Modified Polytetrafluoroethylene

Heitz J, Svorcik V, Bacakova L, Rockova K, Ratajova E, Gumpenherger T, et al. Cell adhesion on polytetrafluoroethylene modified by UV-irradiation in an ammonia atmosphere. J Biomed Mater Res A 2003 67 130-7. 

Figure 29. Fiuman osteoblast-like MG 63 cells in cultures on material surfaces modified with carbon nanoparticles. A fullerene Cgo layers deposited on carbon fibre-reinforced carbon composites (CFRC), B fullerene C o layers deposited on microscopic glass coverslips, C terpolymer of polytetrafluoroethylene, polyvinyldifluoride and polypropylene, mixed with 4% of single-wall carbon nanohorns, D the same terpolymer with high crystalline electric arc multi-wall nanotubes, E diamond layer with hierarchically organized micro- and nanostmcture deposited on a Si substrate, F nanocrystalline diamond layer on a Si substrate. Standard control cell culture substrates were represented by a PS culture dish (G) and microscopic glass coverslip (FI). Immunofluorescence staining on day 2 (A) or 3 (B-Fl) after seeding, Olympus epifluorescence microscope IX 50, digital camera DP 70, obj. 20x, bar 100 pm (A, C, D, G,H)or 200 pm (B, E, F) [16].

Combination Methods. Combination methods refer to those methods that employ both concentration and isolation methodologies. The modified parfait-distillation method that was evaluated used a series of adsorbents coupled with vacuum distillation to recover unadsorbed solutes (11). Porous polytetrafluoroethylene (PTFE) was used to adsorb the hydrophobic neutrals, and in field sampling it serves as a filter for particulate removal. Cation- and anion-exchange resins were then used to remove the ionized organic substances and to deionize the sample prior to the concentration of the nonadsorbed hydrophilic neutrals by vacuum distillation. Organic constituents were selectively... 

The modified parfait method developed here replaced silica gel with porous polytetrafluoroethylene (PTFE, Teflon). Properly wetted Chromosorb T, an aggregate of aqueous dispersion-polymerized PTFE, is an efficient adsorbent for many hydrophobic substances in water... 

Teflon (polytetrafluoroethylene) is a chemically inert polymer used to create nonstick frying pans. Polytetrafluoroethylene can be modified to form a coating, Gore-Tex, which allows the passage of water vapor, but not liquid water, and is used in many articles of clothing. Polymeric perfluorinated ethers are widely used as high performance oils and lubricants. 

There are different ways that low energy surfaces can be applied to textiles. The first way is mechanical incorporation of the water-repellent prodncts in or on the fibre and fabric surface, in the fibre pores and in the spacing between the fibres and the yams. Examples of these are paraffin emulsions. Another approach is the chemical reaction of the repellent material with the fibre snrface. Examples of these are fatty acid resins. Yet another method is the formation of a repellent fihn on the fibre surface. Examples of these are silicone and flnorocarbon prodncts. The final approach is to use special fabric constructions like stretched polytetrafluoroethylene films (Goretex), films of hydrophilic polyester (Sympatex) and microporous coatings (hydrophilic modified polynrethanes). 

Besides the classical polymer introduced by Merrifield (1%-crosslinked chloromethylated polystyrene), a broad variety of polymeric supports is available for SPPS and some of the most popular resins are summarized in Table 1. The chemical structures of some selected resins are presented in Figure 1 and electron micrographs of several examples are displayed in Figure 2. In addition to the solid supports listed in Table 1, there are several other carriers used in peptide synthesis such as the gel-type and macroporous poly(meth-acrylates), coated surfaces like polystyrene films on polyethylene (PEt) sheets, polystyrene-coated polyethylene or polytetrafluoroethylene, and modified glass surfaces. (For recent reviews on polymeric carriers see refs . )... 

Extrusion-Applied Insulations. The polymers used in extrusion applications can be divided into two classes low-temperature applications and high-temperature applications. Polymers in the first category are poly(vinyl chloride), polyethylene, polypropylene, and their copolymers along with other elastomers. Polymers in the second category are mainly halocarbons such as Teflon polytetrafluoroethylene (which requires special extrusion or application conditions), fluoroethylene-propylene copolymer (FEP), perf luoroalkoxy-modified polytetrafluoroethylene (PFA), poly(ethylene-tetrafluoroethylene) (ETFE), poly(vinylidene fluoride) (PVF2) (borderline temperature of 135 °C), and poly(ethylene-chlorotrifluoroethylene). Extrusion conditions for wire and cable insulations have to be tailored to resin composition, conductor size, and need for cross-linking of the insulating layer. 

METABLENTm A3000 (ACRYLIC-MODIFIED POLYTETRAFLUOROETHYLENE, PTEE)... 

Across the grain, 365, 367 Acrylic foam modifier, 91 Acrylic Metafile series P, 173 Acrylic Metablen series L, 173 Acrylic-modified polytetrafluoroethylene, 163, 173... 

Resin manufacturers have long recognized the excessive deformation of polytetrafluoroethylene in applications where parts such as gaskets and seals experience high pressures. Copolymers oftetrafluo-roethylene with small amoimts of other fluorinated monomer are known as Modified PTFE resins and have been reported to exhibit reduced deformation under load. Examples of the properties of some of the commercial products can be seen in Tables 3.22-3.24 and Figs. 3.20 and 3.21. Significant reduction in deformation under load can be achieved, particularly at elevated temperatures and pressures. 

Perfluorinated fluoroplastics have higher creep tendency than partially fluorinated fluoropol5miers. Polytetrafluoroethylene, comprised of 100% tet-rafluoroethylene monomer, has the highest tendency to exhibit cold flow. Copolymers of tetrafluoroeth-ylene containing small amounts (0.1% by weight) of certain other fluorinated monomers, also referred to as modifiers, have significantly lower creep. These modifiers form pendent groups in the polymer chain. 

Polytetrafluoroethylene for these applications is known as modified, which refers to the presence of a small amount of a second perfluorinated monomer, known as a modifier, in its structure. The modifier molecule always contains a pendent group. 

Fluoropolymers such as PVDF, FEP, PFA, and modified polytetrafluoroethylene can be thermo-formedl J by vacuum forming, pressure forming, and matched-die forming (Fig. 7.19). In all methods, a... 

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