing phase change material (PCM) as core material. The phase change temperature of this PCM was 24°C and its phase transition heat was 225.5 J/g. The microencapsulated phase change materials (MicroPCMs) were bedded in indoor‐wall materials to store and release heat energy, which would economize heat energy and make the in‐door condition comfortable. We investigated the structural formation mechanism by microscope and scanning electron microscopy (SEM). The superficial morphology measurements indicated the optimal shell material dropping rate 0.5 mL min^?1, double‐shell, and temperature elevating speed 2°C/10 min. The results obtained in the present investigation were reasonably understood on the basis of getting determinate rigidity and compacted shell. Also, the observed results were used to control the mass of shell material to get desired thickness of shell. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 2006     

界面聚合聚脲/聚氨酯复合壳体香精微胶囊的制备及性能

以茉莉香精为芯材,以异氟尔酮二异氰酸酯（IPDI）分别与二乙烯三胺（DETA）、β-环糊精（β-CD）及β-CD/DETA反应物为壁材,采用界面聚合法制备了聚脲、聚氨酯、聚脲/聚氨酯3种不同结构壳体的香精微胶囊。探究了不同微胶囊壳体对微胶囊表观形貌、热稳定性、香精微胶囊缓释性的影响并通过动力学模型分析了香精扩散方式。结果表明,以β-CD/DETA制备的聚脲/聚氨酯复合壳体微胶囊成囊性优异,壳体致密完整,热稳定性和缓释性能最好,经其整理的纺织品可保持较浓香味90多天。3种香精微胶囊在100℃、120℃高温缓释数据均符合零级、一级、Ritger-Peppas及Higuchi动力学模型。聚脲/聚氨酯复合壳体Ritger-Peppas方程拟合后n值更加接近0.45,更符合Fick扩散,缓释性能更好。     

Preparation and characterization of polyurea/polyurethane double‐shell microcapsules containing butyl stearate through interfacial polymerization

Double‐shell microcapsules containing butyl stearate were prepared through interfacial polymerization. The outer shell is polyurea formed through polymerization of toluene‐2,4‐diisocyanate (TDI) and diethylene triamine, and the inner shell is polyurethane (PU) formed through polymerization of TDI and polypropylene glycol 2000 (PPG2000). Styrene maleic anhydride copolymer was used as emulsifier. The effects of core to monomer ratio and dosage of PPG2000 on core content and encapsulation efficiency of microcapsules were investigated. The core content has a maximum at core to monomer ratio of 3–4, and the encapsulation efficiency has a maximum value of 95% at core to monomer ratio of 2. The prepared microcapsules were smooth and compact and have an obvious latent heat of 85 J/g. The shell structure of microcapsules was polyurea and PU. The average diameter of the microcapsules was 1–5 μm. The stabilities of the double‐shell microcapsule, such as anti‐ethanol wash and antiheat properties are obviously improved than those of single‐shell microcapsule. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Storage stability and solubility of poly(urea‐formaldehyde) microcapsules containing A‐olefin drag reducing polymer

Microcapsules containing α‐olefin drag reducing polymer were prepared by in situ and interfacial polymerization with urea, formaldehyde, and styrene as shell materials, respectively. IR spectrums of prepared shells indicated the formations of poly(urea‐formaldehyde) and polystyrene in the microencapsulating process. The morphologies of uncoated particles and microcapsules were observed by scanning electron microscopy (SEM) which proved that the α‐olefin drag reducing polymer particles were effectively coated. For the purpose of determining the stability of microcapsules in transportation and storage, the static pressure experiment was carried out and lasted for 6 months. In this process, microcapsules with polystyrene as shell material stuck together after 3 months; however, those with poly(urea‐formaldehyde) kept the state of particles. The thermal characteristics of uncoated particles (core), poly(urea‐formaldehyde) (shell), and microcapsules with that as shell material were characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) which proved that thermal stable temperature of microcapsules containing α‐olefin drag reducing polymer with poly(urea‐formaldehyde) as shell material was below 225°C, and the mean heat absorbed by microcapsules in the temperature increasing process was 1.5–2.0 W/g higher than that by cores. The evaluation of drag reducing rate of microcapsules showed that the microencapsulating process had no influence on the drag reduction of α‐olefin drag reducing polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of polyurethane microcapsules containing n‐octadecane with styrene‐maleic anhydride as a surfactant by interfacial polycondensation

A series of polyurethane microcapsules containing a phase change material (PCM) of n‐octadecane was successfully synthesized by an interfacial polymerization in aqueous styrene‐maleic anhydride (SMA) dispersion with diethylene triamine (DETA) as a chain extender reacting with toluene‐2,4‐diisocyanate (TDI). The average diameter of microPCMs is in the range of 5–10 μm under the stirring speed of 3000–4000 rpm. Optical and SEM morphologies of microPCMs had ensured that the shell was regularly fabricated with the influence of SMA. FTIR results confirmed that the shell material was polyurethane and the SMA chains associated on core material reacted with TDI forming a part of shell material. The shell thickness was decreasing in the range of 0.31–0.55 μm with the molar ratio of DETA/TDI from 0.84 to 1.35 and the weight of core material increasing from 40 to 80% (wt %). By controlling the weight ratio of PCM as 40, 50, 60, 70, and 80% in microPCMs, it was found using DSC that the T_m and T_c of microPCMs were in the range of 29.8–31.0^oC and 21.1–22.0°C and an obvious phase change had been achieved nearly the same temperature range of that of PCM. The results from release curves of microPCM samples prepared by 1.4, 1.7, and 2.0 g of SMA indicated the release properties were affected by the amount of the dispersant, which attributed to the emulsion effect and shell polymerization structure. The above results suggest that the shell structure of microPCMs can be controlled and the properties of microPCMs determined by shell will perform proper practical usage. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4996–5006, 2006     

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.     

石蜡－密胺树脂微胶囊相变材料制备与表征

研究中采用了正十八烷石蜡相变材料（ PCM）芯材,密胺树脂作为囊壁材料,用原位聚合法制备成微胶囊材料。通过改变芯材和囊壁材料的质量比,探讨了微胶囊制备过程中O／W乳化液的相稳定性,并采用SEM, FT－IR,粒度分析仪和DSC对微胶囊的形态及性能进行表征。结果表明芯材增大O／W乳化液的相稳定性下降,微胶囊数量平均粒径和体积平均粒径均减小,当芯材和囊壁材料的质量比（ Core／Shell）为1．5：1时,微胶囊表面光滑致密,平均粒径为3．6μm,相变焓为98．6 MJ／mg。     

Preparation,characterization, and prominent thermal stability of phase‐change microcapsules with phenolic resin shell and n‐hexadecane core

Microcapsules with phenolic resin (PFR) shell and n‐hexadecane (HD) core were prepared by controlled precipitation of the polymer from droplets of oil‐in‐water emulsion, followed by a heat‐curing process. The droplets of the oil phase are composed of a polymer (PFR), a good solvent (ethyl acetate), and a poor solvent (HD) for the polymer. Removal of the good solvent from the droplets leads to the formation of microcapsules with the poor solvent encapsulated by the polymer. The microstructure, morphology, and phase‐change property as well as thermal stability of the microcapsules were systematically characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimety (DSC), and thermogravimetric analysis (TGA). The phase‐change microcapsules exhibit smooth and perfect structure, and the shell thickness is a constant fraction of the capsule radius. The initial weight loss temperature of the microcapsules was determined to be 330°C in N₂ and 255°C in air, respectively, while that of the bulk HD is only about 120°C both in air and N₂ atmospheres. The weight loss mechanism of the microcapsules in different atmosphere is not the same, changing from the pyrolysis temperature of the core material in N₂ to the evaporation of core material caused by the fracture of shell material in air. The melting point of HD in microcapsules is slightly lower than that of bulk HD, and a supercooling was observed upon crystallization. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Encapsulation of polar phase change materials via multiemulsification and crosslinking method and its application in building

Phase change microcapsules are prepared using chitosan as shell material and aliphatic alcohol/aliphatic acid as core material via multiemulsification and crosslinking method. During the phase change process, the phase change microcapsules store and release heat energy. The enthalpy value of these phase change microcapsules is high enough to be used for application. Suitable phase change temperature can be obtained by changing the core material easily. The resulted microcapsules showed excellent thermal stability. Thermal gravity analysis results showed that the microcapsules remain stable below 200 °C. The microcapsules also exhibited good solvent resistance because of the crosslinking of the shell material chitosan. By integrating the microencapsulated phase change materials (2.5%) into building walls, the inner temperature of model house remained 2 °C higher than that without PCM during the test process. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47837.     

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     

潜热蓄热用微胶囊化脂肪酸相变材料

采用原位聚合法以蜜胺树脂为壁材合成了芯壁质量比为1∶1的十二酸相变材料微胶囊,利用FTIR、DSC、SEM等表征方法分别研究了微胶囊的红外特征吸收光谱、热性能、表面形貌及粒径大小等性质。结果表明,所得相变材料微胶囊是内部为微孔网状结构、表面平整光滑的球形颗粒,其熔点和熔融焓分别为43.7℃和84.96 J/g,可作为蓄热材料应用于实际的潜热蓄热体系。     

一种水溶性囊芯微胶囊的制备方法

以水为囊芯,以聚对苯二甲酸二乙酯（PET）为囊壁,采用乳液-溶剂蒸发法合成一种水溶性囊芯的微胶囊,微胶囊表面光滑,粒径分布窄,平均粒径约100μm。采用扫描电子显微镜（SEM）和光学显微镜（OM）表征微胶囊的表面形貌特征,粒径及其分布。实验结果表明,乳化剂浓度和芯／壁比例等对PET微胶囊大小和粒径分布有较大影响。     

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     

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.     

Expansion space and thermal stability of microencapsulated n‐octadecane

5.0–50.0 vt% of cyclohexane was mixed with 95.0–50.0 vt% of n‐octadecane as the oil‐phase during the emulsion process in the in situ polymerization of melamine‐formaldehyde. By heat‐treating the microcapsules in an oven at 100°C, the cyclohexane was removed and expansion space was formed inside the microcapsules. The microcapsules were characterized by using FTIR, SEM, DSC, TGA, and gas chromatography. When the microcapsules are heat‐treated at temperatures higher than 180°C, Tm, ΔHm, Tc, and ΔHc of the microcapsules decrease. The attenuation of enthalpy of the microcapsules containing expansion space is obviously lower than that of the control sample, however. The permeability of the microcapsule shell decreases with the increase of cyclohexane content. There is a maximum between the thermal stabilities of the microcapsules and the cyclohexane contents. The microcapsules synthesized with 30.0–40.0 vt% of cyclohexane have the highest thermal stabilities, with 230°C and 289°C in air and nitrogen atmosphere, respectively. The thermal stable temperatures are approximately 67°C and 102°C higher than that of the control sample, respectively. The expansion space inside the microcapsules allows the n‐octadecane to expand in the temperature rising process and exert lower pressure to the shell, therefore keeping the shell intact and increasing the thermal stabilities of the microcapsules. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 390–396, 2005     

Fabrication of Core–Shell Novel Polyurea Microcapsules Using Isophorone Diisocyanate (IPDI) Trimer for Release System

Isophorone diisocyanate (IPDI) trimer based novel polyurea core shell structures were developed by interfacial polymerization. Different operating conditions have been used to fabricate shell to encapsulate core. Characterizations of prepared microcapsules were done by Fourier transform infrared spectroscopy, thermogravimetric analysis, and particle size analyzer. The surface morphology of microcapsules was examined by optical microscopy, scanning electron microscopy, and transmission electron microscopy. The release rate of core from microcapsules was estimated by UV and gas chromatography. The results revealed that tailor made release can be adjusted by varying operational protocol for shell and fabricated shell can be extended to other applications such as self-healing coatings and drug delivery.     

乙二醇双硬脂酸酯/PMMA核壳储能微胶囊制备

以BPO-DMA为氧化还原引发剂,在室温下悬浮聚合法制备了核壳结构的乙二醇双硬脂酸酯（EGDS）- PMMA相变材料微胶囊。采用扫描电镜（SEM）、红外光谱仪（FTIR）、差示扫描量热仪（DSC）和热重分析仪（TG）表征了核壳结构微胶囊的形貌、化学结构及热性能。结果表明,当BPO加入量为1%,DMA为0.2% 时,所得微胶囊成均匀球形,粒径分布在1～5 μm范围;微胶囊相变潜热随芯壳比的增加而增大,最大相变潜热达85.34 J/g,芯材含量达64.6%,且相变材料的热稳定性显著增强。     

溶剂蒸发法制备磁性微胶囊及其相关性能

将共沉淀法所得纳米OA-Fe3O4(油酸改性Fe3O4)分散于不同介质中形成磁流体作为芯材,以PMMA(聚甲基丙烯酸甲酯)作为壁材,采用溶剂蒸发法制备磁性微胶囊。对不同芯材及乳化剂进行筛选;考察乳化剂用量、m(芯材)∶m(壁材)及乳化转速对微胶囊制备的影响。通过XRD、FTIR、TEM、SEM、光学显微镜、VSM(振动样品磁强计)对纳米OA-Fe3O4和磁性微胶囊的有效成分、形貌、热性能、磁性能进行分析表征。结果表明,共沉淀法制备的纳米颗粒有效成分为Fe3O4,且可形成稳定磁流体。OA-Fe3O4粒径在3～15 nm,比饱和磁化强度为43.3 emu/g,具有顺磁性。以分散在n-C16H34的OA-Fe3O4磁流体为芯材,w〔SDS(十二烷基硫酸钠)〕=2%的水溶液为乳化剂,m(芯材)∶m(壁材)=5∶1,乳化转速800 r/min条件下可制得外形规整,壁厚1～2μm,且粒径集中于(10±2)μm的磁性微胶囊。该胶囊比饱和磁化强度为36.9 emu/g,具有良好的磁响应性。     

Microencapsulation of n-hexadecane phase change material by ethyl cellulose polymer

Microencapsulation of phase change materials (PCMs) is an attractive opportunity for broadening their applications. In this respect, a novel encapsulating polymer, ethyl cellulose (EC) was used to entrap n-hexadecane (HD) PCM by an emulsion-solvent evaporation method. Emulsifiers strongly influenced the size and morphology of the forming EC–HD composite microcapsules, and they also had a great impact on their thermal properties. All of the three emulsifiers were suitable to prepare quasi core–shell microparticles, though the high porosity of shells resulted in serious leakage in composites prepared by Tween 80, and permeability of particles manufactured by poly(vinyl alcohol) (PVA), as can be stated from scanning electron microscopy and differential scanning calorimetry analysis. Interfacial tension measurements and spreading coefficient analysis enabled the prediction of preparation conditions for usable core–shell microcapsules. Volume-weighted mean diameters of the microparticles were 319, 92 and 85 μm formed by Tween 80, PVA and poly(methacrylic acid sodium salt) (PMAA), respectively. A significantly higher HD content and latent heat storage capacity could be achieved using PVA and PMAA than with Tween 80. The thermal cycling test indicated good thermal reliability of microcapsules prepared by PMAA, while the energy-storing capacity of composites prepared by PVA decreased substantially, and a dramatic reduction was found in microparticles using Tween 80.