## 2 The Development of the Fluoropolymer Industry from 1930s \(\sim\) 1990s
### 1960s
#### 1970s  
After discovering that ethylene has good copolymerization properties with fluorinated monomers, many new fluoropolymers were developed to achieve more favorable application properties. The first fluoropolymer containing ethylene units was ECTFE, which was introduced to the market by the Italian company Ausimont in 1970. ECTFE is an alternating copolymer of ethylene and CTFE (Figure 7). ECTFE is prepared by the copolymerization of ethylene and CTFE at relatively low temperatures (\(<\)10 \({}^{\circ}\)C) in an aqueous medium using a peroxide catalyst and a halogenated solvent chain transfer agent to regulate the molecular weight [28]. ECTFE polymer chains pack in an extended zigzag confirmation, which results in a crystallinity of 50%-60%. ECTFE has a melting temperature in the range of 220-245 \({}^{\circ}\)C depending on the polymerization methods. ECTFE can be used over a broad temperature range from -100 \({}^{\circ}\)C to 150\({}^{\circ}\). ECTFE can be processed by the standard processing methods for traditional thermoplastics in the range of 260-300 \({}^{\circ}\)C. It is readily converted into fibers, filaments, films, sheets, and wire and cable insulation. Noticeably, the molten ECTFE is corrosive and special corrosion-resistant steels are used for screw and barrel components. As the copolymer with ethylene, ECTFE has moderate chemical resistance, flame resistance, and dielectric constant (2.6). While, it still has excellent radiation resistance, weathering resistance, and barrier properties, as well as good tensile, flexural and wear-related properties. The strength, wear resistance and creep resistance of ECTFE are significantly greater than that of PTFE and FEP. ECTFE film is the most abrasion resistant and highest tensile strength fluoropolymer film available. The single largest use of ECTFE is the flame-resistant insulation for wire and cable applications, extensively used for aircraft, mass transit and automotive wiring. ECTFE also finds applications in chemical process equipments and components. ECTFE is used in aerospace applications, such as gaskets for liquid oxygen and other propellants, components for spacecraft and aircraft cabins, convoluted tubing, abrasion resistant braid and hose for expandable conduit for space suits. At the end of 1999, Ausimont introduced a new family of ECTFE resins under the trademark Vatar, specifically designed to meet the requirements for plenum cable applications. ETCFE is currently manufactured by Solvay under the trademark Halar after acquiring Ausimont in 2002. Figure 8: The preparation of PFA. Figure 7: The preparation of ECTFE. After the introduction of FEP, further research on TFE copolymers led to the development of PFA (Figure 8)--a copolymer of TFE and perfluoropropylvinylether (PPVE), which was introduced in 1972 by DuPont. Generally, PFA is prepared by an aqueous dispersion process. The copolymerization must be controlled carefully to produce a uniform copolymer with the required molecular weight and polydispersity [29, 30]. Due to the PPVE units in the polymer main chain, PFA has lower crystallinity compared to PTFE. Correspondingly, PFA has a lower melting temperature (305-310 \({}^{\circ}\)C), lower melt viscosity and better processability. This improvement for PTFE dramatically enlarged its market by lowering the processing cost and enriched the available product categories by the flexibility of thermoplastic processing. PFA shows comparable mechanical properties as FEP below 200 \({}^{\circ}\)C, and performs comparable mechanical properties as PTFE above 200 \({}^{\circ}\)C. The thermal stability of PFA is almost the same as that of PTFE and better than that of FEP. PFA has the same chemical resistance, flame resistance and radiation resistance as PTFE. The electrical properties of PFA and PTFE are similar. Importantly, PFA thin films have better transparency compared to PTFE. PFA can be processed by conventional melt techniques such as extrusion, injection molding and rotational molding.