The Nature of the Particle Surface in Hevea Latex and Pastes of Rubber Hydrochloride and Polyvinyl Chloride

1958 ◽  
Vol 31 (3) ◽  
pp. 436-445
Author(s):  
G. Schuur
Keyword(s):  
Particle Surface ◽  
Natural Rubber Latex ◽  
Chemical Properties ◽  
Organic Chemical ◽  
Surface Active Agents ◽  
Rubber Particles ◽  
Surface Active ◽  
Technical Interest ◽  
Chemical Groups ◽  
Concentrated Dispersions

Abstract The colloid-chemical properties of natural rubber latex are influenced by many factors, such as the pH, the concentration of surface-active agents and the presence of ions of different kinds. Many of these factors have been studied intensively. However, it has usually been assumed that the surface of the rubber particles consists of plain hydrocarbon. Up to now it has been impossible to investigate the properties of the surface free from adsorbed soaps and proteins, for the removal of these surface-active agents results in coagulation of the latex. But the latex particles can be obtained in a hard and nontacky form by hydrochlorination and crystallization according to the methods of van Veersen and the author. The various surface-active agents can then be removed by filtering, washing, and extraction with organic solvents, without the loss of the surface by coagulation of the particles. The reactions of most organic chemical groups with hydrochloric acid are fairly well known and, though the original properties of the surface may be modified to some extent by the hydrochlorination, an investigation of the surface of rubber hydrochloride may give useful information regarding the properties of the original surface of the rubber particles. A suitable method for studying the nature of the surfaces of various rubber hydrochlorides would be to investigate the rheological properties of concentrated dispersions in organic media. Dispersions in plasticizers were selected, in the first place, because the experimental work is then not complicated by the volatility of the solvents, and secondly, because these dispersions in plasticizers are of some technical interest, since they can be used for the preparation of monofilaments from rubber hydrochloride.

The Preparation of Cyclized Rubber from Natural-Rubber Latex

1951 ◽  
Vol 24 (1) ◽  
pp. 195-196
Author(s):  
G. J. van Veersen
Keyword(s):  
Experimental Study ◽  
Sulfuric Acid ◽  
Natural Rubber ◽  
Hydrogen Chloride ◽  
Hydrogen Fluoride ◽  
Natural Rubber Latex ◽  
Rubber Latex ◽  
Boron Fluoride ◽  
Surface Active Agents ◽  
Surface Active

Abstract The hydrochlorination of rubber in the form of latex which has been stabilized by surface-active agents, such as Emulphor-O, or by cationic agents such as Fixanol, shows that hydrogen chloride molecules diffuse very easily into the latex globules. Accordingly it was to be expected that, by replacing hydrogen chloride gas by hydrogen fluoride gas, which is a cyclizing agent of rubber, a cyclized rubber would be obtained. This line of reasoning was confirmed experimentally. As a result of an experimental study, it was proved that boron fluoride, BF8 also, brings about cyclization of rubber in latex, and van Amerongen has already shown that sulfuric acid likewise can be used as a catalyst. Since sulfuric acid is much easier to handle than either hydrogen fluoride or boron fluoride, it was used in most of the experiments in the present work.

Rheological behavior of natural rubber latex in the presence of surface-active agents

1990 ◽  
Vol 41 (56) ◽  
pp. 975-983 ◽  
Author(s):  
N. R. Peethambaran ◽  
Baby Kuriakose ◽  
Manjari Rajan ◽  
A. P. Kuriakose
Keyword(s):  
Natural Rubber ◽  
Rheological Behavior ◽  
Natural Rubber Latex ◽  
Rubber Latex ◽  
Surface Active Agents ◽  
Surface Active

The Polymerization of Vinyl Monomers in Natural-Rubber Latex

1956 ◽  
Vol 29 (4) ◽  
pp. 1119-1126 ◽  
Author(s):  
George F. Bloomfield ◽  
P. McL. Swift
Keyword(s):  
Natural Rubber ◽  
Natural Rubber Latex ◽  
Vinyl Monomers ◽  
Rubber Latex ◽  
Dispersing Agent ◽  
Rubber Particles ◽  
Surface Active ◽  
Active Substances

Abstract Practical methods are described for polymerizing methacrylic esters, styrene, and other vinyl monomers in natural-rubber latex. The larger rubber particles require an appreciable time to attain equilibrium with the monomer diffusing into them from a liquid monomer phase dispersed in the serum. Provided that substantial proportions of added surface-active substances are avoided, rubber-soluble monomers can be polymerized almost entirely within the rubber particles, and the modified latex then contains no separately emulsified free polymer. Such conditions favor combination of polymer with rubber. The addition of a sufficiently large amount of dispersing agent favors polymerization of emulsified monomer, with less involvement of the rubber. In this way there can be obtained mixtures of rubber and polymer from monomers whose polymerization is otherwise inhibited by the presence of polyisoprene hydrocarbons.

scholarly journals Nanocrystals of Poorly Soluble Drugs: Drug Bioavailability and Physicochemical Stability

2018 ◽  
Author(s):  
Maria Rosa Gigliobianco ◽  
Cristina Casadidio ◽  
Roberta Censi ◽  
Piera Di Martino
Keyword(s):  
Particle Size ◽  
Particle Surface ◽  
Poorly Soluble Drugs ◽  
Drug Bioavailability ◽  
Particle Surface Area ◽  
Drug Products ◽  
Surface Active Agents ◽  
Physicochemical Stability ◽  
Poorly Soluble ◽  
Surface Active

Many approaches have been developed over time to counter the bioavailability limitations of poorly soluble drugs. With advances in nanotechnology in recent decades, science and industry have been approaching this issue through the formulation of drugs as nanocrystals, which consist of pure drugs and a minimum of surface active agents required for stabilization. They are carrier-free submicron colloidal drug delivery systems with a mean particle size in the nanometer range, typically between 10 and 800 nm. By reducing particle size to nanoscale, the particle surface area available for the molecule dissolution in the direction of dissolution medium is increased, and thus bioavailability is enhanced. This approach has proven successful, as demonstrated by the number of such drug products on the market. R&D and industry have offered many technological solutions to reduce the particle size to nanoscale, and also devised solutions for the handling of particle of nanodimensions, such as methods to accurately measure nanoparticle size and techniques to prevent physicochemical and stability related problems, such as aggregation. The present work provides an overview of the more recent achievements in improving the bioavailability of poorly soluble drugs according to their administration route, and describes the methods developed to overcome physicochemical and stability related problems.

scholarly journals Density and surface tension of aqueous solutions of adjuvants used for tank-mixes with pesticides

2012 ◽  
Vol 58 (No. 12) ◽  
pp. 568-572 ◽  
Author(s):  
J. Janků ◽  
L. Bartovská ◽  
J. Soukup ◽  
M. Jursík ◽  
K. Hamouzová
Keyword(s):  
Surface Tension ◽  
Aqueous Solutions ◽  
Chemical Properties ◽  
Calculated Density ◽  
Surface Active Agents ◽  
Physico Chemical ◽  
Pesticide Formulations ◽  
Density Values ◽  
Surface Active

Adjuvants are surface active agents that are added to pesticide formulations or tank-mix to facilitate the mixing, application, or efficacy of these products. Addition of adjuvants changes the physico-chemical properties of spray liquid. In this work, we have focused in particular on surface tension and density of aqueous solutions of different adjuvants registered for mixing with herbicides. Eleven different adjuvants were subject of this study under laboratory conditions. An equation which enables determination of density of aqueous solutions in concentration range of 0–15 g/kg was designed. Average difference between the experimental and calculated density values amounts to ± 0.006%. The concentration dependence of surface tension was utilized to determine the critical micelle concentration (cmc). Evidently, the cmc of most tested adjuvants was lower than the amount recommended by manufacturer, especially in case of adjuvants Dedal 90 EC and Mero 33528. For adjuvant Trend 90 EC the recommended rate is even lower than that obtained for the cmc. Maximum reduction of the surface tension of water was achieved with adjuvants Silwet L-77 and Break Superb.    

The Reversal of Some Effects of a Surfactant on Pesticide Deposits on Foliage by Different Methods of Application

1962 ◽  
Vol 94 (8) ◽  
pp. 874-875 ◽  
Author(s):  
K. Williams ◽  
D. P. Pielou
Keyword(s):  
Physical State ◽  
Chemical Properties ◽  
Plant Surface ◽  
Surface Active Agents ◽  
Mode Of Application ◽  
Wide Range ◽  
Surface Active ◽  
Methods Of Application

The influence of surface active agents (surfactants) such as “wetters”, “spreaders” and “stickers” on the deposition of pesticides on foliage is not always readily predictable. The results are influenced by the physical state of the pesticide (solution, emulsion, suspension), its chemical properties, the concentration of borh pesticide and surfactant, the nature of the plant surface, and the mode of application. Kearns (1) has particularly emphasized that the plant surface must be considered when a formulation of a pesticide is produced, and that there can he no general prescription satisfactory for a wide range of crops. For instance, a fungicide formulation that was excellent for banana, the leaves of which are difficult to wet, produced poor results on coffee, a crop relatively easy to treat. Our results now show that opposing results may also be obtained with the same pesticide, same surfactant and same crop, when two different methods of application are used.

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