In order to improve the brittleness and high elastic modulus of traditional cement mortar in mortar, it is usually necessary to add redispersible latex powder as an additive, which can give cement mortar good flexibility and tensile strength. To resist and delay the generation of cement mortar cracks, because the polymer and mortar form an interpenetrating network structure, a continuous polymer film is formed in the pores, which strengthens the bonding between aggregates and blocks the parts in the mortar Pores, so the modified mortar after hardening has greatly improved performance than cement mortar.
The latex powder is formed by high temperature, high pressure, spray drying and homopolymerization with various active reinforcing micropowders, which can significantly improve the bonding ability and tensile strength of the mortar, and has good construction performance of anti-falling, water retention and thickening, water resistance and freeze-thaw resistance , Excellent heat aging resistance, simple ingredients, easy to use. Xindadi latex powder has excellent compatibility with cement, can be completely dissolved in cement-based dry-mixed mortar paste, does not reduce the strength of cement after curing, not only maintains excellent adhesion, film-forming properties and flexibility, but also has good Weather resistance, stability, bonding performance and crack resistance. After drying, it can effectively prevent the erosion of acidic air on the wall, and it is not easy to pulverize and deliquesce after being wet. It can enhance the strength of the product. Adding redispersible latex powder to putty powder and mortar can increase its strength, and it is very helpful to improve the hardness. It has outstanding waterproof performance, good bonding strength, can also increase the elasticity of the mortar and have a longer open time, and endow the mortar with excellent alkali resistance, and can improve the adhesion/adhesiveness and flexural resistance of the mortar. In addition to strength, wear resistance and constructability, it has stronger flexibility in flexible anti-cracking mortar.
Theoretically speaking, the latex powder with a glass transition temperature below 5°C is more flexible and is mainly used in external wall insulation mortar, and the latex powder with a glass transition temperature above 10°C is mainly used in adhesives and self-leveling mortars .
Depending on the composition of the mortar, the application performance of the mortar will also be affected by the change of the added amount of the redispersible latex powder: the added amount of the redispersible latex powder is less than 1%, which has a certain influence on the construction and adhesion of the mortar; The addition of redispersible latex powder is 1, 2.0%, which improves the strength, water resistance and flexibility of the mortar; the addition of redispersible latex powder is 2.0, 5%, forming a network polymer film in the mortar. Under different climates and interfaces, the strength and flexibility of mortar are obviously improved.
In the case of high latex powder content, the polymer phase in the cured mortar gradually exceeds the phase of the inorganic hydration product, and the mortar undergoes a qualitative change and becomes an elastic body, while 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 the material by the meta-mechanical adhesive is achieved through the principle of mechanical embedding, that is, the hydraulic slurry penetrates into the gaps of other materials, gradually solidifies, and finally grasps the mortar like a key embedded in a lock. On the surface of the material, for the above hard-to-bond surface, due to the inability to effectively penetrate into the material to form a good mechanical embedding, the mortar with only inorganic adhesives is not effectively bonded to it, and the electron microscope observation is also very good. It proves it. The bonding mechanism of polymers is different. Polymers bond with the surface of other materials by intermolecular forces, independent of the porosity of the surface (of course, a rough surface and an increased contact surface will improve the bonding force) , which is more obvious in the case of organic substrates, and the observation of electron microscopes also proves the superiority of its adhesive force.
The latex powder changes the consistency and slipperiness of the system in the wet mixing state, and the cohesion is improved by adding latex powder. After drying, it provides a smooth and dense surface layer with cohesive force, and improves the interface effect of sand, gravel and pores. , enriched into a film at the interface, which makes the tile adhesive more flexible, reduces the elastic modulus, absorbs the thermal deformation stress to a large extent, and has water resistance in the later stage, and the buffer temperature and material deformation are inconsistent. The flexibility and rigidity of latex powder can generally be judged according to the glass transition temperature. If the glass transition temperature is below 0 degrees, it is more flexible. Which type of latex powder is needed in the mortar is generally determined according to the performance characteristics of the product. Tile adhesive needs to use latex powder with better adhesion.