Tribological behavior polymers

We are pleased to present, in this volume, 26 reviewed and revised chapters from the symposium in six parts mechanisms of polymer wear controls of polymer wear tribological behaviors of polymers wear of biomaterials and polymer composites characterization and measurements of polymer wear and degradation and wear of polymeric films and filaments. 

Studies with a pin-on-disk apparatus have been performed to elucidate the tribological behavior of aramid-containing polymer composites. These studies include theoretical considerations and can serve as a directive on how to get information about tribological and wear properties in other related systems [63]. 

Similarly, the transfer film formation during sliding contact affects the tribological behavior of the polymers (Bahadur, 2000). In neat polyamide. 

I. Gofman, B. Zhang, W. Zang, Y. Zhang, G. Song, C. Chen, et al.. Specific features of creep and tribological behavior of polyimide-carbon nanotubes nanocomposite films Effect of the nanotubes functionalisation. Journal of Polymer Research, 20 (10), 1-9, 2013. 

Yilgor, E. Sinmazeelik, T. Yilgor, I., Modification of Polyolefins with Silicone Copolymers. II. Thermal, Mechanical and Tribological Behavior of PP and HDPE Blended with Silicone Copolymers. J. Appl. Polym. Sci. 2002,84, 535-540. 

With these complications in mind, research in this area has blossomed rapidly. Two main foci of research in this area are on (1) how external conditions (such as levels of loadings, the use of different indenters, and scratch rate) and (2) intrinsic materials properties (such as modulus and crystallinity) affect the tribological behaviors of the polymers. Apart from examining the scratch resistance of polymers, a closely related quantity which is of interest would be changes in coefficient of friction. Studies relating mechanical properties (3-5,9,36,71,75,76), deformation patterns (18,33,63,71,77-81), fabrication process (3,5,35,72,77,82-86) with respect to experimental parameters, snch as temperature (18), loading effect (24,71,72,87-96), indenter geometry (21,33,75,82,95,97), and scratch velocity (21,56,57,59,64,65,96,98) have been carried ont. In addition, scratch maps for different polymers have been produced (32,33), and various scratch resistance properties estimated (33,37,56,58,59,99). 

Evstatiev O, Oster F, Friedrich K and Fakirov S (2004) On the tribological behavior of microfibrillar reinforced composites from polycondensate-polyolefin blends, Int J Polym Mater 53 1071-1083. 

Polymers generally exhibit complex tribological behaviors due to different energy dissipation mechanisms, notably those induced by internal friction (chain movement), which is dependent on both time and temperature. Polymer friction is then governed by interfacial interactions and viscoelastic dissipation mechanisms that are operative in the interfacial region and also in the bulk, especially in the case of soft materials. Friction of a polymer can be closely linked to its molecular structure. The role of chain mobility has been studied in the case of elastomers, based on dissipation phenomena during adhesion and friction processes of the elastomer in contact with a silicon wafer covered by a grafted layer [1-5]. 

For other types of polymers, especially glassy polymers that exhibit a high stiffness at room temperatnre, the effect of the snbstrate chemistry on the tribological behavior can be different. For example, previons stndies have been performed on polystyrene (PS) samples sliding against both hydrophobic and hydrophilic wafers [28, 29]. 

The tribological behavior of this glassy polymer is thus completely different compared with PDMS elastomers. The influence of the substrate chanistry on the friction of PDMS and PS is very different. The effect of interface chemistry on friction is thus not so evident. The friction coefficient of hydrophilic and hydrophobic substrates can be identical or different, depending on the experimental conditions. Friction speed also plays a major role through its influence on polymer interfacial rheology, especially in the case of soft polymers. 

Xue Y, Wu W, Jacobs O aud Schadel B (2006) Tribological behavior of UHMWPE/HDPE blends reinforced with multi-wall carbon nanotubes, Polym Testing 25 221-229. 

X. Shao, W. Liu, Q. Xue (2004) The tribological behavior in micrometer and nanometer TiOj particle-filled poly(phthalazine ether sulfone ketone) composites, J. Appl. Polym. Sci. 92,906. 

C. J. Schwartz, S. Bahadur (2001) The role of filler deformability, filler-polymer bonding, and counterface material on the tribological behavior of polyphenylene sulfide (PPS), Near 751,1532. 

Lee, L.-H. (ed.), Polymer Wear and Its Control , ACS, Washington, DC, 1985. Mechanisms and control and measurement of polymer wear, tribological behavior of polymers, and the degradation of biomaterials, films and filaments are presented. 

Wang Q, Xue Q, Liu W and Chen J, Effect of nanometer SiC filler on the tribological behavior of PEEK under distilled water lubrication , J Appl Polym Sci 2000 78 609-14. 

Determination of scratch resistance is one of the most important aspects of tribology of materials, together with friction and wear. As discussed before [1 - 3], polymer tribology is much more difficult than that of metals. Due to the gradual replacement of metal parts by polymeric ones, the need to understand tribological behavior of polymers is increasing. 

Thus, fundamentally the interest is in testing the limits and theory of polymer behavior in end-tethered systems, e.g., viscoelastic behavior, wetting and surface energies, adhesion, shear forces relevant to tribology, etc. It should be noted that relevant surfaces and interfaces can also refer to polymers adsorbed in liquid-liquid, liquid-gas, solid-gas, and solid-liquid interfaces, which makes these polymer systems also of prime importance in interfacial science and colloidal phenomena (Fig. 2). Correspondingly, a wide number of potential applications can be enumerated ranging from lubrication and microelectronics to bioimplant surfaces. 

Pei XW, Xia YQ, Liu WM et al (2008) Polyectrolyte-grafted carbon nanotubes synthesis, reversible phase-transition behavior, and tribological properties as lubricemt additives. J Polym Sci Polym Chem 46 7225-7237... 

Q. Jia, S. Shan, Y. Wang and L. Gu, Tribological performance and thermal behavior of epoxy resin nanocomposites containing polyurethane and organoclay , Adv Polym Technol, 2008,27,859-64. 

Carbon-based polymer nano composites represent an interesting type of advanced materials with structural characteristics that allow them to be applied in a variety of fields. Functionalization of carbon nanomaterials provides homogeneous dispersion and strong interfacial interaction when they are incorporated into polymer matrices. These features confer superior properties to the polymer nanocomposites. This chapter focuses on nanodiamonds, carbon nanotubes and graphene due to their importance as reinforcement fillers in polymer nanocomposites. The most common methods of synthesis and functionalization of these carbon nanomaterials are explained and different techniques of nanocomposite preparation are briefly described. The performance achieved in polymers by the introduction of carbon nanofillers in the mechanical and tribological properties is highlighted, and the hardness and scratching behavior of the nanocomposites are also discussed. 

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