Ethylene latex, effects

An example of the effectiveness of this equation is given by an aqueous HEUR gel made up of a polymer with Mn = 20 x 103 Daltons at a concentration of 30kgm-3 filled with a poly(styrene) latex with a particle diameter of 0.2 pm at q> = 0.2. The unfilled gel had a network modulus of 0.4 kPa, whilst the modulus of the filled gel was 0.7 kPa. Equation (2.68) predicts a value of 0.728 kPa. The poly(styrene) particles act as a non-interactive filler because the surface is strongly hydrophobic as it consists mainly of benzene rings and adsorbs a monolayer of HEUR via the hydrophobic groups, resulting in a poly(ethylene oxide) coating that does not interact with the HEUR network. This latter point was... 

To illustrate how the effect of the adsorption on the modulus of the filled gel may be modelled we consider the interaction of the same HEUR polymer as described above but in this case filled with poly(ethylmetha-crylate) latex particles. In this case the particle surface is not so hydrophobic but adsorption of the poly (ethylene oxide) backbone is possible. Note that if a terminal hydrophobe of a chain is detached from a micellar cluster and is adsorbed onto the surface, there is no net change in the number of network links and hence the only change in modulus would be due to the volume fraction of the filler. It is only if the backbone is adsorbed that an increase in the number density of network links is produced. As the particles are relatively large compared to the chain dimensions, each adsorption site leads to one additional link. The situation is shown schematically in Figure 2.13. If the number density of additional network links is JVL, we may now write the relative modulus Gr — G/Gf as... 

Effects of ethylene oxide-fatty alcohol condensates upon the mechanical and chemical stability of natural rubber latex (10)... 

The results summarised in Figure 7 show that small additions of ethylene oxide-fatty alcohol condensates to natural rubber latex generally cause the mechanical stability of the latex to fall. This phenomenon is attributed to the displacement of adsorbed proteinaceous molecules by the condensate molecules. Although the latter are more surface active than the former, they are presumably less effective in conferring mechanical stability upon the rubber particles, perhaps because, unlike the proteinaceous molecules, they are not ionised. 

We interpret this observation as implying that, for these condensates, the effect upon mechanical stability is determined primarily by the binding of water to the ethylene oxide units which are anchored to the rubber-water interface by the fatty-alcohol moiety of the condensate. In the case of condensates for which the overall mole ratio of ethylene oxide to fatty alcohol exceeds ca. 30, the effect upon mechanical stability is much greater than would be expected on the basis of the total amount of ethylene oxide which has been added to the latex, as evidenced by the... 

Figure 7. Effect of added ethylene oxide-fatty alcohol condensates upon mechanical stability of natural rubber latex ( 0). Levels of condensate are expressed in parts by weight. Numbers appended to curves indicate overall mole ratio ethylene oxide fatty alcohol in condensate.

Fig. 21 (a, b) The frequency dependencies of the storage G (a) and loss G" (b) moduli for different volume fractions of uncoated silica hard spheres (7 h = 210 nm) dispersed in ethylene glycol [238]. The solid lines represent MCT predictions, (c) Respective data (G solid square, G" open square for an aqueous glassy microgel suspension (PNIPAM-coated PS latex particles, overall radius 105.3 nm and effective volume fraction 0.585 at 10°C), along with the MCT lines [256]. The minimum of G" marks the inverse -relaxation time... 

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... 

Although the actual diameter of a polymeric particle can be measured by microscopic or other methods, the effective diameter for hydrodynamic puiposes, and hence the effective volume fraction, may be considerably larger. Surface layers can significantly increase the effective volume of latex particles. Such layers may be due to adsrxbed surfactants, adsrabed or reacted polymeric stabilizers such as poly(vinyl alcohol), hydroxyethyl cellulose or poly(ethylene oxide), and surface charges on the polymer particle. The smaller the particle size, the greater will be the contribution a surface layer (rf given thickness to the effective volume of flie particle. 

Research on the effect of monomer ratio in copolymer dispersions [e.g., SBR latex, poly (ethylene-vinyl acetate) (EVA) and poly (styrene-acrylic ester) (SAE) emulsions] on the strength of polymer-modified mortar using copolymer dispersions [21-23]... 

Polymers such as EVA, are used as admixture because it modify the elastic modulus, toughness, permeability and bond strength to various substrates in cement and mortars [10]. The polymer forms a film that creates a network inside the cement matrix, partially covering hydrated and anhydrous cement particles, sealing pores and bridging microcracks. Besides, this addition also changes the hydration rate. Silva et al [11] compare the effects of two polymers a water soluble polymer (HPMC — hydroxypropylmethylcellulose) and a latex [EVA-poly(ethylene-co-vinyl acetate)] on... 

Uses Defoamer for stripping, foam knock-down, and latex handling for pressure-sensitive adhesives, gravure inks, paints defoamer for food-contact coatings, paper/paperboard food pkg. adhesives Features Easily dispersible multi-component very effective with ethylene copolymers and compds. 

Uses Emulsifier, stabilizer, wetting agent for floor polishes, waxes, paints, personal care prods. polymerization surfactant for vinyl acetate and acrylic emulsions latex stabilizer dyeing assistant for acid and azo dyes emulsifier in mfg. of food-contact articles Features Effective at elevated temps, or in cone, electrolytes Regulatory FDA 21CFR 178.3400, EPA compliance Properties Off-wh. wax aromatic odor sol. in ethanol, water, ethylene dichloride sp.gr. 1.10 (50 C) HLB 18.2 cloud pt. > 100 C (1% aq.) flash pt. (PMCC) > 200 F pour pt. 114 02 F Ross-Miles foam 100 mm (0.1% aq., initial) nonionic 100% cone. 

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