Study On The Modification Of PTFE And The Properties Of Its Composites

Polytetrafluoroethylene (PTFE) has been widely used in all kinds of fields such as chemical and inechnical industry, sealing propective due to its outstanding comprehensive properties. However its applications are hampered in many cases because of its poor anti-wear ability and adhesion property with other materials. In this paper, the BaSO₄/PTFE and the CF/BaSO₄/PTFE composites were prepared. The wear and friction properties and the mechanical properties of the two composites were investigated. Meanwhile, the surface of PTFE was modified by graft copolymeration to enhence the adhesion with the steel. The influence of the interface between the carbon fiber and the PTFE matrix on the mechanical properties and the wear and friction properties were also investigated.The influences of contents and the particle size of BaSO₄ on the properties of the composites were systematically investigated. The results showed that the size and the contents of BaSO₄ particles greatly influence on the properties of the composites. When the size of BaSO₄ is 44μm and the contents of BaSO₄ is 40wt%, the composite has the best wear resistance ability and the wear weight loss of the composite is about 100 times lower than the pure PTFE.To enhance the interfacial property between the carbon fiber and PTFE matrix, tow types of modification methods were used. The tensile properties and the wear rate of the carbon fibers reinforced polytetrafluoroethylene (CF/PTFE) under different methods and different surface treatment conditions were investigated. In both cases, appropriate treatments could effectively improve the mechanical properties and the anti-wear ability of the CF/PTFE composites. The average wear rates for carbon fiber which modified by plasma and gaseous oxidation are 55.6% and 50.8%lower than the untreated carbon filled PTFE composites wear rate respectively and the tensile strength improved 48% and 32% respectively.The hybrid composites was prepared using short carbon fiber and BaSO₄ particle as reinforcing agents, which could improve its mechanical properties and anti-wear property. Experimental research showed the optimized comprehensiveproperties reached when the contents of BaSCXi particle is 20%. Compared with the BaSC>4 filled PTFE composite, the hybrid PTFE composite has the better comprehensive properties than the BaSCVPTFE composite.Surface modification on Polytctrafluoroethylene (PTFE) were pretreated with Ar plasma, followed by thermal-induced graft polymerization with glycidyl methacrylate (GMA). The tensile-shearing strength with steel and the water contact angle of grafted PTFE were greatly influenced by the monomer concentration of GMA and the conditions of plasma treatment. The results showed that the surface hydrophilicities and tensile-shearing strength of modified PTFE significantly enhanced with the modification and the adhesion strength for the grafted PTFE improved from 24.6 to 284.6Ncm"2, by a factor of 12, due to grafting treatment.