Powdered water repellants

Application Dedusting agent for dry cleaning detergent, alkaline powders, water-repellent fabric finishes. Used in emulsion polymerization for formation of polyvinyl acetate and acrylic films. 

A water-soluble white crystalline sofld, CS is disseminated as a spray, as a cloud of dust or powder, or as an aerosol generated thermally from pyrotechnic compositions. The formulation designated CSl is CS mixed with an anti-agglomerant when dusted on the ground, it may remain active for as long as five days. CS2 formulated from CSl and a siUcone water repellent, may persist for as long as 45 days (6). 

Dampproofing admixtures are water-repelling materials such as wax emulsions, soaps and fatty acids which react with cement hydrates [84, 85]. The most widely used water-repelling materials are the calcium or ammonium salts of fatty acids such as stearates. Proprietary products are available both as dry powders and liquids. Usually, a stearate soap is blended with talc or fine silica sand and used at the prescribed dosage per weight or bag of cement. In commercial liquid preparations, the fatty-acid salt (soap) content is usually 20% or less, the balance of the solid material is made up of lime or CaCl2. Some proprietary admixtures combine two or more admixtures, e. 

The semipermeable membrane proposed for the demineralization of sea water is based on H. L. Calendar s theory that osmosis takes place through the membrane as vapor, condensing at the opposite membrane surface. The actual membrane being used consists of two sheets of untreated cellophane separated by a water-repellent powder, such as a silicone-coated pumice powder. The vapor gap is maintained by an air pressure in excess of the pressure on the sea water and the cellophane sheets support the capillary surfaces, which will withstand pressures up to 1500 p.s.i. A number of successful experiments are reported with over 95% desalinization. The present effort is directed toward obtaining reproducible experimental results and better methods of fabricating the vapor gap. 

Finally, gap spacing and pressurization are truly the heart of the problem. The desirable conditions are fineness of the spacer material, its water repellency, and the degree to which it maintains the air pressure excess over the entire membrane surface. Drifilmed talc powder, Xerox powder, and silicone-coated pumice powder have all been used with success with relatively low pressure differentials across the sea water capillary membrane. 

Upon completion of these experiments it became apparent that the differential pressure in the gap was a more important variable than the water repellency of the powder. Hence a 3 X 3 orthogonal set of experiments was planned, using nylon hair nets as the spacer instead of silicone-coated pumice. It was believed that this design would be more reproducible. 

Nylon hair nets had been tried in the past with gap pressure differential of 5 p.s.i., and without the water-repellent powder in the gap there was no marked desalinization. 

Uses Thiram is a dimethyl dithiocarbamate compound and appears as a white to yellow crystalline powder with a characteristic odor. Thiram is used to prevent crop damage in the field and to protect harvested crops from deterioration in storage or transport. Thiram also is used as a seed protectant and to protect fruits, vegetables, ornamentals, and turf crops from a variety of fungal diseases. In addition, it is used as an animal repellent to protect fruit trees and ornamentals from damage by rabbits, rodents, and deer. Thiram is available as dust, flowable, wettable powder, water-dispersible granules, water suspension formulations, and in mixtures with other fungicides. Thiram has been used in the treatment of human scabies, as a sunscreen, and as a bactericide applied directly to the skin or incorporated into soap.17,50,52... 

Combination of metal to be deposited with water repellent powder. In composite plating, the characteristics of particles to be codeposited are the most important. Water repellent fluoroplastic powder represented by Polytetrafluoro-ethylene (PTFE) has various unique and interesting characteristics such as non-adhesiveness, self-lubricity and chemical resistance, as well as water repellency. Incorporation of such powder into the composite plating would give a surface with quite different characteristics from those obtained by conventional surface treatments. Representative water repellent powders used in this study of composite plating are graphite fluoride [(CF) ] and PTFE. 

Silicone resin emulsions. With the aid of suitable emulsifiers and stabilisers, insoluble silicone resins can be converted into water-soluble emulsions and can be diluted with water. Such emulsions are used as water-repellent additives for plaster or silicate emulsion paints as well as for the surface treatment of mineral powders such as perlite, aerated concrete granules, and so on. 

Owing to the large quantity of silicone particles per unit area a similar effect to a closed film is obtained with respect to drops of water. Powdered repellents are also added to aqueous paints to make them water repellent. 

Impregnation of exterior walls. Impregnation is carried out in order to protect vertical surfaces (exterior walls. Figure 6.17) or sharply sloping surfaces (rooves) against rain (Wacker-Chemie, 1983). Addition of dry powders to mineral finishing plaster imparts water repellency to plasters. 

To act as an effective lubricant in a tablet, the lubricant must be dispersed over the surface of the powder particles or granules. The more complete this layer, the more effective the lubricant action will be. However, this has two deleterious consequences. The first is that each powder particle presents a hydrophobic and hence water repellent exterior. It is well known that the presence of a lubricant based on fatty acids slows disintegration and dissolution, and has been shown to cause bioavailability problems. 

Hydrophobic It is related to the water repelling property of a membrane material or a substance. This property is characteristic of all oils, fats, waxes, resins, as well as finely divided powders such as carbon black and magnesium carbonate. 

Aquabead. [Micro Powders] Water beading/repellent wax. 

The surface resistivity of clean glass in air can be very high, of the order 1014 Ohm/square or larger (Morey, 1954). In the case of glass it is possible to increase the surface resistivity with a water repellent which serves to prevent the formation of a continuous layer of water (Holland, 1966). With powders this a common practice using silicone compounds. 

Erythrosine, a food colorant certified as Red No. 3, contains 58% iodine and is used in carbonated soft drinks, powdered drinks, gelatin desserts, icings and pet foods. The solvent Red 73 is used for dyeing and printing cotton, in printing half silk, and in dyeing jute and straw products. Fluoroiodocarbons are intermediates in the manufacture of oil and water repellents, sur-... 

Further liberation of free fat may occur under adverse storage conditions. If powder absorbs water it becomes clammy and lactose crystallizes, resulting in the expulsion of other milk components from the lactose crystals into the spaces between the crystals. De-emulsification of the fat may occur due to the mechanical action of sharp edges of lactose crystals on the fat globule membrane. If the fat is liquid at the time of membrane rupture, or if it becomes liquid during storage, it will adsorb on to the powder particles, forming a water-repellant film around the particles. 

The state of fat in powder has a major influence on wettability, i.e. the ease with which the powder particles make contact with water. Adequate wettability is a prerequisite for good dispersibility. Free fat has a water-repelling effect on the particles during dissolution, making the powder difficult to reconstitute. Clumps of fat and oily patches appear on the surface of the reconstituted powder, as well as greasy films on the walls of containers. The presence of free fat on the surface of the particles tends to increase the susceptibility of fat to oxidation. A scum of fat-protein complexes may appear on the surface of reconstituted milk the propensity to scum formation is increased by high storage temperatures. 

Long-chain diesters of the type CH3(CH2) 0)2P(0)0H with n = 14-22 are soft to the skin and can be used as coatings on cosmetic powders to improve water repellancy. Such esters are less irritating to skin and eyes than the corresponding sulphates or sulphonates [39]. 

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