【作者】 谢莹；

【导师】 李笃信；

【作者基本信息】 中南大学 ， 材料科学与工程， 2013， 硕士

【摘要】 ：尼龙6(PA6)因其优异的机械力学性能、良好的耐磨性能与自润滑特性已作为摩擦材料被广泛应用于机械、石油化工等领域。然而随着工业的迅速发展,单一PA6制品已难以满足实际应用需要。通过对PA6进行改性发展PA6基复合材料可以有效提高PA6综合性能,拓展其应用领域,是目前主要研究方向之一。本论文使用双螺杆挤出成型的方法制备PA6基复合材料,首先采用玻璃纤维进行增强,研究了玻纤含量对复合材料力学与摩擦学性能的影响；在此基础上,通过固体润滑剂PTFE、石墨与UHMWPE单一或两两复合对PA6/GF-15%复合材料进行填充改性,重点研究了润滑剂填充量与配比对复合材料力学与摩擦学性能影响。利用SEM观察磨损表面形貌,探讨了复合材料的磨损机理。研究结果表明：(1)玻纤增强大幅提升了纯PA6的物理与力学性能,且随玻纤含量的增加而呈现上升趋势；同时也对材料摩擦学性能有不同程度的影响。当玻纤含量为15wt%时,复合材料的摩擦系数为0.1177,较纯PA6下降了65%；但质量磨损率有所增加。纯PA6以粘着磨损为主,而玻纤增强PA6复合材料主要发生磨粒磨损。(2)单一固体润滑剂填充改性PA6/GF复合材料时,PTFE可有效降低复合材料的摩擦系数,改性效果优于UHMWPE与石墨；当PTFE填充量为15wt%时,复合材料摩擦系数降低至0.09412,比PA6/GF降低了20%；但复合材料的摩擦稳定性与力学性能有所下降,主要磨损机理为磨粒磨损,伴随有少量粘着磨损。(3)复合固体润滑剂填充时,PTFE-UHMWPE对PA6/GF复合材料质量磨损率改性效果较优,其次是石墨-UHMWPE, PTFE-石墨较差。10wt%/5wt%PTFE-UHMWPE填充复合材料质量磨损率仅为3.65×10-8cm3/Nm,与未填充PA6/GF相比下降了62%,比纯PA6降低了44%,此时复合材料磨损机理主要为磨粒磨损,同时伴随少量粘着磨损的发生(4)在所研究固体润滑剂种类及填充量范围内,15wt%PTFE填充PA6/GF复合材料具有最低的摩擦系数,10wt%/5wt%PTFE-UHMWPE填充PA6/GF复合材料具有最低的质量磨损率,12wt%/3wt%石墨-PTFE填充PA6/GF复合材料具有最高拉伸强度,3wt%/12wt%石墨与UHMWPE填充PA6/GF复合材料则获得最高冲击强度37.4KJ/m2。更多还原

【Abstract】 Polyamide6(PA6) has been wildly used in engineering applications as a friction material due to its excellent mechanical properties, good resistance and self-lubricating performance. The properties of PA6could be improved further by reinforcements and fillers, resulting in higher strength, higher wear resistance and lower coefficient of friction. PA6composites have, therefore, been a promising material to replace many traditional metallic materials for sliding components.In this thesis, PA6composites friction materials were prepared using a modular intermeshing co-rotating twin-screw extruder. Glass fiber (GF) was firstly employed to reinforce PA6material. The effects of GF content on mechanical and tribological behaviors of PA6have been studied. Then, various solid lubricants, such as PTFE, graphite and UHMWPE, were used to further improve tribological properties of PA6/GF composites material. We also investigated the mechanical and tribological performance of PA6/GF composites material filled by different content and proportion of solid lubricants. The worn surfaces were examined using scanning electron microscope (SEM) to discuss wear mechanism. The main results are as following:(1) Glass fiber reinforcement was found effective not only in improving tensile strength and impact strength, but also lowering coefficient of friction of PA6. When filling15wt%GF, COF of composites material was lowered to only0.1177, by65%decrease compared to pure PA6. The wear mechanism for pure PA6was adhesive wear, which changed to abrasive wear after GF reinforcement. However, the wear performance was worse for PA6/GF composites.(2) When filled with single solid lubricant, PTFE was found much more effective to lower COF of PA6/GF composite than graphite and UHMWPE, which can be attributed to formation of the stable transfer film. The maximum reduction in COF was obtained by filling PA6/GF with single15wt%PTFE and the COF was0.09412, decreased by 20%.The wear surface indicated that main mechanism was abrasive wear.(3) The complex solid lubricants were of benefit for improving wear properties.PTFE-UHMWPE performed better than PTFE-Graphite and Graphite-UHMWPE. When filling with10wt%/5wt%PTFE-UHMWPE complex lubricants, PA6/GF composite material showed best wear behavior with the low wear rate of3.65×10-8cm3/Nm, which was56.5%and44%lower than PA6/GF and pure PA6, respectively. The main mechanism was also abrasive wear. However, COF of composite increased, which demonstrated that the friction properties were not effectively improved.(4) By comparing different types and contents of solid lubricant,15wt%PTFE filling PA6/GF composites material showed lowest COF and10wt%/5wt%PTFE-UHMWPE filling PA6/GF composites material had lowest mass wear rate. As for mechanical properties, PA6/GF filled with12wt%/3wt%Graphite-PTFE and3wt%/12wt%Graphite-UHMWPE performed best tensile strength and impact strength, respectively.更多还原