Friction and Wear in Polymers

Yoo et al. (77,78) confirmed this dependence using uniform polystyrene latex films. (See Section 5.4.4.) The process of film formation from a latex can be divided into three stages (a) evaporation of the water containing the latex, (b) coalescence and deformation of the latex particles, and (c) interdiffusion of the polymer chains into adjacent latex particles. The time for complete healing is given by the reptation time, T, = i l 37f D) where r is the end-to-end distance of the chain, D represents the diffusion coefficient, and Tif = 3.14. 

Interestingly, although wear in polymers must take place with the generation of fracture surfaces and concomitant chain scission and pull out (see Section 11.5), there seems to be a paucity of measurements of these fundamental properties. Most of the quantitative measurements are concerned with the macroscopic characteristics of the wear. However, it is known that higher molecular weights and/or extensive entanglements result in reduced frictional wear (79). 

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Bartenev, G.M. and Lavrentev, V.V. Friction and Wear in Polymers, Elsevier Science Publ. Co., Amsterdam (1981)... 

Bely, V.A. et al., "Friction and Wear in Polymer-based Materials", trans. Granville- Jackson, P., Pergamon Press,... 

V.A. Belyi, A.I. Sviridenok, M.I. Petrokovets and V.G. Savkin. Friction and Wear in Polymer-Based Materials. Oxford, Pergamon Press, 1982. 

G. M. Bartenev and V. V. Lavrent ev, Friction and Wear in Polymers [Russian], Khimiya, Leningrad 1972. ... 

PTFE is outstanding in this group. In thin films it provides the lowest coefficient of friction (0.03—0.1) of any polymer, is effective from —200 to 250°C, and is generally unreactive chemically. The low friction is attributed to the smooth molecular profile of PTFE chains which allows easy sliding (57). Typical apphcations include chemical and food processing equipment, electrical components, and as a component to provide improved friction and wear in other resin systems. 

Exposure to gaseous and humid environments affects mechanical properties, friction, and wear of polymers. Synergistic effects between abrasion, wear, and corrosion result in amplified damage (59, 60). The dominant and synergistic influence of some factors may be noted as follows. 

Czichos, H., Introduction to Friction and Weary Chapter 1 in Friction and Wear of Polymer Composites , Ed. K. Freidrich, Elsevier, Holland 1986. 

Another area where it appears that rapid progress will be possible in the future is the friction and wear of polymer surfaces. This area is important in a number of practical applications ranging from the behavior of thin layers of polymers as lubricants for magnetic disk heads to the lifetime of polymer protective coatings for ship hulls affected by wear due to waterborne debris. In the related area of drag reduction, a currently dormant field, precise control of polymer surface structure or the use of slowly released soluble polymers, which might affect hydrodynamics, may offer new approaches. 

Friedrich, K. (1986b) Wear of reinforced polymers by different abrasive counterparts , in Friedrich, K. (Ed), Friction and Wear of Polymer Composites. Elsevier, Amsterdam, pp. 233-287. 

Figure 1 demonstrates a single-asperity sliding friction experiment as frequently used in studying friction and wear of polymers.Traditionally, the lateral friction force is supposed to be the result of an additive decomposition of the contribution of an adhesion- and a deformation-related component. It is proven that this suggestion is not tme by comparing experimental and computational results and using the polymer... 

K. Tanaka and Y. Uchiyrma, in Advances in Polymer Friction and Wear, Lieng-Huang Lee, ed.. Polymer Science and Technology, Vol. 5B, Plenum, New York, 1974. 

Lancaster, J.K. Friction and Wear of Plastics, Chapter 14 in Polymer Science edited by A.D. 

FIGURE 26.56 Log Abrasion loss by a blade (solid lines) and log cut growth rate (dashed hnes) of noncrystallizing rubber compounds as function of log frictional and log tearing energy, respectively isomerized natural rubber (NR), 2 styrene-butadiene rubber (SBR), and 3 acrylate-butadiene rubber (ABR). (From Champ, D.H., Southern, E., and Thomas, A.G., Advances in Polymer Friction and Wear, Lieng Huang Lee (ed.), Plenum, New York/London, 1974, p. 134.)... 

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