【作者】 刘丽娜；

【导师】 方征平；

【作者基本信息】 浙江大学 ， 高分子材料学， 2010， 博士

【摘要】 科学技术和生产的发展,不断对材料提出新的要求,以满足航空航天、电子信息、核能等高新技术领域的需要。双马来酰亚胺树脂这种高比强、高比模、高绝缘、耐高温和耐腐蚀,能在恶劣环境中长期使用的高性能树脂是满足这些日益发展的新需求的先进树脂,然而针对其在使用过程中的损耗和失效所开展的摩擦磨损以及润滑的研究甚为不足。本文正对双马来酰亚胺树脂的这种情况,提出了在两种减小摩擦磨损实现润滑的方案：方案一,直接制备双马来酰亚胺纳米复合材料实现复合材料的固体纳米润滑；方案二,在双马来酰亚胺和金属对磨材料的接触表面添加纳米润滑微乳,减轻摩擦磨损。首先,利用碳纳米管优良的热性能、力学性能以及润滑特性,结合双马来酰亚胺树脂的先进性,制备性能优异的MWCNTs/BMI纳米复合材料降低材料的摩擦磨损。为了进一步研究影响该纳米复合材料的摩擦磨损的因素以实现磨损的最大化降低,并排除环境因素(如温度、湿度等)的影响,通过实验设计,探究了影响材料摩擦磨损的几个重要因素。通过采用不同的长径比的碳纳米管制备MWCNTs/BMI纳米复合材料发现,碳纳米管本身的结构会对所制备的复合材料的摩擦磨损产生影响,长径比大的碳纳米管所制备的复合材料具有较低的摩擦系数和磨损率；然而碳纳米管长径比变化对材料的摩擦磨损带来的影响却远不如碳纳米管带有官能团所带来的影响。当对碳纳米管实现胺基化的时候,碳纳米管本身管状结构遭到破坏,所制备的复合材料的摩擦系数会降低。MWCNTs/BMI纳米复合材料的摩擦磨损特性还跟加入碳纳米管之后引起的树脂交联度的变化有关,当碳纳米管表面上带有羧基时会加速复合材料的固化,进而加大树脂的交联度。这种对树脂的强化对提高整个复合材料的摩擦磨损也是有利的。在保持其他条件相同的情况下,通过对碳纳米管的改性来增强MWCNTs/BMI复合材料的界面是降低该复合材料的摩擦磨损最为显著和有效的手段。用烯丙基双酚A改性后的碳纳米管制备的纳米复合材料,在树脂中分散状态最佳,而且与树脂的界面粘接强度最大,该复合材料的摩擦系数比添加纯碳纳米管制备的复合材料降低了四分之三,磨损率降低了二分之一,达到几种改性碳纳米管/BMI树脂的摩擦磨损的最佳值。利用场发射扫描电子显微镜(FESEM),动态力学分析(DMA)等手段对MWCNTs/BMI复合材料的摩擦磨损表面及机理分析发现,改变以上提到的各因素会改变磨损表面的形貌,而其中界面因素对磨损形貌的影响最大。加入纯碳纳米管可以使树脂磨损表面形貌由存在众多裂纹的波纹状疲劳磨损形貌向表面有碾痕的粘着磨损过渡,加入改性后的碳管后磨损表面显得平滑,很多时候都显示微磨粒磨损的形貌。而且当复合材料的磨损形貌为微磨粒磨损的时候,其磨损率和材料的显微硬度之间存在如下线性关系：dm/dl=-0.01498+0.0059/H。也就是说,当复合材料的磨损机理为微磨粒磨损机理的时候,材料的显微硬度可以成为磨损率的简易判据：硬度越大的复合材料一般磨损率越低,越耐磨。其次,通过在石蜡油中添加硬脂酸改性碳纳米管形成稳定均一的分散,明显地减小所润滑的双马来酰亚胺对磨钢球体系的摩擦系数,减小钢球在双马来酰亚胺表面形成的磨痕的宽度和深度。改性后的碳纳米管在摩擦表面起到微轴承的作用,从而减小了摩擦磨损,但是发现少量碳纳米管会锲入树脂表面,对树脂表面造成微划伤。为了减小这种微划痕,用水解后的苯乙烯-马来酸酐共聚物改性碳纳米管,使碳纳米管形成以力学强度大并且热稳定性高的碳纳米管为核,以高分子聚合物软层为壳的结构,并且呈球形分散在石蜡油中。这种碳纳米管表面的高分子软层在较小添加浓度和较低接触表面温度的时候,能够和钢球表面作用形成保护膜,从而降低摩擦磨损；然而在较高的添加浓度的时候,在钢球表面形成吸附膜剩余的碳纳米管在摩擦力的长期作用下,由于其表面高分子软层的存在,易与树脂表面形成吸附,反而会加速树脂表面的降解与缺陷的形成,使摩擦磨损性能变差。更多还原

【Abstract】 Bismaleimide (BMI) is a kind of high-performance resin with high specific strength, high specific modulus ratio, excellent insulation and good heat resistance to and good anti-corrosion, which meets the new needs in the fields of aviation and astronavigation, electronic devices and also nuclear industry. However, the tribological study of this kind of resin is quite scarce, which is related with the final loss and failure of the material. In order to impeove this properties of BMI resin, two schemes are proposed to reduce the friction and wear of the resin:firstly, prepare bismaleimide nanocomposite solid lubricant to realize lubrication in nano-scale; secondly, add nano-lubricant into the contacting surface between BMI resin and the anti-wear metal to reduce friction and wear of the system.Firstly, combining the excellent thermal, mechanical and also lubricating properties of carbon nanotube with the wonderful properties of advanced BMI resin, MWCNTs/BMI nanocomposite has been prepared in order to reduce friction and wear of the material. For the further study of this nanocomposite to reduce friction and wear of the material, excluding the environmental effects (such as temperature and humidity), several main factors have been found out and studied.Using carbon nanotubes with different slenderness ratios to prepare MWCNTs/BMI nanocomposite, it is found that nanocomposite using MWCNTs with larger slenderness ratio processes lower friction coefficient and wear rate. However, the effect of the slenderness ratio of MWCNTs on the friction and wear of the composite is far less than the effect of functional groups attached to MWCNTs. When carbon nanotubes are aminated, the tubular structure is damaged and the friction coefficient decreases.The friction and wear of MWCNTs/BMI nanocomposite is also related with the crosslinking degree of the resin matrix. When carboxyl groups are attached to carbon nanotubes, the carboxyl groups can accelerate the curing of the resin and increase the crosslinking degree of the resin. And this kind of strengthening for the matrix is favored by the reduce of the friction and wear of the composite.With everything under the same circumatance, it is the most efficient method to improve the tribological properties of MWCNTs/BMI nanocomposite through improving the interface of the composite. Nanocomposite prepared with allyl bisphenol A modified carbon nanotube shows the best tribological properties with only one quarter of friction coefficient and one half of wear loss rate to the composite with unmodified carbon nanotube, which is related with the best dispersing state and best interfacial adhesion.Field emission scanning electronic microscope (FESEM) and dynamic mechanic analysis (DMA) are adopted to analyze the worn surface and wear mechanism of the composite. The factors mentioned above will all affect the worn surface of the material but the interfacial factor plays the key part. The addition of original carbon nanotube into the BMI resin can change the fatigue mechanism of the pure BMI resin with large numbers of cracks and flaws to adhesive mechanism with many roll marks. The addition of modified carbon nanotube into the BMI resin can change the mechanism to abrasive wear mechanism with regular straight grooves on the worn surface. When the worn mechanism meets the mechanism of abrasive wear mechanism, the relationship between wear rate and microhardness is as follows: dm/dl=-0.01498+0.0059/H, which means the microhardness can be the simple criterion of wear loss rate:the higher the microhardness, the lower the wear loss rate and also the better wear resistance of the material.Secondly, stearinic acid modified carbon nanotube dispersed in parafin oil can form the uniform lubricant between the BMI resin and steel anti-wear system. The friction coefficient is reduced significantly and the width and depth of the worn mark are also decreased. The modified carbon nanotube displays the effect of micro-bearings on the contact surface to reduce friction and wear. However, small amount of carbon nanotubes are found to insert into the surface of the resin and micro scratches are formed.In order to reduce these micro scratches on the worn surface, hydrolyzed styrene-maleic anhydride co-polymers are used to modify carbon nanotubes with tough carbon nanotubes as core and soft polymer as shell and dispersed in paraffin oil in spheral shape. This core-shell structured carbon nanotube can reduce the friction and wear of the system at low concentration and low contact temperature for the protecting film formed on the steel ball. However, at high carbon nantube concentration, the residue carbon nanotube with polymer soft shell interacts with the BMI resin, which will accelerate the formation of defects of the surface and deteriorate the friction and wear of the system.更多还原