Solubility coefficient fluorinated polymers

Transport properties of oxygen are better in the fluorinated polymer than in aqueous electrolytes. Although the diffusion coefficient is lower than in water, the oxygen solubility is largely enhanced so that the transport parameter D + c02 is higher than in water (160, 161). 

PTFE is a crystalline polymer consisting of twisted zigzag spirals with at least 13 repeating units per turn. This nonpolar polymer has a solubility parameter of 6.2 H, a high (327 C), and a heat deflection temperature of 121 C PTFE is a tough, flexible polymer which retains its ductility at extremely low temperatures (-269 0. The coefficient of friction of ptfe is the lowest of any known solid material (see Table 13.4). Films of ptfe can be bonded by adhesives to other surfaces if the polymer surface is treated with sodium. It also bonds to diamonds and graphite whose surfaces have been fluorinated. Liquid sodium removes fluoride ions from the surface and leaves free radicals on the polymer surface, ptfe is resistant to almost all corrosives and solvents, but it can be dissolved in hot perfluorinated kerosene, ptfe is difficult to mold or extrude. 

A good rule of thumb to remember is that increasing the fluorine content of a polymer molecule increases its chemical and solvent resistance, flame resistance, and photostabflity. Additionally, fluorine improves a polymer s electrical properties (so that, e.g., it has a lower dielectric constant), lowers the coefficient of friction, raises its melting point, increases its thermal stability and weakens its mechanical properties. The solubility of polymers usually decreases when the fluorine content of the molecule is increased. 

The volatility of stabilizers from polymers is affected by both the properties and structures of the stabilizer and polymer and the external physical conditions of the experiment. Moreover, volatility is governed by diffusion of stabilizer in the polymer since volatilization causes a concentration gradient near the surface and subsequent additive loss from the surface must be replaced by diffusion from the bulk. It was found, for example, that the rate of evaporation of phenyl-2-naphthyl-amine from polymers decreases in the series polyethylene > fluorinated rubber > polybutadiene > butadiene styrene rubber > butadiene acrylonitrile rubber and this parallels the solubility of the naphthylamine in these polymers. The polarity of these polymers increases in the same order which is reflected in a decrease in diffusion coefficient and increasing intermolecular interaction in the polymer-stabilizer system. 

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