Syntheses of acrylate core/shell imbiber beads by seeded suspension copolymerization and one‐stage copolymerization for solvent absorption–desorption

Seeded suspension copolymerization or a one‐stage copolymerization was used to synthesize acrylate core/shell imbiber beads. A two‐stage polymerization technique was used for seeded suspension polymerization. The seed particles for poly(methyl acrylate) or poly(2‐ethylhexyl acrylate) were synthesized first in a mixed solvent of toluene/isooctane containing the ethylene glycol dimethacrylate (EGDMA) crosslinking agent. These beads were swollen in styrene‐EGDMA‐BPO (benzoyl peroxide) and then polymerized in the aqueous phase to produce the polystyrene (PS) shell. The one‐stage copolymerization was carried out in toluene/isooctane containing methyl methacrylate (MMA), styrene (St), EGDMA, and BPO at 75°C for 10 h to give a core/shell copolymer of St‐MMA morphology. The appearance of core/shell imbiber beads prepared from these two techniques varied from monomer to monomer. This article describes the preparation, characterization, and application of the core/shell beads for organic solvent absorption/desorption. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 670–682, 2002     

潜伏性2MMZ-PS微胶囊固化剂的制备与表征

以2-甲基咪唑(2MMZ)为芯材,聚苯乙烯(PS)为壁材,采用溶剂挥发技术,制备了一种新型潜伏性2MMZ-PS微胶囊固化剂。通过红外光谱仪(FT-IR)、热重分析仪(TGA)、扫描电子显微镜(SEM)、粒度分析仪和差热扫描量热仪(DSC)对微胶囊固化剂的化学结构、芯材含量、表面形貌、粒径分布及固化性能等进行了表征。所制备的微胶囊固化剂表面光滑,粒径分布较窄,平均粒径约为10.18 μm,芯材2MMZ含量为40.36%。由微胶囊固化剂与环氧树脂E-51制备的单组分胶黏剂,具有优良的固化特性和潜伏性能,可在相似文献   

乳化-内部凝胶化工艺制备固定化酵母微胶囊

乳化-内部凝胶化技术可制备粒径可控且分布较均匀的海藻酸钙凝胶微球,其工艺易于放大以实现工业规模生产,因而已被用于蛋白、多肽类药物的缓控释载体和酶的固定化研究。本文提出将乳化-内部凝胶化工艺用于微生物固定化培养的研究,以啤酒酵母S.cerevisiae BY4741为模型,重点考察了乳化-内部凝胶化工艺过程相关参数对微生物活性的影响规律,发现酸是影响其活性的主要因素。因此,从内部凝胶化的原理入手,确定了适合微生物包埋的工艺条件,制备过程中微生物活性可保持77.0%,凝胶微球体积产率93.5%。进而制备载细胞海藻酸钠-壳聚糖微胶囊(AC微胶囊),考察AC微胶囊固定化培养过程中啤酒酵母的生长动力学,结果表明：在细胞增殖过程中,微胶囊形态保持良好,酵母菌的生长动力学明显优于游离培养组。因此,乳化-内部凝胶化工艺有望成为规模化微生物固定化培养和生产的新技术。     

Preparation of acetamiprid-loaded polymeric microcapsules: Influence of preparation parameter in emulsion system on microcapsule characteristics

Microencapsulation of pesticides is a promising technique for avoiding high initial doses and multiple applications of the chemicals to agricultural land which cause environmental pollution. It is because the formulation is possible to improve the stability of the chemicals against environmental degradation and control the release rate. In the present study, polymeric microcapsules prepared by the solvent evaporation method via water-in-oil-in-water (W/O/W) emulsion were used as immobilization supports of acetamiprid, a water-soluble pesticide. The pesticide was loaded in the microcapsules by impregnating the polymeric supports with acetamiprid dissolved in an organic solvent. Increased volume ratio (ϕ) of inner aqueous phase to oil phase in the emulsion system contributed to more pores in the microcapsules and increase in the content of acetamiprid in the polymeric supports. Release rate of acetamiprid from the microcapsules could be controlled by changing ϕ.     

EFFECT OF CALCIUM ALGINATE COATING ON THE PERFORMANCE OF IMMOBILIZED YEAST CELLS IN CALCIUM ALGINATE BEADS

A cell immobilization technique to prevent cell leakage from the matrix in a very common system, alginate-Saccharomyces cerevisiae, was investigated. A double coating of immobilized cell beads prevented leakage very well in flask fermentation even when shaking was applied. The suitable concentrations of sodium alginate were 5, 5 and 3 wt% for the core, internal coating and external coating, respectively. The suitable concentration of calcium chloride was 1 wt% for all cases. Fermentation using a fixed bed reactor containing the immobilized cells was carried out successfully for 25 d.     

Compression and filtration characteristics of yeast-immobilized beads prepared using different calcium concentrations

Yeast cells were immobilized on calcium alginate beads prepared using different calcium concentrations. The compression properties of the immobilized beads (e.g., softness index and retardation time for compression) were strongly affected by the calcium concentration. The effects of the bead properties on filtration characteristics, such as cake porosity, specific cake filtration resistance, cake compression creeping effect and cake compressibility, were analysed using a dead-end filtration system. The filtration curve of yeast-immobilized beads had an “S” shape, similar to that of soft gel particles. The cake compression behaviour and variation in cake properties were directly reflected on the curve trend. The Voigt in the series model was employed to describe variation in cake porosity with time during a compression. The yeast immobilization increased the bead softness; therefore, the porosity of a cake formed by yeast-immobilized beads was lower than that formed by pure calcium alginate beads. The cakes formed by yeast-immobilized beads possessed a high compressibility of approximately 1.0 and a high softness index of approximately 1.5. The beads prepared using lower calcium concentrations had higher softness, shorter retardation times for compression, higher cake compressibility, lower cake porosity and higher specific cake filtration resistance. The results demonstrated that immobilizing yeast cells on calcium alginate beads is beneficial for retaining higher yeast activity than that of freely suspended yeast. However, the activity levels of yeast immobilized using different calcium concentrations were nearly the same after 3 h. Therefore, using high concentrations of calcium for yeast immobilization is beneficial for improving yeast activity and filtration characteristics.     

Influence of dual-component microcapsules on self-healing efficiency and performance of metal-epoxy composite-lap joints

Dual-component microcapsules were synthesized by solvent evaporation technique using epoxy resin and hardener as core materials and polymethyl methacrylate (PMMA) as shell wall materials. Morphology, core content, and size distribution of microcapsules were monitored by controlling the various processing parameters such as agitation speed, core–shell weight ratio, and concentration of emulsifiers. The molecular structure, morphologies, and thermal characteristics of the microcapsules were examined under Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and thermogravimetric analysis (TGA), respectively. Synthesized dual-component microcapsules were entrenched into the epoxy polymer to introduce the healing features in single lap shear epoxy adhesive joints. Healing efficiency as high as 89% was achieved when 10 wt% dual-component microcapsules were introduced in adhesives. Investigation of the fractured surfaces of the healing enabled adhesives reveals the presence of crack pinning and crack blunting sites represented by characteristic tails at the wake of microcapsules in cohesive zone. Such failure mechanisms responsibly influence the healing efficiency.     

Immobilization of horseradish peroxidase on chitosan for use in nonaqueous media

Chitosan, a natural polysaccharide, was used for the covalent immobilization of horseradish peroxidase, an enzyme of high synthetic utility, with the carbodiimide method. Of the enzyme, 62% was immobilized on chitosan when 1‐ethyl‐3‐(3‐dimethylaminopropyl carbodiimide) was used as the peptide coupling agent. The influence of different parameters, such as the enzyme concentration, carbodiimide concentration, and incubation period, on the activity retention of the immobilized enzyme was investigated. Kinetic studies using horseradish peroxidase immobilized on chitosan revealed the effects of several parameters, such as the substrate hydrophilicity and hydrophobicity, the solubility of substrates in the medium, the solvent hydrophobicity, and the support aquaphilicity, on the catalytic activity of the immobilized enzyme in nonaqueous media. General rules for the optimization of solvents for nonaqueous enzymology based on the partitioning of the solvent were not applicable for the immobilized horseradish peroxidase. The catalytic efficiency was greatest when o‐phenylene diamine was used as the substrate and least when guaiacol was used. The aquaphilicity of the support played an important role in the kinetics of the immobilized horseradish peroxidase in water‐miscible solvents. The results were promising for the future development of chitosan‐immobilized enzymes for use in organic media. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1456–1464, 2003     

非水相体系中海藻酸钠-壳聚糖微胶囊粒径及强度性能

固定化技术是提高生物催化剂在非水相中活性和稳定性的一种很有工业应用潜力的手段。采用乳化-内部凝胶化与络合反应制备海藻酸钠-壳聚糖(AC)微胶囊作为固定化载体,筛选5种有机溶剂构建了培养基-有机溶剂两相体系,模拟酵母细胞培养条件,将AC微胶囊在培养基-有机溶剂两相体系中振荡48 h,5种两相体系对AC微胶囊形态没有明显影响;在培养基-癸二酸二丁酯两相体系中,当壳聚糖分子量在40000～100000、成膜反应时间在2～5 min范围内变化时,分子量小(40000)和成膜时间长(5 min)的AC微胶囊粒径稳定,破碎率较低、机械强度较大,适于用作进一步非水相细胞催化的固定化载体。两相体系中AC微囊化酵母细胞活性保持良好,能实现生物转化生产。     

Synthesis of trimellitic anhydride microcapsule toner by liquid‐phase separation

A microcapsule toner containing trimellitic anhydride for use as a foam inhibitor in printing applications was synthesized by liquid‐phase separation in organic solvents. It is possible to determine materials appropriate for the microencapsulation of trimellitic anhydride from solubility parameters calculated on the basis of the molecular structures of raw material candidates. Considering solubility parameters of various polymers, the polyethylene/methacrylic acid copolymer was selected for the microcapsule wall material. In addition, two kinds of solvents, toluene [solvent (a)] and isoparaffin [solvent (b)], were employed. It was necessary for the microcapsule materials to meet the following conditions: (1) the wall material must completely dissolve in solvent (a); (2) the core material must disperse well, but not dissolve in solvent (a); and (3) the wall and core materials must not dissolve in solvent (b). By using mixtures of either lecithin and basic barium petronate or lecithin and basic calcium petronate as charge control agents, the trimellitic anhydride microcapsules could be charged either positively and negatively, respectively. The microcapsule toner fabricated in this method was successfully applied in commercial printing machines, where it inhibited foaming effectively enough to satisfy product requirements in the printing industry. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3822–3826, 2003     

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。     

Production of core‐shell polymer particles‐containing cardanol by semibatch combined suspension/emulsion polymerization

The main objective of the present work is to study the copolymerization of cardanol and styrene for production of polymer beads intended for enzyme immobilization. Initially, free‐radical copolymerizations of cardanol and styrene were performed in suspension, showing that effective incorporation of cardanol into polystyrene chains is not possible at usual suspension polymerization conditions. Then, free‐radical copolymerizations of cardanol and styrene were performed in semibatch combined suspension/emulsion reactions, showing that cardanol can be incorporated into polystyrene chains (as confirmed through Nuclear Magnetic Resonance and Differential Scanning Calorimetry analyses) when it is fed as an emulsion constituent. In these cases, the final polymer particles presented the usual core/shell morphology, with high‐specific areas and large average pore diameters, as required by enzyme immobilization applications. POLYM. ENG. SCI., 54:1222–1229, 2014. © 2013 Society of Plastics Engineers     

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。     

超临界乳液萃取法制备载槲皮素微胶囊

采用超临界乳液萃取法(SFEE)制得载槲皮素微胶囊,系统考察了制备过程中萃取温度、压力、CO2流速、配制乳液参数对溶剂残留与微胶囊粒径的影响。采用顶空气相色谱法、场发射扫描电镜、Zeta电位、FTIR对溶剂残留与微胶囊进行表征。结果表明:在313 K、9 MPa、CO2流速为0.4 L/min的条件下,处理40 min,溶剂残留可低至59 mg/L。壁材质量浓度从10 g/L增加至100 g/L时,微胶囊粒径由0.9μm升至3.7μm。与溶剂蒸发法相比,SFEE法可在短时间内有效去除有机溶剂,所制备的微胶囊球形度高,界面清晰,在水中稳定性好。     

毒死蜱农药微胶囊剂制备工艺研究

为探讨溶剂挥发法制备毒死蜱微胶囊剂的工艺条件,本研究以聚甲基丙烯酸甲酯为囊壁材料,二氯甲烷为溶剂,水为连续相讨论芯材与壁材比、有机相与水相体积比,乳化剂浓度以及剪切乳化速度对毒死蜱微胶囊剂成囊的影响。研究结果证明成囊的最佳工艺条件:在室温条件下,以二氯甲烷溶解毒死蜱,芯材与壁材的比(w/w)为1∶2,有机相与水相的比(v/v)为15∶105~20∶100,以1.5%羟乙基纤维素(MW:20000)为乳化剂,有机相和水相混合后在15000 r/min下高速剪切乳化分散6 min,在室温下搅拌直至二氯甲烷完全挥发。在此条件下所得毒死蜱微胶囊剂呈球形,平均粒径约为8.5~8.8μm,包覆率在94.52%以上。     

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     

Fuel ethanol production from concentrated food waste hydrolysates in immobilized cell reactors by Saccharomyces cerevisiae H058

BACKGROUND: Continuous ethanol fermentation of concentrated food waste hydrolysates has been studied. The process was carried out in an immobilized cell reactor with beads of calcium‐alginate containing immobilized Saccharomyces cerevisiae H058 at temperature 30 °C and pH 5.0. RESULTS: The total residual sugar decreased with increase of hydraulic retention time (HRT) under various reducing sugar concentrations. Ethanol production by immobilized cells increased with increase in HRT, regardless of the substrate concentrations employed. The highest ethanol concentration of 89.28 g L^?1 was achieved at an HRT of 5.87 h and reducing sugar concentration of 200 g L^?1. At an HRT of 1.47 h, the maximum volumetric ethanol productivity of 49.88 g L^?1 h^?1 and the highest ethanol yield of 0.48 g g^?1 were achieved at reducing sugar concentration of 160 and 200 g L^?1, respectively. The difference between the fresh and the 30‐day Ca–alginate immobilized cell was also shown by scanning electronic micrographs of beads taken from their outer and inner surfaces. CONCLUSIONS: Continuous ethanol production from concentrated food waste hydrolysates using immobilized yeast cells is promising in view of the high ethanol productivity obtained at relatively high conversion and excellent reactor stability. Copyright © 2011 Society of Chemical Industry     

Understanding the role of internal microstructure in capsule‐based healing of polymeric composites

The efficacy of microcapsules possessing varied internal microstructure toward introducing extrinsic self‐healing functionality in epoxy has been compared. Unsaturated polyester was encapsulated in microcapsules by adopting different methodologies. Microcapsules formed using dispersion polymerization exhibited “reservoir” microstructure while solvent evaporation led to the formation of “monolithic” microcapsules. Theoretical model was developed to predict the amount of healant released in the event of microcapsule rupture, which clearly highlighted the benefits associated with reservoir type microcapsules, especially at lower core contents. At larger core contents (≥50% vol/vol), all the micro‐droplets within the monolithic structure coalesced to form a healant reservoir. Self‐healing composites were prepared by introducing both types of microcapsules in an epoxy matrix and the healing efficiency was quantified. In line with the theoretical predictions, reservoir type microcapsules led to much higher healing efficiencies in comparison to monolithic microcapsules. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45471.     

固定化酵母乙醇萃取发酵研究

以十二烷醇为萃取剂，对固定化酵母乙醇萃取发酵进行了研究。探讨了萃取剂对酵母细胞的毒性，以及萃取剂用量、搅拌转速、基质浓度等因素与乙醇萃取发酵的关系，并测定了萃取过程中乙醇的分配系数。为固定化酵母乙醇发酵与溶剂萃取耦合新工艺的开发研究提供了资料。     

Microwave‐assisted immobilization of lipase from Candida rugosa on Eupergit® supports

BACKGROUND: Immobilization of lipase (triacylglycerol acylhydrolase EC 3.1.1.3) from Candida rugosa on Eupergit^® C and Eupergit^® C 250L was performed under microwave irradiation in order to reduce immobilization time. Lipase loading, hydrolytic activity, esterification activity and operational stability in organic solvent of immobilized lipase preparation were determined. RESULTS: The microwave‐assisted procedure resulted in a 29% lower lipase loadings, compared with immobilized lipase obtained without microwaves. In hydrolytic activity assay, lipase immobilized under microwaves exhibited a 23% higher specific activity. Slight activation of lipase by microwave‐assisted immobilization was observed, since specific activity was around 5% higher than for free lipase. Lipase of highest activity was obtained after 2 min immobilization on Eupergit^® C. The same preparation exhibited high esterification activity in organic medium and a half life of 212 h was determined in multiple use assay. CONCLUSION: The application of microwave irradiation leads to reduction of immobilization time from 2 days to only 2 min. The immobilized lipase obtained has prospects for further application due to its high retained activity and stability. Copyright © 2009 Society of Chemical Industry