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以水包油(O/W)型Pickering乳液为模板,经UV光聚合法制备复合壳层中空微胶囊,探究了乳化剂纳米粒子的加入方式、粒径和光敏低聚物PUA对微胶囊壳层的影响,并将微胶囊加入到树脂涂层中,探究微胶囊作为填料对涂层基本性能的影响。使用傅立叶变换红外光谱、扫描电镜、光学显微镜、热重等仪器对微胶囊结构进行表征,并对涂层性能进行了测试。结果表明:乳化剂SiO2-E纳米粒子加入到油相中制备得到的中空微球表面镶嵌有SiO2-E纳米粒子;乳化剂纳米粒子粒径的增加,影响中空微球的形貌但对尺寸无影响;当PUA的质量分数从10%增加到30%时,中空微胶囊表面分布的纳米粒子减少,断裂伸长率从11.1%增加至34.5%,而最大拉伸应力从21.5 MPa降低至12.1 MPa。中空微胶囊加入到涂料中,随中空微胶囊含量的增加,涂层的铅笔硬度提高且附着力良好。 相似文献
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利用凝胶内溶质分子向缓冲溶液中扩散的方法,测定了溶菌酶、β-乳球蛋白、卵清蛋白、牛血清白蛋白和γ-球蛋白5种蛋白在聚丙烯酰胺凝胶中的有效扩散系数和分配系数,研究了单体质量浓度、交联度和蛋白分子粒径等因素的影响,讨论了聚丙烯酰胺凝胶中蛋白分子的扩散和分配机制,发现不能用Ogston理论解释聚丙烯酰胺凝胶中蛋白分子的扩散和分配特性 相似文献
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微胶囊的制备方法研究进展 总被引:4,自引:1,他引:4
本文介绍了微胶囊的常用天然壁材和微胶囊的制备方法。天然壁材分为碳水化合物、蛋白质和脂类3大类,其中传统天然壁材有海藻酸钠、壳聚糖、明胶等,新型天然壁材包括脂质体、微生物细胞壁(酵母菌细胞壁)、多孔淀粉等。微胶囊的常规制备方法包括:复凝聚法、单凝聚法、界面聚合法、原位聚合法、锐孔-凝固浴法、喷雾干燥法等,微胶囊的新型制备方法有:分子包埋法、微通道乳化法、超临界流体快速膨胀法、酵母微胶囊法、层-层自组装法、模板法等。但是微胶囊技术还存在诸多不成熟之处,有些关键问题还有待解决。 相似文献
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利用同轴电喷射技术,分别以含水甘油和溶解于N,N-二甲基乙酰胺(DMAC)的聚氨酯(PU)溶液为内、外相电喷液,制备中空PU微囊,考察了电喷液组成及流速对其结构的影响. 结果表明,以80%(?)甘油溶液和10%(?) PU溶液为内、外相电喷液,在流速分别为0.05和1 mL/h、电压约22 kV、针头距接收板48 cm、温度30℃、湿度约10%的条件下,可制备出结构均一的中空PU微囊. 在上述电喷射条件下,将南极假丝酵母脂肪酶B (CALB)溶解于内相电喷液中,原位包埋在PU微囊腔室内. 固定化CALB的活性回收率为游离酶的76.19%,重复使用10次后活性仍保持60%以上,60℃下的半衰期比游离酶提高了8倍. 相似文献
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以商业化的Kapton型聚酰亚胺为前驱体制备炭膜,采用容量法研究了不同炭化温度制备的炭膜CO2吸附和扩散行为,并利用Sips模型对实验数据进行拟合,DA方程计算炭膜的孔结构参数,Fick扩散模型求取CO2在炭膜内的扩散系数,采用XRD分析探讨了炭膜的炭结构。结果表明,炭膜孔结构随着热解炭化温度的提高,孔径收缩,且当炭化温度从600℃升高到800℃,炭膜的微孔体积随炭化温度的升高而增大,而800℃以后,微孔体积随炭化温度的升高而下降。CO2在不同炭膜中的扩散系数约为1.04×10-13~8.56×10-12m2·s-1,在实验测定的压力范围内扩散系数随着平衡压力的增大呈现出先增大后减小的规律。 相似文献
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<正>硬球理论的基础是Maxwell-Boltzman的统计力学理论,最早由Chapman等将该理论应用于研究稀薄气体的传递性质。在稠密流体中,必须考虑分子碰撞频率大幅度增加的影响因素。 Dymond等认为该影响与分子接触径向分布函数g(σ)有关,并以此计算了 相似文献
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何潮洪 《中国化学工程学报》1998,6(2):159-165
1 INTRODUCTIONSupercritical fluids have found new and increasing applications in the past decade.Theirunique properties of low viscosity,high diffusivity and adjustable solvency have favored theiremployment as solvents in chemical reactions and extraction processes.Proper evaluation ofthe technical feasibility for supercritical fluids in these processes would involve the hydrody-namic and mass-transfer parameters,the estimation of which calls for reliable molecular dif-fusion coefficients of various solutes in the supercritical fluid of interest.Therefore,it follows 相似文献
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采用氮吸附、扫描电镜和热重分析法研究了石灰石煅烧分解过程中孔结构演变规律及反应特性,构建了双峰孔径分布概率密度函数与有效扩散系数计算模型,并与实验测量结果进行对比验证. 结果表明,石灰石不同分解阶段煅烧产物的孔结构皆为双峰分布,主峰3 nm附近小尺度中孔数随反应深化逐渐增多,在固体转化率达约60%时呈阶跃式增长;在1073 K煅烧固体转化率由50.41%增大到68.27%时,有效扩散系数由0.0162 cm2/s降至0.0093 cm/s,导致分解反应机理随之变化;在1073和1223 K煅烧温度下,反应机理转为传质控制,相应的临界固体转化率分别为60%和75%. 相似文献
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实际分离的混合物大多数为多组分体系,因此,开展多组分传质过程的理论和实验研究具有重要的实际意义。多组分传质过程涉及Fick扩散系数和axwell-Stefan扩散系数的计算。本文阐述Fick扩散系数和Maxwell-Stefan扩散系数的意义和相互关系,以及多组分液体体系扩散系数的计算。 相似文献
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A H2O/dimethyl formamide (DMF) mixture was used as the coagulation bath of wet‐spun process for acrylic fibers. Diffusion coefficient of DMF in the protofibers prepared by acrylonitrile/acrylamide copolymers was determined. It has been found that diffusion coefficient of DMF outflow of the protofibers prepared by acrylonitrile/acrylamide copolymers synthesized by solution polymerization is highest compared with those of acrylonitrile/acrylamide copolymers synthesized by H2O/DMF mixture suspension polymerization and aqueous suspension polymerization. With an increase of copolymer concentration in the dope, diffusion coefficient of DMF decreases continuously. Diffusion coefficient of DMF increases along with the bath temperature, but the changes in diffusion coefficient values are less prominent as temperature goes beyond 55°C. When DMF concentration in the coagulation bath was 50%, the value of the diffusion coefficient of DMF was minimal. Diffusion coefficient of DMF increases along with jet stretch minus ratio increase. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3616–3619, 2006 相似文献
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基于Reamer等的扩散理论 ,测量了 3 11K、1.90 5MPa下二氧化碳在正十四烷中的常扩散系数。根据短时间内扩散量与时间平方根之间存在着线性关系 ,引入不定函数Ft 描述与浓度有关的扩散过程 ,得到了二氧化碳 正十四烷体系与浓度有关的扩散系数数据 ,发展了气体在液相中的Fick扩散理论 相似文献
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Ultrafiltration membranes from acrylonitrile copolymer were chemically modified with different concentrations of hydrogen peroxide (from 5 to 30% H2O2). The amount of the amide groups in the modified membranes was determined. The water flow and permeability coefficients of the initial and modified membranes were also researched. The modified membranes were used as carriers for covalent immobilization of the dual enzyme system of glucose oxidase and catalase (GOD+CAT). It was found that the best matrices for immobilization of the dual system were membranes modified with 20% H2O2 and the optimal activity ratio was GOD : CAT = 1 : 5. The glucose conversion efficiency with the dual enzyme system was twice as high as that of bound GOD alone. Some of the basic characteristics (optimum pH, optimum temperature, pH, temperature stability, and storage stability) of the dual enzyme system were determined and compared with characteristics of free and bound enzymes. The catalytic parameters of the enzyme reaction (Km and Vmax) were determined with GOD immobilized alone and with the dual system GOD+CAT. The higher rate observed with the dual enzyme system clearly showed the advantage and the efficiency of the immobilized system. Glucose oxidase without catalase was deactivated by H2O2 more rapidly than the immobilized dual GOD+CAT system. These experimental evidences can be explained by the protecting effect of catalase on glucose oxidase from inhibition by H2O2. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 4057–4063, 2004 相似文献
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ABSTRACT This naver analvzes the surface emission coefficient corresponding to anv diffusion coefficient expressed as an exponential function of the concentration diffusing substance in capillary porous solids. Theoretical equations for surface emission coefficient for both sorption and desorption are presented. Procedures to derive the diffusion coefficient and to verify the corresponding surface emission coefficient are made using experimental sorption data of aspen (Populur sp.) wood. It is of interest to note that the theoretical models for diffusion and surface emission coefficients can be established and/or evaluated using the same set of experimental dara. 相似文献
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B. J. Gornshteyn 《加拿大化工杂志》2003,81(1):139-146
For calculating mass transfer through a hollow‐fiber asymmetric membrane, a fundamentally new theoretical method based on Fick's first law of diffusion is proposed. The main features of this method, and the ones currently used for the same purpose, have been compared. The current methods, also based on Fick's first law of diffusion, are shown to be theoretically less than adequate. Recommendations are given for the practical implementation of the new method. 相似文献
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Veena B. Kushwaha 《应用聚合物科学杂志》1999,74(14):3469-3472
Permeation of molecules through the membranes plays an important role in immobilized cell systems. Permeation of molecules like glucose and bovine albumin serum was studied through chitosan, polyvinyl alcohol, and polyvinyl acetate membranes using a flow cell made of two detachable compartments. Permeation of molecules through chitosan, polyvinyl alcohol, and polyvinyl acetate membranes increases with decrease in hydrophobic characteristics of the membrane. Permeation of molecules also show its dependency on the molecular weight of the solute. Distribution coefficient of glucose and bovine serum albumin in these polymeric membranes measured by equilibration technique indicates that permeation of molecules through these membranes follows pore type mechanism. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3469–3472, 1999 相似文献
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The capacity of poly(vinyl alcohol) (PVA) to crosslink through freeze/thaw method was used to obtain PVA hydrogel membranes (HG) that were subjected to sorption and diffusion experiments using three dyes: Congo red (CR), methylthymol blue (MTB), and crystal violet (CV). To study the sorption of dyes into the cryogenic membrane, dye solutions at different concentrations were used. After sorption, desorption of dyes from the PVA membrane was monitored to quantify the possible regeneration of the membrane (PVA HG). To have a deep insight on the mechanism behind the desorption process, dye‐release kinetics were studied. The diffusion experiments reveal the fact that CR and MTB do not permeate the PVA HG membrane making it a promising candidate in the advanced purification processes of wastewaters. The effect of the incorporation of dyes (CV, CR, and MTB) on the chemical properties of PVA cryogel matrices has been studied by using several techniques such as: differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献