注射超轻EVA/Fusabond材料的交联发泡动力学

注射硫化交联发泡成型的乙烯-乙酸乙烯酯共聚物(EVA)与马来酸酐接枝的乙烯-丙烯酸酯的共聚物(Fusabond)超轻发泡材料,其力学性能符合adidas鞋材标准,可用于生产注射adidas运动鞋中底;利用流变仪测定转矩和发泡压力随时间的变化来研究其硫化交联反应和发泡作用的动力学,在转矩上升阶段为一级反应,给出了硫化交联反应的速率常数k为1.74×10-2s-1,表观活化能E为108kJ/mol,频率因子A为6.81×1010;发泡作用的速率常数kb为1.32×10-2s-1,表观活化能Eb为58.2kJ/mol,频率因子Ab为8.10×107。     

经济增加值考核办法在发电企业中的运用分析

针对国务院国有资产监督管理委员会2009年12月28日颁布的《中央企业负责人经营业绩考核暂行办法》(以下简称第22号令),从经济增加值(economic value added,EVA)的概念和理财观念入手,深入剖析了第22号令中关于EVA的主要内容,结合发电企业所具有的资源密集、技术密集和资本密集等特点,对EVA在发电企业的运用进行了研究。提出以下观点:应设置股本资本成本,控制股权资本规模;将研发费用支出从当期净利润指标中剔除;将项目筹建费用从损益中剔除;将在建工程等非经营性资产从考核中剔除。     

A novel enzymatic biodegradable route for PLA/EVA blends under agricultural soil of Vietnam

Poly lactic acid (PLA) has attracted a lot of attention in recent years because of its good properties such as high transparency, high tensile strength and excellent biodegradability. However, high modulus and low strain are its shortage, making it unfeasible to be applied as packaging materials. To overcome this limitation, in this study, PLA is mixed with ethylene vinyl acetate (EVA). The morphological, thermal and mechanical properties of the enzymatically degraded PLA/EVA blends were fully investigated under agricultural soil of Red River Delta, Vietnam. It was demonstrated that some new strains were responsible for the biodegradation of PLA/EVA. To best of our knowledge, these strains were not reported in the literature up to now.     

Effect of EVA on the fresh properties of cement paste

The improved workability effect of latex in dry mortars has not been fully clarified. The purpose of this research was to investigate the influence of the EVA copolymer on the cement hydration and on the rheological properties of cement pastes. The results pointed to a minor influence of EVA on cement hydration and to a ball-bearing effect. In fact, the shear thinning behavior of reference paste at 15 min after mixing changed to shear thickening owing to the EVA addition. This behavior could be explained by the decrease in the interparticle separation distance as consequence of the solid content increase in case of shearing detachment of weakly adhered EVA particles from the cement particles surfaces. The expected EVA plasticizing effect was observed at 60 min. Such behavior points to the stabilization of EVA on the cement particles surfaces, thus resulting in a steric barrier effect.     

Polymer/carbon based composites as electromagnetic interference (EMI) shielding materials

The extensive development of electronic systems and telecommunications has lead to major concerns regarding electromagnetic pollution. Motivated by environmental questions and by a wide variety of applications, the quest for materials with high efficiency to mitigate electromagnetic interferences (EMI) pollution has become a mainstream field of research. This paper reviews the state-of-the-art research in the design and characterization of polymer/carbon based composites as EMI shielding materials. After a brief introduction, in Section 1, the electromagnetic theory will be briefly discussed in Section 2 setting the foundations of the strategies to be employed to design efficient EMI shielding materials. These materials will be classified in the next section by the type of carbon fillers, involving carbon black, carbon fiber, carbon nanotubes and graphene. The importance of the dispersion method into the polymer matrix (melt-blending, solution processing, etc.) on the final material properties will be discussed. The combination of carbon fillers with other constituents such as metallic nanoparticles or conductive polymers will be the topic of Section 4. The final section will address advanced complex architectures that are currently studied to improve the performances of EMI materials and, in some cases, to impart additional properties such as thermal management and mechanical resistance. In all these studies, we will discuss the efficiency of the composites/devices to absorb and/or reflect the EMI radiation.     

Effect of the molecular architecture of graft copolymers on the phase morphology and tensile properties of PS/EVA blends

Graft copolymers of poly(ethylene‐co‐vinyl acetate) (EVA) grafted with polystyrene (PS) with different molecular weight and different EVA/PS ratio were prepared by coupling reaction between acyl chloride functionalized PS (PS‐COCl) and hydrolyzed EVA. PS‐COCl with controlled molecular weight was prepared by anionic polymerization of styrene, followed by end capping with phosgene. The effect of the molecular architecture of the graft copolymer on the compatibilization of PS/EVA blends was investigated. Substantial improvement in the elongation at break and ductility was observed using the graft copolymer with PS segments with molecular weight as high as 66,000 g/mol and with a PS proportion equal or higher than EVA. The effect of the compatibilization on the morphology was also investigated by scanning electron microscopy and atomic force microscopy. The blend that presented the highest value of elongation at break also displayed dispersed phase constituted by inclusions of the PS phase inside the EVA particle forming a cocontinuous structure, as observed by AFM. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

空气涡轮制冷机在粉碎EVA技术中的应用

低温粉碎是塑料,特别是低软化温度塑料超细粉碎的发展趋势。本文在深入研究了乙烯-醋酸乙烯共聚物（EVA）材料特性和粉碎机理的基础上,将空气涡轮制冷低温粉碎技术应用于EVA低温细碎中,有效地提高了EVA颗粒的超细粉碎效率;同时指出了该粉碎流程的关键技术及影响粉碎效果的主要因素,开辟了一条规模化、高质量、低能耗回收可再生塑料的新途径。此外,从能量守恒的角度出发,以工程应用为目标,对粉碎过程中的核心环节——冷冻和粉碎,初步进行了理论方面的计算分析。这些分析的结果有益于设备的完善及改进。     

EVA乳液生产工艺与市场分析

介绍了EVA乳液的用途、市场情况,通过生产方法、工艺流程、生产设备等几个方面阐述了EVA乳液的生产工艺.     

EVA增容HDPE/PLA共混体系的研究

以乙烯-醋酸乙烯共聚物(EVA)为增容剂,采用熔融共混法制备了高密度聚乙烯(HDPE)/聚乳酸(PLA)/EVA复合材料,研究了EVA用量对复合材料力学性能及热性能的影响,并利用扫描电镜分析了复合材料的微观形态。结果表明:随着EVA用量的增加,复合材料的断裂伸长率及冲击强度逐渐增加;另外SEM结果显示,EVA可以改善HDPE与PLA的相容性,但EVA的加入对复合材料热性能影响较小。     

光伏组件封装EVA的热空气老化研究

对光伏组件封装EVA胶膜进行了热空气老化研究。将EVA胶膜置于不同温度下进行热空气老化,测试了老化过程中EVA的抗拉强度、透光率和黄度指数,采用FT-IR、GPC、DSC技术对老化后的EVA进行分析。结果表明,随着老化的进行,EVA的抗拉强度快速下降,老化温度越高,抗拉强度下降越快,甚至完全失效,失去弹性;老化过程中EVA会变黄,透光率逐渐下降;老化失效原因主要是发生氧化降解,EVA的交联网状结构破坏,进而失去力学性能。