共查询到18条相似文献,搜索用时 46 毫秒
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概述近年来淀粉接枝共聚中引发体系、接枝单体、聚合方法及其应用,展望淀粉接枝共聚反应的发展趋势。 相似文献
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高锰酸钾引发淀粉/丙烯腈接枝共聚反应动力学 总被引:15,自引:0,他引:15
以高锰酸钾为引发剂,研究了玉米淀粉与丙烯腈的接枝共聚反应动力学。由试验结果得出了接枝反应速度与引发剂浓度、单体浓度、淀粉浓度和反应温度间的关系,并由此关联出接枝反应速度表达式。用顺磁共振原位分析等方法分析了在接枝反应过程中锰离子价态的变化和淀粉的氧化程度,并依据试验结果对接枝反应机理进行了初步的探讨。 相似文献
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反相乳液法淀粉丙烯酰胺接枝共聚反应的研究 总被引:22,自引:4,他引:22
以木薯淀粉为主要原料,研究了淀粉/丙烯酰胺单体/乳化剂/油/水反相乳液体系的接枝共聚反应规律,考察了反应温度、引发剂和乳化剂浓度、淀粉单体比、油水比等因素对淀粉接枝丙烯酰胺共聚反应过程的影响,并对反应机理进行了探讨.结果显示:在本实验考察范围内引发剂浓度、单体淀粉比、反应温度影响显著;乳化剂用量和油水比对反相乳液体系的形成及稳定有重要的影响;淀粉与亲水性单体丙烯酰胺的接枝共聚反应为淀粉团粒表面控制. 相似文献
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碱性条件下,玉米淀粉经环氧氯丙烷交联处理后,在引发剂存在下,与醋酸乙烯酯进一步接枝共聚制得了交联玉米淀粉-醋酸乙烯酯乳液,经红外光谱确认了共聚物,较好的乳液制备工艺:m(淀粉)∶m(环氧氯丙烷)=25∶1,90°C交联1 h,加入过硫酸铵,按m(醋酸乙烯酯)∶m(淀粉)=3∶1,在70°C接枝共聚3 h。各种淀粉胶液的性能对比结果表明:交联玉米淀粉-醋酸乙烯酯接枝聚合乳液冷热稳定性好,耐水性≥54 h,储存期360 d,剪切强度达9.1 MPa。 相似文献
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A structure‐exact starch‐based xanthate agent was prepared and used as chain transfer agent to mediate RAFT polymerization of vinyl acetate, which offered a convenient way to well control the structure and composition of starch‐g‐poly(vinyl acetate). The structures of the intermediate and the polymer were verified with FTIR and 1H‐NMR. Gel permeation chromatography measurement results indicated that the polymerization was performed as expected. It was found that the relationship between number average molecular weight and monomer conversion was linear. The polydispersity index of grafted side‐chain ranged from 1.19 to 1.53 and most of them were around 1.2. There was one more degradation stage appeared on the thermogravimetric analysis profile of starch‐g‐poly(vinyl acetate) than that of starch. TEM observation exhibited that the product was able to self‐assemble into micelles in aqueous solution, which suggested the copolymer was amphiphilic. Both the thermal and amphiphilic properties demonstrated the starch‐g‐poly(vinyl acetate) was successfully synthesized as well. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
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以醋酸乙烯和共聚改性单体为原料,对制备醋酸乙烯共聚体的工艺条件进行了研究。当反应温度为70~72℃、反应时间为2h时,共聚物的收率约为95%,粘度为3000~5000mPa·s,固含量为40%左右,pH值为4~5.其性能优于市售白胶。 相似文献
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Starch‐based biodegradable low‐density polyethylene (LDPE) films were used for graft copolymerization of vinyl acetate with ceric ammonium nitrate (CAN) in aqueous acidic medium as redox initiator with nitric acid. The extent of grafting was examined by Fourier‐transform infrared (FTIR) spectroscopy, attenuated total reflectance (ATR) spectroscopy, X‐ray diffraction (XRD) and scanning electron microscopy (SEM). The objective behind the grafting of vinyl acetate onto the LDPE–starch biodegradable films is to make these suitable for printing and packaging applications without affecting the biodegradability of the original films. Copyright © 2004 Society of Chemical Industry 相似文献
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The free‐radical graft polymerization of vinyl acetate onto nonporous silica particles was studied experimentally. The grafting procedure consisted of surface activation with vinyltrimethoxysilane, followed by free‐radical graft polymerization of vinyl acetate in ethyl acetate with 2,2′‐azobis(2,4‐dimethylpentanenitrile) initiator. Initial monomer concentration was varied from 10 to 40% by volume and the reaction was spanned from 50 to 70°C. The resulting grafted polymer, which was stable over a wide range of pH levels, consisted of polymer chains that are terminally and covalently bonded to the silica substrate. The experimental polymerization rate order, with respect to monomer concentration, ranged from 1.61 to 2.00, consistent with the kinetic order for the high polymerization regime. The corresponding rate order for polymer grafting varied from 1.24 to 1.43. The polymer graft yield increased with both initial monomer concentration and reaction temperature, and the polymer‐grafted surface became more hydrophobic with increasing polymer graft yield. The present study suggests that a denser grafted polymer phase of shorter chains was created upon increasing temperature. On the other hand, both polymer chain length and polymer graft density increased with initial monomer concentration. Atomic force microscopy–determined topology of the polymer‐grafted surface revealed a distribution of surface clusters and surface elevations consistent with the expected broad molecular‐weight distribution for free‐radical polymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 300–310, 2003 相似文献
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A novel polymerization method [Ruckenstein and Li, Polymer Bull., 37, 43 (1996)]—room temperature-initiated, self-heating polymerization—was applied to both bulk and concentrated emulsion copolymerization of acrylonitrile (AN) with vinyl acetate (VAc). A redox system was employed as an initiator, with the oxidant dissolved in the monomers and the reductants (two reductants were employed) in the aqueous phase. In the bulk polymerization, the oxidant (cumene hydroperoxide) was dissolved in the mixture of monomers, and the two reductants (sodium metabisulfite and ferrous sulfate) were introduced as an aqueous solution. In the concentrated emulsion polymerization, a mixture of the monomers containing dissolved oxidant was first used as the dispersed phase of a concentrated emulsion in water, and the aqueous solution of reductants was subsequently added to the concentrated emulsion. In both cases, the polymerization started at room temperature, just after the reductants were introduced. Because the reactor was insulated, the heat generated by the reaction was mostly used to accelerate the polymerization, which reached a high conversion in 30 min. The effects of various parameters on the polymerization were investigated. Optimum values were found for the volume fraction of the dispersed phase, for the wt ratios of the two reductants and of the oxidant to reductants, and for the surfactant and reductant concentrations. One concludes that the concentrated emulsion polymerization method is particularly suitable for the room temperature-initiated, self-heating polymerization. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 999–1011, 1998 相似文献