Processing of fluoropolymers

This chapter contains information about safe processing of fluoropolymers and safe handling of parts made from these plastics. The material in this chapter is in no way intended as a replacement for the specific information and data supplied by the manufacturers of fluoropolymer resins and parts. A source of information that is frequently referenced in this chapter is The Guide to Safe Handling of Fluoropolymers Resins, published by The Society of Plastics Industry, Inc. Disposal and recycling issues are also reviewed. 

Filled or compounded resins contain pigments, surfactants, and other additives to modify the plastic properties. These additives are likely to present risks and hazards in the processing of fluoropolymer compounds. For example, aqueous dispersions of fluoropolymers contain surfactants that may produce... 

Repro - This is short for reprocessed and is applicable to a great variety of scrap generated during processing of fluoropolymers. Scrap materials are treated in multiple step processes using acids and heat for purification. Afterwards they are ground, sized, and consumed. A number of key properties of fluoropolymers decline as a result of purification process. 

For practical purposes there are eight types of fluoropolymers, as summarized in Table F.7. Included in this family of plastics are polytetrafluoroethylene (FIFE), polychlorotrifluoroethylene (PCTFE), polyvinyl fluoride (PVF), fluorinated ethylene propylene (FEP), and others. Depending on which of the fluoropolymers are used, they can be produced as molding materials, extrusion materials, dispersion, film, or tape. Processing of fluoropolymers requires adequate ventilation for the toxic gases (HF) that may be produced. 

Emulsifier Recovery/Removal from Fluoropolymer Dispersions Fluo-ropolymer dispersions contain all of the fiuorinated emulsifier used during the polymerization step unless a part of it is lost during workup (e.g., up-concentration) and stabilization with nonionic nonfluorinated emulsifiers. In any event, some fiuorinated emulsifier always remains in the dispersion, as all of these steps cannot remove the fiuorinated emulsifier completely, even if they are applied several times, for example, by up-concentration via ultrafiltration with repeated dilution of the up-concentrated dispersion [26]. Although further processing of fluoropolymer dispersions usually destroys the bulk of the fiuorinated emulsifier, it is desirable to recover and reuse the expensive polymerization aid completely while keeping or even improving the quality of the dispersions. 

Part Three describes the properties, characteristics, and applications of fluoropolymers. The reader involved in the processing of fluoropolymers is advised to carefully study the safety issues and disposal methods of fluoropolymers. In this book, Ch. 17, Safety,... 

Production of hydrogen fluoride from reaction of Cap2 with sulfuric acid is the largest user of fluorspar and accounts for approximately 60—65% of total U.S. consumption. The principal uses of hydrogen fluoride are ia the manufacture of aluminum fluoride and synthetic cryoHte for the Hall aluminum process and fluoropolymers and chlorofluorocarbons that are used as refrigerants, solvents, aerosols (qv), and ia plastics. Because of the concern that chlorofluorocarbons cause upper atmosphere ozone depletion, these compounds are being replaced by hydrochlorofluorocarbons and hydrofluorocarbons. 

Another impetus to expansion of this field was the advent of World War 11 and the development of the atomic bomb. The desired isotope of uranium, in the form of UF was prepared by a gaseous diffusion separation process of the mixed isotopes (see Fluorine). UF is extremely reactive and required contact with inert organic materials as process seals and greases. The wartime Manhattan Project successfully developed a family of stable materials for UF service. These early materials later evolved into the current fluorochemical and fluoropolymer materials industry. A detailed description of the fluorine research performed on the Manhattan Project has been pubUshed (2). 

A PET oligomer isolation method has utilised chloroform extraction in a Parr bomb lined with a Teflon-TFE fluoro-carbon resin [40]. The analytics of fluoropolymer processing aids (combustion analysis, XRF, EUR, 19F NMR, OM) have recently been described [29]. Combustion analysis (Parr Oxygen Bomb Calorimeter) can be used for quantitative analysis... 

PA-FTIR, IR, TLC, NMR, potentiometry and chemiluminescence [486], Analysis of fluoropolymer-based processing aids with a specific ion (F-) analyser can be carried out within 15 min per sample [29]. 

Electrochemical corrosion processes also include a number of processes in organic chemistry, involving the reduction of various compounds by metals or metal amalgams. A typical example is the electrochemical carbonization of fluoropolymers mentioned on p. 316. These processes, that are often described as purely chemical reductions, can be explained relatively easily on the basis of diagrams of the anodic and cathodic polarization curves of the type shown in Fig. 5.54. 

Poor solubility in most common organic solvents represents an inherent problem in the synthesis and processing of many high molar mass fluoropolymers. In fact, CFCs and carbon dioxide are the best solvents for amorphous varieties of fluoropolymers. Due to the environmental problems associated with CFCs, the international community is seeking to replace them with more benign compounds such as hydrochlorofluorocarbons and hydrofluorocarbons. However, the environmental problems which will be created by the use of these replacement compounds such as the accumulation of trifluoroacetic acid in the atmosphere clouds this issue [71], Carbon dioxide presents an ideal inert solvent to effect the polymerization of these types of highly fluorinated monomers and obviates the use of solvents that are being phased out because of environmental concerns. 

The direct fluorination of inorganic,1,2 organometallic,3 5 and organic compounds,6-8 employing the LaMar9,10 and Exfluor-Lagow" methods, has impacted the synthesis of fluorinated compounds over the past 25 years. Among the most important applications of direct fluorination are the synthesis of fluoropolymers from hydrocarbon polymers and the conversion of the surface of the hydrocarbon polymers to fluoropolymer surfaces.12,13 The direct fluorination process is an excellent approach to the synthesis of fluoropolymers. 

Uses Organic synthesis vapor degreasing and cold cleaning solvent for fabricated metal parts textile processing aerosol propellants synthesis of fluoropolymers production of various coatings and inks may be ingredient in adhesives, cutting oils, and aerosol formulations pesticide. 

Cross-linkable polymers used for wire and cable insulations are polyolefins, certain fluoropolymers, and elastomers. Among these, radiation cross-linked polyethylene is the most widely used. The radiation cross-linking process of PE has also been the most widely studied. ... 

The Processing of PTFE Coagulated Dispersion Powders, Technical Service Note F3/4/5, 4th ed., ICI Fluoropolymers, Imperial Chemical Industries PLC, Blackpool, Lancs, U.K., p. 18 (1992). 

---