Wear-resistant effect other materials

Carbon blacks are the most widely used fillers for elastomers, especially vulcanised natural rubber. They cause an improvement in stiffness, they increase the tensile strength, and they can also enhance the wear resistance. Other particulate fillers of an inorganic nature, such as metal oxides, carbonates, and silicates, generally do not prove to be nearly so effective as carbon black. This filler, which comes in various grades, is prepared by heat treatment of some sort of organic material, and comes in very small particle sizes, i.e. from 15 to 100 nm. These particles retain some chemical reactivity, and function in part by chemical reaction with the rubber molecules. They thus contribute to the crosslinking of the final material. 

Finally, there is another category of lubricants, including the laminated materials, highly ordered organic mono-layers, and various thin solid hlms, which provides effective lubrication via their properties of low shear strength or high wear resistance. Lubrication via ordered molecular films and other solid lubricants, which have been considered by some investigators as a sub-discipline of boundary lubrication, will be discussed more specifically in Section 4. 

Improvement of scratch resistance is one more positive effect of improved crystalline stracture by nucleation." The ultra-high injection speed resulted in the highest surface strength and scratch resistance as compared with lower injection speeds. The high scratch resistance was related to the presence of highly oriented molecules and crystals and the increase in the amoimt of the P-phase crystals near the surface, which were formed at high injection speeds. Crystalhnity and the effective number of entanglements increase scratch resistance of polymer. In addition to the effect of nucleation, there may be other resons for improvement of the scratch resistance of polymeric materials, which include reinforcement of surface layers and reduction of friction coefficient and fiiction wear of the surface. 

In this section, the friction and wear of PTFE-based composites with different nano-scaled fillers are explicitly discussed. The friction coefficients of PTFE-based composites with different nanoscaled fillers differ with each other because of the dissimilar physical and chemical properties of different types of nanofiUers. However, despite the different nanofiller type and content, the variation of friction coefficient between PTFE-based composites and pure PTFE is evident under different experimental conditions. On the one hand, this is caused by the very low friction coefficient of pure PTFE so that a further decrease in friction coefficient becomes a formidable issue. On the other hand, due to the material nature of the nanofillers—for instance the lubrication property of nano-EG significantly lowers the friction coefficient of PTFE/nano-EG composites while friction coefficient of PTFE/nanoserpentine composites barely changes, which is greatly related to the material nature of the nanofillers. Conversely, a dramatic reduction in wear rate is observed in all PTFE-based composites. It is believed that the strong interfacial interaction, high shear strength, enhanced load capacity, and extra lubrication effect of PTFE-based composites with nanoscaled fillers are responsible for the improvement of wear resistance. However, the specific enhancement mechanism remains unsolved. 

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