Tribology scratch behavior

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. 

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). 

Results showing the improved tribological behavior, as obtained in the annulus-on-disk tests, are documented in Fig. 13. The heights of the two bars represent, respectively, the number of scratches on the annuli and the wear... 

Mechanical protection of substrates is one of the most important applications of sol-gel coatings [31,32], and in the literature most of the works are related to enhancing the scratch and abrasion resistance of underlying substrates. Therefore, the mechanical robustness of the coating is vital for its tribological behavior. 

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. 

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