Cement-based tile adhesive is currently the largest application of special dry-mixed mortar, which is composed of cement as the main cementitious material and supplemented by graded aggregates, water-retaining agents, early strength agents, latex powder and other organic or inorganic additives mixture. Generally, it only needs to be mixed with water when used. Compared with ordinary cement mortar, it can greatly improve the bonding strength between the facing material and the substrate, and has good slip resistance and excellent water resistance and heat resistance. And the advantages of freeze-thaw cycle resistance, mainly used to paste building interior and exterior wall tiles, floor tiles and other decorative materials, widely used in interior and exterior walls, floors, bathrooms, kitchens and other architectural decoration places, is currently the most widely used ceramic tile bonding material.

Usually when we judge the performance of a tile adhesive, we not only pay attention to its operational performance and anti-sliding ability, but also pay attention to its mechanical strength and opening time. Cellulose ether in tile adhesive not only affects the rheological properties of porcelain adhesive, such as smooth operation, sticking knife, etc., but also has a strong influence on the mechanical properties of tile adhesive

1. Opening hours
When rubber powder and cellulose ether co-exist in wet mortar, some data models show that rubber powder has stronger kinetic energy to attach to cement hydration products, and cellulose ether exists more in the interstitial fluid, which affects more Mortar viscosity and setting time. The surface tension of cellulose ether is greater than that of rubber powder, and more cellulose ether enriched on the mortar interface will be beneficial to the formation of hydrogen bonds between the base surface and cellulose ether.

In the wet mortar, the water in the mortar evaporates, and the cellulose ether is enriched on the surface, and a film will be formed on the surface of the mortar within 5 minutes, which will reduce the subsequent evaporation rate, as more water is removed from the thicker mortar Part of it migrates to the thinner mortar layer, and the film formed at the beginning is partially dissolved, and the migration of water will bring more cellulose ether enrichment on the mortar surface.

The film formation of cellulose ether on the surface of mortar has a great influence on the performance of mortar:

1. The formed film is too thin and will be dissolved twice, unable to limit the evaporation of water and reduce the strength.

2. The formed film is too thick. The concentration of cellulose ether in the mortar interstitial liquid is high and the viscosity is high. It is not easy to break the surface film when the tiles are pasted.

It can be seen that the film-forming properties of cellulose ether have a greater impact on the open time. The type of cellulose ether (HPMC, HEMC, MC, etc.) and the degree of etherification (substitution degree) directly affect the film-forming properties of cellulose ether, and the hardness and toughness of the film.