Other Fluoropolymers

The polymerization of other fluoroolefins such as TFE with hexafluoropro-pylene (HFP), TFE with ethylene, and vinylidine difluoride - further demonstrates the broad applicability of liquid and supercritical CO in the production and processing of fluorinated polymers. Many of the aforementioned advantages associated with CO2, including tunable solvent properties, integrated synthesis, separation and purification processes, negligible chain transfer in the presence of highly electrophilic species, and relative ease of recycling, make it an ideal solvent for fluoroolefm polymerization. 

These include stability studies on l,l,l-tris(4-trifluorovinyl oxyphenyl), 2,2,2 trifluoroethone [32], perfluoro compounds [33] and fluorinated dioxolane [34]. 

Madorsky, Thermal Degradation of Organic Polymers, Polymer Reviews Volume 7, Wiley Interscience, New York, NY, USA, 1964. 

Minsker, S.V. Kolesov and G.E. Zaikov, Ageing and Stabilisation of Vinyl Chloride Based Polymers, Nauka, Moscow, Russia, 1982. [In Russian] 

Gladyshev, Y.A. Ershov and O. Shustova, Stabilisation of Thermostable Polymers, Khimiya, Moscow, Russia, 1979. [In Russian] 

Shimizu and M.J. Munson, Journal of Polymer Science Polymer Chemistry Edition, 1979, 17, 1991. 

Polyvinyl fluoride (PVF) is generally similar to PVC, but is transparent to UV radiation and therefore has excellent weathering resistance. It is used in laminates because of this property. Its brittle temperature is very low, - 165°C. 

Polychlorotrifluoroethylene, (PCTFE) is less crystalline and less inert than PTFE it can be shaped by normal thermoplastic melt processing methods. Because of its relative transparency, it finds limited use as observation windows (in sheet form), or as specialist tube material. 

Other fluoropolymers are produced in small quantities and for specific applications, including copolymers of ethylene with chlorotrifluoroethylene and TFE. 

---

High temperature resistance of ETEE and other fluoropolymers ia automotive fuels and their permeation resistance have been discussed (28,29). 

Because of its excekent combination of properties, processibkity, and relatively low price compared to other fluoropolymers, PVDF has become the largest volume fluoropolymer after PTFE consumption in the United States has grown from zero in 1960 to about 6200 metric tons in 1991 (186). About 49% of the consumed volume is PVDF modified by copolymerization with 5—12-wt % HFP to enhance flexibkity. In 1992, Hst price for homopolymer powders was 15.32/kg, and for pekets 15.42/kg the reported market price was 14.09—14.22/kg (187). In the United States, almost ak PVDF is suppHed by Ausimont USA, Inc., Elf Atochem North America, Inc., and Solvay Polymers, Inc. Ausimont and Elf Atochem are producers Solvay is an importer of the resin. Smak amounts of resin are imported from Germany by Huls America, Inc, and from Japan by Kureha Chemical Industry Co., Ltd. PVDE producers and their trademarks are Hsted in Table 4. 

In addition to the fluoroplastics and fluororubbers already described other fluoropolymers have been marketed. Polymers of hexafluoropropylene oxide are marketed by Du Pont (Krytox). These materials have a low molecular weight (2000-7000) and are either oils or greases. The oils are uses as lubricants, heat transfer fluids and non-flammable oils for diffusion pumps. The greases are also used as lubricants. They have good heat and oil resistance but it is said that explosions may result from contact with the surfaces aluminium or magnesium cuttings. 

Nonstickiness, low friction, low wettability, and high thermal- and chemical-resistance are the major properties of PTFE, which was accidentally discovered in the DuPont laboratories in 1938, and these properties are more or less typical of other fluoropolymers that have been developed since. 

Thus, the strong C—F bond, the special arrangement of atoms in macromolecule, and low surface energy impart some unique physical properties to PTFE and other fluoropolymers high chemical and thermal resistance, nonstick character, low friction coefficient, and low wettability. This combination of properties... 

Like many other fluoropolymers, Nafion is quite resistant to chemical attack, but the presence of its strong perfluorosulfonic acid groups imparts many of its desirable properties as a proton exchange membrane. Fine dispersions (sometimes incorrectly called solutions) can be generated with alcohol/water treatments. Such dispersions are often critical for the generation of the catalyst electrode structure and the MEAs. Films prepared by simply drying these dispersions are often called recast Nafion, and it is often not realized that its morphology and physical behavior are much different from those of the extruded, more crystalline form. 

When enhanced temperature resistance is required, polyvinylidene fluoride or other fluoropolymers are used. Fluoropolymers have the advantage of being oil resistant and flame retardant, but are also more expensive base materials. PVDF is one of the materials that is very easy to cross-link by EB radiation. 

Storage vessels are commonly constructed of steel lined with lead, PVDF (and certain other fluoropolymers) or glass. If the bromine is dry" then nickel or alloys such as Monel and Hastelloy can be used though all are susceptible to severe attack in the presence of wet bromine. Titanium is unsuitable for bromine duty (wet or dry) and should be avoided. 

Telechelic (or a, co-difunctional) oligomers exhibit functional groups at both ends of the oligomeric backbone. These compounds are quite useful precursors for well defined architectured polymers (e.g. polycondensates, polyadducts and other fluoropolymers previously reviewed [400, 401]). As mentioned above, a... 

PCTFE is highly suitable for applications at extremely low temperatures however, at elevated temperatures it is inferior to other fluoropolymers with the exception of... 

PCTFE. Very little work was done on the effects of radiation on PCTFE but it is known that its resistance to radiation is superior to that of other fluoropolymers.34... 

TFE — Tetrafluoroethylene, a perfluorinated monomer used as a feedstock for the production of PTFE and as a comonomer for the production of a variety of other fluoropolymers. 

Valuable information for future plications to other fluoropolymers or other copolymers can be obtained from such comparisons. For example, the energy location of C-F and bottom of C-C peaks is found to be constant in each spectrum (C-F = 40eV, bottom of C-C = 20eV). A possible use of those peaks is to act... 

In injection molding, THV is processed at lower temperatures than other fluoropolymers, typically at 200°C to 300°C (392°F to 572°F) with mold temperatures being 60°C to 100°C (140°F to 212°F). Generally, standard injection molding equipment is used [41]. 

---