乙烯-醋酸乙烯酯弹性体的制备和研究

制备乙烯-醋酸乙烯酯(EVA)共聚物弹性体,研究溶剂引发剂选择及不同反应乙烯压力对EVA弹性体分子结构、固含量、玻璃化转变温度(Tg)、分子量和特性粘数[η]的影响。研究表明,链转移常数低的小分子醇类宜作为反应溶剂;适量引发剂可提高EVA弹性体醋酸乙烯酯(VAc)含量(w)和分子量;反应压力提高,EVA分子结构亚甲基质子峰向高磁场移动,产物固含量增加,玻璃化转变温度(Tg)和特性粘数[η]降低。     

耐热性α-AS共聚物的研制

以α—甲基苯乙烯、丙烯腈和苯乙烯为原料,用乳液法合成了α—AS树脂。对各种影响因素进行了考察,并做了条件试验。发现α—甲基苯乙烯含量对共聚物转化率、特性粘数[η],熔体指数MI和玻璃化转变温度Tg有显著影响。由于引入α—甲基苯乙烯,共聚物具有耐热性高的特点,α—AS共聚物的Tg为131℃,比AS树脂高30℃。在助溶剂存在下,共聚物与氯化聚乙烯共混,产物α—ASC树脂具有耐热、抗冲击和耐老化的特点。     

EVAC树脂的醇解制备及研究

以碱为催化剂,乙烯-乙酸乙烯酯共聚物(EVAC)共聚物为原料,在一定温度下,通过醇解反应制备出乙烯-乙烯醇共聚物(EVOH),并利用红外、核磁、差示扫描量热仪和熔体速率测定仪对EVOH树脂分子结构和其物理化学性能进行了研究。结果表明,EVAC和EVOH的分子结构发生了明显的变化;随着醇解反应时间的增加,EVOH树脂的玻璃化转变温度(Tg),结晶温度(Tc)和熔点(Tm)逐渐升高;随着乙烯浓度的增加,EVOH树脂的Tg,Tc和Tm逐渐降低,但是EVOH树脂的熔体流动速率逐渐升高。     

聚苯乙烯合成及玻璃化转变特性研究

通过使用乌式黏度计和差示扫描量热仪,分别测定了聚苯乙烯的特性黏度[η]和玻璃化转变温度(Tg),并通过实验数据的回归,得到了其数均相对分子质量(Mn)与Tg的关系。为聚苯乙烯的简易制备和Tg测试提供了一种实用方法。     

悬浮接枝法AAS树脂的合成研究

用悬浮接枝法,以丙烯腑、苯乙烯、丙烯酸丁酯为原料,偶氮二异丁腈为引发荆,羟丙基纤维素为分散剂,在一定的水油比下合成AAS三元接枝共聚物。讨论了反应时间、温度、引发剂用量、分散剂浓度及丙烯酸丁醇含量对合成反应及产品颗粒形态、玻璃化转变温度(Tg)的影响。结果表明,反应8小时后转化率增大的趋势较缓慢;随反应温度的提高及引发剂用量、丙烯酸丁酯含量的增加,产品的相对粘度(η)下降;分散剂用量在0.5%时,可得到良好颗粒形态的产品;当丙烯酸丁酯的含量为30%时,AAS树脂的Tg达最大值;由红外光谱表明,所合成的产物为苯乙烯—丙烯腑—丙烯酸丁酯的接枝共聚物。     

乙烯-乙酸乙烯酯共聚物(EVA)的性能及应用

本文综述了乙酸乙烯酯(VA)含量和熔体流动速率(MFR)对乙烯-乙酸乙烯酯共聚物(EVA)性能的影响以及EVA树脂的应用。     

差示扫描量热法对乙烯-醋酸乙烯酯热性能的研究

乙烯-醋酸乙烯醑（EVA）由于在分子链中引入了醋酸乙烯酯（VA）单体,降低了分子链的规整性．随着VA含量的增加,EVA树脂的结晶度降低。文章通过改变DSC测试条件对EVA树脂的热性能做进一步研究,分别讨论了常规方法与恒温结晶后的方法的玻璃化转变以及结晶的行为。从而估算出EVA的玻璃化转变温度。     

乙烯—醋酸乙烯树脂

乙烯一醋酸乙烯(EVA)树脂系乙烯和醋酸乙烯(其含量低于40%)的共聚物,它是聚乙烯(PE)树脂中具有特殊性能的品种之一。     

溶剂对rac-Et[Ind]_2ZrCl_2/MMAO催化体系催化乙烯-降冰片烯共聚合的影响

采用乙基桥连二茚基二茚基二氯化锆(rac-Et[Ind]2ZrCl2)/MMAO催化体系催化乙烯/降冰片烯共聚合,比较了甲苯、苯、正己烷、环己烷及其混合溶剂作为反应介质对共聚合活性及共聚物结构的影响。通过差示扫描量热分析(DSC)对共聚产物进行了热力学性质的表征。结果表明,聚合活性和产品的玻璃化转变温度(Tg)在不同溶剂体系中有着显著的差异,在相同聚合条件下,当甲苯/苯体积比为80/20时,聚活活性达到最高,但产品的Tg和降冰片烯的插入率较低。     

醋酸乙烯-乙烯共聚物需求持续增长

醋酸乙烯最具发展潜力的消费方向就是生产共聚物,而醋酸乙烯-乙烯共聚物(VAE乳液或EVA树脂)是生产与应用较多的品种。     

Nano-silica modification of UV-curable EVA resin for additive manufacturing

Due to layer by layer printing, the interlayer adhesion of resin used in extrusion-based additive manufacturing (AM) is poor, while thermal curing affects the accuracy of the resin. Therefore, methods of photo-curing and nanomodification were used in this work to improve the adhesion between layers and the overall performance of AM resins. Specifically, ethylene-vinyl acetate (EVA) copolymer with dual curing agent of benzophenone/triallyl isocyanurate (BP/TAIC) and nano-silica (NS) were introduced. The results of light transmittance, scanning electron microscopy and gel content test showed that BP/TAIC with NS were proved to be able to improve the curing process of EVA. The filling of a small amount of NS did not act as ultraviolet light barrier, but instead improved the photo-curing of the resin and reduced the amount of agents. UV curing also improved the adhesion between layers of EVA resin. The tensile strength was 7.1% higher than that of EVA/NS/BT without curing. At the same time, due to good interface bonding and dispersion, the thermal conductivity of resin improved from 0.212 W/m·k to 0.252 W/m·k. A 16.1% raise in tensile strength and a 10.0% increase in the volume resistivity were demonstrated for the 3.0 wt% NS. Furthermore, this resin is potential to be used in AM.     

纳米粒子改性环氧树脂玻璃化转变温度的研究

采用示差扫描量热分析(DSC)研究了纳米A l2O3粒子改性的环氧树脂基体玻璃化转变温度与纳米粒子含量之间的关系以及纳米粒子含量对改性体系固化剂用量的影响。结果表明,随着纳米粒子含量的提高,改性树脂的玻璃化转变温度逐渐下降,由纯树脂的224℃下降到182.5℃(纳米粒子用量30%,固化剂添加量70%)。并且纳米粒子的加入会影响树脂基体的固化反应。达到玻璃化转变温度峰值时的固化剂用量并非按照改性体系中环氧树脂含量等当量比加入,而是与纳米粒子含量有关,纳米粒子含量越高,达到玻璃化转变温度峰值时固化剂用量越少。     

动态交联PP/EVA共混物的制备与性能研究

本文将动态交联技术应用于PP/EVA共混体系中,制得动态交联PP/EVA共混物。采用Hakke转矩流变仪研究了动态交联对PP/EVA共混物扭矩的影响;研究了DCP和EVA含量对共混物力学性能的影响;考察了动态交联共混物的维卡软化点。结果表明：加入DCP后,PP/EVA共混物扭矩先升后降,DCP的添加量为EVA含量的1%为宜。随EVA用量的增加,动态交联EVA/PP共混物的冲击强度大幅提高,但拉伸强度有所降低。少量经动态交联的EVA颗粒可以促进共混物中PP的结晶, 提高共混物的维卡软化点。     

EVAC/PPF/石墨烯复合材料的制备与性能

采用熔融和溶液共混相结合的方法制备了乙烯–乙酸乙烯酯共聚物(EVAC)/萜烯酚醛树脂(PPF)/石墨烯复合阻尼材料。通过动态热机械分析仪、电子万能试验机和热重分析仪研究了复合材料的阻尼性能、力学性能和热稳定性。结果表明,随着PPF用量的增加,复合材料的玻璃化转变温度(T_g)逐渐提高,损耗角正切值(tanδ)峰值位置向常温区域移动,且峰值大幅提升,峰宽拓宽明显。添加40%PPF时,复合材料的拉伸强度与断裂伸长率得到了大幅度的提升,分别提高了176.1%和83.9%。随着石墨烯添加量增加,复合材料的tanδ呈增大趋势,T_g也随之升高;当石墨烯添加量为0.6%时,tanδ峰值达到最大值。     

乙烯-醋酸乙烯共聚物树脂改性天然木粉的性能研究

采用一种新型方法以改善木粉与烯烃树脂的相容性,利用乙烯-醋酸乙烯共聚物(EVA)对天然木粉进行表面改性。通过漫反射红外光谱分析木粉改性前后的表面化学基团变化,利用热失重曲线分析木粉的热稳定性,并结合微观扫描电镜分析改性前后木粉表面微观形态变化。结果表明,红外谱图中改性后木粉的羟基峰基本消失,从而降低了原始木粉表面的化学极性,改善了改性木粉与聚合物基体的相容性;EVA 的加入会提高木粉的热稳定性,并且阻止木粉吸附空气中的水分;扫描电镜分析表明,EVA 可以包覆木粉表面,添加过量 EVA 会使木粉颗粒之间相互粘接,当 EVA 用量为15%(质量分数,下同)时,在木粉表面可以形成比较完整的 EVA 包覆层。     

环氧改性有机硅树脂的制备及其性能研究

采用化学方法制备了环氧改性有机硅树脂。通过红外分析表明,环氧树脂与有机硅树脂发生了化学反应。研究发现：环氧改性有机硅树脂的水接触角、瓦均有变化,微观形态仍呈均相结构。研究还发现：随环氧树脂用量增大,改性有机硅树脂微观结构的粗糙度提高,水接触角增大。     

Morphology,resistivity, and thermal behavior of EVOH/carbon black and EVOH/graphite composites prepared by simple saponification method

Poly(ethylene‐co‐vinyl alcohol) (EVOH)/carbon black (CB) and EVOH/graphite (GP) electro‐conductive composites were prepared by saponification of poly(ethylene‐co‐vinyl acetate) (EVA)/CB and EVA/GP composites in ethanol/KOH solution. The electrical resistivity change and positive temperature coefficient (PTC) behavior of these composites were investigated. The volume resistivity of EVA/CB and EVA/GP composites was decreased with saponification time. It can be observed that EVA/CB10 and EVA/GP05 composites showed a significant reduction in resistivity after saponification for 1 h. With the increase in saponification time, PTC peak temperature of both composites was shifted at a higher temperature. Tensile properties, morphology, and thermal behavior of the prepared composites have been also evaluated using universal test machine, scanning electron microscopy, and differential scanning calorimetry, respectively. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Mechanical and thermal properties of EVA blended with biodegradable ethyl cellulose

In this study, biodegradable blend of Poly (Ethylene‐co‐Vinyl Acetate) (EVA) and Ethyl Cellulose (EC) were prepared. Ethylene vinyl alcohol (EVOH) copolymer was used as an interfacial compatibilizer to enhance adhesion between EVA and EC. The melt blended compatibilized biocomposites were examined for mechanical and thermal properties as per the ASTM standards. It has been found that the EC has a reinforcing effect on EVA leading to enhanced tensile strength and also impart biodegradability. Thus, a high loading of 50% EC could be added without compromising much on the mechanical properties. Analysis of the tensile data using predictive theories showed an enhanced interaction of the dispersed phase (EC) and the matrix (EVA). The compatibilizing effects of EVOH on these blends were confirmed by the significant improvement in the mechanical properties comparable with neat EVA as also observed by SEM microscopy. The TGA thermograms exhibits two‐stage degradation and as EC content increases, the onset temperature for thermal degradation reduces. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010