Blends with Fluoropolymers

PEEK and polytetrafluoroethylene (PTFE) are highly incompatible. However, fine PTFE powder is commonly added to PAEK to act as an internal lubricant in tribiological applications. The PTFE smears across the wear surface and reduces interfacial friction. This reduces interfacial forces and the heat build-up that can lead to failure by melting. PTFE is particularly suitable in applications where there is no external lubricant and the compounds are often reinforced with carbon fibre. PEEK can also be added to PTFE to improve the wear properties of PTFE - although other less expensive polymers can have similar effects. More recently PAEK and PTFE have been blended so as to produce melt-processable PTFE which has a number of interesting properties [24]. This is perhaps the most luilikely example of the use of PAEK to improve the melt-processability of an otherwise hard-to-process material. 

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PSF Blends with Fluoropolymers PSF/PPS/5-40 wt% PTEE fibrils processability, lubricity, anti-corrosive Bailleux etal., 1984... 

There are two main lines of work here one is improving the tribological properties of specific polymers. Blending with fluoropolymer [4], addition of inorganic filler [5 - 6] and y-radiating the surface [7] have been used to migitage wear and to lower friction. Another is the improved understanding of wear mechanisms in polymers. 

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. ... 

PPS and PEEK blended with a fluoro(co)-polymers and reinforced with either CF or GF were wear resistant with a short break-in period for forming a self lubricating film [Davies and Hatton, 1994]. Many commercial blends contain fluoropolymers (primarily PTFE) for the improved weatherability, wear and solvent resistance SUPEC — self-lubricating blend of crystalline PPS with PTFE and 30 wt% GF, Lubricomp blends from LNP and similar/JTP blends from RTP Co. (e.g., 15 wt% PTFE, 30 wt% GF and any of the following resins ABS, PA, PEST, PC, PE, PEI, POM, PP, PPE, PPS, PS, PSF, PVDF, SAN, TPU, PEEK, PES, etc.), Sumiploy from Sumitomo Chem. Co., etc. [Utracki, 1994]. 

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]. 

Size exclusion chromatography (SEC) of semicrystalline polyamides, polyesters with high melting point, and certain fluoropolymers is reviewed in this chapter. Because of their semicrystalline nature, polyamides are hard to dissolve in common chromatographic solvents. The SEC of nylons, or different types of polyamides with strong intermolecular H bonding, is reviewed based on the types of solvents in which they are soluble. These solvents are high-temperature m-cresol (neat or blended with other solvents), certain common solvents after trifluoroacetylation of the polymers, and fluorocarbon solvents, such as trifluoroethanol and hexafluoroisopropanol. The merits and limitations of each solvent systems are discussed here. 

The most common POM blends are homologous mixtures of POMs having different molecular structures (linear, branched, cross-linked) (Matsuzaki 1991), different molecular weights (Ishida and Sato 1970), or with different end groups (Nagasaki et al. 1991 Hanezawa and Ono 1991). On the secmid place are blends of POM with TPU, preferably polyester type. POMs are also blended with core-shell acrylic elastomers, MBS or MBA. Commercial blends of POM with PEST are available. To improve weatherability of POM, the resin was blended with PMMA and a fluoropolymer (viz. PTFE, PVF, PVDF) (Katsumata 1991). 

PPS and PEEK which blended with fluoro(co)polymers and reinforced with either CF or GF were wear resistant with a short break-in period for forming a self-lubricating film (Davies and Hatton 1994). Many commercial blends contain fluoropolymers (primarily PTFE) for the improved weatherability and wear and solvent resistance SUPEC - self-lubricating blend of crystalline PPS with... 

It is made by emulsion polymerization, spray-dried and sold as a fine particle powder. Pigment and fluoropolymer particles are separately dispersed in a solution of an acrylic copolymer compatible with PVdF, the two dispersions being blended to give the final paint. After application of paint, the coil is heated to 240-260 °C in 30-60 s, when the PVdF particles melt and lose their identify, forming a blend with the acrylic. 

Lubricants such as fluoropolymers [e.g., polytetrafluoroethylene (PTFE)], molybdenum disulfide, or graphite have also been blended with PEI polymers to achieve enhanced tribological properties, particularly improved lubricity, and reduced friction and wear. 

Trimethylsilyl-terminated siloxanes containing 4-20 fluoroaliphatic groups have been blended with acrylic fluoropolymers to form oilproofing and waterproofing emulsions for textiles [90,91]. 

It is interesting that the PEMA-PVdF blends are amorphous up to at least 50 wt % PVdF even though the Tg of the latter is 24°C. The crystallization of PVdF observed in the analogous PMMA blend does not occur under the same conditions with PEMA—PVdF. This suggests that there is a specific interaction between the fluoropolymer and the methacrylate polymer which is sufficient to "dissolve PVdF in the PMMA and PEMA, and that this specific interaction is superimposed on the conventional diluent-crystalline polymer interactions. The complexity of the rate processes involved with high molecular weight systems arising from molecular mobility makes it impossible to elucidate the nature of... 

Yi et al. reported a new type of PVDF membrane prepared by blending two very different polymers, a PVDF fluoropolymer such as Kynar with a sulfonated poly-electrolyte. The new membrane is inexpensive and displayed good performance and durability based on 1,000-h test data. 

Fluoropolymers are notoriously immiscible with any other polymer. Usually, they are dispersed in blends of engineering and specialty polymers either to improve processability or to induce lubricity and abrasion resistance. Examples of the PC/Specialty resin blends are listed in Table 1.68. 

In blends, fluoropolymers are used in small quantities to enhance throughput, reduce the frictional properties and increase the wear resistance. Blends comprising 0.3-50 wt% of a low molecular weight PTFE (T 350°C) with engineering resin showed improved anti-friction properties [Asai et al, 1991]. 

Another, more common commercial use of the phenomenon is the addition of fluoropoly-mers to polyolehns. In this case, a small amount of fluoropolymer progressively migrates to the die surface, reducing the die pressure drop and making it possible to extrude the resin at high throughput without the melt fracture. It has been shown that this approach also works for other polymers, viz. PEEK. Thus, blends of PEEK with polytetrafluoroethylene, 1-5 wt% PTFE, were extruded. The pressure drop across the die was reported to decrease with time to an equilibrium value, R.. The value of P,. depended on PTFE content, whereas the time to reach it depended on the rate of extrusion — the higher was the rate, the shorter was the saturation time [Chan et al., 1992]. 

Plastics find extensive use in several areas of fiber optic cables. Buffer tubes, usually extruded from high-performance plastics such as fluoropolymers, nylon, acetal resins, or polybutylene terephthalate (PBT) are used for sheathing optical fibers. A blend o PVC and ethylene vinyl acetate (EVA) polymer, such as Pantalast 1162 of Pantasote Incorporated, does not require a plasticizer, which helps the material maintain stability when in contact with water-proofing materials. PVC and elastomer blends, Carloy 6190 and 6178, of Cary Chemicals are also used for fiber optic applications (Stiffening rods for fiber optics are either pultruded epoxy and glass or steel. Around these is the outer jacketing, which is similar to conventional cable.)... 

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