Polytetrafluoroethylene peroxide

Polytetrafluoroethylene contains only C—C and C—F bonds. These are both very stable and the polymer is exceptionally inert. A number of other fluorine-containing polymers cU e available which may contain in addition C—H and C—Cl bonds. These are somewhat more reactive and those containing C—H bonds may be cross-linked by peroxides and certain diamines and di-isocyanates. 

PTFE polytetrafluoroethylene PUFA polyunsaturated fatty acid PV peroxide value PVDF polyvinylidene difluoride PVP polyvinylpyrrolidone PVPP polyvinylpolypyrolidone RAS retronasal aroma stimulator RDA recommended dietary allowance RF radio frequency RFI relative fluorescence intensity RI retention index RNU relative nitrogen utilization ROESY rotational nuclear Overhauser enhancement spectroscopy RP-HPLC reversed-phase HPLC RPER relative protein efficiency ratio RS resistant starch RT retention time RVP relative vapor pressure S sieman (unit of conductance)... 

Surface oxidation reactions have been carried out on a number of polymers, particularly polyethylene. Surface oxidation techniques include the use of corona discharge, ozone, hydrogen peroxide, nitrous acid, alkaline hypochloride, UV irradiation, oxidizing flame, and chromic acid The reactions lead initially to the formation of hydroperoxides, which catalyze the formation of aldehydes and ketones and finally, acids and esters. Surface oxidation treatment has been used to increase the printabdity of polyethylene and poly(ethylene terephthalate) and to improve the adhesion of polyethylene and polypropylene to polar polymers and that of polytetrafluoroethylene to pressure-sensitive tapes. Surface-oxidized polyethylene, when coated with a thin film of vinylidene chloride, acrylonitrile, and acryhc acid terpolymers becomes impermeable to oxygen and more resistant to grease, oil, abrasion, and high temperatures. The greasy feel of polyethylene has also been removed by surface oxidation. 

The objects of our investigations were four kinds of elastomers, of different structure and polarity, viz. cis-1,4-polybutadiene (BR)> butadiene-acrylonitrile copolymer (NBR), isobutylene-isoprene copolymers (IIR) and ethylene-propylene-diene terpolymer (EPT). They were mixed with plastomers low density polyethylene (PE] ), polystyrene (PS), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polycaproamide (PCA) and polyacrylonitrile (PAN) (Table 1). The concentration of the plastomers in the mixtures was changed in the range from 0 to 50 pph of the elastomer. The polymers were blended at temperature T = 423 K by means of the micromill of the Plasti--Corder apparatus. After 24 hours, crosslinking substances, dicurayl peroxide (DCP) or sulphur and diphenylguanidine (S, DPG), were added at room temperature. The composition of the mixtures is given in Table 2. 

Polytetrafluoroethylene (PTFE) is a fully fluorinated polymer, which was discovered by chance in 1938 by Roy Plunkett. Later, the polymerization process was initiated at high pressure with peroxide. In 1941, DuPont received the patent on PTFE, therefore it is often denoted colloquially by Teflon , the original trade name of DuPont PTFE (ref DuPont). Other examples of PTFE trade names used by manufacturers are PTFE Dyneon , formerly ffostaflon (ret Dyneon), and Gore-Tex (ret Gore). 

PTFE fluoroplastic n. Polytetrafluoroethylene is prepared by free radical polymerization of tetrafluoroethylene in aqueous systems with persulfate or peroxide initiators to give granular or dispersion polymers. The... 

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. 

To predict the stability of fluorinated polymers in the atmosphere polluted with nitrogen oxides, the ratio of rates of peroxynitrates in polytetrafluoroethylene (PTFE) by two mechanisms has been determined [19]. Chain peroxide radicals R 02 were obtained by photolysis of PTFE powder in a vacuum with the subsequent oxidation of fluoroalkyl macroradicals. The end peroxide radicals R 02 were generated by photolysis of the R 02 containing PTFE in the air. The exposure of PTFE samples containing chain or end peroxide macroradicals to NO2 results in decay of these radicals. The kinetics of the decay of peroxide radicals of both types is practically identical, and is likely to be determined by the rate of diffusion of NO into the... 

Grafting of polytetrafluoroethylene (Teflon) on polydimethylsiloxane has been carried out by milling with the aim of improving solvent (benzene) resistance, tensile strength, and tear resistance [7]. As organosilicone rubber does not readily undergo scission by mechanical action, it was necessary to add benzoyl peroxides to the blend before mixing. Apparently the process is related to the scission of polydimethylsiloxane initiated by peroxide. The... 

PTFE Fluoroplastic n Polytetrafluoroethylene is prepared by free radical polymerization of tetrafluor-oethylene in aqueous systems with persulphate or peroxide initiators to give granular or dispersion polymers. The polymers have exceptionally high thermal and thermo-oxidative stability and are completely solvent resistant. PTFEs are tough, relatively flexible materials which have outstandingly good electrical insulation properties as well as unusually low coefficients of friction. 

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