Miscibility and adhesive properties of EVA‐based hot‐melt adhesives. II. Peel strength

A series of ethylene vinyl acetate copolymers (EVA) were blended with some tackifier resins that were made from wood extracts, and possible relations between their miscibility and properties as hot‐melt adhesives (HMA) were investigated. From our previous report on miscibility of various EVA‐based HMAs, we chose some blends that represent some of the typical miscibility types and investigated their peel strengths. When the blends were miscible at testing temperatures, the temperature at which the maximum value of peel strength was recorded tended to move toward higher temperature as tackifier content of blends increased. This result corresponds to the storage modulus of the blends whose curves tended to move toward higher temperature as tackifier content of blends increased when blend components were miscible as well as their maximum values of tan δ, or glass transition temperatures. It was characteristic for peel strength that there existed second peaks on peel strengths curves at ～ 100°C, which adhesive tensile strengths for the blends did not have. In terms of relationship between miscibility and HMA performances, we suggest that there are several factors other than miscibility that affect absolute values of peel strength more directly than miscibility; this idea has to be investigated further in the a future study. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 726–735, 2002     

Dynamic–mechanical properties of modified poly(ethylene‐co‐vinyl acetate)

To study the relationship among relaxation peaks observed in dynamic mechanical experiments and the structure of poly(ethylene‐co‐vinyl acetate) (EVA), EVA copolymers with different substitution in the carbonyl group were synthesized. EVA was hydrolyzed to obtain poly (ethylene‐co‐vinyl alcohol) and was subsequently reacted with formic, hexanoic, and octanoic acids. The copolymers synthesized were characterized by infrared spectroscopy. Analysis of the DMA spectra of the copolymers showed that their relaxation behavior depends on the vinyl acetate concentration. The α‐ and β‐transitions were observed in EVA copolymers with 8 and 18 wt % of functional groups, and the relationship among relaxation process with the structure of polymer was investigated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1371–1376, 2005     

辐射交联EVA/MVQ复合绝缘子的研制

探讨辐射交联乙烯－醋酸乙烯酯共聚物（EVA）／甲基乙烯基硅橡胶（MVQ）复合绝缘子的配方和生产工艺。绝缘子的优化配方为：EVA／MVQ（77－67）／（23－33）；氢氧化铝 13－46；其它 1．3－3．9。成型采用模压工艺，模具的阴模温度为70℃，阳模温度为50℃，模压压力为30MPa，模压时间（保压时间）为1．5－2min。辐射交联剂量不超过200kGy。EVA／MVQ复合绝缘子可替代陶瓷绝缘子用于户外高压电器设备的绝缘器。     

热塑性淀粉塑料的力学性能研究

以淀粉和增塑剂为原料制备了热塑性淀粉 (TPS)塑料及TPS/EVA共混材料 ,研究了材料的力学性能。结果表明 :TPS塑料的拉伸强度和弹性模量随着增塑剂用量的增加而降低 ,断裂伸长率和冲击强度则随之升高 ;用量相同时 ,3种增塑剂对TPS塑料的冲击强度和断裂伸长率的改善程度依次为 :乙二醇 >丙三醇 >丙二醇 ,而对拉伸强度和弹性模量的影响正好相反 ;相同条件下 ,3种热塑性淀粉塑料的韧性为 :玉米TPS >木薯TPS >小麦TPS。加入经马来酸酐改性后的乙烯 -醋酸乙烯酯共聚物 (EVA)后 ,TPS的韧性显著提高 ,其中 ,以玉米TPS/改性EVA共混物的断裂伸长率最高     

高能辐射与增容剂作用下的高密度聚乙烯与聚氯乙烯废薄膜混杂物回收

以EVA为增容剂，对高密度聚乙烯与聚氯乙烯废薄膜混杂物进行挤增容剂，对高密度聚乙烯与聚氯乙烯废薄膜混杂物进行挤出回收加工并进行高能辐照。结果表明，适量的增容剂与γ－射线能够促进混合，并使扯断伸长率大幅度提高。照射产生的相互交联是增容化的主因。     

LDPE/EVA/Mg(OH)2阻燃复合材料流变行为的研究

借助HAAKE RHEOCORD 90流变仪分别在140℃、160℃、和180℃3个温度下，研究了LDPE／EVA和LDPE／EVA／Mg(OH)2阻燃复合材料的流变行为。研究结果表明：LDPE／EVA／Mg(OH)2阻燃复合材料的熔体流动行为同LDPE／EVA一样，仍属于非牛顿型假塑性流体流动行为。不同剪切速率下，LDPE／EVA／Mg(OH)2阻燃复合材料与LDPE／EVA粘流活化能相差很小，说明LDPE／EVA／Mg(OH)2阻燃复合材料与LDPE／EVA一样，其熔体粘度对温度不十分敏感。相同温度下，LDPE／EVA／Mg(OH）2阻燃复合材料的挤出膨胀比低于LDPE／EVA，这一特性说明LDPE／EVA／Mg(OH)2阻燃复合材料制品尺寸稳定性较LDPE／EVA有所提高。     

POM共混增韧改性研究

研究了POM COPA、POM LDPE和POM HDPE三种共混体系,测试了不同配比共混物的冲击强度,对POM COPA及紫外线辐射的HDPE进行了红外光谱(FT IR)分析。结果表明:(1)在三种共混体系中,COPA对POM的增韧效果最佳,且COPA与POM分子间有氢键作用;(2)EVA在POM LDPE及POM HDPE共混体系中起相容剂的作用;(3)HDPE经紫外线辐射后,由于在其分子链上引入了极性羰基,从而大大提高了对POM的增韧效果。     

PGS@P-N阻燃剂的制备及增强EVA复合材料的 阻燃性能的研究

利用坡缕石表面的羟基，采用化学方法首先将坡缕石（PGS）用磷酸进行了改性，随后通过酸碱中和的方法，将十二胺接枝到磷酸分子上，得到改性的含P、N型复合阻燃剂PGS@P-N。通过SEM、 XRD、 FTIR等方法对所合成阻燃剂PGS@P-N的形貌和结构进行了表征，利用氧指数法(LOI)、垂直燃烧法(UL-94)和锥形量热法(CCT)对复合材料的阻燃性能进行了测试，并对复合材料的力学性能和相容性进行了考察。结果表明：当向EVA中加入质量分数为30%的PGS@P-N/EG后，EVA/PGS@P-N/EG(可膨胀石墨)复合材料的氧指数达到了36.3%，与EVA/PGS/EG比较，接入烷基链后，EVA/PGS@P-N/EG复合材料的断裂伸长率提高了40%。     

北京地铁王府井站东南风道防水工程效果分析

北京地铁王府井站东南风道防水工程采用先进的复合式衬砌防水工艺。本文针对实际施工中防水出现的问题来对其进行质量分析，探索出该防水工艺的局限性。     

乙烯-醋酸乙烯共聚乳液水解动力学研究:Ⅱ.乳胶粒内?…EI

当乙烯－醋酸乙烯共聚物乳液（ＥＶＡ）胶粒表面水解完成后，水解反应将继续在胶粒内部进行，采用滴定法跟踪测试体系碱的浓度进行动力学研究，并建立一数学模型对其进行描述，研究表明，胶粒内部水解反应呈现前后两个阶段。反应速率主要由ＯＨ＾－在胶粒内部的扩散速率所控制，前半阶段反应活化能为５３．２１ＫＪ／ｍｏｌ，指前因子为１．５２５×１０＾７ｍｉｎ＾－１，后半阶段反应活化能为４４．８６ＫＪ／ｍｏｌ，指前因子为３