The water retention of mortar refers to the ability of mortar to retain and hold water. The higher the viscosity of cellulose ether, the better the water retention.
The water retention of mortar refers to the ability of mortar to retain and hold water. The higher the viscosity of cellulose ether, the better the water retention. Due to the hydroxyl and ether bonds in the cellulose structure, the oxygen atoms on the hydroxyl and ether bond groups combine with water molecules to form hydrogen bonds, making free water become bound water and entangled water, thus playing the role of water retention.
The coarser particles of cellulose ether in water are easy to disperse without agglomeration, but the dissolution rate is slow. Until 60 mesh cellulose ethers were dissolved in water for about 60 minutes.
2. Fine cellulose ethers are easy to disperse in water without agglomeration, and the dissolution rate is moderate. Dissolve the cellulose ether above 80 mesh in water for about 3 minutes.
Cellulose ether ultrafine particles disperse quickly in water, dissolve quickly, and form viscosity quickly. Cellulose ether above 120 mesh dissolves in water for about 10-30 seconds.
The finer the cellulose ether particles, the better the water retention, and the contact surface between the coarse cellulose ether particles and water immediately dissolves and forms a gel phenomenon. The glue will wrap the material to prevent water molecules from constantly penetrating, sometimes stirring for a long time to unevenly disperse and dissolve, forming a cloudy flocculent solution or agglomerates. Fine particles disperse and dissolve immediately upon contact with water, forming a uniform viscosity.
The pH value of cellulose ether manufacturers at home and abroad is basically controlled at around 7, showing an acidic state. Since there are still a large number of glucose ring structures in the molecular structure of cellulose ether, the anhydroglucose ring is the main group that causes cement retardation. The anhydroglucose ring can make the hydrated calcium in the cement hydration solution generate calcium-calcium compounds, reduce the concentration of calcium ions during the induction period of cement hydration, prevent the precipitation of calcium hydroxide and calcium crystals, and delay the hydration of the cement process. If the PH value is alkaline, the mortar will appear in an early-strength state. Now most factories use sodium carbonate to adjust the PH value. Sodium carbonate is a quick-setting agent, which improves the performance of sodium carbonate on the surface of cement particles, promotes the further increase of the cohesion of particles, and improves the viscosity of mortar. At the same time, sodium carbonate and mortar The calcium ions in the cement combine quickly to promote the formation of ettringite and make the cement condense rapidly. Therefore, the pH value in the actual production process should be adjusted according to different customers.
The gas entrainment of cellulose ether is mainly due to the fact that cellulose ether is also surface active. The interfacial activity of cellulose ether mainly occurs at the gas-liquid-solid interface, firstly the introduction of air bubbles, followed by dispersion and wetting. Cellulose ether contains an alkyl group, which greatly reduces the surface tension and interfacial energy of water, making it easy to generate many tiny closed bubbles during the stirring process of the aqueous solution.
Cellulose ether gel
Cellulose ether dissolves in the mortar due to the methoxyl and hydroxypropyl groups in its molecular chain, forms a thick gel with calcium ions and aluminum ions, and fills in the voids of cement mortar, improving the compactness and elastic filling of the mortar and reinforcement. However, when the composite substrate is compressed, rigid support cannot be achieved, and the strength and folding rate of the mortar decrease.
Cellulose ether is added with water and cement particles to form a thin layer of latex film, which has a sealing effect and the phenomenon of dry mortar on the surface is improved. Because cellulose ether has good water retention, the water molecules are stored inside the mortar, so as to ensure the hydration hardening and strength of the cement to fully develop, improve the bonding strength of the mortar, and increase the viscosity of the mortar at the same time. The mortar has good plasticity and The interfacial activity of vinyl ether mainly occurs at the gas-liquid-solid interface. First is the introduction of air bubbles, followed by dispersion and wetting. Cellulose ether contains an alkyl group, which greatly reduces the surface tension and interfacial energy of water, making it easy to generate many tiny closed bubbles during the stirring process of the aqueous solution.