Fillers tribological properties

In the last two decades, polymer nanocomposites have attracted the interest of researchers and industries because of their excellent mechanical, physical and tribological properties. The addition of nanosize inorganic fillers like clay, Al Oj, CaCOj, TiOj, ZnO and SiO has altered the mechanical and physical properties of the polymers significantly, and in general the nanocomposites are superior to virgin polymers in many aspects. 

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. 

Thongsang S, Vorakhan W, Wimolmala E, Sombatsompop N (2012) Dynamic mechanical analysis and tribological properties of NR vulcanizates with fly ash/precipitated silica hybrid filler. Tribol Int 53 134... 

Tribological properties of polymer-based composites with nanoscaled fillers... 

PTFE powders were applied as an additional filler together with micron size CuS particles or SiC nanoparticles, respectively, in a PEEK matrix. 1 vo opposite trends were observed. In the former case, the addition of PTFE contributed to a reduction of both the wear rate and the frictional coefficient. However, in the latter case, PTFE brought a negative effect to the tribological properties, which was believed by the authors to be due to a chemical reaction between the SiC nanoparticles and the PTFE. 

J. Wang, M. Gu, S. Bai, S. Ge (2003) Investigation of the influence of MoSj filler on the tribological properties of carbon fiber reinforced nylon 1010 composites. Wear 255,774. 

There are two main lines of work here one is improving the tribological properties of specific polymers. Blending with fluoropolymer [4], addition of inorganic filler [5 - 6] and y-radiating the surface [7] have been used to migitage wear and to lower friction. Another is the improved understanding of wear mechanisms in polymers. 

Surface Property Modifiers with further division into a) solid lubricants/tribological additives that include molybdenite, graphite, PTFE and boron nitride and b) antiblocking fillers such as silica. Chapter 19. 

Friction and wear properties Both friction and wear belong to the discipline of tribology. Friction is the force of two surfaces in contact or the force of a medium acting on a moving object, and wear is the erosion of material from a solid surface by the action of another solid. Factors that exert influence on friction and wear characteristics of polymer composites are the particle size, morphology, and concentration of the filler [38]. 

Improvement in wear is frequently cited as a motivation for current composite research in UHMWPE for orthopedic implants [43, 44, 47—51]. Thus far, the use of fillers alone has not proven effective in reducing the wear rate of UHMWPE by an order of magnitude, as has been observed with extensive radiation crossfinking. Whereas conventional UHMWPE may have been the state of the art when early research on UHMWPE composites was initiated, today UHMWPE matrix composites need to demonstrate superior properties when compared with unfilled radiation crosshnked materials. Because the tribology of UHMWPE in artificial joints is strongly dependent on the kinematics and lubricant, additional research is needed to fuUy characterize the biotribological behavior of UHMWPE micro- and nanocomposites for specific orthopedic bearing applications. 

---