Fluoropolymers wear rate

Coefficient of friction is inversely proportional to pressure and proportional to velocity. Wear rate of fluoropolymers is proportional to load (/ ) and velocity (V). Combinations of pressure and velocity are defined where the material can be used, thus a FV limit is defined. Above this PV limit, the wear increases exponentially because of the heat that is generated as a result of motion. Generally, a polymer or its compounds can be characterized by PV limit, deformation under load, and wear factor. Wear factor or specific wear rate is defined as the volume of material worn away per unit of sliding distance and per unit of load. 

The thermo/radiation degraded PTFE-micropowders are mostly used as additives to plastics, inks, oils, lubricants, and coatings to import fluoropolymer-like properties such as reduced wear rates and friction. 

Fluoropolymers have outstanding chemical resistance, low coefficient of friction, low dielectric constant, high purity, and broad use temperatures. Most of these properties are enhanced with an increase in the fluorine content of the polymers. For example, polytetrafluoroethylene, which contains four fluorine atoms per repeat unit, has superior properties compared to polyvinylidene fluoride, which has two fluorine atoms for each repeat unit. Generally, these plastics are mechanically weaker than engineering polymers. Their relatively low values of tensile strength, deformation under load or creep, and wear rate require the use of fillers and special design strategies. 

FIGURE 13.8 Effect of PTFE on wear rate. (Adapted from Lubricomp Internally lubricated reinforced thermoplastics and fluoropolymer composites, LNP Bulletin, 254-691.)... 

Braiding - The name of the process in which fluo-ropolymer tubes, wires, and cables are reinforced. Strands of metal and plastic and other thin wire shape materials are formed into braids and wrapped around the fluoropolymer tube or wire to improve pressure rating, and wear and puncture resistance. 

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