Mechanism of the Gelling of Hevea Latex by Zinc Compounds

1952 ◽  
Vol 25 (4) ◽  
pp. 995-1005
Author(s):  
G. M. Kraay ◽  
M. van den Tempel
Keyword(s):  
Zinc Oxide ◽  
Reaction Mechanism ◽  
Ammonium Chloride ◽  
Room Temperature ◽  
Ammonium Salts ◽  
Zinc Ions ◽  
Latex Particles ◽  
Zinc Compounds ◽  
New Methods ◽  
Rubber Particles

Abstract Zinc oxide is known to be soluble to a certain extent in ammoniated Hevea latex. The solubility may be enhanced by several means, such as the addition of ammonium salts, and is due to the formation of zinc-ammonia complexes. The complexes themselves have no coagulating power. When heated, however, zinc ions are produced by dissociation of the complexes, and these ions react chemically with the adsorbed soap on the rubber globules, forming an insoluble zinc soap which links up all the rubber globules into a gel. Evidence in favor of the proposed mechanism was obtained by displacing the adsorbed natural higher fat acids of the rubber particles by a soap which does not form an insoluble zinc soap, such as Igepon-T. A latex treated in this manner does not gel when heated with zinc oxide and ammonium chloride at 70° C. By displacing the Igepon-T with ammonium oleate, the original rapid gelation is restored. Depending on the concentration of zinc ions available at room temperature and the amount and types of higher fat acids on the latex particles, thickening or even gelling may occur at room temperature. The above interpretation of the reaction mechanism may lead to new methods for the evaluation of latex.

The Interaction of Sulfur and Sulfur Compounds with Olefinic Substances. VII. Low-Temperature Sulfuration of Trialkylethylenes with Hydrogen Sulfide-Sulfur Dioxide and with a Sulfur-Zinc Dithiocarbamate System

1955 ◽  
Vol 28 (2) ◽  
pp. 470-479
Author(s):  
E. H. Farmer ◽  
J. F. Ford ◽  
J. A. Lyons
Keyword(s):  
Zinc Oxide ◽  
Hydrogen Sulfide ◽  
Sulfur Dioxide ◽  
Low Temperature ◽  
Room Temperature ◽  
Cross Linking ◽  
Sulfide Sulfur ◽  
Tetramethylthiuram Disulfide ◽  
Zinc Compounds ◽  
Low Concentrations

Abstract The sulfuration of trialkylethylenes with hydrogen sulfide-sulfur dioxide at 0° C (Peachey process) results in disubstitutive cross-linking of the olefins, yielding dialkenyl tetrasulfides. At higher temperatures, substitutive-additive cross-linking occurs, and alkyl alkenyl polysulfides are formed. Dialkenyl tetrasulfides are similarly formed by causing the olefin to react with sulfur at room temperature in the presence of zinc oxide and zinc dibutyldithiocarbamate, low concentrations of hydrogen sulfide acting as a catalyst for this reaction. At higher temperatures, the reaction is also exclusively disubstitutive, a feature connected with the function of zinc compounds in influencing the cross-linking reaction. The sulfuration of olefins with tetramethylthiuram disulfide at 140° C shows a similar influence of zinc compounds.

A Freeze Shadow Technique for the Preparation of Soft Paint Latexes for Electron Microscopy

1977 ◽  
Vol 35 ◽  
pp. 314-315
Author(s):  
Earl R. Walter ◽  
Glen H. Bryant
Keyword(s):  
Sample Preparation ◽  
High Vacuum ◽  
Vacuum System ◽  
Latex Particles ◽  
New Methods ◽  
Diffusion Pump ◽  
Film Forming ◽  
Routine Basis ◽  
Distribution Studies ◽  
Preparation Techniques

With the development of soft, film forming latexes for use in paints and other coatings applications, it became desirable to develop new methods of sample preparation for latex particle size distribution studies with the electron microscope. Conventional latex sample preparation techniques were inadequate due to the pronounced tendency of these new soft latex particles to distort, flatten and fuse on the substrate when they dried. In order to avoid these complications and obtain electron micrographs of undistorted latex particles of soft resins, a freeze-dry, cold shadowing technique was developed. The method has now been used in our laboratory on a routine basis for several years.The cold shadowing is done in a specially constructed vacuum system, having a conventional mechanical fore pump and oil diffusion pump supplying vacuum. The system incorporates bellows type high vacuum valves to permit a prepump cycle and opening of the shadowing chamber without shutting down the oil diffusion pump. A baffeled sorption trap isolates the shadowing chamber from the pumps.

scholarly journals Mechanisms and effects of zinc oxide nanoparticle transformations on toxicity to zebrafish embryos

2021 ◽  
Author(s):  
Gyudong Lee ◽  
Byongcheun Lee ◽  
Ki-Tae Kim
Keyword(s):  
Zinc Oxide ◽  
Physicochemical Properties ◽  
Zebrafish Embryos ◽  
Zinc Ions ◽  
Zno Nps ◽  
Zinc Oxide Nanoparticle ◽  
Toxicity Reduction ◽  
Oxide Nanoparticle

Environmental transformations modify the physicochemical properties of ZnO NPs, modulate their ability to reduce zinc ions, and determine the degree of toxicity reduction in zebrafish embryos.

scholarly journals Sensing mechanism of an optimized room temperature optical hydrogen gas sensor made of zinc oxide thin films

2020 ◽  
Vol 9 (5) ◽  
pp. 10624-10634
Author(s):  
Siti Nor Aliffah Mustaffa ◽  
Nurul Assikin Ariffin ◽  
Ahmed Lateef Khalaf ◽  
Mohd. Hanif Yaacob ◽  
Nizam Tamchek ◽  
...  
Keyword(s):  
Thin Films ◽  
Zinc Oxide ◽  
Gas Sensor ◽  
Room Temperature ◽  
Hydrogen Gas ◽  
Oxide Thin Films ◽  
Sensing Mechanism

scholarly journals Mechanism studies of hydrothermal cold sintering of zinc oxide at near room temperature

2019 ◽  
Vol 102 (8) ◽  
pp. 4459-4469 ◽  
Author(s):  
Xiaoyu Kang ◽  
Richard Floyd ◽  
Sarah Lowum ◽  
Matthew Cabral ◽  
Elizabeth Dickey ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Room Temperature

Notizen:Phosphorescence Decay in Thallium-Doped Ammonium Chloride

1978 ◽  
Vol 33 (10) ◽  
pp. 1241-1242 ◽  
Author(s):  
S. Chaudhari ◽  
T. R. Joshi ◽  
R. V. Joshi
Keyword(s):  
Aqueous Solution ◽  
Ammonium Chloride ◽  
Mechanical Treatment ◽  
Room Temperature ◽  
Host Lattice ◽  
Luminescence Decay ◽  
Decay Rates ◽  
Negative Ion ◽  
Ultraviolet Emission ◽  
Near Ultraviolet

Abstract The phosphorescence decay rates of thallium-doped ammonium chloride (NH4Cl:Tl) phosphors, prepared by crystallization from aqueous solution, have been studied at room temperature for near-ultraviolet emission. The effects of impurity concentration as well as thermal and/or mechanical treatment on the decay rates have been examined. Phosphorescence centres consisting of a Tl+ion and a nearby negative ion vacancy are suggested to be responsible for the observed luminescence decay. The changes in the decay characteristics after pretreatments are explained on the basis of the location of the centres in normal and distorted regions of the host lattice.

Crystal Perfection in Zinc Oxide with Occluded Carboxyl-Functionalized Latex Particles

2007 ◽  
Vol 7 (9) ◽  
pp. 1584-1589 ◽  
Author(s):  
Rafael Muñoz-Espí ◽  
Amreesh Chandra ◽  
Gerhard Wegner
Keyword(s):  
Zinc Oxide ◽  
Latex Particles ◽  
Crystal Perfection
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