Systematic development for high performance fluoropolymer materials and applications

Abstract

The aim of the work includes several steps. After the material characterization of the PTFE itself, the processing technologies and the tribological characterization of compounds, a revision of suitability has to be done and the correlation between the filler and the processing technology must be respected. If the suitability or the correlation is not fitting for the favoured application it is recommended to return to the material characterization of the PTFE to find the best solution. By using this systematic way the optimized material for nearly every application can be found. Only by a broad knowledge of the different PTFE materials, their properties and the processing technologies in combination with the manufacturing process enables to find the material and process solution. Depending on the targeted applications the required performance profile may be different. In this work all important chemical, physical and mechanical influences are determined and analyzed. The study of mechanical and thermal behaviour of these materials gives a better unterstanding of the relationship between molecular weight, molecuar weight distribution, particle composition and material characteristics. By utilising these processes the following conclusions are made: · The particle size and the weight percentage of the d10-fraction of the material are specific for each material type. The increased specific surface enables an improved coalesence of the particles. In addition, a rough surface compared to a smooth one generates a better surface contact during moulding. Producing compounds will be done with low flow material because due to the lower particle size the filler distribution is more homogenious. · In difference to Standard PTFE, modified PTFE has a reduced molecular weight, a reduced cold flow, enhanced mechanical properties and a better melting behaviour during sintering as a consequence of the reduced melting viscosity. · PTFE processing is not critical for local pressure variations inside the mould. But lower moulding pressure generates higher shrinkage during sintering. · Compounds with low phyiscal strength are not acceptable for high strain. It can be said, that low elongation is a disadvantage for the manufacturing and assembly process and recovers the danger of crack formation at impact load. A low shrinkage behaviour during sintering is advantageous for the manufacturing of stress-relieved components. After testing the samples on the different conditions the best results are obtained for material No. 7 which is a compound composed of Standard PTFE + 15% PPS + 10% Carbon Coke + 2%MoS2. This compound generates a high wear resistance and a reduced coefficient of friction. The comparison of mechanical and tribological performance of Standard PTFE, modified PTFE and PTFE compounds show the potential of this materials for industrial applications. In general, the mechanical properties of PTFE play an important role for XX material selection for any application and can potentially provide…