Friction And Wear Performances Of Polytetrafluoroethylene Promoted By Fillers

Polytetrafluoroethene (PTFE) possesses good chemical stability, low friction coefficient, high temperature resistance and thermal stability due to its unique structure. Thus, PTFE can be widely applied in chemical field. However, the pure PTFE are required to promote its tribological performances because of its poor wear resistance. PTFE was filled with mullite, carbon fiber and wollastonite by mechanical blending, heat compression followed by a sintering at an elevated temperature in this thesis, and the mechanical properties, thermal properties, friction and wear properties of the resulting PTFE composites were studied. The main studies can be outlined as follows:1. Tribological performances of PTFE composites filled with mullitePTFE composites filled with mullite were prepared and their microscopic structure, mechanical properties and thermal properties were characterized by FT-IR, XRD, a universal material testing machine, a Rockwell hardometer, DSC and TMA, respectively. The friction coefficient and wear rate of the prepared PTFE composites were tested by an MRH-3 high speed friction and wear tester, and the morphologies of friction surface of the composites were analyzed by a field-emitting scanning electron microscope. It was found that mullite fillings were well dispersed in PTFE, and the properties of the resulting blends in mechanics and thermology were enhanced, such as modulus of elasticity, glass transition temperature and average linear expansion coefficient. The friction coefficients of the composites were found smaller than that of pure PTFE at a mullite filling concentration of 10%, and the larger coefficient found at the elevated mullite concentration. It was more important to find that wear rate of the resulting composites filled with 40% mullite was decreased to 1/530 of the pure PTFE.2. Tribological performances of PTFE composite synergistically filled with mullite and carbon fiberPTFE composites filled with mullite and carbon fiber were prepared and their microscopic structure, mechanical properties and thermal properties were characterized. The friction coefficient and wear rate of the prepared PTFE composites were tested by an MRH-3 high speed friction and wear tester, and a sand slurry apparatus with silicon oil heated by oil bath was used to detect the wear rate of the promoted PTFE composites at the increased temperature. The morphologies of friction surfaces of the composites were analyzed by a 3D laser microscope. It is found that mullite and carbon fiber fillings are well dispersed in PTFE, and the modulus of elasticity of the resulting blends is enhanced. The wear rate of the composites filled with mullite and carbon fiber are found a decrease of more than three orders compared with the pure PTFE under dry friction conditions in spite of an increase in friction coefficient, and a low friction coefficient and wear rate are also found under wet friction conditions. Further, a low wear rate of the promoted PTFE composites was detected even at a high temperature.3. Tribological performances of PTFE composite synergistically filled with wollastonite and carbon fiberPTFE composites filled with wollastonite and carbon fiber were prepared and their microscopic structure, mechanical properties and thermal properties were characterized. The friction coefficient and wear rate of the prepared PTFE composites were tested by an MRH-3 high speed friction and wear tester, and the morphologies of friction surfaces of the composites were analyzed by a 3D laser microscope. It is found that wollastonite and carbon fiber fillings are well dispersed in PTFE, and the modulus of elasticity of the resulting blends is enhanced. The low wear rate and the lowest friction coefficient of the composites filled with wollastonite and carbon fiber are kept at low values under dry and wet friction conditions.This thesis investigated microscopic structure, mechanical properties, thermal properties and friction wear properties of mullite/PTFE composites, mullite-carbon fiber/PTFE composite and wollastonite-carbon fiber/PTFE composite. The results showed that wear performance of the three kinds of composites are better under dry friction conditions. The friction and wear properties of mullite/PTFE composites are poor under wet friction conditions, but their friction and wear properties of mullite-carbon fiber/PTFE composite and wollastonite-carbon fiber/PTFE composite are still good under this condition. These results offered theoretical support for the use of PTFE composites in the oil wells with greater depth and higher temperature.of the PTFE composites can explore in more deep well, high temperature oil wells using.