Polymerization polytetrafluoroethylene

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.

Co-coagulation is the method by which large quantities of fillers can be incorporated in dispersion polymerized polytetrafluoroethylene. The addition of fillers takes place prior to coagulation of the resin from its dispersion state. In the process of co-coagu-lation, the additives are added to the polytetrafluoroethylene dispersion and mixed. This dispersion is coagulated and the compound is recovered. The smaller the filler particles, the smaller the points of stress rise in the compound will be. Significantly larger quantities of filler can be compounded in PTFE by this technique. 

Hydrocarbon oil is added to the dispersion polymerization reactor to stabilize the polytetrafluo-roethylene emulsion. Temperature and agitation control are easier in this mode than suspension polymerization. Polytetrafluoroethylene fine powder and dispersion are produced by this technique. 

Fine Cut PTFE - Particles of suspension polymerized polytetrafluoroethylene (PTFE) which has undergone size reduction (usually by cutting) to less than 50 pm average size. 

Reduction Ratio - This factor is the ratio of cross-sectional surface areas of the preform and the extrudate in paste extrusion. Different dispersion polymerized polytetrafluoroethylene powders accommodate different reduction ratio ranges. In general, reduction ratio of the resin decreases as molecular weight increases. Melt fracture and defects appear in the extrudate if it is processed at above its maximum reduction ratio. 

Dedusting Powder - Refers to dispersion polymerized polytetrafluoroethylene which is added to powdery material to prevent formation of dust during powder handling. The polymer can be added in the form of fine powder or dispersion. 

Dispersion Polymerization - This technique is a heterogenous regime where a significant amount of surfactant is added to the polymerization medium. Characteristics of the process include small uniform polymer particles which may be unstable and coagulate if they are not stabilized. Hydrocarbon oil is added to the dispersion polymerization reactor to stabilize the polytetrafluoroethylene emulsion. Temperature and agitation control are easier in this mode than suspension polymerization. Polytetrafluoroethylene fine powder and dispersion are produced by this technique. 

Hydrocarbon Lubricant - A hydrocarbon liquid added to dispersion polymerized polytetrafluoroethylene powder (fine powder) to form a paste for extrusion. 

Polymerization polyethylene (PE), Teflon (polytetrafluoroethylene, PTFE), polystyrene (PS), and etc. 

Being microwave-transparent, the reaction vessels will be no hotter than their contents. As mentioned above, they usually are made from insulating polymeric materials like polytetrafluoroethylene (PTFE), which have inherent advantages for cleaner processing. In contrast with other materials, PTFE is resistant to attack by strong bases or HF and is not corroded by halide ions. 

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... 

Fluorinated polymers, especially polytetrafluoroethylene (PTFE) and copolymers of tetrafluoroethylene (TFE) with hexafluoropropylene (HFP) and perfluorinated alkyl vinyl ethers (PFAVE) as well as other fluorine-containing polymers are well known as materials with unique inertness. However, fluorinated polymers with functional groups are of much more interest because they combine the merits of pefluorinated materials and functional polymers (the terms functional monomer/ polymer will be used in this chapter to mean monomer/polymer containing functional groups, respectively). Such materials can be used, e.g., as ion exchange membranes for chlorine-alkali and fuel cells, gas separation membranes, solid polymeric superacid catalysts and polymeric reagents for various organic reactions, and chemical sensors. Of course, fully fluorinated materials are exceptionally inert, but at the same time are the most complicated to produce. 

Aqueous corrosion resistance, 13 513 Aqueous dispersion polymerization, 18 291 of acrylonitrile, 11 197-200 Aqueous dispersions, 13 292. See also Aqueous polytetrafluoroethylene dispersions... 

Aqueous perchlorate solutions, 18 274 Aqueous plugs, in microfluidics, 26 968 Aqueous polytetrafluoroethylene dispersions, 18 291 Aqueous potassium permanganate solutions, 15 597-600 Aqueous ring-opening metathesis polymerization (ROMP), 15 495... 

Polytetrafluoroethylene (Tf) is a polymeric fluorine compound that consists of a -C2F4- molecular structure,ini which contains a mass fraction of fluorine of 0.75. Tf is insoluble in water and its specific mass is in the range 3550-4200 kg nr in peUe-... 

Since many polymeric materials are used as clothing, household items, components of automobiles and aircraft, etc. flammability is an important consideration. Some polymers such as polytetrafluoroethylene and PVC are naturally flame-resistant, but most common polymers such as PE and PP are not. Small-scale horizontal flame tests have been used to estimate the flammability of solid (ASTM D-635), cellular (ASTM D-1692-74), and foamed (ASTM D-1992) polymers, but these tests are useful for comparative purposes only. Large-scale tunnel tests (ASTM E-84) are more accurate, but they are also more expensive to run than ordinary laboratory tests cited before. 

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. 

Polymeric hydrocarbons, such as polyolefins, are readily combustible and can actually serve as a fuel source. In contrast, polytetrafluoroethylene (ptfe) does not bum in air but burns in oxygen or in nitrogen-oxygen mixtures which have a very high oxygen concentration. 

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