Membranes amorphous fluoropolymer

Hyflon AD amorphous fluoropolymer is used in optical devices, pellicles in semiconductor manufacture, as a dielectric and as a separation membrane. Small amounts of TDD have been used as a modifier in ethylene-chlorotrifluoroethylene polymers to increase stress crack resistance. Minute amounts of TDD are used also as a modifier in polytetrafluoroethylene to improve elastic modulus, reduce creep and permeability and increase transparency. It has been suggested that the much higher reactivity of TDD and other fluorinated dioxoles relative to other modifiers gives a more uniform distribution of the modifier in the polymer chain that results in a greater increase in the desired properties at lower concentration of modifier in the polymer. 

These amorphous fluoropolymers are chemically as well as thermally stable, soluble in fluorinated solvents, have low dielectric constants, and the films are transparent. They have unique properties compared to traditional fluoropolymers. The amorphous polymers have high potential in many applications. The following are representative examples that are being pursued polymer waveguides [24,25], pellicles used in the photolithographic reproduction of semiconductor integrated circuits [26], insulators and hydrophobic surfaces for electrowetting [27,28], polymer optical fibers [29,30], and membranes for gas separations [31-33], Here, we describe two examples of the use of the amorphous perfiuorinated polymers optical fibers and gas separation membranes. 

Several recent studies report gas permeation, sorption, and free volume characteristics of these two amorphous fluoropolymers. Nemser and Roman (1991 Nemser, 1993) reported permeability properties of Teflon AF polymer membranes prepared by a melt-press method. Similar to PTMSP, these polymers are permeable to permanent gases. For example, oxygen... 

Hyflon AD is an amorphous perfluorinated copolymer of tetrafluoroethylene (TFE) and 2,2,4-trifluoro-5-trifluoromethoxy-l,3-dioxole (TTD). Compared to the situation in the Teflon AF series, the reduced intermolecular distance due to the structural change result in moderate fractional free volume of 23%. Thus, the gas permeabilities are lower than those of Teflon AF membranes, allowing the increase of permselectivities. While this fluoropolymer has the advantage of solubility in fluorinated liquid, such as Galden FIT 55 and HFE 7100, the permeation properties are affected by the kind of residual solvents as well. 

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