【作者】 段应军；

【导师】 李同生；

【作者基本信息】 复旦大学 ， 高分子化学与物理， 2009， 博士

【摘要】 含硫特种工程塑料聚苯硫醚（PPS）及其复合材料具有优良的摩擦磨损性能,在摩擦领域有广泛的应用。有文献论及PPS的优良摩擦学性能可能与其活性硫元素与金属对偶之间发生的摩擦化学有关,但目前尚无定论。为了澄清这一问题,本论文选择具有相似结构的含硫特种工程塑料—PPS、聚醚砜（PES）、聚砜（PSU）作为研究对象,系统考察了多种内、外因素对含硫聚合物摩擦磨损性能的影响。采用端面摩擦磨损试验机和可控温往复式试验机评价了材料的摩擦学性能;用扫描电镜（SEM）、动态力学分析（DMA）、差示扫描量热分析（DSC）、热失重分析（TGA）、红外光谱（FT-IR）、X射线衍射分析（XRD）、X射线光电子能谱（XPS）等对材料磨损面、磨屑进行了观察和分析。在此基础上,比较深入地探讨了含硫聚合物的摩擦磨损机理。论文得到的主要创新性研究结果如下:1干摩擦时,随PV值的增加,PPS的摩擦系数在0.4-0.96间变化,波动较大,PES和PSU的摩擦系数随载荷变化很小,稳定在0.48左右,随速率增加逐渐减小到0.3;PPS的磨损率先下降后上升,PES和PSU的磨损率持续上升;在速率为0.2m/s载荷100N时,PPS的磨损率为1.8×10^-5mm³/N·m,约为PES和PSU磨损率的1/10。2载荷、速率等实验条件主要通过摩擦界面温度影响PPS、PES和PSU的摩擦磨损性能。随着摩擦界面温度的升高,三种聚合物磨损机理由磨粒磨损向粘着磨损、熔融磨损转变。当磨损表层温度达到玻璃化转变温度时,PES和PSU力学性能急剧下降而使材料磨损迅速增加;PPS因其固有的半结晶结构而使其力学性能降低缓慢,磨损变化不大。3含硫聚合物与金属干摩擦时摩擦化学反应的发生及其产物与硫元素的价态、金属对偶的活性和摩擦界面温度有关。PES和PSU中高价态的硫元素活性较弱,与金属对偶摩擦时不易发生摩擦化学反应;PPS中低价态的硫元素活性较大,与金属对偶干摩擦时易于发生摩擦化学反应,有助于转移膜的生成。4在较低PV值时,由化学活性导致的转移膜对三种含硫聚合物的磨损性能的影响起主要作用,PPS的低磨损与PPS和金属对偶形成了牢固的转移膜有关;在较高PV值时,影响含硫聚合物磨损性能的主要因素是聚集态结构,半结晶性和PPS特有的热固性,是PPS显示低磨损的主要原因。以上研究结果有利于深化对含硫聚合物的摩擦学规律的认识,进一步丰富聚合物摩擦化学理论研究,具有重要的理论意义;同时为摩擦材料的选材提供了判断依据,具有重要的应用价值。更多还原

【Abstract】 The special sulfur-containing engineering plastics and their composites have excellent tribological properties and have been extensively applied in tribological field. The opinion from literatures that the excellent tribological properties of polyphenylene sulfide （PPS） and its composites probably have a relationship with the tribochemical reaction has not been confirmed yet.To clarify the above point, the influence of internal and external factors on the tribological properties of three special sulfur-containing engineering plastics, PPS, polyethersulfone （PES） and polysulfone （PSU） which have the similar structure was investigated systematically. The tribological properties were tested by an end-face contact mode and a pin-on-disc contact configuration wear testers. The pattern of worn surface and debris was observed with the aid of Scanning Electron Microscopy （SEM）, Dynamic Mechanical Analysis （DMA）, Differential Scanning Calorimetry （DSC）, Thermo Gravimetric Analysis （TGA）, Fourier Transform Infrared Spectrometry （FT-IR）, X-Ray Diffraction （XRD）, and X-Ray Photoelectron Spectroscopy （XPS）. The friction and wear mechanism of sulfur-containing polymers was discussed on that basis.The conclusions of this dissertation were drawn as follows:1 In dry sliding, the friction coefficient of PPS fluctuated between 0.4 and 0.96 with the PV value increasing. However, that of PES and PSU kept stable at about 0.48, afterwards declined to 0.3 as the velocity increased. The wear rate of PPS declined first, and then rose up, while that of PES and PSU kept increasing. At 0.2m/s, 100N, the wear rate of PPS was 2.1×10^-5 mm³ /N·m which is the 1/10 of PES and PSU.2 Various external factors such as load and velocity influenced the tribological properties of PPS, PES and PSU by affecting the temperature of the worn interface. With the interfacial temperature increasing, the wear mechanism transited from abrasive wear to adhesion and melt wear. When it arrived at the glass transition temperature, the mechanical properties of PES and PSU sharply decreased and resulted in the high wear rate. But the mechanical properties of PPS decreased slowly because of its inherent semi-crystalline structure, so the wear rate changed slightly.3 The tribochemical reactions and reaction products between metal couple and sulfur-containing polymers were related to the valence state of sulfur, metal activity and interfacial temperature. The tribochemical reactions were difficult to happen for PES and PSU due to the low activity of high valence state sulfur in them. The lower valence state sulfur in PPS has higher activity which leads to the tribochemical reaction between PPS and metal couple by forming a firm transfer film.4 The transfer film plays a main role in the wear properties of the three polymers at lower PV value. The lower wear rate of PPS was associated with the firm transfer film formed between PPS and the metal couple. The aggregation structure is the major factor affecting the wear properties of these polymers at higher PV value. The semi-crystalline structure and its inherent thermosetting characteristics mainly caused the excellent wear properties of PPS.The above results are important to understanding the tribological law of sulfur-containing polymers and developing new friction materials, furthermore enrich the theoretical study of polymer tribochemistry.更多还原