【作者】 陶克梅；

【导师】 向定汉；

【作者基本信息】 南京航空航天大学 ， 材料加工工程， 2007， 硕士

【摘要】 聚甲醛(POM)是一种高结晶工程塑料,具有高的机械强度、良好的尺寸稳定性、耐蚀性、耐磨性以及抗疲劳性能,被广泛应用于汽车、电子与精密仪器等领域。然而纯POM的滑动摩擦系数较大,不宜用作滑动部件。迄今为止,降低POM的摩擦系数最有效的方法是添加聚四氟乙烯(PTFE)制备成POM-PTFE复合材料。为了进一步改善POM的摩擦磨损性能,扩大其应用范围,以PTFE为润滑剂分别与石墨、玻璃纤维及高岭土改性POM,选择商用的POM-20%PTFE作摩擦对比研究,希望获得更优异的性能。本研究选择PTFE-石墨、PTFE-GF与PTFE-kaolin添加到POM中,通过单螺杆挤出后,采用热模压法制备出不同配方的POM-PTFE-石墨、POM-PTFE-GF复合材料与POM-PTFE-kaolin复合材料。利用广角X-射线衍射对POM复合材料进行了分析,通过仪器自带的积分软件计算POM基体结晶峰与非结晶峰的面积,从而得到POM复合材料的结晶度。将POM-PTFE-石墨与POM-PTFE-GF复合材料在两种不同载荷(6.2 Mpa和3.3 Mpa)条件下,在往复式滑动摩擦实验机上进行实验,实验条件为:相对湿度为(60±3)%,往复频率为1.0 Hz,往复行程为14.0 mm。结果发现:在载荷为6.2 Mpa条件下,POM+20%PTFE+10%GF复合材料的耐磨性为POM+20%PTFE复合材料的1.47倍;在载荷为3.3 Mpa条件下,POM+20%PTFE+5%石墨复合材料的摩擦系数比POM+20%PTFE复合材料降低了18%。将POM-PTFE-kaolin复合材料也在往复式滑动摩擦实验机上进行实验,结果表明:含高岭土的POM+20%PTFE+7.5%kaolin复合材料的摩擦系数和磨损率最低,与POM+20%PTFE复合材料相比分别降低了10%和18%。可见, PTFE与无机颗粒能够协同降低POM的摩擦系数和磨损率。更多还原

【Abstract】 Polyoxymethylene (POM) is a high-crystalline engineering plastic, which has high mechanical strength, good stability, corrosion resistance and wear resistance as well as anti-fatigue properties. So POM is widely used in automobile, electrical appliance, precision apparatus, etc. However, pure POM against steel exhibits a high coefficient of friction, and which is not suitable for sliding components. So far, the most effective way to reduce coefficient of friction of POM is to prepare the PTFE-POM composites filled with polytetrafluoroethylene (PTFE). In order to increase the applicability of the POM in the bearing industry, the graphite, glass fiber, kaolin and PTFE, which was acted as a solid lubrication, were selected for the modifying agents, then the POM composites were prepared. A commercial POM-20%PTFE composite was chosen to carry out a comparative investigation. It is expected to further improve the tribological properties of POM.The different contents of the PTFE-graphite, PTFE-GF and PTFE-kaolin, respectively, were added into POM, then they were extruded with a single-screw extruder.The POM-PTFE-graphite, POM-PTFE-GF and POM-PTFE-kaolin composites were hot-molded into slab specimens.Wide angle x-ray diffraction (WAXD) patterns were taken on a Bruker D8 ADVANCE diffract-meter (Germany) with Cu-filtered Cu kαradiation at room temperature. The crystalline area and the amorphous area were calculated with a software of this apparatus, then the mass fraction crystallinity of the POM composites were obtained.For the POM-PTFE-graphite and POM-PTFE-GF composites, the friction and wear tests were carried out in a reciprocating tribometer under two different loading conditions. These composites were tested against a 45 carbon steel track, at room temperature in ambient atmosphere (60±3)%RH. The conditions were a reciprocating frequency of 1.0 Hz. Results show that by comparison to a POM+20%PTFE composite, a POM+20%PTFE+5%graphite composite exhibited a relatively low coefficient of friction under loading conditions of 3.3 Mpa and a POM+20%PTFE+10%GF composite exhibited a relatively low specific wear rate under loading conditions of 6.2 Mpa.For the POM-PTFE-kaolin composites, the friction and wear tests were also carried out in a reciprocating tribometer. It is found that a POM+20% PTFE+7.5%kaolin composite exhibited a relatively low coefficient of friction and high wear resistance compared to a POM+20%PTFE composite.更多还原