外墙乳胶漆耐候性研究

采用天然曝晒和人工老化方法研究了各种纯丙乳液和硅丙乳液的耐候性,由该类乳液制备的不同PVC白色乳胶漆的耐候性,以及白色乳胶漆与各色色浆配制的浅色乳胶漆的耐候性。结果表明:硅丙乳液和核壳型纯丙乳液具有较好的耐候性,高PVC乳胶漆容易变色,炭黑和氧化铁系色浆适合于配制浅色外墙乳胶漆,有机颜料色浆应用在外墙时应谨慎。     

Characterization of a double emulsion system (oil-in-water-in-oil emulsion) with low solid fats: Microstructure

A double emulsion system [oil-in-water-in-oil (O/W/O)] with 16.3% (w/w) water and 83% (w/w) oil was prepared and stabilized using a novel method of mixing two oil-in-water (O/W) emulsions together. The first emulsion consisted of 85% (w/w) liquid canola oil, 14.4%(w/w) water, 0.5% (w/w) sodium caseinate, and 0.1% (w/w) lecithin and the second emulsion contained 73% (w/w) canola oil, 8% (w/w) palm-cotton stearin (50∶50), 0.2% (w/w) lecithin, 18.2% (w/w) water, and 0.6% (w/w) sodium caseinate. Mixing the two emulsions (50∶50) by weight produced a product with 79% (w/w) liquid canola oil and 4% (w/w) palm-cotton stearin. The two O/W emulsions were prepared separately at 50°C, mixed together at 45°C for 2–5 min, and then supercooled in a −5°C ice/salt bath while mixing at low shear rates (2,000–3,000 rpm). Under supercooling conditions the fat globules in the second emulsion (containing liquid oil and stearin) began to break down as a result of fat crystal growth and shearing action and release plastic fat. During this stage, the continuous aqueous phase underwent a phase transition and the emulsion viscosity dropped from 37,000–50,000 to 250 cP. The released plastic fat continued to harden as the temperature dropped and stabilized the first O/W emulsion (containing only liquid oil). The low shear rate mixing was stopped when the temperature dropped below 15°C and before the O/W/O emulsion hardens. Microstructural analysis of the first emulsion before and after supercooling showed essentially intact fat globules. The microstructure of the second emulsion before supercooling showed the same intact globules as the first emulsion, but after supercooling, an amorphous mass with only a few intact globules was seen. By mixing the two emulsions together and supercooling, a stable O/W/O emulsion was formed with plastic fat as the continuous phase and the first O/W emulsion as the dispersed phase.     

静电植绒VAE乳液的研制

以醋酸乙烯(VAc)、丙烯酸异辛酯(2-EHA)、乙烯、N-羟甲基丙烯酰胺(NMA)为单体,合成出了玻璃化转变温度(Tg)-15℃的静电植绒用VAE乳液;考察了2-EHA、交联单体NMA、引发剂、乳化体系、缓冲剂对聚合过程及产品质量的影响;分析了乳液及其膜发黄的原因。应用结果表明产品性能满足用户要求。     

STUDIES ON SYNTHESIS OF SILICA SOL-ORGANIC POLYMER COMPOSITE EMULSION

An emulsion of polystyrene/poly (butylacrylate-methyl methacrylate acrylic acid) core/shell latex particles (PS/P (BA-MMA-AA)) has been prepared by use of three synthetic methods. The effects of synthetic methods on the distribution of carboxyl groups in latex particles were studied. The results show that the seed emulsion polymerization in which the pre-emulsified monomers were added by dropping method to the second stage is the best technique for obtaining the optimum distribution of carboxyl groups on the surface of the latex particles. Furthermore, by using PS/P (BA-MMA-AA), a type of novel composite emulsion of silica sol-PS/P (BA-MMA-AA) was synthesized with the above method. By observation through transmission EM, the morphology of the latex particles obtained shows that a composite structure has been formed between silica sol particles and organic polymer particles.     

Improving the physical properties of PEA/PMMA blends by the uniform dispersion of clay platelets

Poly(ethyl acrylate) (PEA)/poly(methyl methacrylate) (PMMA) emulsion blends that were combined with unmodified montmorillionite (MMT) to improve the physical properties via nanocomposite formation. We prepared a cationic PEA/PMMA latex and used a heterocoagulation process to create a homogeneous dispersion of the clay platelets in the matrix. The cationic PEA/PMMA emulsion blends were prepared using a cationic initiator in the presence of free surfactant, cetyl trimethylammonium bromide (CTABr), followed by mixing with an aqueous slurry of MMT. The PEA/PMMA-MMT nanocomposites could be processed at low temperatures. Low temperature processing prevented the commonly observed discoloration associated with many thermoplastic nanocomposites. DSC, SAXS, TEM and AFM were used to study the dispersion of MMT and morphology of PEA/PMMA-MMT nanocomposites. Tensile stress, elongation at break and Young's modulus demonstrated a significant reinforcing effect of clay.     

Altering the sequence specificity of HaeIII methyltransferase by directed evolution using in vitro compartmentalization

Engineering the specificity of DNA-modifying enzymes has proven extremely challenging, as sequence recognition by these enzymes is poorly understood. Here we used directed evolution to generate a variant of HaeIII methyltransferase that efficiently methylates a novel target site. M.HaeIII methylates the internal cytosine of the canonical sequence GGCC, but there is promiscuous methylation of a variety of non-canonical sites, notably AGCC, at a reduced rate. Using in vitro compartmentalization (IVC), libraries of M.HaeIII genes were selected for the ability to efficiently methylate AGCC. A two-step mutagenesis strategy, involving initial randomization of DNA-contacting residues followed by randomization of the loop that lies behind these residues, yielded a mutant with a 670-fold improvement in catalytic efficiency (k(cat)/K(m)(DNA)) using AGCC and a preference for AGCC over GGCC. The mutant methylates three sites efficiently (AGCC, CGCC and GGCC). Indeed, it methylates CGCC slightly more efficiently than AGCC. However, the mutant discriminates against other non-canonical sites, including TGCC, as effectively as the wild-type enzyme. This study provides a rare example of a laboratory-evolved enzyme whose catalytic efficiency surpasses that of the wild-type enzyme with the principal substrate.     

热致变色再生纤维素纤维及织物的研制和性能

介绍了热致变色再生纤维素纤维及织物的研制,研讨了热致变色材料对再生纤维素纤维纺丝溶液的熟成度、黏度和可纺性的影响,借助扫描电子显微镜对纤维结构形态进行了观测,对纤维力学性能进行了分析,讨论了加热时间、测试温度和洗涤次数对热致变色再生纤维素纤维织物的变色效果的影响。结果表明:热致变色微胶囊乳液的加入量对黏胶纺丝溶液的熟成度和黏度都有影响;纤维织物变色效果受加热时间影响相对较小,受温度影响较大。     

Chemical deterioration and discoloration of semi-dried tilapia processed by sun drying and microwave drying

Drying methods can affect the chemical deterioration and discoloration of fish muscle. This study aimed to monitor the effect of microwave drying at different effective powers in comparison with sun drying on the physicochemical changes of semidried tilapia. Lipid deterioration, protein oxidation and discoloration of semidried tilapia (Oreochromis niloticus) muscle processed by sun drying and microwave drying were investigated. Results of the study revealed that the pH of microwaved tilapia was higher than that of the sun-dried tilapia (p?p?p?p?p?p?a* value with a significantly decreased redness index (p?相似文献   

亲水性低黄变氨基改性硅微乳的合成

以D4和改性氨基硅烷偶联剂为原料，采用磺酸类催化剂和非离子型复合乳化剂，通过将预乳液滴入催化剂的水溶液的方法，制成了氨基改性硅微乳。预乳液的滴加速度对产品的透明度有很大影响；硅微乳具有良好的酸、碱、阴离子表面活性剂、离心、热稳定性，并可与荧光增白剂、还原性染料、活性染料同浴使用；用其整理的织物具有良好的亲水性和低黄变性。     

明胶和海藻酸钠的协同作用对乳液稳定性的影响

为了改善目前单一蛋白质明胶（GE）作为乳化剂所制备乳液的不稳定性,研究了明胶和海藻酸钠（AL）复合凝聚物对水包油乳液配方的影响。ζ电位法和比浊法的分析表明,在总浓度为0.05%和GE与AL的质量浓度之比R为8：1~1：1的比例下,明胶和海藻酸钠由于静电相互作用形成了复合凝聚物。在pH值低于5.1时,2种生物大分子的静电相互作用随pH值的降低而增大。在pH值（4.5~7.0）和GE与AL的质量浓度之比R为4：1~1：2下制备了含有5%大豆油（质量分数,下同）和2%生物聚合物的乳液,并且通过粒度分布分析、显微镜观察和稳定分析仪（LUMiFuge116）对其进行表征。结果表明随着pH值从7.0降低至4.5,乳液液滴的粒径在所有浓度比均呈下降趋势。在1：1的比例下,明胶和海藻酸钠对乳液的稳定性表现出更好的协同作用,因为在这一条件下的乳液具有较小的液滴尺寸和更好的乳析稳定性。此外,乳液在50℃以下显示出更好的稳定性,液滴发生较少的聚集。     

氧化石墨烯/硅烷复合乳液对混凝土防渗透性能的影响

用溶胶合成法将氧化石墨烯(GO)与异丁基硅烷单体合成出一种新型的渗透型复合乳液。通过混凝土毛细吸水实验和混凝土的毛细吸盐实验,对比研究了GO/异丁基硅烷复合乳液、异丁基硅烷乳液和GO分散液对混凝土渗透性能的影响。结果表明:在防水方面,GO/异丁基硅烷复合乳液效果最好,毛细吸水系数比空白试样降低92.5%(W/C=0.4)和93%(W/C=0.6)。接触角测试结果表明:未经防护处理的混凝土表面水接触角为65.65°,属于亲水性表面;而经GO/异丁基硅烷复合乳液处理后,混凝土表面的水接触角为121.53°,属于憎水性表面,憎水性极大增强。在抗氯离子侵蚀方面,效果最好的也是GO/异丁基硅烷复合乳液,毛细吸盐28 d后,混凝土表层2 cm处的氯离子含量比空白试样降低了80.9%(W/C=0.4)和54.3%(W/C=0.6)。     

Efficient Encapsulation of a Water-Soluble Molecule into Lipid Vesicles Using W/O/W Multiple Emulsions via Solvent Evaporation

We developed a novel method for preparing lipid vesicles with high entrapment efficiency and controlled size using water‐in‐oil‐in‐water (W/O/W) multiple emulsions as vesicle templates. Preparation consists of three steps. First, a water‐in‐oil (W/O) emulsion containing to‐be‐entrapped hydrophilic molecules in the water phase and vesicle‐forming lipids in the oil phase was formulated by sonication. Second, this W/O emulsion was introduced into a microchannel emulsification device to prepare a W/O/W multiple emulsion. In this step, sodium caseinate was used as the external emulsifier. Finally, organic solvent in the oil phase was removed by simple evaporation under ambient conditions to afford lipid vesicles. The diameter of the prepared vesicles reflected the water droplet size of the primary W/O emulsions, indicating that vesicle size could be controlled by the primary W/O emulsification process. Furthermore, high entrapment yields for hydrophilic molecules (exceeding 80 % for calcein) were obtained. The resulting vesicles had a multilamellar vesicular structure, as confirmed by transmission electron microscopy.     

新型双组分室温自交联共聚物乳液体系的研究

用马来酸酐和乙二胺合成了含有双键的伯胺化合物(UPA),并用其与丙烯酸系单体进行乳液共聚合制各了双组分室温固化涂料的第一组分。研究了乳化剂种类和UPA用量对聚合稳定性的影响,结果表明,若采用p-壬基酚聚氧化乙烯醚硫酸钠为乳化剂,且UPA用量低于单体总量2．5％(wt)时,可以制得稳定的UPA／丙烯酸酯共聚物乳液。通过对乳液聚合物的红外光谱分析表明,UPA与丙烯酸酯发生了共聚反应。将乙二醇二缩水甘油醚乳化形成水乳液,作为水乳型涂料的第二组分。将两种乳液复合后在室温下干燥成膜,通过对聚合物涂膜的DSC及力学性能的测试表明,双组分体系在成膜过程中发生了交联反应,而未加环氧化合物的单组分聚合物乳液成膜时则不发生交联。研究了不同UPA含量对涂膜拉伸强度的影响,结果表明,在适量UPA用量时可获得最高的涂膜拉伸强度。     

Interfacial Crystallization of Diacylglycerols Rich in Medium‐ and Long‐Chain Fatty Acids in Water‐in‐Oil Emulsions

The effects of diacylglycerols rich in medium‐ and long‐chain fatty acids (MLCD) on the crystallization of hydrogenated palm oil (HPO) and formation of 10% water‐in‐oil (W/O) emulsion are studied, and compared with the common surfactants monostearoylglycerol (MSG) and polyglycerol polyricinoleate (PGPR). Polarized light microscopy reveals that emulsions made with MLCD form crystals around dispersed water droplets and promotes HPO crystallization at the oil‐water interface. Similar behavior is also observed in MSG‐stabilized emulsions, but is absent from emulsions made with PGPR. The large deformation yield value of the test W/O emulsion is increased four‐fold versus those stabilized via PGPR due to interfacial crystallization of HPO. However, there are no large differences in droplet size, solid fat content (SFC), thermal behavior or polymorphism to account for these substantial changes, implying that the spatial distribution of the HPO crystals within the crystal network is the driving factor responsible for the observed textural differences. MLCD‐covered water droplets act as active fillers and interact with surrounding fat crystals to enhance the rigidity of emulsion. This study provides new insights regarding the use of MLCD in W/O emulsions as template for interfacial crystallization and the possibility of tailoring their large deformation behavior. Practical Applications: MLCD is applied in preparing W/O emulsion. It is found that MLCD forms unique interfacial Pickering crystals around water droplets, which promote the surface‐inactive HPO nucleation at the oil‐water interface. Thus MLCD‐covered water droplets act as active fillers and interact with surrounding fat crystals, which can greatly enhance the rigidity of emulsion. This observation would provide a theoretical reference and practical basis for the application of the MLCD with appreciable nutritional properties in lipid‐rich products such as whipped cream, shortenings margarine, butter and ice cream, so as to substitute hydrogenated oil. MLCD‐stabilized emulsions can also be explored for the development of novel confectionery products, lipsticks, or controlled release matrices.     

An integrated device for monitoring time-dependent in vitro expression from single genes in picolitre droplets

Microdroplets have great potential for high-throughput biochemical screening. We report the design of an integrated microfluidic device for droplet formation, incubation and screening. Picolitre water-in-oil droplets can be stored in a reservoir that contains approximately 10(6) droplets. In this reservoir droplets are stable for at least 6 h, which gives an extended timescale for biochemical experiments. We demonstrate the utility of the system by following the in vitro expression of green fluorescent protein. The high efficiency allows protein expression from a single molecule of DNA template, creating "monoclonal droplets" in which genotype and phenotype are combined in one emulsion compartment.     

Hydrogen formation by the photodecomposition of water over Pt/TiO2 suspended in a water in oil emulsion

Hydrogen formation by the photodecomposition of water has been successfully achieved in a water in oil emulsion (w/o emulsion) system containing Pt/TiO₂. The hydrogen formation rate was affected by the amount of water added to the emulsion. It was concluded that water in the w/o emulsion containing Pt/TiO₂ was more active than free water for the photodecomposition to form hydrogen. This revised version was published online in July 2006 with corrections to the Cover Date.     

Novel color stabilization concepts for decorative surfaces of native dark wood and thermally modified timber

UV and visible light exposure of dark colored wood and thermally modified timber (TMT) is strongly connected with discoloration and photobleaching of the respective wood surfaces. Conventional and nanoscale UV absorbers as well as radical scavengers (HALS), mainly effective for the protection of softwood and bright hardwood, were found to be improper for the light stabilization of dark wood surfaces. In the current work discoloration mechanisms are discussed considering the role of wood extractives and the sensitivity of dark colored wood types to visible light and results are presented which were obtained by applying novel protecting systems for the light stabilization of transparently coated surfaces from dark colored wood types and TMT.     

聚氨酯/聚丙烯酸酯复合乳液的研制进展

综述了近年来聚氨酯－丙烯酸酯（PUA）复合乳液研究的新进展，总结介绍了各类聚氨酯－聚丙烯酸酯复合乳液（PUA共混复合乳液、PUA复合核／壳乳液、互穿网络PUA复合乳液）的制备方法和性能特点。并对该领域进一步的发展作了展望。     

Stability of vitamin A in oil-in-water-in-oil-type multiple emulsions

The stabilityof vitamin A was studied in thee different emulsions: oil-in-water (O/W), water-in-oil (W/O), and oil-in-water-in-oil (O/W/O). The stability of retinol (vitamin A alcohol) in the O/W/O emulsion was the highest among the thee types of emulsions; remaining percentages at 50°C after 4 wk in the O/W/O, W/O, and O/W emulsions were 56.9, 45.7, and 32.3, respectively. With increasing peroxide value of O/W and W/O emulsifiers, the remaining percentage of vitamin A palmitate and retinol in the emulsions decreased significantly, indicating that peroxides in the formulae accelerate the decomposition of vitamin A. Organophilic clay mineral (an oil gelling agent and a W/O emulsifier) also affected the stability of retinol; synthesized saponite was better than naturally occurring bentonite for retinol stability. The stability of retinol in the O/W/O emulsion increased with increasing inner oil phase ratio (φ_i), whereas in O/W it was unaffected by φ_i. Encapsulation percent of retinol in the O/W/O emulsion, the ratio of retinol in the inner oil phase to the total amount in the emulsion, increased with increasing φ_i. The remaining percent of retinol in the O/W/O emulsion was in excellent agreement with encapsulation percent, suggesting that retinol in the inner oil phase is more stable than that in the outer oil phase. Addition of antioxidants (tert-butylhydroxytoluene, sodium ascorbate, and EDTA) to the O/W/O emulsion improved the stability of retinol up to 77.1% at 50°C after 4 wk. We conclude that the O/W/O emulsion is a useful formula to stabilize vitamin A.     

可再分散乳胶粉在新型外墙柔性腻子中的应用

采用可再分散乳胶粉等原料制备了用于外墙外保温体系的新型柔性腻子,探讨了可再分散乳胶粉的用量对柔性腻子的粘接性能、抗动态开裂性能等影响。结果表明:可再分散乳胶粉对该腻子具有明显的增强作用,并且可改善其柔韧性;当聚灰比为14%时,该腻子可获得较理想的柔性。