Polyperfluorobutadiene. II. Fractionation and crosslinking

Abstract

Perfluorobutadiene was polymerized in bulk under low pressure and temperature in the presence of diisopropyl peroxydicarbonate, bis(trifluoromethyl) peroxide, and benzoyl peroxide. Fractional solvent extraction of polyperfluorobutadiene by n‐hexane and hexafluorobenzene into three polymeric fractions was described. The hexafluorobenzene‐soluble fraction was used for crosslinking studies. Direct fluorination of solid polyperfluorobutadiene required no catalyst. The fluorine–polyperfluoropolyene reactions furnished a mechanism for crosslinking the unsaturated chains. Fluorination by gaseous fluorine formed free radical sites on the polymer chains besides saturation reactions. The presence of excess monomer in contact with these partially fluorinated solid polyperfluorobutadienes under controlled conditions were capable of crosslinking and grafting to the linear chains. Direct fluorination of solid polyperfluorobutadiene tends to involve reaction with the internal double bonds rather than the pendant perfluorovinyl group; the converse is true for crosslinking with hexamethylenediamine. The mechanisms are discussed.

Surface modification of polymers by direct fluorination: A convenient approach to improve commercial properties of polymeric articles

“…But such an affirmation was based only on the fact that long-life radicals were detected in the fluorine-treated polymers, but no radicals taking part in the processes of chain initiation and propagation were detected except by research carried out by our group [2,4,6,7,[41][42][43]. Authors of [1,23,24,44,45] detected long-lived radicals in fluorinated (at room temperature and up to 55°C) PE, PS, PVC, PVDC, etc. ESR spectra represented a mixture of peroxy RO 2 radicals and an unidentified very broad component, which was tentatively assigned to metal fluorides with altering valency [23].…”

“…Fluorination results in a remarkable increase of the specific gravity [2,4,[6][7][8]27], the free volume is decreased, and hence the permeability of fluorinated polymers should be decreased. Also, direct fluorination leads to the cross-linking of polymers [1,[5][6][7][23][24][25]. Such an effect results in a suppressing of the swelling and plasticization effects under the action of hydrocarbons and a permeability value decreases.…”

“…Would all the conjugated bonds be saturated with fluorine, the content would be C 8 F 14 . It is known that under the action of fluorine, both breakdown (disruption) and cross-linking take place [1,[23][24][25], hence, the discrepancy between the above-mentioned formulae (C 8 F 12 , C 8 F 8 , and C 8 F 14 ) can be attributed to simultaneous breakdown and cross-linking of polymer chains and the number of cross-links (or additional C-C bonds) per each monomeric unit is 2 units more than the number of scissions. It is necessary to mention that our results do not agree with data for the chemical composition of fluorinated PS by other authors: C 8 F 14 [18] and C 8 F 9.1 [26].…”

Modification of surface properties of carbon-based and polymeric materials through fluorination routes: From fundamental research to industrial applications

“…At first fluorination results in a significant increase of the specific gravity [11,20,22,24,26] and the free volume is decreased and hence the permeability of fluorinated polymers should be decreased. Also direct fluorination results in the crosslinking of polymers [9,20,[28][29][30] so the swelling and plasticization effects under the action of hydrocarbons are suppressed and permeability values decrease. Finally the surface energy of fluorine-treated polymer surfaces in many cases is increased and hence the solubility (permeability also) of low polarity organic liquids in fluorinated polymers is decreased.…”

On the polymerization reactivity of fluorinated vinyl monomers

“…Radical polymerizations of HFBD initiated with diisopropyl peroxydicarbonate or c-ray irradiation were reported to produce grease-like oligomers in low yields 10,11) . Toy et al found that the microstructure of the HFBD oligomer showed mainly 1,2-sequences with some extent of 1,4-addition structure, as derived from the measurements of infrared spectra.…”