Hydroxyethyl cellulose (HEC) and hydroxypropyl methyl cellulose (HPMC) are two common water-soluble cellulose derivatives, which are widely used in coatings, medicine, food and building materials industries.
1. Cellulose and its derivatives form viscous liquids in aqueous solution and are widely used for thickening, stabilization and film formation. HEC and HPMC are of great value in industrial production due to their excellent solubility and thickening effect. Studying their rheological properties helps to optimize their application performance, improve product quality and production efficiency.
2. Experimental part
2.1 Materials and reagents
This study used commercially available HEC and HPMC powders, and the solvent was deionized water.
2.2 Solution preparation
HEC and HPMC solutions with different mass fractions (0.5%, 1.0%, 1.5%, 2.0%) were prepared respectively, fully stirred and placed at a constant temperature for 24 hours to completely dissolve them.
2.3 Rheological properties test
The relationship between the viscosity and shear rate of the solution was determined by a rotational rheometer, and the effects of temperature and shear on its rheological behavior were investigated.
3. Results and discussion
3.1 Relationship between viscosity and shear rate
The experimental data showed that both HEC and HPMC solutions behaved as typical non-Newtonian fluids, and their viscosity decreased with increasing shear rate, which was consistent with the shear-thinning characteristics. This behavior was mainly attributed to the gradual orientation of polymer molecules under the action of shear force, which reduced the degree of entanglement between molecules.
3.2 Effect of concentration on rheological properties
With the increase of solution concentration, the initial viscosity of HEC and HPMC solutions increased significantly, and a stronger shear-thinning effect was shown. This indicates that the interaction between polymer molecules is more obvious at higher concentrations, making the solution more elastic and structural.
3.3 Effect of temperature on rheological properties
Within a certain range (20℃~60℃), the increase in temperature leads to a decrease in solution viscosity. HPMC may gel under high temperature conditions, while HEC solution maintains good fluidity. This shows that HPMC is more sensitive to temperature and is suitable for applications that require thermo-induced gelation properties.
3.4 Thixotropy Analysis
The experiment found that the HPMC solution can partially recover the initial viscosity after the shear stops, indicating that it has a certain thixotropy, while HEC has a weaker recovery ability. The thixotropy of HPMC helps to improve the stability of products such as coatings and pharmaceutical preparations.
Both HEC and HPMC solutions show the shear-thinning characteristics of non-Newtonian fluids, and their rheological behavior is affected by concentration, temperature and shear. HPMC has stronger temperature sensitivity and thixotropy than HEC, and is suitable for thermo-induced gelation applications, while HEC maintains stable rheological properties over a wider temperature range. These research results provide an important theoretical basis for the application of HEC and HPMC in different industrial fields.
Post time: Apr-15-2025