hydroxypropyl methylcellulose HPMC in Plastering MortarFebruary 2nd 2023
The Thickening of Cellulose Ethers
Cellulose ether thickening effect depends on: the degree of polymerization of cellulose ether, solution concentration, shear rate, temperature and other conditions. The gelling properties of the solution are unique to alkyl cellulose and its modified derivatives. The gelation properties are related to the degree of substitution, solution concentration and additives. For hydroxyalkyl-modified derivatives, the gel properties are also related to the degree of modification of the hydroxyalkyl group. For MC and HPMC with low solution concentration, 10%-15% concentration solution can be prepared, medium viscosity mc and HPmc can be prepared with 5%-10% solution, and high viscosity mc and HPmc can only be prepared with 2%-3% solution, and usually The viscosity grade of cellulose ether is also graded in 1%-2% solution. High molecular weight cellulose ether has high thickening efficiency. In the same concentration solution, different molecular weight polymers have different viscosities. The viscosity and molecular weight can be expressed as follows, [η]=2.92×10-2(DPn)0.905, DPN is the average polymerization high degree.
The target viscosity can be achieved only when the low molecular weight cellulose ether is added in a large amount. Its viscosity has little dependence on shear rate, high viscosity reaches the target viscosity, and the required addition amount is small, and the viscosity is determined by the thickening efficiency. Therefore, to achieve a certain consistency, a certain amount of cellulose ether (the concentration of the solution) and the viscosity of the solution must be guaranteed. The gelation temperature of the solution also decreased linearly with the increase of the concentration of the solution, and gelled at room temperature after reaching a certain concentration.