Styrene-butadiene dispersions

The consumption of polymer dispersions in 1997 was 10xl06 t. The market is divided among styrene-butadien dispersions (35 %), dispersions containing vinyl acetate (32 %), styrene and styrene-acrylate dispersions (25 %) and others in minor quantities. They have many applications coatings and paints, adhesives, textile finishing, paper coatings and others. When used as coatings the dispersions should be suitable for food contact. Many substances can be used as monomers ... 

Styrene butadiene dispersions are generally stabilized with anionic, or anionic and nonionic emulsifiers. Carboxylation (incorporation of a small proportion of unsaturated carboxylic acids) of SB dispersions increases their stability and improves adhesion to various substrates. Almost all SB dispersions used in the coating sector are carboxylated. 

Styrene butadiene dispersions may undergo oxidative post-cross-linking via the double bond in the butadiene unit. Uncontrolled oxidation leads to embrittlement and, finally, to breakdown of the binder (chalking). The dispersions are thus unable to satisfy stringent requirements regarding color stability and UV resistance. 

Tests carried out on cement-polymer composites specimens. In conducted research program for modification of concrete series there were used different amount of styrene-butadiene dispersion additive (SBR). The following levels of polymer addition dosage were used 5, 10, 20 % of cement mass. Concretes were designed on the base of CEM I 32,5R cement, assuming its application on the level of 350 kg/m3. W/c ratio for all concrete mixes was equal to 0.50. As control the specimens made of concrete C 30/37 without any addition of SBR (0%) were adopted. 

Styrene-butadiene dispersions lead to varying film hardness, depending on the proportion of styrene used. Approximately equal proportions of styrene and butadiene result in binders which provide a relatively soft film and a very good pigment binding capacity. Disadvantages are the odor of the dispersion and the tendency of the films to yellow when exposed to hght Acrylate dispersions are specialties and... 

Initially starches and natural rubber latex were used as binders for improved tuft bind. They were replaced in the late 1950s by carboxylated styrene-butadiene dispersions (XSB). XSB emulsion polymers are very cost effective and easy to formulate, and they have become the working horse of the carpet backing industry and are almost exclusively used today. 

Carboxylated styrene-butadiene dispersions have a solids content of about 52%, a pH between 7.5 and 9.0, and a monomodal particle size distribution with an average diameter of about 150 nm. With this small particle size, the instantaneous conversion during emulsion polymerisation is high, which leads to low concentrations of by-products, such as 4-phenyl-cyclohexene (4-PCH) and 4-vinyl-cyclohexene (4-VCH) generated by Diel-Alder reaction of styrene and butadiene. 4-PCH and 4-VCH concentrations are required to be below certain limits, since they have a very low odour threshold. 

Fig. 1-10 Major suppliers of aqueous polymers dispersions. Product lines A acrylic dispersions, SB styrene butadiene dispersions, NB acrylonitrile butadiene dispersions, VAc vinyl acetate dispersions, EVA ethylene vinyl acetate...

Polymer type Carboxylated styrene butadiene dispersion (XSB)... 

Almost all synthetic binders are prepared by an emulsion polymerization process and are suppHed as latexes which consist of 48—52 wt % polymer dispersed in water (101). The largest-volume binder is styrene—butadiene copolymer [9003-55-8] (SBR) latex. Most SBRlatexes are carboxylated, ie, they contain copolymerized acidic monomers. Other latex binders are based on poly(vinyl acetate) [9003-20-7] and on polymers of acrylate esters. Poly(vinyl alcohol) is a water-soluble, synthetic biader which is prepared by the hydrolysis of poly(viayl acetate) (see Latex technology Vinyl polymers). 

Polymers. In combination with various metal salts, sorbitol is used as a stabilizer against heat and light in poly(vinyl chloride) (qv) resins and, with a phenohc antioxidant, as a stabilizer in uncured styrene—butadiene mbber (qv) compositions and in polyolefins (see Heat stabilizers Olefin POLYMERS Rubbercompounding). Heat-sealable films are prepared from a dispersion of sorbitol and starch in water (255). Incorporation of sorbitol in coUagen films gready restricts their permeabiUty to carbon dioxide (256). 

Styrene—butadiene—styrene modified bitumen is an elastomeric material mixed into an asphalt between 10 and 15%. By using high energy mixing, the SBS is uniformly dispersed throughout the asphalt to form a network, referred to as phase reversal because the minor component s (SBS) physical properties are displayed by the final mixture. A properly formulated SBS asphalt blend has an elongation of 100% or greater and is flexible down to temperatures below —6°C. 

Standard-grade PSAs are usually made from styrene-butadiene rubber (SBR), natural rubber, or blends thereof in solution. In addition to rubbers, polyacrylates, polymethylacrylates, polyfvinyl ethers), polychloroprene, and polyisobutenes are often components of the system ([198], pp. 25-39). These are often modified with phenolic resins, or resins based on rosin esters, coumarones, or hydrocarbons. Phenolic resins improve temperature resistance, solvent resistance, and cohesive strength of PSA ([196], pp. 276-278). Antioxidants and tackifiers are also essential components. Sometimes the tackifier will be a lower molecular weight component of the high polymer system. The phenolic resins may be standard resoles, alkyl phenolics, or terpene-phenolic systems ([198], pp. 25-39 and 80-81). Pressure-sensitive dispersions are normally comprised of special acrylic ester copolymers with resin modifiers. The high polymer base used determines adhesive and cohesive properties of the PSA. 

A bond coat of a polymer latex (also called polymer emulsions or dispersions) such as styrene butadiene (SBR), polyvinyl acetate (PVA) acrylics or modified acrylics. These are applied to the prepared concrete as... 

Emulsion paints are based on aqueous synthetic resin dispersions, which afford a lacquer-like paint film. The resin dispersions which are commonly used by the paint industry contain water as the carrier phase. A large number of such dispersions are available, based on different resins such as poly(vinyl acetate), which may be employed as a copolymer with vinyl chloride, maleic dibutyl ester, ethylene, acrylic acid esters, polyacrylic resin, and copolymers of the latter with various monomers, as well as styrene-butadiene or poly(vinyl propionate). These disper-... 

In copolymers having both a readily cross-linked structure and an aromatic component, such as styrene-butadiene copolymers, it is found that radiation protection is greatest when the aromatic units are randomly dispersed in the copolymer rather than in segregated units, as with a block copolymer... 

The MABS copolymers are prepared by dissolving or dispersing polybuiadiene rubber in a methyl methacrylate—acrylonitrile—styrene monomer mixture. MBS polymers are prepared by grafting methyl methacrylate and styrene onto a styrene—butadiene rubber in an emulsion process. The product is a two-phase polymer useful as an impact modifier for rigid polytvinyl chloride). 

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