【作者】 王其磊；

【导师】 杨逢瑜；

【作者基本信息】 兰州理工大学 ， 流体机械及工程， 2011， 博士

【摘要】 橡胶密封制品是以橡胶为基材制造的、用于防止流体介质从机械、仪表的静止部件或运动部件泄漏,并防止外界灰尘、泥沙及空气（对于高真空而言）进入密封机构内部的部件。橡胶密封制品的作用重要、结构独特,具有装配维修方便、使用可靠、成本适中、与液压和气动工作液或润滑剂有较好的相容性、用途广泛等特点,早已引起国内外各工业部门的关注。近年来随着对橡胶密封制品的需求量不断增加,对其技术水平的要求不断提高,使得研究如何提高密封件的使用效果成为热点课题。改善橡胶密封制品的性能,首先应从改善橡胶材料的基本性能入手,研究橡胶材料及其性能,不仅对密封装置中的密封件有用,触类旁通,对其他橡胶制品的研究也有参考价值。并且为了提高密封件的使用寿命,除了要考虑密封材料必须的力学性能、弹性和耐油性外,还必须最大限度地提高材料的抗磨、减摩性能。本课题在调研了国内、外橡胶密封的现状和发展的基础上,提出了应用纳米技术对复合橡胶进行改性,以磁性纳米Fe₃O₄粒子与纳米SrO·6Fe₂O₃粒子为研究的突破点。纳米颗粒具有尺寸小、比表面积大、表面间形态不同于颗粒内部、表面原子配位不全、表面活性强等特性。采用磁性纳米材料填充橡胶以期使丁腈橡胶的性能获得提高如耐磨耗性能并使丁腈橡胶带有磁性。本课题选择纳米Fe₃O₄粒子和纳米SrO·6Fe₂O₃粒子作为橡胶的填充剂,并且选用具有优良的耐油、耐热和耐腐蚀性的丁腈橡胶作为基材。从设计和制备磁性NBR/Fe₃O₄复合材料和NBR/SrO·6Fe₂O₃复合材料入手,研究纳米粒子的存在状态与橡胶复合材料结合后的力学性能、磁学性能、摩擦、磨损性能;探究纳米粒子复合橡胶材料的抗磨、减摩机理,为设计密封用高性能弹性体复合材料提供理论和应用依据。本文的主要工作及成果如下:1.探讨了纳米Fe₃O₄粒子和纳米SrO.6Fe₂O₃粒子作为填充剂的特性,利用WL2000SP型混炼机制备了磁性NBR/Fe₃O₄复合材料和NBR/SrO·6Fe₂O₃复合材料。利用JSM-5600LV低真空电子显微镜对复合材料表面进行研究发现:纳米Fe₃O₄粒子的加入有效地改善了NBR基体的表面结构,具有较好的补强作用。随着纳米Fe₃O₄粒子的添加量不断加大,复合材料的表面结构逐渐变差,当添加量为10%左右时,表面结构较为理想。并且复合材料中具有较好的相态结构,纳米粒子随着添加量的不断加大,不均匀现象逐渐增多,不利于纳米粒子对材料的改性作用。2.利用DXL-10000电子拉力试验机等测试设备对复合材料的物理机械性能进行了测试,测试结果表明:随着纳米粒子的加入,NBR/Fe₃O₄复合材料和NBR/SrO·6Fe₂O₃复合材料的拉伸强度和扯断伸长率逐渐减小。复合材料的硬度明显大于普通NBR。普通NBR的邵尔A硬度为63度,而复合材料的硬度则随着纳米粒子填充量的不断加大逐渐得到提高。随着纳米粒子添加量不断提高,磁性NBR/Fe₃O₄和NBR/SrO·6Fe₂O₃复合材料的门尼粘度NBR的门尼粘度略有升高,复合材料的挥发分,灰分含量、结合丙烯腈含量在小范围内变化。从细观层面上分析了磁性丁腈橡胶的热粘弹性理论并修正了加入磁性粒子后橡胶的内能、熵和Helmholtz自由能之间的关系以及非线性热粘弹性本构关系模型,实验得出应力应变与温度的关系,并分析了磁性粒子含量的变化所来的性能变化,确定了10%含量时的磁性NBR/Fe₃O₄复合材料具有较好的性能。3.利用U10充磁机和摩擦磨损试验机对复合材料的磁性能与摩擦磨损性能测试后发现:随着纳米粒子含量的增多,复合材料的磁性能单调增加,表现出典型的顺磁性特征,并且两种复合材料矫顽力均有较小幅度的增长;纳米粒子作为填充物可有效降低NBR摩擦系数与磨损率。当添加量为10%时NBR/Fe₃O₄复合材料的综合摩擦磨损效果较好,摩擦系数与磨损率低于普通NBR近300%。纳米SrO·6Fe₂O₃粒子作为填充物,在添加量为10%时,可有效降低NBR摩擦系数与磨损率。但是随着添加量的不断加大,NBR/SrO·6Fe₂O₃复合材料的综合摩擦性能明显变差,劣于普通NBR。4.对磁性橡胶的密封应用前景研究发现:纳米磁性橡胶复合材料轴封具备普通橡胶轴封不具备的一系列优点:较低的摩擦系数和磨损率、良好的自修复能力和自密封性能等,有效地提高了轴封的密封能力。更多还原

【Abstract】 Rubber seal is made by rubber materials, which used to prevent any liquid leak from the static and moving components of the machine, and prevent dirt, soil and air （the vacuum environment） into internal parts of the sealed machine. Rubber is the polymer material with the unique mechanic performance, which mainly shows by: producing great shape for low strain, elasticity of restoring their original shape after deformation, the size of materials remain unchanged under pressure, and have better compatibility with hydraulic oil and lubricant. The important of rubber seal shows unique structure, convenient assembly and maintenance, usage credibility, low cost, wide application and so on, which causes concern of various industry departments at home and abroad. In recent years, with the increasing of demand of rubber seal, the skill level of requirements is increasing, which the research about improve the effectiveness of the seals to be a hot topic. The improving performance of rubber seal should the first improve the performance of rubber materials, which will not only benefit for rubber, but also other rubber products. To improve the life of seals, the anti-friction and anti-wear properties of material are improved at the greatest level in addition to improve mechanical properties, flexibility and oil resistance of material.On the basis of the survey of present and future prospects of rubber seal at home and abroad, we propose the modification of rubber composites by nanotechnology based on magnetic nano-Fe₃O₄ particles and nano-SrO·6Fe₂O₃ particles in the project. Nano particles employed smaller size, specific surface, surface morphology is different from inside particles, the surface atoms, strong surface reactivity and so on.Rubber composites are made by filling magnetic nano-material into nitrile-butadiene rubber（NBR）, which improve anti-friction and anti-wear properties as well as rubber magnetic properties. Nano-Fe₃O₄ particles and nano-SrO·6Fe₂O₃ particles are applied as filler, and NBR with excellent oil resistance, heat-resisting and corrosion resistance is applied as matrix material. Started with design and preparation of magnetic NBR/Fe₃O₄ composites and NBR/SrO·6Fe₂O₃composites, the existence conditions of nano-particles, mechanical properties, magnetic properties, friction and wear properties of composites are studied, which lay the foundation of high-performance elastomer composites for sealing. The major work and results are as follows:1. The characteristics of nano-Fe₃O₄ particles and nano-SrO·6Fe₂O₃ particles as filler are discussed, magnetic NBR/Fe₃O₄ composites and NBR/SrO·6Fe₂O₃ composites was prepared by WL2000SP mixing rolls, and the surface microstructure of composites are surveyed by JSM-5600LV electron microscope. The result shows that after the addition of nano-Fe₃O₄ particles, the surface microstructure of NBR/Fe₃O₄ composites are greatly improved, which shows the good reinforcement of nano- particles. With addition of nano-Fe₃O₄ increasing, the surface microstructure of composites become inferior gradually, and the composites have good microstructure and phase structure with mass fraction of nano-Fe₃O₄ particles10%. With addition of nano-Fe₃O₄ increasing, the uneven phenomenon of nano-particles increasing, which are unfavorable to modification of nano-particles for materials.2.The physical and mechanical properties of composites are tested by DXL-10000 electronic tensile tester and so on. Test result shows: with adding different mass fraction of nano-particles, maximum elongation、300%stress at definite elongation and tensile-strength of composites are decreased, but shore A hardness and mooney viscosity of composites are improved, while the volatile component, ash content and content of bound acrylonitrile are changed in a small range. From the microscopic level, We also investigated the relationship between internal energy, entropy and Helmholtz free energy after adding nano-Fe₃O₄ particles, and nonlinear thermoviscoelastic constitutive model are deduced, Stress-strain curves of NBR/Fe₃O₄ composites with different mass fraction of nano-Fe₃O₄ particles at were obtained in this experiment. The composites have good performance with mass fraction of nano-Fe₃O₄ particles10%. 0oC3. The magnetic properties and frictional wear properties of the composites are tested by U10 magnetizer and friction-abrasion testing machine. Test result shows: with increasing the mass fraction of nano-particles, magnetic properties of the composites monotonely increase, saturation magnetization strength of the composites increase constantly. The composites show typical characteristics of paramagnetism. And the coercive force of two composites have increased in small scope. The properties of anti-wear for NBR composites are improved when two kinds of nano-particles were filled in, and the tribological properties of NBR/Fe₃O₄ composites are better. When addition of nano-Fe₃O₄ particles are 10%, the wear rate of NBR/Fe₃O₄ composites are 300% lower than ordinary rubber. while the friction coefficient and wear rate of NBR are small reduced at the beginning by adding nano-SrO·6Fe₂O₃ particles, but the friction coefficient and wear rate are incessant larger with the increasing addition of nano-SrO·6Fe₂O₃ particles.4.The application of magnetic rubber seal in the future have a series of merits relative to ordinary rubber seal, for example: lower friction coefficient and wear rate, favourable repaire themselves and self-sealing performance, which help improve sealing performance of shaft gland.更多还原