The latex powder finally forms a polymer film, and 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 resin 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. With the increase of the content of redispersible latex powder, the whole system develops towards plastic. In the case of high latex powder content, the polymer phase in the cured mortar gradually exceeds the inorganic hydration product phase, and the mortar will undergo a qualitative change and become an elastomer, while the hydration product of cement becomes a “filler”. “.
The tensile strength, elasticity, flexibility and sealability of the mortar modified by redispersible latex powder are all improved. The blending of redispersible latex powder allows the polymer film (latex film) to form and form part of the pore wall, thereby sealing the high porosity structure of the mortar. The latex membrane has a self-stretching mechanism that exerts tension where it is anchored to the mortar. Through these internal forces, the mortar is maintained as a whole, thereby increasing the cohesive strength of the mortar. The presence of highly flexible and highly elastic polymers improves the flexibility and elasticity of the mortar. The mechanism for the increase in yield stress and failure strength is as follows: when a force is applied, microcracks are delayed until higher stresses are reached due to improved flexibility and elasticity. In addition, the interwoven polymer domains also hinder the coalescence of microcracks into penetrating cracks. Therefore, the redispersible polymer powder improves the failure stress and failure strain of the material.
The polymer film in polymer modified mortar has a very important effect on hardening mortar. The redispersible latex powder distributed on the interface plays another key role after being dispersed and film-forming, which is to increase the adhesion to the contacted materials. In the microstructure of the powder polymer modified tile bonding mortar and tile interface, the film formed by the polymer forms a bridge between the vitrified tiles with extremely low water absorption and the cement mortar matrix. The contact zone between two dissimilar materials is a particularly high risk area for shrinkage cracks to form and lead to loss of cohesion. Therefore, the ability of latex films to heal shrinkage cracks is of great importance for tile adhesives.