Polymers friction properties

We shall discuss three types of phenomena for polymer solutions thermodynamic properties in Chap. 8, frictional properties in Chap. 9, and lightscattering properties in Chap. 10. A common feature of virtually all phenomena in these areas is that they all depend on the molecular weight of the solute. Thus observations of these properties can be interpreted to yield values for M we shall use this capability as a unifying theme throughout these chapters. 

The inability to process PTFE by conventional thermoplastics techniques has nevertheless led to an extensive search for a melt-processable polymer but with similar chemical, electrical, non-stick and low-friction properties. This has resulted in several useful materials being marketed, including tetrafluoro-ethylene-hexafluoropropylene copolymer, poly(vinylidene fluoride) (Figure 13.1(d)), and, most promisingly, the copolymer of tetrafluoroethylene and perfluoropropyl vinyl ether. Other fluorine-containing plastics include poly(vinyl fluoride) and polymers and copolymers based on CTFE. 

High stiffness, fair resistance to corrosion and good frictional properties sometimes make nylons more attractive than metals. The stiffness of the polymer may be increased by glass filling. Nylons containing molybdenum... 

The all-important difference between the friction properties of elastomers and hard solids is its strong dependence on temperature and speed, demonstrating that these materials are not only elastic, but also have a strong viscous component. Both these aspects are important to achieve a high friction capability. The most obvious effect is that temperature and speed are related through the so-called WLF transformation. For simple systems with a well-defined glass transition temperature the transform is obeyed very accurately. Even for complex polymer blends the transform dominates the behavior deviations are quite small. 

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