Ethylene content bound

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 4.36 Effect of bound ethylene content on 28-day drying shrinkage of EVA-modified mortars.

Figure 4.48 Relation between bound ethylene content and flexural and compressive strengths of EVA-modified mortars.

Styrene block copolymers are the most widely used TPEs, accounting for close to 45 percent of total TPE consumption worldwide at the close of the twentieth century. They are characterized by their molecular architecture, which has a hard thermoplastic segment (block) and a soft elastomeric segment (block) (see Fig. 3.2). Styrenic TPEs are usually styrene butadiene styrene (SBS), styrene ethylene/butylene styrene (SEES), and styrene isoprene styrene (SIS). Styrenic TPEs usually have about 30 to 40 percent (wt) bound styrene certain grades have a higher bound styrene content. The polystyrene endblocks create a network of reversible physical cross links that allow thermoplasticity for melt processing or solvation. With cooling or solvent evaporation, the polystyrene domains reform and harden, and the rubber network is fixed in position. ... 

Water molecules can be bound to both ethylene oxide (EO) groups of Brij 97 and to the hydroxyl (OH) groups of butanol. Unfortunately, it is not known for this system how many moleeules are bound to eiflier alcohol or surfactant. Therefore, two curves are presented in Fig. 35. The curves demonstrate the number of bound water molecules calculated per EO group and per EO -I- OH group versus the total water content, respectively. As the water content increases, the number of water molecules bound to EO or EO + OH groups increases and reaaches a maximum at 2.5 molecules for one curve and 1.5 for the other. This increase means that the water-binding centers do not become saturated until 0.6 of the total water volume fraction is ob-... 

---