Acrylic polymer mortars

Advances came quickly. Chemists designed special acrylic polymers that could be used in the manufacture of leak-proof tape to wrap around undersea cables. Or blended with rubber to produce a mortar that swelled on contact with water, providing a tight seal. This was used in the construction of the Chunnel, the artery that connects England and France beneath the waters of the English Channel. You sure wouldn t want any water seeping through those walls. Super slurpers have also proven themselves useful in the little pads you sometimes... 

Acrylic polymer concrete and mortars fast curing good chemical properties patch repairs... 

When acrylic polymers are added into a cement mortar mix, their spheres coalesce to form a continuous polymer matrix which coats the hydrating cement grains and aggregate. This polymer matrix acts as a barrier which helps to improve the hydration of the cement and also provides a polymeric network which increases the toughness and durability of the finished product. 

Table 5.9 Properties of acrylic-modified mortars compared with unmodified mortars. Source Tsai, M.C, Burch, M.J. and Lavelle, J.A., Solid grade acryhc cement modifiers, in Polymer Modified Hydraulic Cement Mixtures, ASTM STP 1176 (eds L.A. Kuhlam and D.G. Walter), Table 2 published by the American Society for Testing and Materials, Philadelphia, PA, 1993...

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... 

When considering a cementitious mortar mix for use in the manufacturing of an ultra-lightweight thin film product, the addition of a suitable polymer modifier can enhance both the fresh and hardened properties of such lightweight material. The addition of styrene butadiene rubber latex (SBR) latex yielded the best overall results in terms of workability, formability, mouldability, flowability, compressive and flexural strengths. The improvements offered by the addition of the acrylic polymer were less impressive and the use of an acrylic modifier is thus not recommended for use in ultra-lightweight thin film products. It is also confirmed that small adjustments to the water cement ratio alter the workability of such mixes and may be used to tweak mix designs to suit specific applications and uses. Thus with the addition of either a SBR latex or acrylic polymer and... 

Acrylic concretes and mortars are used in applications which require fast curing. Acrylic crack-injecting systems are suitable for wet cracks. Products such as adhesives, asphalt modifiers and floor-care polymers find only a small percentage of applications. 

Acrylic emulsions (or acrylic latices) are characterised as high-solids polymers having a film-forming temperature at or below room temperature (Lavelle, 1986). They have excellent hydrolysis resistance compared with other resins and are well suited as modifiers for portland cement mortars. Studies have shown that certain acrylic latices impart excellent workability at lower water demand, thin section adhesion and toughness, improved flexural strength and tensile strength and outstanding adhesion (Lavelle, 1983). 

Polymer modifier Acrylic powder A Acrylic latex Unmodified mortar ... 

The acrylic resins may be so polymerized that a resultant product may be obtained which can be dispersed in water to form a true polymer emulsion. Such a product is now available as a cement mortar modifier. By dry blending this resin with appropriate cementitious materials, it is possible to formulate a one-package acrylic modified cement mortar. Addition of water to the dry blend will produce a mortar with superior adhesion and physical strength properties. 

Polymer-modified mortars can be obtained by replacing part of the mixing water with a synthetic latex (e. g. styrene butadiene or acrylate) to the mix. Although the binder is still cementitious, and thus alkalinity is guaranteed, the latex may improve the workability, the waterproofness, the carbonation and chloride resistance, the tensile and flexural strength of the repair mortar [8]. It can also reduce the modulus of elasticity, increase the bond to the substrate, reduce the rate of drying out and thus the rate of shrinkage. 

In conventional exterior-use paints SB dispersions have largely been replaced by styrene-acrylate dispersions, and their use is now restricted to special applications (corrosion protection primers, wood primers, mortar modification) where low film permeability to gases, water vapor, etc., and complete resistance of the polymer to hydrolysis are necessary. In order to achieve a uniform surface and thus improve printability, paper and card are coated with paper-coating colors. Carboxylated SB dispersions are used in these paints as binders. 

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]... 

Y. Ohama, K. Demura, M. Hamatsu and M. Kakegawa Properties of polymer-modified mortars using styrene-butyl acrylate latexes with various monomer ratios. ACI Materials Journal Vol.88, No.l (1991), pp.56-61. 

In Fig. 1 the hopper flow time of the various mortars is shown. It can clearly be seen that the addition of the polymer dispersions has no significant effect on the hopper flow time. After adding the styrene-acrylate, the hopper flow time of the reference mortar composition decreased slightly from 42.8s to 36.4s/40.0s without segregation of the mortar. Furthermore, the addition of styrene-butadiene has led to a decrease in the hopper flow time, which can be attributed to the improvement of workability after the addition of the polymer dispersion. However, the two polymer types showed different tendencies in the hopper flow time. With styrene-butadiene, the hopper flow time decreases with higher polymer content, whereas the hopper flow time increases with a higher content of styrene-acrylate. 

The addition of styrene-acrylate causes a significant increase in the bending tensile strength (Fig.2). An increase from 7.4 MPa to 11.7 MPa at the age of 28 days can be observed. This value is reached with the 10% as well as the 20% dosage. Adding styrene-butadiene does not result in a considerable increase in the flexural strength, which is in compliance with the conclusion that not all of the polymer modifications bring about the desired properties. The required properties of the modified mortar are dependent up on the used dispersion and the composition. However, this can only be determined from experiments. 

For this reason, the penetration depths are much lower in comparison with the reference mortar composition. For the mixtures with 20% concentration of styrene-butadiene and styrene-acrylate, the depth of water penetration after dry storage is lower compared to the depth after storage under water. This is contrary to the results of the reference mortar composition and shows that a drying out of the mortar is necessary to activate the effects of the polymer dispersions. 

The first test results after 28 days of storage under water already show a reduction of chloride migration coefficients for the mortars with polymer additives (Fig. 4). When compared to the reference mortar composition, a reduction in the chloride-migration-coefficient from 1.55x10-12 mVs to 0.80x10-12 mVs was achieved, by using styrene-acrylate of 20 % concentration. 

An MIP adsorbent is prepared for the extraction of 7-diethylamino-4-methyl-coumarin (Fig. 3). The print molecule, 7-diethylamino-4-methylcoumarin (4 mmol, 0.925 g), a functional monomer, 2-(trifluoromethyl) acrylic acid (12 mmol, 1.681 g), a cross-linking monomer, ethylene glycol dimethacrylate (60 mmol, 11.893 g) and a polymerization initiator, 2,2 -azobis(2,4-dimethylvaleronitrile) (0.140 g) are dissolved in anhydrous toluene (18 mL) in a 50-mL borosilicate PYREX tube.The solution is briefly purged with dry nitrogen for 5 min and sealed with a screw cap. The PYREX tube is transferred to a water bath preset at 45°C and maintained for 16 h. After polymerization, the polymer monolith is taken from the PYREX tube and fractured. This is further ground with a mechanical mortar (Retsch, Haan, ERG) and wet-sieved with 5% ethanol (v/v), and subjected to repetitive sedimentation in... 

Thinset mortars are employed in demanding interior and exterior floor and waU applications where there may be standing water or high moisture exposure. Both one component polymer modified thinsets and two component cementitious adhesives are used. Ethylene vinyl acetate copolymers (EVA) are the predominant powder polymer base used in one component polymer modified thinsets, they are described in Chapter 13. Recently styrene acrylics or straight acrylics and styrene butadiene copolymer powders gain an increasing market share. Two component thinsets systems combine a cementitious powder mix and a separate polymer dispersion admixture. 

---