Influence of the Counterion Nature on the Stability Sequence of Hydrophobic Latex Particles

Abstract 1. From measurements of the cataphoretic mobility of latex particles in potassium and calcium buffers, respectively, it has been calculated that in order to obtain high stability in latex compounds, the concentration of divalent ions must be of the order of 0.002 M or less. 2. Measurements of the cataphoretic mobility of latex particles suspended in solutions of constant zinc and ammonia concentrations indicate that in the presence of dissolved zinc oxide the stability of latex is increased with increasing pH above pH 9.6. This is attributed to conversion of divalent zinc ammonia ion (Zn(NH3)4++) into monovalent zinc ammonia hydroxide ion (Zn(NH3)3OH+). 3. A consideration of the mass action equations for zinc hydroxide and zinc ammonia hydroxide shows that the concentration of divalent zinc ion decreases rapidly as the ammonia concentration is reduced or as the pH is increased. 4. The EOH number of latex is defined as the number of grams of KOH per 100 grams of rubber corresponding to the end point (at pH 10.7–11) in the electrometric titration of latex with KOH. Experimental precautions in determining the KOH number are discussed. 5. Data are given which show that the KOH number of a normal latex may be reduced more than tenfold by creaming three times from 33% T.S. to 62% T.S. 6. The KOH numbers of commercially available normal latices have been found to vary between 1.2 and 2.4, and those of creamed or centrifuged latices between 0.55 and 0.95. 7. The amount of KOH for optimum stabilization (i.e., maximum stability, minimum viscosity and minimum change of properties with time) of zinc oxide compounds containing no added buffering ingredients varies with the latex, and is numerically equal to the KOH number. This quantity of KOH produces a pH of 10.7–11.0. 8. If appreciable amounts of protective ingredients such as casein, glue or gum arabic are added in compounding, sufficient additional KOH must be added to maintain a pH of 10.7–11 in the latex compound. The amounts of KOH required may be determined by electrometric titration of the protective ingredients.

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The Effect of Rapid Stirring on Latex and on Its Creaming

Rubber Chemistry and Technology ◽

10.5254/1.3540027 ◽

1941 ◽

Vol 14 (2) ◽

pp. 315-322

Author(s):

J. W. Van Dalfsen

Keyword(s):

Mechanical Stability ◽

Latex Particles ◽

The Stability ◽

Rapid Stirring

Abstract 1. The paper first discusses the determination of the mechanical stability of latex when stirred in a Hamilton-Beach mixer. Data are given on the stability of fresh latex, ammoniated latex, and concentrated latex. Particular attention is called to the increase in stability of ammoniated latex which takes place during storage, a phenomenon which is probably attributable to the formation of soap and accompanying increase in the charge of the latex particles. Soap added to latex increases considerably its stability and creaming capacity. 2. Fresh latex, stirred rapidly in a Hamilton-Beach mixer, undergoes microflocculation. The rapidly stirred latex coagulates entirely when it is allowed to stand quietly within a period of time which becomes shorter to the extent that stirring causes the mixture to approach more closely the point of actual coagulation in the mixer. This offers the possibility of coagulating fresh latex completely without the use of chemicals, but the method could be applied on a factory scale only with extreme difficulty. 3. When ammoniated latex is stirred rapidly for a time shorter than required for coagulation to become appreciable, microflocculation results. If, after having been stirred, such latex stands quietly, partial coagulation results. In this case the quantity of coagulum is greater, and the time for it to form is shorter, the more closely the mixing period approaches the coagulation point in the mixer.

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Influence of adsorbed proteins on the stability of polystyrene latex particles

Faraday Discussions of the Chemical Society ◽

10.1039/dc9786500264 ◽

1978 ◽

Vol 65 ◽

pp. 264 ◽

Cited By ~ 22

Author(s):

At van der Scheer ◽

Marcel A. Tanke ◽

Cees A. Smolders

Keyword(s):

Polystyrene Latex ◽

Latex Particles ◽

Adsorbed Proteins ◽

Polystyrene Latex Particles ◽

The Stability

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Open discussion

Symposium - International Astronomical Union ◽

10.1017/s0074180900029533 ◽

1982 ◽

Vol 99 ◽

pp. 605-613

Author(s):

P. S. Conti

Keyword(s):

Buenos Aires ◽

Large Mass ◽

List Type ◽

Common Phenomenon ◽

Open Discussion ◽

The Stability ◽

Ring Nebulae

Conti: One of the main conclusions of the Wolf-Rayet symposium in Buenos Aires was that Wolf-Rayet stars are evolutionary products of massive objects. Some questions:–Do hot helium-rich stars, that are not Wolf-Rayet stars, exist?–What about the stability of helium rich stars of large mass? We know a helium rich star of ∼40 MO. Has the stability something to do with the wind?–Ring nebulae and bubbles : this seems to be a much more common phenomenon than we thought of some years age.–What is the origin of the subtypes? This is important to find a possible matching of scenarios to subtypes.

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Symmetric Multistep Methods Revisited: II. Numerical Experiments

International Astronomical Union Colloquium ◽

10.1017/s0252921100031602 ◽

1999 ◽

Vol 173 ◽

pp. 309-314 ◽

Cited By ~ 3

Author(s):

T. Fukushima

Keyword(s):

Multistep Methods ◽

Computational Time ◽

Integration Time ◽

Implicit Methods ◽

Symmetric Methods ◽

Celestial Bodies ◽

The Stability ◽

Predictor Corrector ◽

Symmetric Multistep Methods ◽

Integration Errors

AbstractBy using the stability condition and general formulas developed by Fukushima (1998 = Paper I) we discovered that, just as in the case of the explicit symmetric multistep methods (Quinlan and Tremaine, 1990), when integrating orbital motions of celestial bodies, the implicit symmetric multistep methods used in the predictor-corrector manner lead to integration errors in position which grow linearly with the integration time if the stepsizes adopted are sufficiently small and if the number of corrections is sufficiently large, say two or three. We confirmed also that the symmetric methods (explicit or implicit) would produce the stepsize-dependent instabilities/resonances, which was discovered by A. Toomre in 1991 and confirmed by G.D. Quinlan for some high order explicit methods. Although the implicit methods require twice or more computational time for the same stepsize than the explicit symmetric ones do, they seem to be preferable since they reduce these undesirable features significantly.

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Uniformity of Magnification from Different Electron Microscopes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100060179 ◽

1967 ◽

Vol 25 ◽

pp. 32-33

Author(s):

Godfrey C. Hoskins ◽

V. Williams ◽

V. Allison

Keyword(s):

Diffraction Grating ◽

The Other ◽

Carbon Replica ◽

Electron Microscopes ◽

The Stability

The method demonstrated is an adaptation of a proven procedure for accurately determining the magnification of light photomicrographs. Because of the stability of modern electrical lenses, the method is shown to be directly applicable for providing precise reproducibility of magnification in various models of electron microscopes.A readily recognizable area of a carbon replica of a crossed-line diffraction grating is used as a standard. The same area of the standard was photographed in Phillips EM 200, Hitachi HU-11B2, and RCA EMU 3F electron microscopes at taps representative of the range of magnification of each. Negatives from one microscope were selected as guides and printed at convenient magnifications; then negatives from each of the other microscopes were projected to register with these prints. By deferring measurement to the print rather than comparing negatives, correspondence of magnification of the specimen in the three microscopes could be brought to within 2%.

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