Enhancing Durability and Performance with Redispersible Polymer Powders

Redispersible latex powder is a white or light-colored polymer powder, which is the main additive for dry mixed mortar such as cement-based or gypsum-based. It mainly improves the overall performance of the mixed material by enhancing the bonding force between particles. According to Dr., Senior Engineer at BASF in Germany According to Michael Smith, “RDP can form a continuous organic phase in cement substrates, significantly improving the toughness of materials.”

Mainstream products include vinyl acetate-ethylene copolymer powder (VAC/E), ethylene vinyl chloride and vinyl laurate ternary copolymer powder (E/VC/VL), and vinyl acetate-ethylene and higher fatty acid vinyl ester ternary copolymer powder (VAC/E/VeoVa). Among them, VAC/E holds a leading position in the global field, representing the technical characteristics of re-dispersible latex powder. Latex powder used in dry mixed mortar requires it to be dispersible in water, have good adhesion, and have good flowability. When used in dry powder coatings, new requirements have been put forward for their performance, such as low-temperature film-forming, thick coating without cracking, and good water resistance. The advantages of VAE series products are good bonding strength, low cost, and can meet their requirements when used in dry mixed mortar.

Redispersible Polymer Powder RDP Powder

Performance of rubber powder

The re-dispersible emulsion powder has good dispersibility. When it contacts with water, it is redispersed into lotion under the shear force, and retains the chemical properties of the initial lotion. Adding re-dispersible latex powder to dry mix mortar, such as cement-based or gypsum-based mortar, can improve various properties of the mortar, such as:

• (1) Improve the bonding and cohesion of mortar;

• (2) Reduce the water absorption of mortar and the elastic modulus of materials;

• (3) Enhance the flexural strength, wear resistance, and durability of mortar;

• (4) Improve the construction performance of mortar.

The mechanism of action of rubber powder in dry mixed mortar

Dry mixed mortar can be made by physically mixing re-dispersible latex powder with inorganic cementitious materials, fine aggregates, fillers, and other additives. When dry-mixed mortar is mixed with water, under the action of hydrophilic protective colloid and mechanical shear force, rubber powder particles form lotion. Normally, the time required for the dispersion of rubber powder is very short. Wet mortar, with the absorption of the base surface, the reaction consumption of hydraulic materials, and the evaporation of the surface layer, leads to a decrease in moisture in the mortar.

Polymer particles approach and fuse to form a continuous polymer film. This process mainly occurs in the pores and solid surfaces of the mortar. Therefore, a brittle and hard skeleton composed of hydraulic materials and a flexible connection formed by adhesive powder on the solid surface is formed in the cured mortar. The flexibility of polymers and their ability to deform are much higher than the rigid structure of mortar.

The variability and cohesion of mortar are improved, and the role of stress dispersion is greatly enhanced, which can further improve the crack resistance of mortar. The film formed by the re-dispersible latex powder can also increase its adhesion to the materials in contact, which is particularly important for surfaces with extremely low or no water absorption (glass tiles, smooth steel plates), organic materials (plastics, wood) and other difficult to adhere surfaces.

Different dry mix mortars and special mortars have different performance requirements, so it is necessary to choose the appropriate re-dispersible latex powder to match their corresponding properties.

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