Emulsion polymerization of tetrafluoroethylene: effects of reaction conditions on particle formation

Kim, Cu; Lee, Jang-Ming; Ihm, Son Ki

doi:10.1016/s0022-1139(98)00328-5

Cited by 27 publications

(34 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The previous published data (0.01 kg of TFE/100 kg of water at 1 bar and 30°C 24 ) coincide with the data obtained by our experiment. 27 The TFE uptake (mol) increases linearly with reaction times when the agitation speed is less than 750 rpm. In Figure 7(a), no induction reaction is observed in the polymerization of TFE because nucleation or particle generation is completed in a few minutes due to the hydrophobic property observed in our previous article.…”

Section: Effects Of Impeller Typesmentioning

confidence: 66%

“…27 The Table I. coagulation can be accelerated when the surfactant concentration is too high, due to the steric effect. In the first stage, the polymerization rate decreases sharply with reaction time.…”

Section: Effects Of Surfactant Concentrationsmentioning

confidence: 89%

“…In Figure 7(b), the polymerization rate increases sharply with the agitation speed, but when the speed is greater than 500 rpm, the opposite trend prevails. 27 It was observed in this study that the crystallinity of as-polymerized PTFE in this polymerization is as high as 90%; the polymer particles were rigid, so the monomer hardly diffused to the inside of the particles. 5).…”

Section: Effects Of Impeller Typesmentioning

confidence: 99%

See 2 more Smart Citations

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

Kim

Lee

Ihm

1999

J. Appl. Polym. Sci.

View full text Add to dashboard Cite

The emulsion polymerization of tetrafluoroethylene (TFE) was carried out in a semibatch reactor using a chemical initiator (ammonium persulfate) and a fluorinated surfactant . The effects of the reaction condition were investigated though the polymerization rate, molecular weight of polytetrafluoroethylene (PTFE), and stability of the dispersion. The emulsion polymerization of TFE was different from conventional emulsion polymerization. The polymerization rate was suppressed when the polymer particles were significantly coagulated. The polymerization rate increased with operating temperature, surfactant concentration, and agitation speed, due to the enhanced stability of the polymer particles. However, once the parameter value was reached, the rate decreased due to the coagulation of the particles. Stable PTFE dispersion particles were obtained when the surfactant concentration was in the range between 3.48 ϫ 10 Ϫ3 and 32.48 ϫ 10 Ϫ3 mol/liter, which is below critical micelle concentration (CMC). The molecular weight of the PTFE obtained was a function of the surfactant and initiator concentrations, and the polymerization temperature. The molecular weight increased as each parameter decreased. This is against the phenomena observed in a conventional emulsion polymerization. A stable PTFE dispersion polymer having a high molecular weight was obtained by optimizing the reaction conditions.

show abstract

Section: Effects Of Impeller Typesmentioning

confidence: 66%

Section: Effects Of Surfactant Concentrationsmentioning

confidence: 89%

Section: Effects Of Impeller Typesmentioning

confidence: 99%

See 1 more Smart Citation

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

Kim

Lee

Ihm

1999

J. Appl. Polym. Sci.

View full text Add to dashboard Cite

show abstract

“…This finding appears analogous to that of other researchers who reported on the conditions of emulsification of fluoroethylene particles wherein aggregates formed both at very low and very high concentrations of surfactant. 28 It appears that the reduction of drop (and subsequent particle) size at low concentrations of surfactant is related to a reduction of interfacial tension, as indicated by eqn (1). However, increased concentrations of Span 80 apparently promoted multiple layers of surfactant on drop surfaces with a concomitant increase of complex droplet interactions involving coalescence.…”

Section: The Effect Of Surfactant Concentration On Particle Size and mentioning

confidence: 99%

Fabrication by three‐phase emulsification of pellicular adsorbents customised for liquid fluidised bed adsorption of bioproducts

Jahanshahi

Pacek

Nienow

et al. 2003

J of Chemical Tech & Biotech

View full text Add to dashboard Cite

A novel dense pellicular adsorbent, custom-designed for liquid fluidised bed adsorption of protein bioproducts, has been fabricated by coating zirconia-silica particles with agarose gel in a threephase emulsification process. A slurry feedstock comprising solid zirconia-silica particles (120 µm average diameter) suspended in an aqueous solution of agarose was emulsified in an oil-surfactant mixture in a stirred vessel to yield composite droplets. These were subsequently stabilised by cooling to form spherical pellicular particles characterised by a porous, pellicular coat cast upon a solid core. The impact of agitation speed, surfactant concentration, oil viscosity and slurry composition upon the pellicle depth and overall particle diameter was investigated. Pellicle depth decreased with increasing impeller speed and decreased oil viscosity, whilst increased slurry viscosity enhanced that parameter. Initial increases from low concentrations of Span 80 surfactant (0.1% w/v oil) reduced the depth of the agarose pellicle, but the highest values investigated (1.5% w/v oil) promoted particle aggregation. The fluidisation behaviour of particles fabricated under various conditions was characterised by the measurement of expansion coefficients and axial dispersion coefficients for the liquid phase when operated in a standard fluidised bed contactor. Both parameters were found to be comparable or superior to those reported for conventional, composite fluidised bed adsorbents. The controlled coating of porous agarose upon a solid core to yield specific pellicular geometries is discussed in the context of the fabrication of adsorbents customised for the recovery of a variety of bioproducts (macromolecules, nanoparticulates) from complex particulate feedstocks (whole broths, cell disruptates and unclarified bio-extracts). Given the agreement between the size of the pellicular particles and the trends expected from theory, the large-scale manufacture of such particles for customised industrial use is recommended.

show abstract

“…[4] Rod-like cylindrical particles on the micrometer scale could also form the basis of materials with unique properties, although very few processes for making such particles have ever been developed. For decades the entropic self-assembly of rod-like colloidal particles has been of intense interest, [5] but it has been studied mainly with viruses [6] and, in a few cases, with inorganic particles, [7] as suitable anisotropic particles were not readily available.…”

Section: ±1mentioning

confidence: 99%

Scalable Synthesis of a New Class of Polymer Microrods by a Liquid–Liquid Dispersion Technique

et al. 2004

View full text Add to dashboard Cite

ExperimentalFabrication of PPy Nanoparticles: For the synthesis of the PPy nanoparticles with an average diameter of 2 nm, octyltrimethylammonium bromide (OTAB; 6.0 g) was magnetically stirred in 40 mL of distilled water at 3 C. Pyrrole (1.0 g) was then added dropwise to the surfactant solution, and iron(III) chloride (5.561 g) dissolved in a small amount of distilled water was added to the reaction mixture. Chemical polymerization proceeded for 3 h at 3 C. The reaction product was then transferred to a separating funnel and excess methanol was added to remove the surfactant and residual iron(III) chloride. A small amount of isooctane was added to promote the precipitation of the PPy nanoparticles. The upper solution containing surfactant and unreacted iron(III) chloride was discarded and the nanoparticle precipitate was dried in a vacuum oven at room temperature. PPy nanoparticles with a diameter of about 6 nm were prepared using decyltrimethylammonium bromide (DeTAB; 2.3 g), following the same procedure.Carbonization Process: In a typical carbonization procedure, the PPy nanoparticles (about 2 g) collected from two runs of the microemulsion polymerization were precarbonized at 800 C for 3 h under Ar gas flow (0.2 L min ±1 ). Carbon felt was put at the inlet of Ar flow to reduce the oxidation of the polymer precursor. After the pretreatment at 800 C, the weight of the carbonized product was reduced to 30±35 % of the initial loading weight. The ªmissingº components, formed as a result of carbonization reactions such as denitrogenation, dehydrogenation, and dehalogenation, are removed by the Ar flow. The products of two runs of the pretreatment were collected and transferred to a quartz tube 4 cm in diameter. The quartz tube was evacuated and refilled with argon repeatedly. The argon-filled quartz tube was then placed in an electrical furnace equipped with a larger diameter alumina tube (6 cm in diameter). The valve of the quartz tube was opened and the alumina tube containing the quartz tube was evacuated and refilled with argon repeatedly. The second carbonization proceeded with streaming argon at a heating rate of 3 C min ±1 . After 6 h of carbonization, the residual soot was collected and toluene was added to the quartz tube containing the sublimed fullerene film. The quartz tube was sonicated with gentle heating. The crude soot was refluxed with toluene in a standard Soxhlet extractor at 100 C for 12 h.Instrumental Analysis: TEM images were taken with a JEOL 2010 F microscope and EDX analysis was performed using a Philips CM 20 microscope. MALDI-TOF mass spectra were obtained with a Voyager-DE STR Biospectrometry Workstation (Applied Biosystems) operating in positive mode at an accelerating voltage of 20 kV using dithranol as the matrix. HPLC analysis was performed with a HP1100 liquid chromatograph. A 250 mm 4.6 mm i.d. monomeric octadecylsilica (ODS) column was used as the stationary phase. A mixture of toluene and methanol (55:45) was used as the mobile phase at a flow rate of 0.6 mL min ±1 . Detection was...

show abstract

Emulsion polymerization of tetrafluoroethylene: effects of reaction conditions on particle formation

Cited by 27 publications

References 12 publications

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

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

Fabrication by three‐phase emulsification of pellicular adsorbents customised for liquid fluidised bed adsorption of bioproducts

Scalable Synthesis of a New Class of Polymer Microrods by a Liquid–Liquid Dispersion Technique

Contact Info

Product

Resources

About