Polytetrafluoroethylene solubility parameter

There are thus no solvents at room temperature for polyethylene, polypropylene, poly-4 methylpent-l-ene, polyacetals and polytetrafluoroethylene. However, as the temperature is raised and approaches F , the FAS term becomes greater than AH and appropriate solvents become effective. Swelling will, however, occur in the amorphous zones of the polymer in the presence of solvents of similar solubility parameter, even at temperatures well below T. ... 

The incorporation of polar groups in unvulcanized polymers reduces their solubility in benzene. Thus the copolymer of acrylonitrile and butadiene (NBR), polychlorobutadiene (Neoprene), and fluorinated EP (the copolymer of ethylene and propylene) are less soluble in benzene and lubricating oils than the previously cited elastomers. Likewise, silicones and phosphazene elastomers, as well as elastomeric polyfluorocarbons, are insoluble in many oils and aromatic hydrocarbons because of their extremely low solubility parameters (silicons 7-8 H polytetrafluoroethylene 6.2 benzene 9.2 toluene 8.9 pine oil P.6). 

Polytetrafluoroethylene (PTFE Teflon) was discovered accidently by PlunkettCZ nd commercialized by DuPont in the 1940 s. This polymer has a solubility parameter of about 6H and a high melting point of 327°C and is not readily moldable. Poly-chlorotrifluoroethylene (CTFE, Kel-F), the copolymer of tetrafluoroethylene and hexafluoropropylene (FEP), polyvinylidene fluoride (PVDF, Kynar), the copolymer of tetrafluoroethylene and ethylene (ETFE), the copolymer of vinylidene fluoride and hexafluoroisobutylene (CM-1), perfluoroalkoxyethylene (PFA) and polyvinyl fluoride (PVF, Tedlar) are all more readily processed than PTFE. However, the lubricity and chemical resistance of these fluoropolymers is less than that of PTFE. 

Complications such as these extend also to the case of polytetra-fluoroethylene. The large difference in estimated solid-vacuum tensions between this polymer and polyethylene is not imexpected, since a proportionately large difference exists for the liquid surface tensions of hydrocarbons and fluorocarbons having five to eight carbon atoms [58]. The underlying cause of this difference is, however, more obscure. The inter molecular forces for fluorocarbons apparently have features wuich lead to anomalous behavior, at least from the point of view of solubility parameter theory [59]. Thus, theoretical calculations of the surface tension for the bare solid in the case of polytetrafluoroethylene would face a number of difficulties not encountered with paraffin crystals. 

Solubility parameter (SP, 8) n. The square root of the cohesive energy density of a polymer, solvent, or adhesive. For solvents, SP equals the square root of the heat of vaporization per unit volume (J/cm )°. Values for polymers (which do not vaporize) are found by indirect methods. If the solubility parameters of a polymer and solvent differ by 3 (J/cm )° or less, the polymer will probably dissolve in the solvent differ by (J/cm )° or less, the polymer will probably dissolve in the solvent. SPs for organic solvents range from 13 for neopentane to 30 methanol for polymers, from 13 for polytetrafluoroethylene to 32 for Polyacrylonitrile. Wypych G (ed) (2001) Handbook of solvents. Chemtec Publishing, New York. Barton AFM (1983) Handbook of solubility parameters and other cohesion parameters. CRC Press, Boca Raton, FT. Brandrup J, Immergut EH, Elias HG (eds) (1975) Polymer handbook. Interscience Publishers Inc., New York. 

If the solvent of the coating solution does not wet the porous substrate, no pore penetration will occur. This method can be applied to coat porous hydrophobic polymers such as polyethylene, polypropylene, polytetrafluoroethylene or poiyvinylidene fluoride with a water soluble polymer. Since water does not wet the membrane (at least if the Laplace pressure is not e.xceeded) the polymer wB definitely not penetrate. The. solution properties are very important and this is determined by four parameters... 

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