Redispersible latex powder is a special water-based emulsion and polymer binder made by spray drying with vinyl acetate-ethylene copolymer as the main raw material. After part of the water evaporates, the polymer particles form a polymer film by agglomeration, which acts as a binder. When the redispersible latex powder is used together with inorganic gelling minerals such as cement, it can modify the mortar. The main functions of redispersible latex powder are as follows.
(1) Improve bond strength, tensile strength and bending strength.
Redispersible latex powder can significantly improve the bond strength of mortar. The greater the amount added, the greater the lift. High bonding strength can inhibit shrinkage to a certain extent, and at the same time, the stress generated by deformation is easy to disperse and release, so bonding strength is very important for improving crack resistance. Studies have shown that the synergistic effect of cellulose ether and polymer powder helps to improve the bond strength of cement mortar.
(2) Reduce the elastic modulus of the mortar, so that the brittle cement mortar has a certain degree of flexibility.
The elastic modulus of redispersible latex powder is low, 0.001-10GPa; while the elastic modulus of cement mortar is higher, 10-30GPa, so the elastic modulus of cement mortar will decrease with the addition of polymer powder. However, the type and amount of polymer powder also have an effect on the modulus of elasticity. In general, as the ratio of polymer to cement increases, the modulus of elasticity decreases and the deformability increases.
(3) Improve water resistance, alkali resistance, abrasion resistance and impact resistance.
The network membrane structure formed by the polymer seals the holes and cracks in the cement mortar, reduces the porosity of the hardened body, and thus improves the impermeability, water resistance and frost resistance of the cement mortar. This effect increases with increasing polymer-cement ratio. The improvement of wear resistance is related to the type of polymer powder and the ratio of polymer to cement. In general, wear resistance improves as the ratio of polymer to cement increases.
(4) Improve the fluidity and workability of mortar.
(5) Improve the water retention of mortar and reduce water evaporation.
The polymer emulsion formed by dissolving the redispersible polymer powder in water is dispersed in the mortar, and a continuous organic film is formed in the mortar after solidification. This organic film can prevent the migration of water, thereby reducing the loss of water in the mortar and playing a role in water retention.
(6) Reduce cracking phenomenon
The elongation and toughness of polymer modified cement mortar are much better than ordinary cement mortar. The flexural performance is more than 2 times that of ordinary cement mortar; the impact toughness increases with the increase of the polymer cement ratio. With the increase of the amount of polymer powder added, the flexible cushioning effect of the polymer can inhibit or delay the development of cracks, and at the same time it has a good stress dispersion effect.
Post time: Jun-20-2023