Polytetrafluoroethylen fabrication techniques

Polytetrafluoroethylene is manufactured and sold in three forms granular, fine powder, and aqueous dispersion each requires a different fabrication technique. Granular resins are manufactured in a wide variety of grades to obtain a different balance between powder flows and end use properties (Fig. 1). Fine powders that are made by coagulating aqueous dispersions are also available in various grades. Differences in fine powder grades correspond to their usefiilness in specific applications and to the ease of fabrication. Aqueous dispersions are sold in latex form and are available in different grades. A variety of formulation techniques are used to tailor these dispersions for specific applications. 

Excitation sources for the production of radicals in grafting include chemicals, light, plasma, and radiation. Radiation-induced graft polymerization is superior to other grafting techniques because the high density of electron beams and gamma rays can create a large amount of radicals of arbitrary shapes of the p>olymer, such as a hollow fiber [2-41], nonwoven fabric [42] and film [43- ], and the quality of the polymer, such as polyethylene [2-41], polytetrafluoroethylene [42], and cellulose [55]. 

Copolymers of tetrafluoroethylene with hexafluoropropylene are truly thermoplastic polyper-fluoroolefms that can be fabricated by common techniques. Such copolymers soften at about 285 and have a continuous-use temperature of -260 C to +205 C. Their properties are similar to, though somewhat inferior to, polytetrafluoroethylene. 

Charnley develops the technique of low friction arthroplasty (LFA). Usirig polytetrafluoroethylene (PTFE) as the bearing material (Charnley 1961) implants were fabricated either by Charnley in his home workshop or in the machine shop at Wrightington and chemically sterilized. 

Fluoropolymers have evolved over six decades. New monomers have allowed the synthesis of new polymers with new methods of processing. Most newer perfluoropolymers have the same basic properties as polytetrafluoroethylene (PTFE) but they offer new methods of processing. These new techniques have greatly increased the range of parts that can be fabricated from fluoropolymers at reduced cost. Today, fluoropolymers are processed by methods almost identical to those used a half century ago as well as by state of the art molding technologies. 

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