Effect of the amount of redispersible latex powder on the bond strength and water resistance of putty

Effect of the amount of redispersible latex powder on the bond strength and water resistance of putty

Redispersible latex powder is used as the main adhesive of putty, and its dosage has an influence on the bonding strength of putty.

With the increase of the amount of redispersible latex powder, the bonding strength gradually increases. When the amount of latex powder is small, as the amount of latex powder increases, the bonding strength increases. For example, when the amount of latex powder is 2%, the bonding strength reaches 0182MPa, which has met the national standard of 0160MPa. The addition of latex powder can improve the bonding strength of the putty and the substrate. The reason is that the hydrophilic latex powder and the liquid phase of the cement suspension penetrate into the pores and capillaries of the matrix together, and the latex powder forms a film in the pores and capillaries and is firm. The ground is adsorbed on the surface of the substrate, thus ensuring a good bond strength between the cementing material and the substrate. When removing putty on the test board, it can also be found that the increase in the amount of latex powder does improve the adhesion of the putty to the substrate. But when the amount of latex powder exceeds 4%, the increasing trend of bonding strength slows down. Contributing to the bond strength of putty is not only redispersible latex powder, but also inorganic materials such as cement and heavy calcium carbonate. Therefore, the bond strength does not show a linear law with the increase of the amount of latex powder.

Water resistance and alkali resistance of putty is an important test index for judging whether putty can be used as water resistance of interior wall or exterior wall.

When the amount of latex powder is less than 4%, as the amount of latex powder increases, the water absorption rate shows a downward trend. When the dosage is greater than 4%, the water absorption rate decreases more slowly. The reason is that cement is used as a binding substance in putty. When redispersible latex powder is not added, there are a large number of voids in the system. When redispersible latex powder is added, the emulsion polymer formed after redispersion can condense in the voids of putty. Film formation, seals the voids in the putty system, makes the surface of the putty dry and forms a denser film, which can effectively prevent water infiltration, reduce water absorption, and enhance water resistance. When the amount of latex powder reaches 4%, the polymer emulsion after redispersible latex powder can basically completely fill the voids in the putty system to form a complete and dense film, so that the water absorption of the putty decreases with the amount of latex powder. The increase becomes flat.

Redispersible latex powder can improve the bonding strength of putty. When the amount is 3% to 4%, putty has higher bonding strength and good water resistance.