EVA latex

Table 5.1 Rec for Emulsion Polymerization of Typical EVA Latex for Redi rsible EVA Powder. ( 1990, American Concrete Institute, reprinted wiA permission.)...

Alcogum 9710 thickener, EVA copolymers Alcogum 1370 thickener, EVA latex compds. 

Adhesives are used in tufted carpets to anchor and stabilize the yarns they can also be used to attach a foam backing or a laminated secondary backing. Latices predominate with SBR (cross-linked) being the most widely used EVA latex (see Ethylene-vinyl acetate copolymers) is cheaper but has lower bond strength and is water sensitive. Other adhesives used are PVC plastisols in carpet tiles and hot melts and two-component polyurethanes in top-quality products (because hot melts and polyurethanes are relatively expensive). 

Uses Defoamerfor latex paints based on acrylic, S/B, PVAc, and EVA latexes defoamerfor acrylics, P Ac, PVOH, neoprene, and nat. latexes for adhesives and glues... 

Latexes are usually copolymer systems of two or more monomers, and their total solids content, including polymers, emulsifiers, stabilizers etc. is 40-50% by mass. Most commercially available polymer latexes are based on elastomeric and thermoplastic polymers which form continuous polymer films when dried [88]. The major types of latexes include styrene-butadiene rubber (SBR), ethylene vinyl acetate (EVA), polyacrylic ester (PAE) and epoxy resin (EP) which are available both as emulsions and redispersible powders. They are widely used for bridge deck overlays and patching, as adhesives, and integral waterproofers. A brief description of the main types in current use is as follows [87]. 

The reduction in porosity, decreased water content, and air entrainment that results when latexes are used in mortar and concrete mixes make them much more resistant to freezing and thawing conditions than conventional mortar and concrete. Figure 6.17 presents the freeze-thaw durability in water (-18 to 4°C) of combined water-and dry-cured SBR-, PAE- and EVA-modified mortars [98], The frost resistance of mortars made with these latexes is markedly improved even at polymer-cement ratios of 5%. However, an increase in the polymer-cement ratio does not necessarily produce further improvement in freeze-thaw resistance. EMM and EMC, when exposed to outdoor conditions involving freeze-thaw, UV radiation and carbonation show better weatherability when compared with conventional mortar and concrete. 

TNPP is used as a phospite antioxidant and a stabilizer for elastomers such as SBR, NBR, and SIS. Used as a stabilizer and a chelator/complexing agent in PC, PE, PP, PVC, copolymers such as ABS (Acrylonitrile-Styrenic based), SBR, and EVA (Ethylene-vinyl acetate) and in polymer latex and other aqueous systems. TNPP also prevents gel formation during polymerization finishing, storage, and factory processing. 

AranoK . [Uniroyal] Amines sutbiliz-ers, antioxidants fa polypropylene, polyethylene, EVA, polyamid used in fabric (uoofing, clothing, wire insulation, latex, foam. 

In particular, the commercial latexes widely used in the world are styrene-butadiene rubber (SBR), polychloroprene rubber (CR), polyacrylic ester (PAE) and poly(ethylene-vinyl acetate) (EVA) copolymers. Most commercial polymer latexes for cement modifiers contain proper antifoaming agents, and can be generally used without the addition of the antifoaming agents during mbcing. 

Ohamal ll l studied the effect of monomer ratio in EVA, SBR, and poly (styrene-butyl acrylate, SAE) latexes on the strengths of latex-modified mortars (Fig. 4.10). The monomer ratio affects the strengths of the latex-modified mortars to the same extent as the polymer-cement ratio. The maximum strengths of EVA- and poly(styrene-butyl acrylate)-modified mortars are obtained at a bound ethylene content of 13% and a bound styrene content of 55% respectively. The strengths of SBR-modified mortar increase with a rise in the bound styrene content. These results are similar to those obtained by Cherkinskii, et al.f i The tensile strength of the dry films made from SBR latexes increases sharply when the bound styrene content is raised, and there is a positive correlation between the strength of the films and the flexural strength of SBR-modified mortars with polymer-cement ratios above 10% as shown in Fig. 4.11.li l... 

Figure 4.10 Effects of monomer ratio in EVA, SBR and poly(styrene-butyl acrylate, SAE) latexes on flexural and compressive strengths of latex-modified mortars.

The thermal resistance of latex-modifled mortar and concrete is governed by the nature, especially glass transition temperature of polymers used, polymer-cement ratio, and heating conditions, and ultimately by the thermal degradation of the polymers. Figure 4.59f l indicates the thermal resistance of SBR-, PAE-, and EVA-modified mortars at 100 to 200°C. The flexural strength of most latex-modified mortars at 100°C tends to initially... 

Similar to latex-modified systems, the properties of redispersible polymer powder-modified systems are improved in comparison with ordinary cement mortar and concrete, and these depend on the nature of polymer and polymer-cement ratio. Figs. 5.3 to 5.5i l represent the strengths, adhesion to cement mortar, water resistance, and water absorption of the redispersible polymer powder-modified mortars. The properties are improved with an increase in the polymer-cement ratio. This tendency is very similar to that of the latex-modified systems. In general, the redispersible polymer powder-modified mortars are inferior to SBR-modified mortar (control) in certain properties. VAA eoVa powder-modified mortars show tetter properties than EVA powder-modified mortars as seen in Fig. 5.5. The film formation characteristics of recent redispersible polymer powders for cement modifiers are improved, and continuous polymer films can be found in the redispersible polymer powder-modified systems as seen in Fig. 5.6. This contributes greatly to improvements in their properties. 

According to a recent study, Bright, et al.1 1 compared the physical properties of various latex-modified mortars and redispersible EVA powder-modified mortars, and showed that the properti of EVA powder-modified mortars are at least equal to those of the latex-modified mortars as seen in Fi. 5.7 to 5.9i i Figure 5.10 exhibits the strength properties of patching mortars using redispersible polymer powders.i l... 

Figure 5.7 Comparison of tensile strength of latex- and redispersible EVA powder-modified mortars. ( 1993, ASTM, reprinted with permission.)...

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