Redispersible polymer powder and other inorganic adhesives (such as cement, slaked lime, gypsum, clay, etc.) and various aggregates, fillers and other additives (such as cellulose, starch ether, wood fiber, etc.) are mixed physically to make dry mortar. When the dry mortar is added to the water and stirred, under the action of the hydrophilic protective colloid and mechanical shear force, the latex powder particles can be dispersed quickly into the water, which is enough to fully form the redispersible polymer powder into a film. The composition of the redispersible polymer powder has different effects on the rheological properties of the mortar and various construction properties: the affinity of the latex powder to water when it is redispersed, the different viscosities of the latex powder after dispersion, the impact on the air content of the mortar and the distribution of air bubbles, The interaction between latex powder and other additives makes different latex powders have the effects of increasing fluidity, increasing thixotropy, and increasing viscosity.
The affinity of latex powder and protective colloid to water when dispersed increases the viscosity of the slurry and improves the cohesion of the construction mortar. After the freshly mixed mortar containing redispersible powder dispersion is formed, with the absorption of water by the base surface, the consumption of hydration reaction, and the volatilization to the air, the water will gradually decrease, the particles will gradually approach, the interface will gradually blur, and gradually merge with each other, and finally aggregate film forming.
With the final formation of the polymer film, a system composed of inorganic and organic binder structures is formed in the cured mortar, that is, a brittle and hard skeleton composed of hydraulic materials, and a film formed by redispersible latex powder in the gap and solid surface. flexible network. The tensile strength and cohesion of the polymer film formed by the latex powder are enhanced. Due to the flexibility of the polymer, the deformation ability is much higher than that of the cement stone rigid structure, the deformation performance of the mortar is improved, and the effect of dispersing stress is greatly improved, thereby improving the crack resistance of the mortar.
After curing, the polymer phase in the mortar gradually outnumbers the inorganic hydration product phase, causing the mortar to undergo a qualitative change, becoming an elastomer. Simultaneously, the cement hydration products become a "filler." Modification with redispersible polymer powder improves the mortar's tensile strength, elasticity, flexibility, and sealing properties. The addition of redispersible polymer powder forms a polymer membrane (latex film) that forms part of the pore walls, sealing the mortar's highly porous structure. The latex film exhibits a self-stretching mechanism, exerting tension at its anchoring points with the mortar. These internal forces maintain the mortar as a single unit, enhancing its cohesive strength. The presence of highly flexible and elastic polymers improves the mortar's flexibility and elasticity. The mechanism of increased yield stress and failure strength is as follows: When applied force, the improved flexibility and elasticity delay the formation of microcracks until higher stresses are reached. Furthermore, the interwoven polymer domains hinder the merging of microcracks into through-cracks. Therefore, redispersible polymer powder increases the material's failure stress and failure strain.
The polymer film in polymer-modified mortar plays a crucial role in hardening the mortar. The redispersible latex powder distributed at the interface, through dispersion and film formation, plays another key role: enhancing adhesion to the materials in contact. In the microstructure of the interface between the powder polymer-modified tile adhesive mortar and the tile, the polymer film forms a bridge between the extremely low-water-absorption vitrified tile and the cement mortar matrix. The contact area between the two dissimilar materials is a particularly high-risk area for shrinkage crack formation and resulting adhesion loss. Therefore, the latex film's ability to heal shrinkage cracks plays a crucial role in tile adhesives.
Post time: Aug-28-2025