Strength monomer ratio affects

The properties of a latex depend on the nature of polymers in the latex, particularly the monomer ratio in copolymers and the type and amount of plasticizers. The monomer ratio affects the strengths of the latex modified mortars to the same extent as the polymer-cement ratio [87, 92]. Mechanical and chemical stability, bubbling and coalescence on drying all depend on the type and amount of surfactants and antifoamers and the size of dispersed polymer particles. It is important that the use of selected antifoamers and surfactants as stabilizers or emulsifiers produces no adverse effect on cement hydration. 

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... 

Thermoplastics grades have a norbomene content in the range 60-80% with Tg values from 60-180°C, in this range the glass transition being almost linearly related to the norbomene content. The modulus of elasticity increases with norbomene content and for commercial materials is in the range 2600-3200 MPa but density (1.02g/cm), tensile strength 66 MPa and water absorption (<0.01 %) is little affected by the monomer ratio. 

The nature of the polymer latex is determined by the monomer ratio in the copolymer and this property of the latex affects strength values in manner similar to that obtained with the polymer-cement ratio. The effects of polymer-cement ratio on strength are presented in Table 6.14 [87]. 

In order to minimize swelling, MIP is often synthesized in a polar solvent, such as dimethylformamide (DMF) or ACN [113]. Most importantly, a (cross-linker)-to-(functional monomer) mole ratio affects the chemosensor performance. That is, a high (5 1) ratio enhances mechanical strength of an MIP film and favours formation of binding sites. But a low (1 5) ratio leads to a flexible MIP film of improved template memory and stronger adherence to the transducer surface [114]. Therefore, this ratio must be compromised for preparation of MIP of superior performance [114]. 

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