Views: 15 Author: Site Editor Publish Time: 2022-07-01 Origin: Site
Basic knowledge of redispersible polymer powder
1. basic concept Redispersible polymer powder is the main additive for dry powder ready-mixed mortar such as cement-based or gypsum-based. Redispersible latex powder is a polymer emulsion that is spray-dried and aggregated from the initial 2um to form spherical particles of 80~120um. Because the surfaces of the particles are coated with an inorganic hard-structure resistant powder, we obtain dry polymer powders. They are extremely easy to pour and bag for storage in warehouses. When the powder is mixed with water, cement or gypsum-based mortar, it can be redispersed, and the basic particles (2um) in it will re-form into a state equivalent to the original latex, so it is called redispersible latex powder. It has good redispersibility, re-disperses into an emulsion on contact with water, and has exactly the same chemical properties as the original emulsion. By adding dispersible polymer powder to cement-based or gypsum-based dry powder ready-mixed mortar, various properties of the mortar can be improved, such as: Improve the adhesion and cohesion of mortar; Reduce the water absorption of the material and the elastic modulus of the material; Flexural strength, impact resistance, abrasion resistance and durability of reinforcement materials; Improve the construction performance of materials, etc.
2. Type of Redispersible Polymer Powder
At present, the main application in the market can be divided into dispersed latex:
Vinyl acetate and vinyl copolymer powder (Vac/E), vinyl and vinyl silicate ternary copolymer powder (E/Vc/VL), vinyl acetate and vinyl and higher fatty acid ternary copolymer powder (Vac/E/VeoVa), vinyl acetate and higher fatty acid vinyl ester copolymer powder (Vac/VeoVa), acrylate And styrene copolymerized rubber powder (A/S), vinyl acetate and acrylic ester and high fatty acid vinyl terpolymer rubber powder (Vac/A/VeoVa), vinyl acetate homopolymer rubber powder (PVac), styrene and butadiene copolymer rubber powder (SBR), etc.
3. Composition of Redispersible Polymer Powder
Redispersible latex powder is usually white powder, but a few have other colors. Its ingredients include:
Polymer resin: located in the core part of rubber powder particles, is also the main component of redispersible latex powder play a role.
Additive (inside) : in conjunction with the resin to modify the resin.
Additive (external) : additional materials are added to further expand the properties of redispersible latex powder.
Protective colloid: a layer of hydrophilic material wrapped on the surface of redispersible latex powder particles. Most of the protective colloid of redispersible latex powder is polyvinyl alcohol.
Anti-caking agent: fine mineral filler, mainly used to prevent the caking of rubber powder in the process of storage and transportation and facilitate the flow of rubber powder (dumped out of the paper bag or tank car).
4. Effect of redispersible latex powder in mortar
Redispersible latex powder disperses into a film and plays a strengthening role as a second adhesive;
Protective colloid is absorbed by mortar system (film will not be destroyed by water, or "secondary dispersion";
Film forming polymer resin is distributed in the whole mortar system as reinforcement material, which increases the cohesion of mortar.
5. Function of Redispersible Polymer Powder in wet mortar:
Improve construction performance;
Improve flow performance;
Increased thixotropy and sag resistance;