Cement latex

Three generations of latices as characterized by the type of surfactant used in manufacture have been defined (53). The first generation includes latices made with conventional (/) anionic surfactants like fatty acid soaps, alkyl carboxylates, alkyl sulfates, and alkyl sulfonates (54) (2) nonionic surfactants like poly(ethylene oxide) or poly(vinyl alcohol) used to improve freeze—thaw and shear stabiUty and (J) cationic surfactants like amines, nitriles, and other nitrogen bases, rarely used because of incompatibiUty problems. Portiand cement latex modifiers are one example where cationic surfactants are used. Anionic surfactants yield smaller particles than nonionic surfactants (55). Often a combination of anionic surfactants or anionic and nonionic surfactants are used to provide improved stabiUty. The stabilizing abiUty of anionic fatty acid soaps diminishes at lower pH as the soaps revert to their acids. First-generation latices also suffer from the presence of soap on the polymer particles at the end of the polymerization. Steam and vacuum stripping methods are often used to remove the soap and unreacted monomer from the final product (56). 

Use Rubber-base adhesives and cements latex and asphalt emulsions. 

Pressure sensitive adhesives based on a variety of elastomers and applied from either latex, solvent, or hot melt systems have shown rapid growth in recent years. In addition, the development of hot melt assembly adhesives based on the styrenic thermoplastic elastomers is a key factor in the production of disposable diapers and other sanitary products. Even though the current emphasis of elastomer-based adhesive development is on pressure sensitive adhesives, large volumes of solvent cements, latex cements, and mastics are still produced. 

Chem. Descrip. Organo-modified silicone-based defoamer Uses Defoamer in aq. applies., e.g., inks, coatings, adhesives, cements, latex-containing formulations Features Self-emulsifying... 

To Protect Adhesives Joint Cements Latex Emulsion... 

Styrene—Butadiene Latex. SB latex is used in coatings, carpet backing, paper adhesives, cement additives, and latex paint. 

In contrast to other polymers the resistance to water permeation is low due to the hydrolysis of the poly(vinyl acetate) (163,164). Ethylene copolymers have been developed which have improved water resistance and waterproofness. The polymer can be used in the latex form or in a spray-dried form which can be preblended in with the cement (qv) in the proper proportion. The compressive and tensile strength of concrete is improved by addition of PVAc emulsions to the water before mixing. A polymer-soHds-to-total-soHds ratio of ca 10 90 is best. The emulsions also aid adhesion between new and old concrete when patching or resurfacing. 

An appHcation where latex paints show outstanding performance is over masonry such as stucco or ciader block constmction. This performance results from saponification resistance ia the preseace of the alkaH from the cement. Furthermore because masoary surfaces are porous, having both small and large pores, the low viscosity external phase of a latex paint can penetrate rapidly iato the small pores, causiag a rapid iacrease ia the viscosity of the remaining paiat. The bulk paiat, ia turn, sinks iato the larger holes more slowly than a solution-based paint. Thus less latex paint is required to cover the same surface area as compared to alkyd paints. 

Type of dryer tions, extracts, milk, blood, waste liquors, rubber latex, etc. gents, calcium carbonate, bentonite, clay sbp, lead concentrates, etc. trifuged sobds, starch, etc. dry. Examples centrifuged precipitates, pigments, clay, cement. ores, potato strips, synthetic rubber. objects, rayon skeins, lumber. sheets. her sheets. 

Applicability Most hazardous waste slurried in water can be mixed directly with cement, and the suspended solids will be incorporated into the rigid matrices of the hardened concrete. This process is especially effective for waste with high levels of toxic metals since at the pH of the cement mixture, most multivalent cations are converted into insoluble hydroxides or carbonates. Metal ions also may be incorporated into the crystalline structure of the cement minerals that form. Materials in the waste (such as sulfides, asbestos, latex and solid plastic wastes) may actually increase the strength and stability of the waste concrete. It is also effective for high-volume, low-toxic, radioactive wastes. 

Well cementing materials vary from basic Portland cement used in civil engineering construction of all types, to highly sophisticated special-purpose resin-based or latex cements. The purpose of all of these cementing materials is to provide the well driller with a fluid state slurry of cement, water and additives that can be pumped to specific locations within the well. Once the slurry has reached its intended location in the well and a setup time has elapsed, the slurry material can become a nearly impermeable, durable solid material capable of bonding to rock and steel casing. 

Rubber latex cement Rubber latex cement consists of mixtures of sand and other fillers which are gauged with rubber latex solution. These cements are suitable for dilute acid conditions and are particularly useful in conditions where dilute acid alternates with water or dilute alkalis. They remain very slightly resilient and adhere very well to stoneware. They are not of course... 

Salts of a-sulfo fatty acid esters can work as emulsifying agents for the preparation of asphalt emulsions and asphalt-latex emulsions. The ester sulfonates improve the storage stability of the emulsions [101,102]. In the manufacture of lightweight gypsum products air bubbles have to be mixed into the slurries. The use of salts of sulfonated C10 l8 fatty acid alkyl esters as foaming agents produces uniformly distributed fine bubbles [103]. Salts of C10 16 fatty acid alkyl ester sulfonates can also be added to cement mixtures to prevent slump loss of the mixtures [104]. 

Pressing is carried out within a cemented carbide die between two steel or cemented carbide punches. In order to impart enough mechanical strength to the blank to permit further manipulation without risk, removable organic binders (camphor, natural or synthetic waxes, latex or synthetic rubber, methyl polymethacrylate, polyvinyl alcohol, carboxymethylcellulose, ammonium alginate) are mixed into the powder, dissolved in a convenient volatile solvent. Some of these also act as lubricants thus minimizing the wear on the die. 

Vashkevitch Sychev (1982) have identified the main reaction product of the cement-forming reaction between copper(II) oxide and phosphoric acid as Cu3(P04)2. SHjO. The addition of polymers - poly(vinyl acetate) and latex - was found to inhibit the reaction and to reduce the compressive strength of these cements. However, impact strength and water resistance were improved. 

Resin cements or polymer cements have been reviewed by Chandra, Justnes, and Ohama [343]. Polymer cements are materials made by replacing the cement at least partly with polymers. Cements can be modified by latex, dispersions, polymer powders, water-soluble polymers, liquid resins, and monomers. 

Compositions of high-alumina cement containing quartz or glass, calcium carbonate, microsilica, carbon black, iron oxide red mud or screened fly ash, and styrene-butadiene latex have been described [141,1803,1804]. 

On the other hand, the addition of fibers may cause undesired properties of the cement [1759]. Fibers can actually increase pore and fracture systems in latex cements. The amount of fibers in a fiber seal cement influences the porosity and permeability while affecting compressive strength. During acid treatment of the formation, the fibers in the cement can be easily dislodged and extracted from the cracks, leaving pore spaces behind. 

Foam cement is a special class of lightweight cement. The gas content of foamed cement can be up to 75% by volume. The stability of the foam is achieved by the addition of surfactants, as shown in Table 10-9. A typical foamed cement composition is made from a hydraulic cement, an aqueous rubber latex in an amount up to 45% by weight of the hydraulic cement, a latex stabilizer, a defoaming agent, a gas, a foaming agent, and a foam stabilizer [359,362]. Foamed high-temperature applications are based on calcium phosphate cement [257]. 

However, the mechanism of action of filtration control additives is not yet completely understood. Examples are bentonite, latex, various organic polymers, and copolymers. Many additives for fluid loss are water-soluble polymers. Vinyl sulfonate fluid loss additives based on the 2-acrylamido-2-methyl-propane sulfonic acid (AMPS) monomer are in common use in field cementing operations [363]. The copolymerization of AMPS with conjugate monomers yields a fluid loss agent whose properties include minimal retardation, salt tolerance, high efficiency, thermal stability, and excellent solids support. 

Gilsonite is active as a fluid loss additive because the permeability of cement is reduced. Latex additives also act as fluid loss additives. They also act as bonding aids, gas migration preventers, and matrix intensifiers. They improve the elasticity of the cement and the resistance to corrosive fluids [921]. A styrene-butadiene latex in combination with nonionic and anionic surfactants shows less fluid loss. The styrene-butadiene latex is added in an amount up to 30% by weight of the dry cement. The ratio of styrene to butadiene in the latex is typically 2 1. In addition, a nonionic surfactant (octylphenol ethoxylate and polyethylene oxide) or an anionic surfactant, a copolymer of maleic anhydride, and 2-hydroxypropyl acrylate [719] can be added in amounts up to 2%. 

Carbon black may serve as a low-cost additive for controlling the gas migration in cement slurries [303]. It is intended as a suitable substitute for polymer latex and silica fume and has been tested in field applications [304,1256]. The concentration of carbon black varies from 2 to 20 parts, based on the weight of the dry cement [1220]. The particle size varies from 10 to 200 nm. A surfactant is necessary for dispersion, for example, formaldehyde-condensed naphthalene sulfonate or sulfonated cumarone or indene resins. 

R. R. Jones and R. B. Carpenter. New latex, expanding thixotropic cement systems improve job performance and reduce costs. In Proceedings Volume, pages 125-134. SPE Oilfield Chem Int Symp (Anaheim, CA, 2/20-2/22), 1991. 

Polymeric materials are commonly used for bonding materials. Impact or contact adhesives are mainly based on highly crystalline polychloroprene (Neoprene), NR latex is used as a flexible adhesive very suitable for use with fabrics. Rigid adhesives based on materials such as polystyrene cement, epoxy resin or cyanoacrylates are suitable for bonding of rigid materials. The bond is provided by intramolecular forces between the adhesive and the adherend. Adiabatic... 

Polyelectrolytes provide excellent stabilisation of colloidal dispersions when attached to particle surfaces as there is both a steric and electrostatic contribution, i.e. the particles are electrosterically stabilised. In addition the origin of the electrostatic interactions is displaced away from the particle surface and the origin of the van der Waals attraction, reinforcing the stability. Kaolinite stabilised by poly(acrylic acid) is a combination that would be typical of a paper-coating clay system. Acrylic acid or methacrylic acid is often copolymerised into the latex particles used in cement sytems giving particles which swell considerably in water. Figure 3.23 illustrates a viscosity curve for a copoly(styrene-... 

Alkyl alkoxy silanes have been found to be very effective in reducing alkali-aggregate expansion [11] (Fig. 6.4). Of the silanes used in the study, hexyl trimethyl siloxane and decyl trimethoxyl silane were found to be more effective in decreasing the expansion than the others. In the same study, Ohama et al. [11] investigated the effect of sodium silicofluoride, alkyl alkoxy silane, lithium carbonate, lithium fluoride, styrene-butadiene rubber latex and lithium hydroxide on compressive strength and the expansion of mortar containing cement with 2% equivalent Na20. The reduction of the level of expansion shown in Fig. 6.4 with the siloxanes was attributed to... 

Of the several types of the polymer-modified mortars and concretes used for various construction applications, latex-modified mortar and concrete are by far the most widely used materials. Latex-modified mortar and concrete are prepared by mixing a latex, either in a dispersed liquid or as a redispersible powder form with fresh cement mortar and concrete mixtures. The polymers are usually added to the mixing water just as other chemical admixtures, at a dosage of 5-20% by weight of cement. Polymer latexes are stable dispersions of very small (0.05-5 pm in diameter) polymer particles in water and are produced by emulsion polymerization. Natural rubber latex and epoxy latex are exceptions in that the former is tapped from rubber trees and the latter is produced by emulsifying an epoxy resin in water by the use of surfactants [87]. 

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