Water retention of hydroxypropyl methylcellulose ether
The water retention of dry mix mortar refers to the ability of mortar to hold and lock water. The higher the viscosity of hydroxypropyl methylcellulose ether, the better the water retention. Because the cellulose structure contains hydroxyl and ether bonds, the oxygen atoms on the hydroxyl and ether bond groups associate with water molecules to form hydrogen bonds, so that free water becomes bound water and entangles water, thus playing a role in water retention.
Solubility of Hydroxypropyl Methyl Cellulose Ether
1. Coarse particle cellulose ether is easy to disperse in water without agglomeration, but the dissolution rate is very slow. Cellulose ether below 60 mesh is dissolved in water for about 60 minutes.
2. Fine particle cellulose ether is easy to disperse in water without agglomeration, and the dissolution rate is moderate. Cellulose ether above 80 mesh is dissolved in water for about 3 minutes.
3. Ultra-fine particle cellulose ether disperses quickly in water, dissolves quickly, and forms viscosity quickly. Cellulose ether above 120 mesh dissolves in water for about 10-30 seconds.
The finer the particles of hydroxypropyl methylcellulose ether, the better the water retention. The surface of coarse-grained cellulose ether dissolves immediately after contacting with water and forms a gel phenomenon. The glue wraps the material to prevent water molecules from continuing to penetrate. Sometimes it cannot be uniformly dispersed and dissolved even after long-term stirring, forming a cloudy flocculent solution or agglomeration. The fine particles disperse and dissolve immediately after contacting with water to form a uniform viscosity.
PH value of hydroxypropyl methylcellulose ether (retarding or early strength effect)
The pH value of hydroxypropyl methylcellulose ether manufacturers at home and abroad is basically controlled at about 7, which is in an acidic state. Because there are still a large number of anhydroglucose 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 calcium ions in the cement hydration solution generate sugar-calcium molecular compounds, reduce the calcium ion concentration during the induction period of cement hydration, prevent the formation and precipitation of calcium hydroxide and calcium salt crystals, and delay the hydration of cement. process. If the PH value is in an alkaline state, the mortar will appear in an early-strength state. Now most factories use sodium carbonate to adjust the pH value. Sodium carbonate is a kind of quick-setting agent. Sodium carbonate improves the performance of the surface of cement particles, promotes the cohesion between particles, and further improves the viscosity of mortar. At the same time, sodium carbonate quickly combines with calcium ions in the mortar to promote the formation of ettringite, and the cement coagulates rapidly. Therefore, the pH value should be adjusted according to different customers in the actual production process.
Air Entraining Properties of Hydroxypropyl Methyl Cellulose Ether
The air-entraining effect of hydroxypropyl methylcellulose ether is mainly because cellulose ether is also a kind of surfactant. The interfacial activity of cellulose ether mainly occurs on the gas-liquid-solid interface. First, the introduction of air bubbles, followed by dispersion and Wetting effect. Cellulose ether contains alkyl groups, which significantly reduce 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.
Gel Properties of Hydroxypropyl Methyl Cellulose Ether
After the hydroxypropyl methylcellulose ether is dissolved in the mortar, the methoxyl and hydroxypropyl groups on the molecular chain will react with the calcium ions and aluminum ions in the slurry to form a viscous gel and fill in the cement mortar void. , improve the compactness of the mortar, play the role of flexible filling and reinforcement. However, when the composite matrix is under pressure, the polymer cannot play a rigid supporting role, so the strength and folding ratio of the mortar decrease.
Film Formation of Hydroxypropyl Methyl Cellulose Ether
After hydroxypropyl methyl cellulose ether is added for hydration, a thin layer of latex film is formed between the cement particles. This film has a sealing effect and improves the surface dryness of the mortar. Due to the good water retention of hydroxypropyl methylcellulose ether, enough water molecules are stored inside the mortar, thereby ensuring the hydration hardening of the cement and the full development of the strength, improving the bonding strength of the mortar, and at the same time It improves the cohesion of the mortar, makes the mortar have good plasticity and flexibility, and reduces the shrinkage and deformation of the mortar.
Post time: May-23-2023