PTFE polyamide materials

Keywords Block copolymers, Interface reactive injection moulding, Polyamide degradation, Polyolefine polyamide graft copolymers, PTFE polyamide materials... 

Upon dissolution of physical mixtiues (blends) of PTFE micropowders (without carboxylic acid groups) and PA-6 in formic acid, pure PTFE separates very fast from the solution. If the new melt-modified PTFE polyamide materials (PTFE irradiated 2,000 kGy) are dissolved in formic acid, the separation is very difficult. After separation of the insoluble content by centrifugation and ehmination of the soluble pure polyamide, the presence of an amide bond R1-CF2-CO-NH-CH2-PA between the PTFE and e.g. PA-6 was proved by IR spectroscopic investigations. The 1,708-cm band in the IR difference spectrum (Fig. 8 blue line) deriving from the direct PTFE polyamide linkage was in agreement with the IR spectra of low molecular model substances. 

The tribological investigation of the chemically bonded PTFE-PA materials shows that besides the low friction coefficients the high wear resistance is the most important property of such products. Examinations with several different PTFE polyamide materials certify this predicate. This phenomenon could be explained by the chemical coupling of the PTFE distributed in PA. The compati-bilisation of PTFE by block copolymer formation causes a better connection to the PA matrix as compared to physical blends. 

The following PTFE weight% to volume% relations demonstrate the composition conditions in PTFE polyamide materials ... 

Component parts with PTFE polyamide materials as the skin component and reinforced polyamides as the core materials made by sandwich moulding will lower the material and processing costs and reduce the amount of PTFE polyamide... 

Figure 16 shows the values for the tensile strength of the sandwich test specimen (skin component PTFE PA-6 with different contents of PTFE micropowder, core component reinforced PA-6 with 30% glass fibre). The tensile strength is mainly determined by the reinforced material, the PTFE polyamide material contributes only to a lesser degree. In a first approximation it is possible to calculate the skin content and the skin thickness. 

These new PTFE-PA materials can be processed without any problems on commercial processing equipment like twin-screw extruders and injectionmoulding machines. The specific adjustment of the melt viscosity could be realised through additives (lowering of MFI additive [10,18] increase of MFI acid-terminated oligoamides [9,10]). The new materials combine the good material properties of PTFE and polyamide with the processability of polyamide and are particularly well-suited for wear-resistant maintenance-free bearings. 

In all cases PTFE polyamide residues can be observed on the fracture surface of glass fibre-reinforced polyamide materials. These results are the basis to transfer... 

Fig. 15 Interface reactive two-component injection moulding - image of fractured specimen after tensile test, PTFE polyamide bulk material rai the ftucture surface of the polyamide material...

Most commonly used matrix materials for thermoplastic PMC in construction are polyolefinics (PE, PP), vinylic polymers (PVC, PTFE), polyamides (Nylons), polyacetals, polyphenylenes [polyphenylene sulfide (PPS)], polysulfone and poly-ether-ether-ketone (PEEK). All of these are discussed in the first part of this chapter and some of their characteristic properties are presented in Table 6.8. 

Uses of the polyamide-imides include pumps, valves, gear wheels, accessories for refrigeration plant and electronic components. Interesting materials may be made by blending the polymer with graphite and PTFE. This reduces the coefficient of friction from the already low figure of 0.2 (to steel) to as little as 0.02-0.08. 

The materials used in nonwoven fabrics include a single polyolefin, or a combination of polyolefins, such as polyethylene (PE), polypropylene (PP), polyamide (PA), poly(tetrafluoroethylene) (PTFE), polyvinylidine fluoride (PVdF), and poly(vinyl chloride) (PVC). Nonwoven fabrics have not, however, been able to compete with microporous films in lithium-ion cells. This is most probably because of the inadequate pore structure and difficulty in making thin (<25 /rm) nonwoven fabrics with acceptable physical properties. 

Polymeric materials for MF membranes cover a very wide range from relatively hydrophilic to very hydrophobic materials. Typical hydrophilic materials are polysulfone (PS), poly ether sulfone (PES), cellulose (CE) and cellulose acetate (CA), polyamide (PA), polyimide (PI), polyetherimide (PEI), and polycarbonate (PC). Typical hydrophobic materials are polyethylene (PE), polypropylene (PP), polytetra-fluoroethylene (PTFE, Teflon), and polyvinylidene fluoride (PYDF). 

Bag filters are traditionally used for very fine-particle collection. The filtering media are either woven textile or nonwoven paper or fiber mats. In the present case, the filtering media should be chosen in materials both compatible with the processed fluids (especially for antisolvent processes where the filter is contacted with SCF and organic solvents) and acceptable for drug manufacture. We currently tested various filter types woven or nonwoven polymer (like PTFE or polyamides) fibers to form bags or paper bags (as for vacuum cleaners), woven stainless-steel fibers to from a disk, or filter paper supported by a sintered disk at the bottom of a basket at a smaller scale ceramic filters can also be considered favorably. 

Polymeric membranes are prepared from a variety of materials using several different production techniques. Table 5 summarizes a partial list of the various polymer materials used in the manufacture of cross-flow filters for both MF and UF applications. For microfiltration applications, typically symmetric membranes are used. Examples include polyethylene, polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) membrane. These can be produced by stretching, molding and sintering finegrained and partially crystalline polymers. Polyester and polycarbonate membranes are made using irradiation and etching processes and polymers such as polypropylene, polyamide, cellulose acetate and polysulfone membranes are produced by the phase inversion process.f Jf f ... 

Further developments are still being made in membrane materials and membrane modules. There are reports, in particular, of hydrophobic membranes made of polyolefins, crosslinked polyolefins, polyamides, polyaramids, poly(vinylidene fluoride), PTFE, polyimides, and suchlike. 

Cotton, polyamide, polyester, glass fibre, aramids, carbon fibres, fluoro-polymer fibres (polytetrafiuoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene-tetrafluoroethylene (ETFE)) and metal wires can all be used as fibre materials. 

Commonly used natural fibres are cotton and silk, but also included are the regenerated cellulosic fibres (viscose rayon) these are widely used in non-implantable materials and healthcare/hygiene products. A wide variety of products and specific applications utilise the unique characteristics that synthetic fibres exhibit. Commonly used synthetic materials include polyester, polyamide, polytetrafluoroethylene (PTFE), polypropylene, carbon, glass, and so on. 

Polyamide is the most reactive material, losing its overall strength after only 2 years as a result of biodegradation, and PTFE is the least reactive, with polypropylene and polyester coming in bet ween. ... 

Figure 1.15 shows polyisobutylene, a vinylidene polymer with symmetric substitution, and thus without stereoisomers. Cis and trans isomers are possible in butenylene polymers. Two examples are at the bottom of Fig. 1.15. They are not interconvertable by rotating of the molecule. Shown in the figures are the trans isomers (). In the cis isomers the backbone chain continues on the same side of the double bond ( /). In Figs. 1.16 and 1.17 a series of vinyl and vinylidene polymers are shown. The above-mentioned PTFE, poly(vinyl butyral), and poly (methyl methacrylate) are given, starting in Fig. 1.17. Polyoxides are drawn at the bottom of Fig. 1.17, and the top of Fig. 1.18. Poly(ethylene terephthalate) and two aliphatic polyamides (nylon 6,6 and nylon 6) round out Fig. 1.18. The 20 polymers just looked at should serve as an initial list that must be extended many-fold during the course of study of thermal analysis of polymeric materials.

Polyvinyl alcohol was soon abandoned due to excessive ruptures. Polyamide and polyacrylonitrile were discovered to be biodegradable, although it took 12 to 24 months to occur. Thus polyethylene terephthalate (polyester) and polytetrafluorethylene (PTFE) became the polymers of choice. Both these materials have demonstrated their longevity as an implant. ... 

A variety of membrane materials have been tested for SILM preparation, including, among others, polymeric Nylon (hydrophilic polyamide) [57] and PTFE (hydrophobic polytetrafluoroethylene) [58], PES (hydrophiHc polyethersuUbne) [59,... 

In fact, all solvent-sensitive or soluble material will be either dissolved or swollen on exposure to the liquid adhesive the hard adhesive is, however, inert. Some thermoplastic m rials are unaffected by the liquid adhesives. These are Poly acetal. Polyethylene, Polypropylene, Nylon (polyamide) and Teflon (PTFE). 

Polyamide-imide powders may be compression-molded into standard shapes and geometries. This operation produces parts that may be used as is or further machined into intricate parts. The mechanical properties of compression-molded parts are somewhat less than those of the corresponding injection-molded grades. The tjtpical compression-molding operation uses a fine particle size of polyamide-imide powder. The powder material should have particles which are 100% less than 150 pm and 95% less than 75 pm. Polyamide-imide powders may also be used as an additive or adhesive binder in the sintering of other shapes based on PTFE powders, metal powders, or abrasive materials. 

The Swiss company, WW Fischer, offers PTFE (Teflon PTFE or Hostaflon), PBT (Celanex, Crastin, Ultradur or Valox) or PEEK (Victrex) insulator material options in its 405 series of cylindrical connectors according to the requirements of working temperature and other criteria. PEEK is an expensive polymer which tends to be employed when other materials fail to meet the specification requirements of the application. Other Fischer connector types use polyamide-imide (Torlon) or POM (Celcon, Delrin or Hostaform). Elastomeric seals used by Fischer in conjunction with their connectors are made from acrylonitrile-butadiene rubber (NBR N BUNA) or to MIL-P-25732, fluoroelastomer (FPM VITON), polychloroprene elastomer (CR Neoprene), ethylene-propylene diene elastomer (EPDM) and styrene-ethylene-butadiene-styrene thermoplastic elastomer (TPE-S or TPE-O) where each compound is followed by its trade name. Fischer s Swiss competitor, Lemo, manufactures a similar range of connectors including the Redel types which have a plastic body. 

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