超声技术制备蒙脱土/天然橡胶纳米复合材料

采用超声技术制备了有机膨润土、钠基膨润土/天然橡胶复合材料，进行了力学性能和热氧老化性能测试，用TEM研究了粘土在橡胶中的分散结构及结合状态。结果表明，有机膨润土经过超声辐射后产生层间剥离，橡胶能够插层进入粘土层间，形成纳米分散结构的复合材料并具有较好的界面作用，从而提高材料的性能。而钠基膨润土难以产生有效剥离，与橡胶的结合较差；当有机膨润土的填充量为3%时，材料的拉伸强度即达到20mpa，老化后性能下降仅为35%。而钠基膨润土复合材料的拉伸强度为17MPa，老化后性能下降达68%。     

粘土的分散性对粘土胶性能的影响

填料的分散性对聚合物材料力学性能可产生显著的影响 ,首先是白炭黑[1] 在橡胶中的分散性 ,是决定其性能的主要因素 ;其次为碳酸钙[2 ] ,其分散性对橡胶材料的性能也产生明显影响。对于粘土矿物填充的橡胶复合材料 ,尚未有详尽的介绍。本文采用超声分散方法与常规方法对照 ,探讨在不同分散性下粘土胶力学性能及老化性能。材料与方法将粘土原土试样与天然胶乳共混 ,经以下几种处理 :Ａ :搅拌 1ｍｉｎ ,Ｂ :搅拌 1 0ｍｉｎ ,Ｃ :搅拌2 0ｍｉｎ ,Ｄ :超声波分散 5ｍｉｎ ,Ｅ :超声波分散 1 0ｍｉｎ ,Ｆ :超声波分散 2 0ｍｉｎ。将上述试样经共…     

粘土胶老化后性能与结构的研究

由于炭黑价格的不断上涨 ,人们一直寻找价廉的非炭黑补强填料。红粘土可替代ＨＡＦ、ＧＰＦ和ＳＲＦ等炭黑制成橡胶制品[1] 。但粘土胶耐老化性能较差 ,对于其宏观性能与微观结构的关系尚未见报道。本文研究了粘土胶经热氧、光氧和臭氧老化后结构与性能的变化。1　实验将粘土试样与天然胶乳经凝固、压片、干燥等步骤制成粘土胶试样。粘土胶按国家标准进行热氧老化 1 0 0℃× 36ｈ ;氧老化分 30ｈ和 45ｈ及臭氧老化。进行性能测试 ,结构研究在ＰｈｉｌｉｐｓＸＬ 30型扫描电镜上完成。2　结果与讨论粘土胶的力学性能见表 1。表 1　粘土胶老化…     

天然橡胶/改性粘土复合材料结构与性能研究

为提高非碳黑填料对橡胶等高分子材料的补强作用，人们研究了多种的填料改性方法，包括偶联剂、分散剂及其它化学、物理改性［１—２］。本工作采用还原剂、强酸、热处理等对二种不同粘土进行化学改性并进行结构研究，再制备粘土胶复合材料，测定其硫化胶的物理力学性能和...     

压电复合材料PVC—PZT的低温热释电性

利用化学配比在三方与四方相界附近的PZT陶瓷粉料,用两种不同的填充量,填充PVC材料,制备了性能良好的PVC-PZT复合材料。热释电测量结果表明,填充量较多者,热释电性能强;且热释电系数在室温最大;而未填充PZT的PVC材料未观测到热释电性。     

天然鲜胶乳制备蒙脱土/NR纳米复合材料的结构与性能

采用多溶剂分散法制备片层尺寸达微、纳米级蒙脱土,并与天然鲜胶乳混合制备蒙脱土/天然橡胶复合材料,用扫描电镜研究蒙脱土结构及其在复合材料中的分布,并测定其力学性能.结果表明,通过多溶剂分散法可制备片层厚度为100nm～200nm的蒙脱土;在蒙脱土填充量为7%时,复合材料500%定伸应力从6.96MPa提高到11.22MPa;加入2%蒙脱土,复合材料拉伸强度从17.71MPa提高到21.01MPa;在4%填充量下,拉伸强度达23.56MPa,体现蒙脱土纳米增强效应.材料扯断伸长率随蒙脱土填充量增加而下降的幅度小,复合材料保持高弹性.复合材料硬度在蒙脱土填充量为8%时达到稳定值.上述结果表明,天然鲜胶乳可与蒙脱土直接复合,制备高性能天然橡胶复合材料.     

防老化体系处理的粘土胶光氧老化的

红粘土可用于替代或部分替代炭黑生产自行车胎、鞋底等橡胶制品,但由于粘土中存在变价态金属组分,使粘土胶抗氧老化性能明显下降[1],本工作研究了经防老化处理后粘土胶光氧老化的性能与结构变化.     

埋容电路用高介电常数热塑性聚酰亚胺的性能研究

通过填料预分散法和原位聚合法合成了一种BaTiO3填充的热塑性聚酰亚胺树脂。考察不同填充量的填料对热塑性聚酰亚胺的力学性能,热性能和电性能的影响。结果发现:随着BaTiO3添加量的增大,TPI的介电常数和介电损耗都增大,力学性能急剧下降,尤其是柔韧性急剧降低;玻璃化转变温度不变,热分解温度相应增加,热膨胀系数减小,吸潮率降低,TPI与铜箔之间的粘接力减少。     

两种炭黑导电橡胶复合材料的电磁屏蔽性能

采用炭黑分别填充丁苯和丁腈橡胶,研究两种不同橡胶基体对炭黑的分散性能及复合材料导电性能、电磁屏蔽性能的影响。对比发现,丁苯橡胶基体中炭黑分散性能随炭黑含量增多而变差,而在丁腈橡胶中炭黑的分散性能呈相反趋势,随炭黑含量增多而变好。丁腈导电橡胶的导电性能以及电磁屏蔽性能要好于相同炭黑含量的丁苯导电橡胶。     

橡胶塞的老化和电容器寿命

铝电解电容器橡胶塞的质量是影响寿命的关键因素。根据电容器的工作特点,研究了对橡胶塞用橡胶的要求,指出橡胶塞的老化机理是热氧老化。对比了各种橡胶的结构和性能特点,对国内现有EPDM和IIR的105℃系列的橡胶塞进行了试验研究,指出开发长寿命橡胶塞应该注意的问题。     

底涂剂在大面阵红外探测器粘接工艺中的应用研究

硅橡胶粘接剂具有良好的耐低温性能,因此常被用于制冷型红外探测器复合基板的粘接工艺。研究了底涂剂对硅橡胶粘接强度的影响。拉伸试验结果表明,直接粘接的试样在液氮温度下的平均粘接强度为4.07 MPa,而使用底涂剂预处理的试样的平均粘接强度则达到6.34 MPa。另外,通过观察拉伸试样断口,发现使用底涂剂预处理的试样的断口表面有更多的硅橡胶残留。因此,使用底涂剂预处理可以有效地增加硅橡胶的粘接强度,有助于提高红外探测器的可靠性。     

炭黑填充丁苯/天然橡胶的电磁屏蔽性能

研究炭黑分别填充丁苯橡胶和丁苯/天然（50：50）并用橡胶的力学性能、导电性能和电磁屏蔽效能。对比发现,单组分丁苯橡胶体系的硬度、拉伸和撕裂性能均小于丁苯/天然橡胶并用体系。由于炭黑在并用体系中分布偏聚,体系的导电渗流阈值降低,相同炭黑含量时并用体系样品的体电阻率变小,电磁屏蔽效能增大。采用并用橡胶体系是减小复合材料导电渗流阈值,改善其力学性能的有效方法。     

Soldering method using longitudinal ultrasonic

An efficient ultrasonic soldering method of inserting the metal bumps into the solder is investigated in this work for electronic packaging. The effects of the process parameters such as the ultrasonic frequency, amplitude, dimensions of the metal bump and solder are analyzed through the viscoelastic modeling. The ultrasonic soldering was conducted using the Cu and Au bumps, and the acceptable bonding condition was determined from the tensile strength. Localized heating of the solder was achieved and the stirring action due to the ultrasonic influences the bond strength and microstructure of the eutectic solder. Since higher temperature is obtained with smaller solder, the proposed ultrasonic soldering method appears to be applicable to the high-density electronic packaging.     

A multiplicative damage model for strength of fibrous compositematerials

Knowledge of the tensile strength properties of a fibrous composite material is essential in the design of reliable structures from that material. Determination of statistical models for the tensile strength of a composite material which provide good fits to experimental data from tensile tests on material specimens is therefore important for engineering design. Perhaps the most commonly used statistical model is the Weibull distribution, based on `weakest link of a chain' arguments. However, in many cases the usual Weibull distribution does not adequately fit experimental data on tensile strength for composite materials made from brittle fibers such as carbon. Here, an alternative model is developed for tensile strength of carbon composites, which is based on a multiplicative cumulative-damage approach. This approach results in a 3-parameter extension of the Birnbaum-Saunders fatigue model and incorporates the material specimen size (size effect) as a known variable. This new distribution can also be written as an inverse Gaussian-type distribution, which can be interpreted as the first passage of the accumulated damage past a damage threshold, resulting in material failure. The new model fits experimental tensile-strength data, for carbon micro-composites better than existing models, providing more accurate estimates of material strength     

An Exponential Damage Model for Strength of Fibrous Composite Materials

When modeling experimental data observed from carefully performed tensile strength tests, statistical distributions are typically used to describe the strength of composite specimens. Recently, cumulative damage models derived for predicting tensile strength have been shown to be superior to other models when used to fit composite strength data. Here, an alternative model is developed which is based on an exponential cumulative damage approach. The model is shown to exhibit a similar structural form to the other models in the literature so that previous theory for cumulative damage models can be utilized to find parameter estimates.     

质子交换膜燃料电池的垫片机械性能研究

为了将石墨复合材料用于燃料电池的双极板材料中,研究了湿度环境对双极板力学性能的影响。制造了两种类型的样品,对两种样品进行了一系列的实验：吸水率、弯曲和拉伸试验的强度和模量。结果表明,添加石墨复合材料的试样吸水率低于没有石墨/环氧复合材料碳纤维织物的试样,所以有碳纤维织物试样的总吸水率较低。两种试样的弯曲强度和模量均会下降。另外在石墨-颗粒/环氧复合材料中加入碳纤维织物能够显著提高了拉伸强度。     

智能结构中光纤智能夹层系统的研究

根据光纤自诊断系统模块化、集成化要求，提出并研制了光纤智能夹层。这种智能夹层易于制作，且制作过程中光纤传感器完好率达100％，智能夹层的埋入对复合材料拉伸强度影响较小。在此基础上，对光纤智能夹层试件进行了轴向拉伸试验。试验表明，在一定应变范围内，单膜交错光纤中光强-应变之间具有良好的线性关系，可以在埋入复合材料之前进行标定。利用智能夹层内的光纤传感器网络和先进的信息处理技术，可以建立结构损伤主动、在线和实时监测系统。     

High Performance Nanotube‐Reinforced Plastics: Understanding the Mechanism of Strength Increase

Polymer–multiwalled carbon nanotube composite films were fabricated using two types of polymer matrices, namely poly(vinyl alcohol), (PVA) and chlorinated polypropylene. In the first case, the PVA was observed to form a crystalline coating around the nanotubes, maximising interfacial stress transfer. In the second case the interface was engineered by covalently attaching chlorinated polypropylene chains to the nanotubes, again resulting in large stress transfer. Increases in Young's modulus, tensile strength, and toughness of × 3.7, × 4.3, and × 1.7, respectively were observed for the PVA‐based materials at less than 1 wt.‐% nanotubes. Similarily for the polypropylene‐based composites, increases in Young's modulus, tensile strength and toughness of × 3.1, × 3.9, and × 4.4, respectively, were observed at equivalent nanotube loading levels. In addition, a model to describe composite strength was derived. This model shows that the tensile strength increases in proportion to the thickness of the interface region. This suggests that composite strength can be optimized by maximising the thickness of the crystalline coating or the thickness of the interfacial volume partially occupied by functional groups.