Fluoropolymers thermoplastic

Following the discovery of TFE homopolymerization by Dr Roy Plunkett, the commercial development of PTFE required enormous effort Among the major obstacles that had to be overcome were the explosion hazard associated with TFE handling, its tendency to form extremely dai erous polymeric peroxides and the requlr ents for specialized processing techniques This effort, coming as it did in the midst of the second World War, not only occupied all available resources, but strongly Inhibited the normal Inclination to search for alternative solutions to the problem of polymer intractability. 

Molecular Weight Crystalline Melting Points Melt Viscosity (372°C) 

One theoretical possibility, of course, is to break up crystallinity just enough to permit chain entanglements to substitute for interchain forces as the mechanism for generating adequate toughness This substitution should then permit reduction both in molecular weight and in melt viscosity to levels which would allow conventional melt processing In the late 1940 s the only olefin known that could be introduced into the PTFE structure to disrupt crystallinity without loss of the perfluorocarbon composition was hexafluoropropylene (HFP). 

Fortunately for its commercial prospects, HFP could be synthesized by the same basic route as was used for TFE. That is, the pyrolysis of CF2HCI to difluorocarbene, followed by dimerization to TFE, could be conducted in such a way as to force addition of CF2 to TFE giving, not perfluorocyclopropane, but its rearranged isomer, HFP. While this looks simple on paper, the reader should contemplate the problems associated with removal from HFP of the dozens of impurities formed in the 800°C pyrolysis step. 

In the case of TFE homopolymers, the extremely high molecular weight renders the fate and nature of end groups for all practical purposes a moot point. This is not the case with the lower molecular weight FEP polymers. Attempts to injection mold or extrude as-synthesized polymers result in excessive gas evolution. Not only this, but the gas, being a mixture of CO2 and HF could result in serious corrosion and environmental problems. 

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The carbon chain is in a planar zigzag orientation and forms an orthorhombic lattice with interpenetration of adjacent chains.61 As a result of this structure, ETFE has an exceptionally low creep, high tensile strength, and high modulus compared to other thermoplastic fluoropolymers. Interchain forces hold this matrix until the alpha transition occurs at about 110°C (230°F), where the physical properties of ETFE begin to decline and more closely resemble perfluoropolymers properties at the same temperature. Other transitions occur at -120°C (-184°F) (gamma) and about -25°C (-13°F) (beta).62... 

PVDF is correctly named poly(l,l-difluoroethylene) and represented by (-CF2CH2-)n- It is a hard, tough thermoplastic fluoropolymer. PVDF is prepared by free-radical initiated polymerization, either in suspension or (usually) in emulsion systems. The basic raw material for PVDF is vinylidene fluoride (CH2=CF2), a preferred synthesis of which is dehydrochlorination of chlorodifluoroethane. 

Coating is one of the important uses of fluoropolymers, since it enables them to exhibit their characteristics on the surface of a substrate. Some of the conventional fluoropolymers such as polytetrafluoroethylene [9002-84-0] (PTFE), tetrafluo-roethylene-hexafluoropropylene copolymer [25067-11-2] (FEP), and ethylene-tetrafiuoroethylene copolymer [25038-71-5] (ETFE) have been used as antistick or anticorrosive coatings. Only poly(vinylidene fluoride) [9002-58-1] (PVDF) has so far been used in paints. The major difficulties in employing thermoplastic fluoropolymers in paints and coatings result from their poor solubility in organic solvents and... 

Coatings with Thermoplastic Fluoropolymers. Poly(vinylidene fluoride), PVDF, is the only conventional thermoplastic fluoropolymer that is used as a commercial product for weather-resistant paints. This crystalline polymer is composed of -CHjCFj- repeating units it is soluble in highly polar solvents such as dimethyl-formamide or dimethylacetamide. Poly(vinylidene fluoride) is usually blended with 20 30 wt% of an acrylic resin such as poly(methyl methacrylate) to improve melt flow behavior at the baking temperature and substrate adhesion. The blended polymer is dispersed in a latent solvent (e.g., isophorone, propylene carbonate, dimethyl phthalate). The dispersion is applied to a substrate and baked at ca. 300 °C for ca. 40-70 s. The weather resistance of the paints exceeds 20 years [2.16]-[2.18]. 

Poly(vinylidene fluoride) (PVDF) has been recently tested as the base polymer in ionic liquid (IL)-based PIMs [13-15]. PVDF is a thermoplastic fluoropolymer with high hydrophobicity, good chemical resistance, and excellent thamal and mechanical stability making it attractive as a base polymer for PIMs. 

Korton Thermoplastic fluoropolymer alloy Norton Performance Plast. 

FRP piping lined with fluoropolymer is manufactured by forming FRP over a fluoropolymer tube. The resulting structure is a called a dual laminate. Typically, this tube is a thermoplastic fluoropolymer such as PFA or FEP so that glass fabric can be readily embedded in its outer wall. This fabric bonds with the FRP structure so that the lining is held firmly in place. 

The thermoplastic fluoropolymers also can be applied as coatings or linings by powder coating and rotational lining. Both processes can provide relatively thick, void-free fluoropolymer layers compared with coatings that can be achieved with PTFE dispersions. 

Thermoplastic fluoropolymers are also used in this way to line vessels. Compared with PTFE, they are easier to weld, and unlike PTFE, they can be readily... 

For the thermoplastic fluoropolymers, rotolining is proving to be a reliable and versatile method for lining complex parts. The need to eliminate flanged connections wherever possible is increasing interest in dual laminate constructions that permit welding of joints. 

High-performance engineering thermoplastics Fluoropolymers (PTFE, FEP, PVDF), liquid crystal polymers (LCP), polyphenylene oxides or ethers (PPO, PPE), aromatic polyketones (PEEK, PAEK), polyphenylene sulphides (PPS), polysulphones (PSU), polyether sulphones (PES), polyamideimides (PAI), polyetherimides (PEI), polyimides (TPI). 

Examples of thermoplastic coatings an fluoropolymers, eg. Teflon or polyamides, eg, nylon. Thermosetting coatings are more resistant to ... 

Non-Metallic Materials Numerous engineering thermoplastics have been commercialised including materials such as polyetherether ketone (PEEK) and polyether sulphate (PES) with much improved thermal/chemical resistance. The usage of FRP equipment has increased, and fluoropolymer lining technology/applications have come of age. Of particular interest is the development of stoved, fluoropolymer coating systems for process industry equipment. 

This research was an attempt to develop new polymers with the mechanical properties of polyarylene ethers and the dielectric properties of fluoropolymers. After initially testing the viability of the [2n+ 2n] cyclodimerization reaction for preparing high-molecular-weight polymers and testing the dielectric properties of these polymers, two polymers (one thermoplastic and one thermoset) were prepared in larger quantities to evaluate the thermal and mechanical performance of these novel compositions. The high Te thermoset was also quantitatively tested for thermal/oxidative stability. 

As shown in Figure 2.33, polyethylene has the highest consumption (nearly 60%) in both thermoplastic and thermoset (PEX) forms, and also foamed PE (2%). PVC is second (roughly 30%) and the others are polypropylene,TPEs, polyamide, fluoropolymers. .. 

The tensile moduli (see Figure 4.87(c)) of some fluoropolymers are in the same range as common structural thermoplastics and the others are flexible with moduli similar to LDPE. 

PVC, another widely used polymer for wire and cable insulation, crosslinks under irradiation in an inert atmosphere. When irradiated in air, scission predominates.To make cross-linking dominant, multifunctional monomers, such as trifunctional acrylates and methacrylates, must be added. Fluoropolymers, such as copol5miers of ethylene and tetrafluoroethylene (ETFE), or polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), are widely used in wire and cable insulations. They are relatively easy to process and have excellent chemical and thermal resistance, but tend to creep, crack, and possess low mechanical stress at temperatures near their melting points. Radiation has been found to improve their mechanical properties and crack resistance. Ethylene propylene rubber (EPR) has also been used for wire and cable insulation. When blended with thermoplastic polyefins, such as low density polyethylene (LDPE), its processibility improves significantly. The typical addition of LDPE is 10%. Ethylene propylene copolymers and terpolymers with high PE content can be cross-linked by irradiation. ... 

Multilayer sheets containing poly(chlorotrifluoroethylene) and COC for blister packaging applications have been described (63). In the production of the multilayered film, the fluoropolymer layer is joined with the thermoplastic polymer layer and an adhesive tie layer. 

Fluoropolymers. These form one of our oldest and most spectacular families of engineering plastics. Polytetrafluoroethylene was developed by DuPont over two decades ago, and more recently by Allied Chemical, Hoechst, ICI, Pennwalt, and other manufacturers as well. It combines unusually low adhesion and friction, high temperature and flame resistance, excellent electrical properties, and extreme chemical inertness. Its high melting point and melt viscosity make thermoplastic processing extremely difficult, so that many... 

Poly(vinylidene fluoride) (PVDF) is the second most important thermoplastic within the fluoropolymer family after PTFE. Although, both the thermal and chemical stability of PVDF are somewhat lower compared to PTFE, the hydrogenated polymer can be more easily processed with conventional equipment, and it offers an advantageous compromise between quality and price. When the... 

When the relation between D and M is established, we can easily convert G(D) obtained by dynamic LLS into a differential molecular weight distribution, such as fw(M). We have successfully applied the above methods to various kinds of polymeric and colloidal systems, such as for Kevlar [15, 23], fluoropolymers (Tefzel Teflon) [12,30-35,52], epoxy [53-55],polyethylene [56,57], water-soluble polymers [18,50-51,58,59], copolymers [60-62], thermoplastics [63-65] and colloids [66-72]. Three of those applications are illustrated below. 

During the last two decades, many special fluoropolymers have been developed, such as fluorosilicones fluorinated polyurethanes fluorinated thermoplastic elas-... 

The most common polymers used in FR wire and cable applications are PVC, polyolefins, fluoropolymers, and silicone polymers. Thermoplastic polyurethanes (TPUs) and other specialty polymers such as chlorosulfonated polyethylene also serve niche applications in wire and cable. The approaches to achieve flame retardancy in each of these polymer systems along with issues unique to wire and cable application are discussed in the following sections. 

Thermoplastic materials often have a lower surface energy than do thermosetting materials. Thus, physical or chemical modification of the surface is necessary to achieve acceptable bonding. This is especially true of the crystalline thermoplastics such as polyolefins, linear polyesters, and fluoropolymers. Methods used to increase the surface energy and improve wettability and adhesion include... 

Details about the basic chemistry and polymerization methods are inclnded in Chapter 2 fnndamental properties of the resulting prodncts are discnssed in Chapter 3, and processing and applications of thermoplastics in Chapter 4. Becanse flno-roelastomers and aqueous systems have specific and different technologies from other commercial fluoropolymers, they are discussed in Chapters 5 and 6, respectively. 

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