Adding polymers can improve the impermeability, toughness, crack resistance and impact resistance of mortar and concrete. Permeability and other aspects have a good effect. Compared with improving the flexural strength and bonding strength of mortar and reducing its brittleness, the effect of redispersible latex powder on improving the water retention of mortar and enhancing its cohesion is limited.
Redispersible polymer powder is generally processed by spray drying by using some existing emulsions. The procedure is to firstly obtain polymer emulsion through emulsion polymerization, and then obtain it through spray drying. In order to prevent the agglomeration of the latex powder and improve the performance before spray drying, some additives are often added, such as bactericides, spray drying additives, plasticizers, defoamers, etc., during the spray drying process, or just after drying. A release agent is added to prevent clumping of the powder during storage.
With the increase of the content of redispersible latex powder, the whole system develops towards plastic. In the case of high latex powder content, the polymer phase in the cured mortar gradually exceeds the inorganic hydration product, the mortar undergoes a qualitative change and becomes an elastic body, and the hydration product of the cement becomes a “filler”. . The film formed by the redispersible latex powder distributed on the interface plays another key role, that is, to enhance the adhesion to the contacted materials, which is suitable for some difficult-to-stick surfaces, such as extremely low water absorption or Non-absorbent surfaces (such as smooth concrete and cement material surfaces, steel plates, homogeneous bricks, vitrified brick surfaces, etc.) and organic material surfaces (such as EPS boards, plastics, etc.) are particularly important. Because the bonding of inorganic adhesives to materials is achieved through the principle of mechanical embedding, that is, the hydraulic slurry penetrates into the gaps of other materials, gradually solidifies, and finally attaches the mortar to it like a key embedded in a lock. The surface of the material, for the above difficult-to-bond surface, cannot effectively penetrate into the interior of the material to form a good mechanical embedding, so that the mortar with only inorganic adhesives is not effectively bonded to it, and the bonding mechanism of the polymer is different. , The polymer is bonded to the surface of other materials by intermolecular force, and does not depend on the porosity of the surface (of course, the rough surface and the increased contact surface will improve the adhesion).
Post time: Mar-07-2023