Ethylene and tetra fluoroethylene

In Table 5 (p. 55) we compared the relative rates of addition of methyl, fluoromethyl, difluoromethyl and trifluoromethyl radicals to ethylene and tetra-fluoroethylene. Figure 3 shows the Arrnehius plots for these competitive reactions. These indicate in a very graphic way the fact that this systematic variation in relative rate can be entirely attributed to variation in the activation energy differences. 

C. ESCA Studies of Structural Details. Copolymers of ethylene/ tetrafluoroethylene. So far we have shown how a consideration of the detailed structure of the C core levels of certain copolymers may be used to obtain information on composition. A further example which also illustrates the utility of ESCA for providing structural data is provided by studies of copolymers of ethylene and tetra-fluoroethylene. Fig. 3 shows the C and Fjs levels for a series of samples of varying bulk composition. From the ESCA data, the copolymer compositions may be calculated in two independent ways. Firstly, from the relative ratios of the high to low binding energy peaks in the C g spectrum attributable to F2 and H2 type environments respectively. Secondly, from the overall C /F intensity ratios taken in conjunction with data obtained from the study of the homopolymers previously discussed. The results are tabulated in Table 7. 

Fig. 35. C.g spectra for copolymer of ethylene and tetra-fluoroethylene showing the deconvolution into component peaks.

Seguchi, T., Hayakawa, N., Yoshida, K., and Tamura, N., Fast neutron irradiation effect. II. Crosslinking of polyethylene, ethylene-propylene copolymer, and tetra-fluoroethylene-propylene copolymer, Radiat. Phys. Chem., 26, 221-225 (1985). Keller, A., and Ungar, G., Radiation effects and crystallinity in polyethylene, Radiat. Phys. Chem., 22, 155-181 (1983). 

Recently Stone has reported the addition of methyl- and phenylmanganese pentacarbonyl to highly fluorinated ethylene derivatives. For example, tetra-fluoroethylene reacted readily with methylmanganese pentacarbonyl at 90°C., or under ultraviolet light at room temperature, to produce 1,1,2,2-tetrafluoropropyl-manganese pentacarbonyl in high yield (103). 

Most of the research effort on the ionomers has been devoted to only a small number of materials, notably the ethylenes the styrenes, the rubbers(9)5 and those based on poly(tetra-fluoroethylene), the last of which is the subject of the present volume. As a result of these extensive investigations, it has become clear that the reason for the dramatic effects which are obsverved on ion incorporation is, not unexpectedly, the aggregation of ionic groups in media of low dielectric constant. Small angle X-ray and neutron scattering, backed up by a wide range of other techniques, have demonstrated clearly the existence of ionic... 

Tubular blood-contacting polymeric materials were modified by plasma polymerization and evaluated in animals (baboons) with respect to th r c iadty to induce acute and chronic arterial thrombosis. Nine plasma polymers based on tetrafluoro-ethylene, hexafluoroethane, hexafluwoethane/H, and methane, when deposited on silicone rubber, consumed platetets at rates ranging from l.l-5.6x 10 platelets/on day. Since these values are close to the lower detection limit for this test system, tl plasma polymers were considered relatively nonthrombogenk. Thus, artificial blood tube made of polyesters, having the inner side coated with plasma-pcrfymerized tetra-fluoroethylene, is now commercially available. 

A number of theoretical studies of varying degrees of sophistication have appeared on fluoroethylenes, but they have yet to attain the accuracy of precise experimental studies. They include the following ab initio calculations on tetra-fluoroethylene, mono-, di-, - and tri-fluoroethylenes, extended Hiickel MO calculations on fluorinated ethylenes and buta-l,3-dienes, semi-empirical calculations on ionic reactivities of fluoro-olefins,i CNDO- and INDO-type calculations on fluoroethylenes, 1,1-dichlorodifluoro- and chlorotrifluoro-ethylene, hexafluoropropene and octafluoroisobutene, on the polymerization of vinyl fluoride,... 

The basic monomer unit is a totally fluorinated ethylene molecule (—CF —CF —). It is well known under its common trade name Teflon. It was discovered in 1938 by Roy J. Plunkett a DuPont scientists. Industrially, polytetrafluoroethylene is obtained from several consecutive of steps. First, chloroform reacts with hydrofluoric acid to yield chlorodifluoromethane. The chlorodifluoromethane is then pyrolized at 800-1000 C to yield the monomer, i.e., tetra-fluoroethylene (CF2=CF2, TFE) which is purified and polymerized in aqueous emulsion or suspension using organic peroxides, persulfates or hydrogen peroxide as catalysts. The simple polymerization reaction is as follows. 

Free-radical Reactions.—Publications have appeared dealing with the bidirectional addition of trifluoroiodomethane and hydrogen bromide across the C=C bond in the olefin CF3 CH CHMe, peroxide-initiated addition of 1,2-dibromotetrafluoroethane to ethylene, propene, and isobutene, the addition of pentafluoroiodoethane to 3,3,4,4-tetrafluorohexa-l,5-diene (see p. 29), peroxide-initiated cyclodimerization of 3,3,4,4-tetrafluoro-4-iodobut-l-ene (see p. 29), and telomers from tribromofluoromethane or tetrabromomethane and bromotrifluoroethylene as high-density fluids for gyroscope flotation. The telomerization of chloromethanes with tetra-fluoroethylene provides a measure of the relative reactivity for both chlorine and hydrogen abstraction by the CF2 CF2 radical. The chain-transfer... 

The reinforced thermoplastic polyimide, fluor-inated ethylene-propylene, and ethylene-tetra-fluoroethylene exhibited little or no tensile strength loss after 1500 h at 400° F. The tensile strength of the remaining composites ranged from a loss of measurable strength to a 30% reduction. Their ranking is as follows polyphenylene sulfide (30%)>polyethersulfone (50%)> nylon 6/6 (61%)>polyester (77%). 

The thermoplastic polyimide had less than a 15% loss in tensile strength after 1500 h at 500° F. The polyphenylene sulfide (40% loss) and the polyethersulfone (54% loss) exhibited outstanding thermal resistance at 500° F, considering their rather ordinary performance at the 400° F test temperature. The ethylene-tetra-fluoroethylene had an 80% loss after 1500 h at 500° F. The polyester and polysulfone distorted severely at 500° F and had to be removed. ... 

The relatively low solubility parameters (solpars) of the amorphous poly(l-olefins) have been compared with the solpars at 25°C) of other polymers poly(tetra-fluoroethylene), 13.5 poly(dimethylsiloxane) 15.5 polypropylene, 16.5 polyisobutylene, 16.5 polyethylene, 17.0 poly(ethyl methacrylate) 18.5 polystyrene, 18.5 poly(vinyl acetate) 20 cellulose nitrate, 21 poly(ethylene oxide), 24 and cellulose acetate, 24 [16]. 

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