The effect of modifiers on the stability of a vinyl acetate/ethylene copolymer dispersion

This paper examines the effect of modifiers on the stability of a vinyl acetate/ethylene copolymer dispersion adhesive upon aging. Eighteen common modifiers were added to a well-characterized vinyl acetate/ethylene copolymer dispersion (Dur-O-Set^® E-150) in known concentrations and dry-film samples were subjected to 16–17 years of dark aging and seven to eight years of light aging. Yellowing, pH, gloss, swelling, cohesive strength, and flexibility were monitored for changes upon aging. Generally, the neat Dur-O-Set^® E-150 (no additives) was found to become acidic on aging, but was fairly resistant to yellowing. It also swelled substantially in toluene, was of high gloss, medium strength, and flexible, and remained so on aging. No modifier was found to improve these properties. Various solvents, wetting agents, and thickeners did not alter the properties by much, while plasticizers, freeze-thaw stabilizer, glycerin, and certain fillers had a more negative effect.     

使用过滤溶媒作为润湿液进行除菌过滤泡点验证

通常对于疏水性的除菌过滤滤芯使用异丙醇作为润湿液进行泡点测试,通过对比异丙醇做润湿液采用了过滤溶媒(乙酸乙酯)作为润湿液进行了泡点测试,取得了最小泡点值。     

乙酸苄酯的合成研究进展

综述了固体超强酸、有机酸、无机盐、阳离子交换树脂、H-β沸石、铌酸和相转移催化剂等催化合成乙酸苄酯的方法．通过对比分析发现固体超强酸及有机固体酸类催化剂催化合成乙酸苄酯有较大的实用价值。     

Early aqueous dispersion paints: Portuguese artists’ use of polyvinyl acetate, 1960s–1990s

Abstract

The ageing of poly(vinyl acetate), PVAc, paints was assessed in works by Ângelo de Sousa and Joaquim Rodrigo. The materials and techniques of the artists were studied through interviews and by chemical analysis. They were both using PVAc in 1961, preparing their own paints by mixing commercial PVAc emulsions with selected colorants. It is shown that in most cases the emulsion employed was based on a PVAc homopolymer and that the paints are in good condition with no signs of deterioration. Finally, this study allowed a comparison to be made between paint samples aged naturally and those aged under artificial conditions. This means that these artificially aged samples may be used as reference materials for PVAc paintings. Both sets exhibit molecular infrared fingerprints that are undistinguishable from an unaged PVAc, suggesting little chemical degradation over 50 years of natural ageing.     

聚苯乙烯──醋酸乙烯酯互贯聚合物网络的合成与醇解反应

悬浮聚合法合成聚苯乙烯—醋酸乙烯酯（PSt－VAC）序贯型聚合物网络,并进一步得到其醇解产物。讨论了两网不同交联度对醇解产物上羟值的影响。     

聚乙烯醇—聚苯胺复合膜的制备及其电致变色性能研究

在聚苯胺复合膜的制备过程中以成膜剂聚乙烯醇(PVA),掺杂剂十二烷基苯磺酸(DBSA)及氧化剂过硫酸铵(APS)．在非有机溶剂的两相体系中用乳液聚合法合成了电致变色的聚苯胺PAn/PVA乳液．并以玻片为载体,采用提拉法制备了(PAn)/PVA复合膜．研究了PVA含量、苯胺(An)与DBSA的量比、过硫酸铵(APS)与An的量比及反应温度对膜的电致变色性、导电性的影响．并用循环伏安法对其电化学进行表征．实验结果表明：在w(PVA)=4．3％,n(DBSA)∶n(An)∶n(APs)=1．25∶1∶0．42、反应温度为25℃时,所制得的PAn/PVA复合膜具有良好电致变色性和粘结性能．     

用Aspen Plus模拟醋酸正丁酯反应精馏工艺过程

利用Aspen Plus对醋酸正丁酯的合成工艺流程进行了模拟计算。选用反应精馏技术,用强酸性阳离子交换树脂取代硫酸,在反应精馏塔中一次完成反应和分离,取代原有的分步流程,可连续生产出99．9％的高纯度醋酸正丁酯。     

纳米级SO_4~(2-)/TiO_2固体超强酸催化合成乙酸丁酯

研究了以纳米级二氧化钛制备的纳米级SO42 -/TiO2 固体超强酸为催化剂 ,冰醋酸和丁醇为原料合成乙酸丁酯 ,考察了影响反应的因素。结果表明 ,醇酸比为 1 .2 2∶1 ,催化剂用量为0 .1 5g(冰醋酸为 0 .0 9mol的情况下 ) ,反应时间为 3 .0小时是最适宜的反应条件 ,冰醋酸转化率为98.8%。