KimaCell® MHEC MH20M methyl hydroxyethyl cellulose, the non-ionic cellulose ether, is used in construction projects becaause it has good dispersion, water retention, bonding and thickening effects. The addition of cellulose ether can significantly improve the water retention of gypsum, but the flexural and compressive strengths of gypsum hardened body also decrease slightly with the increase of the content, which is because cellulose ether has a certain air-entraining effect. Bubbles will be introduced during the stirring of the slurry, which will reduce the mechanical properties of the hardened body. At the same time, too much cellulose ether will make the gypsum mixture too viscous, resulting in a decrease in its workability.
|Chemical name||Methyl Hydroxyethyl Cellulose|
|Synonym||Cellulose ether, 2-hydroxyethyl methyl cellulose, Cellulose, 2-hydroxyethyl methyl ether, hydroxyethyl Methyl cellulose, MHEC, HEMC|
|Product Grade||MHEC MH20M|
|Solubility||Water Soluble Cellulose ether|
|Physical form||White to off-white cellulose powder|
|Viscosity Brookfield 2% solution||10000-20000mPa.s|
|Viscosity NDJ 2% solution||16000-24000mPa.S|
|Mesh size||99% pass 100mesh|
KimaCell® MHEC MH20M methyl hydroxyethyl cellulose is used in gypsum slurry to have obvious thickening effect. At room temperature, with the increase of the viscosity and dosage of cellulose ether, its thickening effect becomes more obvious. However, as the temperature increases, the viscosity of cellulose ether decreases, its thickening effect weakens, the yield shear stress and plastic viscosity of the gypsum mixture decrease, the pseudoplasticity weakens, and the workability becomes poor.
Cellulose ether improves the water retention of gypsum, but as the temperature increases, the water retention of modified gypsum also decreases significantly, and even completely loses the water retention improvement effect at 60 °C. The water retention rate of gypsum slurry was significantly improved by cellulose ether, and the water retention rate of HPMC modified gypsum slurry with different viscosities gradually reached the saturation point with the increase of the content. The water retention of gypsum is generally proportional to the viscosity of cellulose ether, and has little effect at high viscosity.
The internal factors of the water retention of cellulose ethers changing with temperature are closely related to the microscopic morphology of cellulose ethers in the liquid phase. At a certain concentration, cellulose ether tends to aggregate to form large colloidal associations, blocking the water delivery channel of the gypsum mixture to achieve efficient water retention. However, as the temperature rises, due to the thermal gelation properties of cellulose ether itself, the previously formed large colloidal associations re-disperse, resulting in a decrease in water retention.