Other Fluoroplastics

Polychlorotrifluoroethylene (PCTFE), according to one source, degrades upon ionizing irradiation in a similar fashion as PTFE at ambient and elevated 

The copolymer of ethylene and tetrafluoroethylene (ETFE) can be cross-linked by irradiationl Furfher improvemenf is achieved wifh fhe use of prorads, such as TAG or TAIC, in amounfs up fo 10%. 

The copolymer of ethylene and trichlorofluoroethylene (ECTFE) behaves upon irradiation like ETFE, including improvement of cross-linking efficiency with prorads. 

Polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF) cross-link upon irradiation, particularly with the use of prorads, such as TAG, TIAG, diallyl itaconate, ethylene bis-maleimide, and others.  

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Other Fluoroplastics Electron Beam Processing of Elastomers... 

FLUOROPLASTICS. These plastic materials may be placed into two convenient categories III fluorocarbon plastics, and (2) other fluoroplas-lies. Fluoroplastics are produced by free radical initiated polymerization or copolymerizaiion of the monomers. Fluorocarbon plastics contain no C-H bonds other fluoroplastics contain some C-H and/or C-CI bonds in the basic slructure. 

THV Fluoroplastic can be readily bonded to itself and to many plastics and elastomers and unlike other fluoroplastics does not require surface treatment, such as chemical etching or corona treatment. However, in some cases tie layers are required to achieve a good bonding to other materials.92... 

It has extremely low water vapor transmission, even with extruded thin transparent film. Chemical resistance is generally good, although not comparable to PTFE and other fluoroplastics. Chlorinated solvents, in particular, can affect PCTFE, and it can be subjected to stress cracking at elevated temperatures. The presence of chlorine atoms, used to enhance flame retardancy, keeps PCTFE in the non burning category with PTFE. It causes, however, a serious increase in dielectric losses, particularly at high frequencies. 

HTE fluoroplastic exhibits exceptional balance of tensile strength, good electrical properties, good resistance to permeation of vapors and fuels, as well as excellent chemical resistance. Because of its relatively low melting temperature, it is easy to process and can be processed on equipment without the high level of corrosion protection usually required by many other fluoroplastics. HTE is suitable for wire and cable insulation and for extruded Aims used for chemically resistant linings, release layers, and other applications. A summary of properties of the two current grades of HTE is shown in Table 3.13. 

One aspect of eluent compatibility with EC detection is that there should be no effect on the components of the detector. Detector cell bodies are now routinely constructed of PTFE, other fluoroplastics, glass or stainless steel, and seem stable to most eluents. Nevertheless electrodes are vulnerable to chemical attack. Problems with the longer term use of some eluents at potentials around +1 V vs Ag/AgCl have been experienced. For example, ammonium acetate buffers have caused flaking of the surface of glassy carbon electrodes held at as little as +0.1 V for one batch of electrodes. Noble metal electrodes are easily contaminated by a number of eluents unless the electrode is cleaned by pulsing the applied voltage as in carbohydrate analysis (Chapter 3, Section 6). 

PTFE does not melt like a true thermoplastic but sinters . As with other fluoroplastics, PTFE is relatively inert chemically. It is prepared for bonding by the techniques described in Chapter 6. 

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. 

The construction materials for the plates include most corrosion-resistant metals, usually 304SS, 316SS, titanium, Incoloy 825 , Hastelloy , and others, plus nonmetallic fused graphite, and fluoroplastic Diabon F . Typical gaskets between the plates include nitrile rubber, butyl, and EPDM elastromers, Hypalon and Viton , based on the various manufacturers literature. 

All fluoroplastics except polyietrafluiiruetliylune can be processed using melt techniques commonly applicable to thermoplastics. Processing temperatures are somewhat higher than normally used with other thermoplastics and corrosion-resistant equipment is required to resist the corrosive effects of the molten polymer,... 

TF1V has a unique combination of properties that include relatively low processing temperatures, bondability (to itself and other substrates), high flexibility, excellent clarity, low refractive index, and efficient electron-beam cross-linking.91 It also exhibits properties associated with fluoroplastics, namely, very good chemical resistance, weatherability, low friction, and low flammability. Typical properties of the dry grades are summarized in Table 3.9 and those of THV in aqueous dispersion form in Table 3.10. 

HFP — Hexafluoropropylene, a monomer used for the production of FEP and other copolymers, such as THY Fluoroplastic and fluorinated elastomers. 

The vulcanizates have a much-improved solvent resistance, especially to fuels and other hydrocarbons, compared with other silicone rubbers. They also retain their rather extreme low temperature flexibility and excellent high temperature resistance of silicones and fluoroplastics. Uses include seals and 0-rings for fuel pumps, aerospace applications, and underground use. 

This behavior results from stress relaxation and other viscoelastic phenomena that are typical of TPs. In addition to using heat TPs such as polyolefins, neoprenes, silicones, and other cross-linkable TPs are example of plastics that can be given memory either by radiation or by chemically curing. Fluoroplastics need no such curing. When this phenomenon of memory is applied to fluoroplastics such as TFE, FEP, ETFE, ECTFE, CTFE, and PVF, interesting and useful high-temperature or wear-resistant applications become possible. 

Chemical etching requires immersion of the part into a bath for a period of time, then rinsing and drying. This process is more expensive than most other surface treatments, such as flame treatment, thus it is used when other methods are not sufficiently effective. Fluoroplastics are often etched chemically because they do not respond to other treatments, ABS are usually etched for metallic plating, and so on. 

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