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采用水-乙醇混合溶剂法以PVA、丁醛、盐酸为原料,合成了高缩醛度聚乙烯醇缩丁醛(PVB),利用单因素试验法研究了乙醇加入量、二步丁醛加入温度、丁醛加入量、盐酸加入量因素对PVB缩醛度及产量的影响,研究结果表明,最佳的合成工艺为:乙醇与水的质量比为1∶10,在二步丁醛加入温度,15℃,丁醛与PVA质量比为0.7,盐酸与PVA质量比为0.55时,得到的PVB缩醛度为83.1%。 相似文献
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以醋酸乙烯为原料,碳酸二甲酯和甲醇为混合溶剂,进行溶液聚合反应制备了高聚合度聚乙烯醇。考察了搅拌转速、甲醇的加入时间、引发剂质量分数、混合溶剂体积分数、溶剂体积比和聚合时间对醋酸乙烯聚合反应的影响,采用正交试验法对醋酸乙烯溶液聚合的反应条件进行了筛选。并通过傅里叶红外光谱和凝胶色谱对最优条件下制得的产品进行确认和分析。结果表明,最佳的聚合条件为:引发剂质量分数为0.01%,混合溶剂体积分数为10%,溶剂体积比V(DMC)∶V(MeOH)为4∶1,聚合时间为2.5 h,所得产品的聚合度为3 557;在最优条件下制备的产品结构未发生变化,且得到了高聚合度、相对分子质量分布较窄的产品。 相似文献
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优质PAN原丝是生产高性能碳纤维的前提,采用高分子量聚丙烯腈共聚树脂进行干喷湿纺是提高原丝性能的有效途径之一。本文采用混合溶剂法合成了分子量为5.2×10^5~3.14×10^6的PAN共聚树脂,系统地讨论了实验条件对聚合结果的影响,并对反应机理进行了初步探讨,对合成的树脂进行热分析时发现树脂的热行为更适合预氧化反应。 相似文献
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聚乙烯醇缩醛—环氧结构胶粘剂 总被引:3,自引:2,他引:3
介绍了一种新型结构胶——聚乙烯醇缩醛——环氧胶粘剂,它是由聚乙烯醇缩醛、环氧树脂、固化剂、混合溶剂及其他配合剂制成。在飞机及宇航工业中,可广泛用于金属蜂窝结构件的制造。 相似文献
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选用DMAc和辛烷作为非溶剂致相分离法(NIPS)的混合溶剂制备聚醚砜(PES)膜,利用两种溶剂在高温下互溶、低温下相分离的特点,制备得到具备高孔隙率和纳米级表面孔径的PES膜。为进一步优化膜的结构性能,研究了辛烷加入量和预蒸发时间对膜性能的影响,最终制备得到孔径为12.50 nm、孔隙率高达89%的海绵状截面结构PES膜,其渗透通量可达65.23 L/(m2hbar),较优化前提升了160%;而对牛血清白蛋白(BSA)的截留率始终维持在95%以上,对同时实现膜的高渗透性和高选择性具有深刻意义。 相似文献
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The relationship between the polymer–solvent interaction and gelation behavior of poly(vinyl alcohol) (PVA) solutions prepared from ethylene glycol/water (EG/water) mixed solvents was investigated using a viscometer, light scattering, FTIR, X‐ray, and pulsed NMR analyses. The viscometric result showed that the affinity to PVA for water is higher than that for EG. The light scattering result showed that the spinodal decomposition rate of the PVA solution decreases rapidly as the water content in the EG/water mixed solvent is increased. On the other hand, the FTIR and X‐ray results both indicated that the crystallinity of the PVA gel decreases with water content. These results imply that the water molecules must improve the affinity of the solvent to PVA to inhibit the aggregation or crystallization of PVA chains. The pulsed NMR measurement results showed that the spin–spin relaxation times related to the polymer‐rich and polymer‐poor phases of the PVA gel increase, and the fractional amount of the polymer‐poor phase increases while that of the polymer‐rich phase decreases with increasing water content. These facts indicated that the increase in the mobility of PVA chains must give rise to the difficulty in chain aggregation of PVA solutions with increasing water content. Two transition temperatures were found in the phase transition of the polymer‐rich phase. The lower transition temperature was attributed to the destruction of the denser chain entanglements in the polymer‐rich phase and the higher transition temperature was mainly concerned with the melting of the crystallites. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1113–1120, 2001 相似文献
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Poly(vinyl acetate) (PVAc)/poly(ethylene oxide) (PEO) blends were prepared by casting from either benzene or chloroform. The solvent effects on the crystallization behavior and thermodynamic properties of the blends were studied by the differential scanning calorimeter (DSC). Two grades of PEO with different molecular weights (PEO200 with Mw = 200,000 g/mol and PEO2 with Mn = 2000 g/mol) were used in this work. The thermal analysis revealed that the blends cast from either benzene or chloroform were miscible in the molten state. The crystallization of PEO in the benzene-cast blends was more easily suppressed than it was in the chloroform-cast blends. Furthermore, the benzene-cast blends showed a greater negative value of Flory-Huggins interaction parameter than those cast from chloroform in the PVAc/PEO200 poly-blend system. It was supposed that the benzene-cast blends had more homogeneous morphology. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 411–421, 1997 相似文献
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Poly(vinyl acetal) from poly(vinyl alcohol) and 4-dimethylaminobenzaldehyde (DMAB) is synthesized. Fluorescence behavior of the polymer is investigated in acetic acid glacial (HAc), dimethylsulfoxide (DMSO), and dimethylformamide (DMF) solvents. Fluorescence emission intensities of the polymer solutions are different with the change of concentration. The result suggests that the maximum fluorescence emission intensities of the polymer solutions depend on the optimal concentration of the polymer. It has been found that the fluorescence intensity of DMAB is dramatically lower than that of the polymer in the same chromophore concentration, and such phenomenon is termed as structural self-quenching effect (SSQE). The strong fluorescence of the polymer can be quenched by adding electron-deficient monomers which have no chromophore moieties such as lactic acid, adenine, etc., and their Stern–Volmer constants are determined. It is observed that the higher the electron deficiencies of the quenchers, the higher the Stern–Volmer constants, which means stronger quenching effect. The result indicates that the polymer can recognize these biologic small molecules. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2385–2390, 1999 相似文献
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Youn-Mee Choi Byoung-Ho Lee Ji-Won Park Hyun-Joong Kim Sung-Wook Jang 《Journal of Adhesion Science and Technology》2013,27(5-6):536-550
An eco-friendly poly (vinyl acetate) emulsion adhesive was synthesized without phthalate. Four types of eco-friendly plasticizers for use in these adhesives were selected to confirm their primary properties by injecting the eco-friendly plasticizer without any prior change to its processing or cost. The four types of eco-friendly plasticizers used were dibutyl phthalate DBP-based product, dialkyl ester, acetyl tributyl citrate, and pentandiol-di-isobutyrate. Their properties were determined by comparison with the existing (DBP)-based product. As a result, an emulsion adhesive was produced without addition of phthalate or need for additional additives, resulting in a significant decrease in cost. However, the low temperature characteristics of the eco-friendly plasticizers were slightly inferior to those of DBP. These adhesives containing eco-friendly plasticizer were studied and their characteristics for adhesion strength, water resistance, ability for low temperature film formation, excellent storage stability, and lack of volatile organic compounds productions (including phthalate) were confirmed. 相似文献
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High-molecular weight (HMW) poly(vinyl alcohol) (PVA) was prepared via an emulsifier-free emulsion polymerization of vinyl acetate (VAc) using a redox initiation system in low temperatures, and the subsequent saponification with potassium hydroxide in methanol. The effect of the polymerization conditions on the conversion, molecular weight, and branching degree was investigated. PVA with maximum viscosity-average degree of polymerization (DP) of 8270 could be prepared by saponification of poly(vinyl acetate) (PVAc), with DP of 10,660 obtained at temperature of 10°C, monomer concentration of 30%, potassium persulfate molar ratio to monomer of 1/2000, agitation speed of 160 rpm. The conversion was above 90%. From the emulsifier-free emulsion polymerization of VAc in low temperature, PVAc with HMW and high linearity was effectively prepared, which might be useful for the preparation of high-strength and high-modulus PVA fiber. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
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M. M. Castillo‐Ortega J. Romero‐García F. Rodríguez A. Nájera‐Luna P. J. Herrera‐Franco 《应用聚合物科学杂志》2010,116(4):1873-1878
Fibrous membranes of cellulose acetate (CA), poly(vinyl pyrrolidone) (PVP) and composite membranes of these polymers, were obtained by the electrospinning method. Using systematic method, the optimal conditions for preparation of fibrous membranes were found. Both CA and PVP a concentration of 8% weight was found. The CA was dissolved in a acetone:water solution, volume ratio 80 : 20 and the PVP is dissolved in ethanol:water solution, ratio volume 85 : 15. The flow rate for both polymers was 1.5 mL h?1. The same applied voltage value and the distance between the needle and collection plate were for polymer both, 15 kV and 15 cm respectively. The morphology of fibrous membranes and composite membranes were evaluated by scanning electron microscopy (SEM). The CA fibers showed ribon morphology, while the PVP fibers were cilindric, in both cases with diameters in the micrometer range. Thermogravimetric analysis showed that CA had a complete degradation to 445°C, while the fibrous membranes PVP required a value of temperature for degradation of up to 571°C. Fibrous composite membrane PVP/CA/PVP shows a higher value of strain at break (%), and a lower value of tensile strength (MPa) compared to CA/PVP/CA. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
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Poly(vinyl acetate) latices were prepared in the presence of an ammonium persulfate initiator, 10–50 mol of an ethoxylated nonylphenol nonionic emulsifier, and a poly(vinyl alcohol) colloid stabilizer by applying semicontinuous emulsion polymerization (delayed monomer and initiator addition process) in a laboratory scale similar to industrial practice. Two approaches were applied: the molar concentration of the nonionic emulsifier was kept constant and the weight ratios in the polymerization recipe varied or the weight ratios were kept constant. The effects of the change in the ethoxylation degree of the emulsifier to the final latex viscosity, average polymer molecular weight, polymer grafting degree, surface tension of the latex, and the surface free energy of the dried films were investigated. It was determined that the resultant latex viscosity decreases and the viscosity‐average polymer molecular weight increases with increase of the nonionic emulsifier ethoxylation degree. The increase of the ethoxylation degree does not seriously affect the surface tension of the resultant latex or the surface free energy of the dried poly(vinyl acetate) films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 844–851, 2002 相似文献