Effect of dosage of redispersible emulsion powder on mortar

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Redispersible latex powder

With the formation of the final polymer film, a frame system composed of inorganic and organic adhesives is formed in the cured mortar, that is, the hydraulic material constitutes a brittle skeleton, and the redispersible latex powder forms a flexible connection with the solid surface film in the gap. This connection can be imagined as a number of small springs connected to the rigid skeleton, because the tensile strength of the polymer resin film formed by the latex powder is usually more than an order of magnitude higher than that of the hydraulic material, so that the strength of the mortar itself can be enhanced, that is, the cohesion can be improved. Since the flexibility and deformation ability of the polymer is much higher than that of the rigid structure formed by cement, the deformability of the mortar is improved, and the effect of dispersing stress is greatly improved, thereby improving the crack resistance of the mortar.

With the increase of the dosage of redispersible latex powder, the whole system develops towards plastics. In the case of high latex powder content, the polymer phase in the solidified mortar gradually exceeds the inorganic hydration product, the mortar changes qualitatively and becomes an elastomer, while the hydration product of cement becomes a "filler". The film formed by dispersing the redispersible latex powder distributed on the interface plays another key role, that is, to enhance the adhesion to the contacted materials, which is difficult to stick to some surfaces, such as extremely low water absorption or non-water absorption surfaces (such as smooth concrete and cement material surfaces, steel plates, homogeneous bricks, vitrified bricks, etc.) and organic material surfaces (such as EPS plates, plastics, etc.), appear to be particularly important. Because the bonding of inorganic adhesive to materials is achieved through the principle of mechanical embedding, that is, the hydraulic slurry penetrates into the gap of other materials, gradually solidifies, and finally grasps the mortar on the surface of the material like the key is embedded in the lock. For the above difficult-to-stick surface, because it cannot effectively penetrate into the inside of the material to form a good mechanical embedding, the mortar with only inorganic adhesive is not effectively bonded to it, while the bonding mechanism of the polymer is different. The polymer is bonded to the surface of other materials by intermolecular force without depending on the porosity of the surface (of course, the rough surface and the increased contact surface will improve the bonding force).

Key words:

Polymer, Redispersible Emulsion Powder