EPS granular thermal insulation mortar is a lightweight thermal insulation material mixed with inorganic binder, organic binder, admixture, admixture and light aggregate in a certain proportion. In the current research and application of EPS particle insulation mortar, the recyclable redispersible latex powder has a great influence on the performance of the mortar and occupies a relatively high proportion in the cost, so it has always been the focus of attention. The bonding performance of the EPS particle thermal insulation mortar external wall thermal insulation system mainly comes from the polymer binder, and its component is mostly vinyl acetate/ethylene copolymer. This type of polymer emulsion can be spray-dried to obtain redispersible latex powder. Due to the precise preparation of redispersible latex powder in construction, convenient transportation and convenient storage, the loose powder for polymers has become a development trend because of its precise preparation, convenient transportation and convenient storage. The performance of EPS particle insulation mortar depends largely on the type and amount of polymer used. Ethylene-vinyl acetate latex powder (EVA) with high ethylene content and low Tg (glass transition temperature) value has better properties in terms of impact strength, bond strength and water resistance.
The optimization of the performance of redispersible latex powder on mortar is due to the fact that the polymer powder is a high molecular polymer with polar groups. When RDP is mixed with EPS particles, the non-polar segment in the main chain of the polymer powder will physically adsorb with the non-polar surface of EPS. The polar groups in the polymer are oriented outward on the surface of the EPS particles, making the EPS particles change from hydrophobic to hydrophilic. Due to the modification of the surface of the EPS particles by the polymer powder, the problem that the EPS particles are easy to meet water is solved. Floating, large problems of mortar delamination. At this time, when adding cement and stirring, the polar groups adsorbed on the surface of the EPS particles interact with the cement particles and combine closely, which significantly improves the workability of the EPS insulation mortar. This is reflected in the fact that EPS particles are easily wetted by cement slurry, and the bonding force between the two is greatly improved.
After the emulsion and redispersible latex powder are formed into a film, they can form higher tensile strength and bonding strength on different materials. They are used as the second binder in the mortar to combine with the inorganic binder cement, cement and polymer respectively. Play the corresponding strength and improve the performance of the mortar. By observing the microstructure of the polymer-cement composite material, it is considered that the addition of redispersible latex powder can make the polymer film form a part of the hole wall, and make the mortar form a whole through internal force, which improves the internal force of the mortar. Polymer strength, thereby increasing the failure stress of the mortar and increasing the ultimate strain. To study the long-term performance of redispersible latex powder in mortar, observed by scanning electron microscope, after 10 years, the microstructure of the polymer in the mortar has not changed, maintaining stable bonding, flexural strength and compressive strength as well as good Hydrophobic. Taking redispersible latex powder as the research object, the formation mechanism of tile bonding strength was studied, and it was found that after the polymer was dried into a film, the polymer film formed a flexible connection between the mortar and the tile on the one hand, and on the other hand, The polymers in the mortar increase the air content of the mortar, affecting the flatness and wettability of the surface, and subsequently during the setting process, the polymers also have a favorable effect on the hydration process and shrinkage of the cement. Adhesives, these all help to increase the bond strength.
Adding redispersible latex powder to the mortar can significantly improve the bonding strength with other materials, because the liquid phase of the hydrophilic polymer powder and cement suspension penetrates into the pores and capillaries of the matrix, while the latex powder penetrates into the pores and In the capillary. The inner film is formed and firmly adsorbed on the surface of the substrate, thus ensuring good bonding strength between the gelled material and the substrate.
Post time: Jun-16-2023