Emulsion polymerization of tetrafluoroethylene: effects of reaction conditions on the polymerization rate and polymer molecular weight

Kim, C. U.; Lee, J. M.; Ihm, Son Ki

doi:10.1002/(sici)1097-4628(19990801)73:5<777::aid-app18>3.0.co;2-c

Cited by 18 publications

(14 citation statements)

References 21 publications

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“…No articles could be found in the literature that set down reactor-independent correlations for the polymerization rate in terms of fundamental polymerization rate constants of TFE. The polymerization rates reported by Kim et al, Xu et al, Lai et al, etc., as well as all the patent literature, are lumped terms that include reactor hydrodynamics as well as diffusion effects. Significant research scope exists for determining the kinetics of polymerization and, in particular, the effects of temperature and pressure on the dispersity of PTFE.…”

Section: Discussionmentioning

confidence: 93%

“…Other configurations reported include unbaffled reactors with anchor-type agitators and horizontal reactors with paddle-type agitators (these are mostly used in copolymerization). Kim et al investigated the efficacy of various stirrer types for TFE polymerization and found that vortex formation and the maximization of gas-to-liquid surface area are the most important criteria to look at when selecting a stirrer. They recommend the use of an anchor-type stirrer with a baffled tank.…”

Section: Polymerization Process and Equipmentmentioning

confidence: 99%

“…The intrinsic kinetics of dispersion polymerization is the same as for suspension polymerization, and the polymerization still bears a heterogeneous character. Kim et al reported the effects of the polymerization conditions on the molecular weight of PTFE produced by polymerization under a continuous TFE dosing regimen. The observed kinetics of dispersive TFE homopolymerization is closely tied with the mechanism of polymer-particle formation (discussed in section ) and is divided into a nucleation phase and a particle growth phase.…”

Section: Polymerization Process and Equipmentmentioning

confidence: 99%

“…Particle consolidation results in a decreased reaction-surface area, which, concomitantly, causes a drop in the reaction rate. Kim et al , demonstrated that, for dispersion polymerization under nonagglomerating conditions, at least two different kinetic regimes are at play, viz. gas–liquid and gas–solid diffusion-controlled reactions, and that the rate of polymerization is a strong function of the number of nuclear polymer particles.…”

Section: Polymerization Process and Equipmentmentioning

confidence: 99%

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Polytetrafluoroethylene: Synthesis and Characterization of the Original Extreme Polymer

2019

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This Review aims to be a comprehensive, authoritative, and critical review of general interest to the chemistry community (both academia and industry) as it contains an extensive overview of all published data on the homopolymerization of tetrafluoroethylene (TFE), detailing the TFE homopolymerization process and the resulting chemical and physical properties. Several reviews and encyclopedia chapters on the properties and applications of fluoropolymers in general have been published, including various reviews that extensively report copolymers of TFE (listed below). Despite this, a thorough review of the specific methods of synthesis of the homopolymer, and the relationships between synthesis conditions and the physicochemical properties of the material prepared, has not been available. This Review intends to fill that gap. As known, PTFE and its marginally modified derivatives comprise some 60−65% of the total international fluoropolymer market with a global increase of ca. 7% per annum of its production. Numerous companies, such as Asahi Glass, Solvay Specialty Polymers, Daikin, DuPont/Chemours, Juhua, 3F, 3M/ Dyneon, etc., produce TFE homopolymers. Such polymers, both high-molecular-mass materials and waxes, are chemically inert and hydrophobic and exhibit an excellent thermal stability as well as an exceptionally low coefficient of friction. These polymers find use in applications ranging from coatings and lubrication to pyrotechnics, and an extensive industry (electronic, aerospace, wires and cables, and textiles) has been built around them. South Africa, being the third largest producer of fluorspar (CaF 2 ), the precursor to hydrogen fluoride and fluorine, has embarked on an industrial initiative to locally beneficiate its fluorspar reserves, with the local production of fluoropolymers being one projected outcome. As our manuscript focuses specifically on the homopolymerization of TFE (the starting point for all fluoropolymer industries), it will be of considerable use to start-up companies and other commercial entities looking to enter the fluoropolymer market, as well as to end-user companies. The manuscript commences with a short discussion on the synthesis and production of TFE (both at industrial and laboratory scales), including the safety aspects surrounding handling (because that monomer is regarded as explosive if brought into contact with oxygen due to the formation of peroxides), transport, and storage, and then expands into detailed discussions dealing with aspects such as the various additives used (buffers, chain transfer agents, surfactants, etc.), the solvent environment, and the reaction conditions. A further section reports the properties of PTFE with respect to the polymerization conditions as well as an overview on the specialized techniques used to characterize PTFE. Finally, the applications of PTFE in various fields, ranging from electrical insulation to tribological to medical applications, as well as chemically resistant coatings and pyrotechnics, are discussed.

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Section: Discussionmentioning

confidence: 93%

Section: Polymerization Process and Equipmentmentioning

confidence: 99%

Section: Polymerization Process and Equipmentmentioning

confidence: 99%

Section: Polymerization Process and Equipmentmentioning

confidence: 99%

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Polytetrafluoroethylene: Synthesis and Characterization of the Original Extreme Polymer

2019

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“…Early reports by Ziegler and coworkers of metal-catalyzed alkene polymerization promoted by Et 2 AlCl have evolved 5 decades later to a tour de force of organometallic chemistry with molecular control of polypropylene tacticity, living catalysts for block co-polymer formation, and late metal chain-walking as only three of many highlights [23][24][25]. In contrast, polymerization of fluoroalkenes traditionally utilizes radical processes, either in the gas phase or in aqueous emulsions [26][27][28][29]. As a result, while the properties of fluoropolymers can be tuned by altering reaction conditions or changing the relative amounts of co-monomers, attempts at molecular control have met with little success.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Reactivity of Mn–CF3 Complexes

et al. 2019

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The synthesis, characterization and reactivity of several bi- and tridentate, N-ligated manganese carbonyl trifluoromethyl complexes are presented. These complexes exhibit elongated Mn–CCF3 bonds (versus Mn(CF3)(CO)5), suggesting a lability that could be utilized for the transfer or insertion of the CF3 functional group into organic substrates. Unlike their Mn–X congeners (X = Cl, Br), these Mn–CF3 complexes exhibit a preference for hard donor ancillary ligands, thus enabling the synthesis of 4 N-ligated Mn–CF3 complexes including a mixed-donor tridentate complex using an NNS Schiff base ([2-(methylthio)-N-(1-(pyridin-2-yl)ethylidene)aniline]). Although we have not yet identified efficient CF3 transfer reactions, fluoride abstraction from the Mn–CF3 complexes using trimethylsilyl triflate affords the first stable Mn fluorocarbenes as evidenced by 19F NMR spectroscopy.

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Formation of polyurethane membranes by immersion precipitation. II. Morphology formation

Kim¹,

Kim²,

Lee³

et al. 1999

J. Appl. Polym. Sci.

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Polyurethane membranes were prepared by an immersion precipitation process. The effects of dope concentration, coagulation bath composition, and the chemical structure of the polyurethane on the morphology of the membranes were studied. The degree of contraction was measured by quenching freshly formed polyurethane membranes in liquid nitrogen. A mechanism for the formation of membrane morphology during immersion precipitation is proposed.

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Emulsion polymerization of tetrafluoroethylene: effects of reaction conditions on the polymerization rate and polymer molecular weight

Cited by 18 publications

References 21 publications

Polytetrafluoroethylene: Synthesis and Characterization of the Original Extreme Polymer

Polytetrafluoroethylene: Synthesis and Characterization of the Original Extreme Polymer

Synthesis and Reactivity of Mn–CF3 Complexes

Formation of polyurethane membranes by immersion precipitation. II. Morphology formation

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