Solubility of HPMC in Organic Solvents
October 29th 2024
HPMC(Hydroxypropyl Methyl Cellulose) and HEMC(Hydroxyethyl Methyl Cellulose) have similar roles in building materials. They can function as a dispersant, water-retaining agent, thickener, and binder to increase cohesiveness, workability, reduce flocculation, improve viscosity and shrinkage. Their water retention property will help to reduce concrete surface water loss, increase strength, prevent cracks and weathering of water-soluble salts. They are widely used in cement-based mortars, gypsum plasters, EIFS, masonry mortars, joint fillers, tile adhesives, self-leveling compounds, etc.
The gel temperature of cellulose ether determines its thermal stability in the application. The gel temperature of HPMC is usually between 60°C and 75°C, depending on the model, group content, and different production processes of different manufacturers. Due to the characteristics of the HEMC group, it has a higher gel temperature, usually above 80°C, so its stability under high-temperature conditions is better than that of HPMC. In practical applications, under the very hot summer construction environment, the water retention of HEMC with the same viscosity and content in wet-mixed mortar has a greater advantage than HPMC.
Especially in south China, the mortar will sometimes be applied at high temperatures. Cellulose ether with too low gel temperature will lose the inherent thickening and water retention of cellulose ether at high temperature, thereby accelerating the curing of cement and the hardening of mortar. , It directly affects the workability and cracks resistance. Since HEMC has more hydrophilic groups in its structure, which makes it has better hydrophilicity. The water retention rate of HEMC in mortar is slightly higher than that of HPMC for products of the same viscosity at the same dosage. In addition, the anti-sagging ability of HEMC is relatively better. Therefore, HEMC will have a better effect when applied to tile adhesive.
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