Plasma polytetrafluoroethylene

The general structure of this class of materials can, therefore, be summarized as a fine dispersion of metal oxide in a polymer matrix very similar to plasma polytetrafluoroethylene and in principle any metal should be able to be incorporated. Clearly, if the films are protected from the atmosphere, for metals which form involatile fluorides having a relatively weak metal-fluorine bond strength, it should be possible to produce films having metal atoms dispersed in the matrix. It is expected that these films will have many interesting chemical, optical, electrical and magnetic properties., ... 

Figure 9. Core-level spectra of plasma polytetrafluoroethylene...

The similarity of the Cls spectra for the three films in Figure 11 suggests that the polymer structure is the same irrespective of the excitation electrode material used. It has been noted that the Cls spectra in Figure 11 are also similar to that of plasma polytetrafluoroethylene formed under similar conditions (9, 2 ). This observation, coupled with mass spectrometric... 

Dekker A, Reitsma K, Beugeling T, Bant]es A, Fei]en J and van Aken W G 1991 Adhesion of endothelial-oells and adsorption of serum-proteins on gas plasma-treated polytetrafluoroethylene S/omaferfa/s 12 130-8... 

Instead of using plasma-polymerized polyfluorocarbon as HIL, Qiu et al. utilized a thermally deposited Teflon (polytetrafluoroethylene) thin layer as a HIL, which results in... 

V.N. Vasilets, G. Hermel, U. Konig, C. Werner, M. Muller, F. Simon, K. Grundke, Y. Ikada, H.J. Jacobasch, Microw/ave CO2 plasma-initiated vapour phase graft polymerization of acrylic acid onto polytetrafluoroethylene for immobilization of human thrombomodulin. Biomaterials 18 (1997) 1139-1145. 

Another field of application of fluorinated biomaterials is connected to lesions or evolving disease pathology of blood vessels. In particular, arteries may become unable to insure an adequate transport of the blood to organs and tissues. Polytetrafluoroethylene (PTFE) and expanded e-PTFE are the preferred materials for vascular prostheses. The interactions of blood cells and blood plasma macromolecules with both natural and artificial vessel walls are discussed in terms of the mechanical properties of the vascular conduit, the morphology, and the physical and chemical characteristics of the blood contacting surface. 

Several commercial polymers (polyethylene, polyimide, polytetrafluoroethylene, polyvinylchloride and polycarbonate) have been treated by low temperature glow discharge plasmas in various gases, namely NH3, 02, Ar, and CF4. 

The following commercial polymeric substrates have been investigated low density polyethylene (PE, Dow Chemical Canada Inc.) polyimide (PI, DuPont Kapton H), polytetrafluoroethylene (PTFE, DuPont Teflon), polycarbonate (PC, Mobay Corp.) and surface-lubricated (with glycerol ester) polyvinylchloride (FVC, Canadian Occidental Petroleum Ltd). After plasma treatment, the samples were exposed to ambient atmosphere for 10 - 30 minutes while being transferred to the following... 

Figure 9.2 Dynamic electrical properties of polytetrafluoroethylene thin films at 20°C Key Q, sputtered polytetrafluoroethylene x, plasma-polymerized polytetrafluoroethylene. Adapted from Ref. 4.

Substrates used included fiber-reinforced epoxy base polymer [FRP], nylon 66, polytetrafluoroethylene [Teflon], poly(ethylene terephthalate) [PET], phenolic resin, and thermoplastic polyimide [ULTEM, GE]. FRPs were the primary substrates used. Initially, they were cleaned with detergent in an ultrasonic bath followed by rinsing with deionized water and alcohol. For further cleaning, they were treated with oxygen plasma (1.33 seem, 60 W, 5 min) followed by a hydrogen plasma treatment (3 seem, 60 W, 5 min). 

Precursors and catalysts were characterized in ambient conditions by X-ray diffraction (XRD) on a Rigaku Powder Diffractometer using CuK radiation with a Ni filter. LiF was used as an internal standard for the activated catalysts. Laser Raman spectra (LRS) were collected using Ar ion laser excitation (514.5 nm) at a power of 25 mW at the sample. Spectra for the precursors were collected in ambient conditions, and reaction-used catalysts were characterized in-situ at 400°C in a 70 ml/min flow of C4H,(/02/He (0.99/10.2/88.81). Phosphorus to vanadium ratios (molar) were determined by inductively coupled plasma (ICP). Diffuse reflectance spectra (DRS) were collected in ambient conditions using polytetrafluoroethylene as a reference. 

Excitation sources for the production of radicals in grafting include chemicals, light, plasma, and radiation. Radiation-induced graft polymerization is superior to other grafting techniques because the high density of electron beams and gamma rays can create a large amount of radicals of arbitrary shapes of the p>olymer, such as a hollow fiber [2-41], nonwoven fabric [42] and film [43- ], and the quality of the polymer, such as polyethylene [2-41], polytetrafluoroethylene [42], and cellulose [55]. 

To examine this possibility, the degree of complement activation that results when rabbit plasma is incubated with polytetrafluoroethylene (PTFE) or silicone rubber or cellophane has been measured (26). Each of these materials was primed in two ways before it was exposed to the plasma. One method of priming removed the air nuclei from the surface roughness of the material and the other was simply the normal priming technique in which the material was immersed in the physiological saline before it was exposed to the plasma... 

Most plasma-treated hydrophobic surfaces of biomaterials are formed with tetra-fluoromefhane (CF4) plasma interactions [3, 4]. The modified surface represents a nonadherent polytetrafluoroethylene (PTFE)-like structure (-(CF2) -) with low surface energy that could vary from 20 mj mT down to only a few mj uT when the super-hydrophobic character is pronounced. The chosen operating conditions lead to a low fluorine atom density in the plasma, thus avoiding surface degradation. Such surfaces are applied in order to prevent the formation of the biofilm. 

Analysis for diborane in air may be performed by NIOSH Method 6006 (NIOSH 1984). Air is passed through a polytetrafluoroethylene (PTFE) filter and oxidizer-impregnated charcoal at a flow of 0.5 -1 L/min. Diborane is oxidized to boron, which is desorbed with 3% H2O2 and analyzed by plasma emission spectrometry. Alternatively, boron may be analyzed by inductively coupled plasma atomic emission spectrometry (NIOSH 1984, Method 7300). 

Urokinase has been widely used for the clinical treatment of thrombogenetic disease and hemorrhoidal disease. Artificial organ materials, on which urokinase was immobilized for its fibrinolytic activity, have been developed for blood-compatible materials. For example, Liu et al. immobilized urokinase by encapsulation in poly(2-hydroxyethyl methacrylate) and Kbnig et al. introduced urokinase on the surface of the polytetrafluoroethylene using plasma modification technique by covalent bond. Another example of immobilized urokinase application was reported by Kato and coworkers, who had used mokinase immobilized in a Teflon catheter for treatment of thrombosis. 

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