1. Introduction

Methylcellulose ether (MCE), as an important building additive, has been widely used in modern building materials, especially in gypsum mortar. Gypsum mortar has become an important material in the construction field due to its excellent workability, adhesion and water retention. As a polymer compound, the viscosity of methylcellulose ether plays a vital role in regulating the performance of gypsum mortar.

2. Properties and mechanism of action of methylcellulose ether

2.1 Basic properties of methylcellulose ether
Methylcellulose ether is a water-soluble polymer compound obtained by methylation modification. Its structural unit is mainly composed of glucose. The ether bond formed by methylation improves its solubility and thermal stability. Methylcellulose ethers with different methylation degrees and molecular weights show different viscosity characteristics, which have a profound impact on their application in building materials.

2.2 Effect of methyl cellulose ether in gypsum mortar
In gypsum mortar, methyl cellulose ether mainly affects the performance of mortar through the following mechanisms:

Thickening effect: By increasing the viscosity of mortar, the suspension stability of mortar is improved.

Water retention: By forming a network structure in the mortar, the loss of water is reduced, thereby improving the setting time and hardening process of the mortar.

Improving construction performance: Improving the workability of mortar, reducing bleeding and segregation, and improving adhesion.

3. Effect of methyl cellulose ether viscosity on the performance of gypsum mortar

3.1 Effect on the physical properties of gypsum mortar
The viscosity of methyl cellulose ether directly affects the physical properties of gypsum mortar. High-viscosity methyl cellulose ether can significantly improve the anti-sagging ability and water retention of mortar, but it may also lead to increased resistance during stirring and increased mixing difficulty.

3.2. Rheology
High-viscosity methyl cellulose ether can increase the yield stress and plastic viscosity of gypsum mortar, making the mortar show stronger anti-sagging properties. This is especially important for construction on vertical surfaces, which can reduce the flow of mortar and improve the construction quality. However, too high viscosity may make the mortar too dense and difficult to operate, and a balance needs to be found in construction practice.

3.3. Water retention
Water retention is a key factor affecting the hardening process of gypsum mortar. High-viscosity methyl cellulose ether can significantly improve the water retention of mortar due to the denser network structure formed, preventing early cracking caused by too fast water loss. However, too high water retention may prolong the initial and final setting time of mortar, which needs to be adjusted according to the specific application scenario.

3.4. Effect on mortar workability
The viscosity of methyl cellulose ether has a significant effect on the workability of gypsum mortar:

3.5. Workability
Moderate viscosity helps to improve the workability of mortar, making it smoother and easier to operate during construction. Methyl cellulose ether with too high viscosity will increase the consistency of mortar, reduce its fluidity, and make construction difficult. In actual construction, it is necessary to select methyl cellulose ether with appropriate viscosity according to construction requirements to ensure optimal workability.

3.6. Adhesion
The viscosity of methyl cellulose ether has a significant effect on the adhesion of mortar. High-viscosity methyl cellulose ether can enhance the adhesion of mortar to the substrate, improve the adhesion strength and anti-peeling ability of mortar. This is particularly important in vertical and high-altitude operations, which can reduce the slippage and shedding of mortar.

3.7. Effect on mortar durability
The viscosity of methyl cellulose ether also affects the durability of gypsum mortar, especially under dry-wet cycle and freeze-thaw cycle conditions.

3.8. Dry-wet cycle
High-viscosity methyl cellulose ether can form a more stable network structure in mortar, thereby improving the mortar’s resistance to cracking. Under dry-wet cycle conditions, mortar with higher viscosity can maintain better integrity and crack resistance.

3.9. Freeze-thaw cycle
Under freeze-thaw cycle conditions, the pore structure and water retention of mortar have an important influence on its anti-freeze-thaw performance. High viscosity methyl cellulose ether can reduce the capillary pores in the mortar and reduce the migration of water, thereby improving the freeze-thaw resistance of the mortar.

4. Application examples and actual effects

4.1 Performance of methyl cellulose ethers with different viscosities in actual applications
In construction, methyl cellulose ethers with different viscosities are used in different occasions. For example, wall plastering and caulking require cellulose ethers with higher viscosity to provide better vertical stability and anti-sagging properties; while floor self-leveling and other applications require cellulose ethers with lower viscosity to ensure good fluidity.

4.2 Actual case analysis
Actual cases show that the use of high viscosity methyl cellulose ethers in the process of wall plastering can significantly reduce mortar sagging and improve construction efficiency and quality. When leveling the ground, choosing medium and low viscosity cellulose ethers can improve fluidity and make the construction smoother and faster.

The viscosity of methyl cellulose ether has a significant effect on the performance of gypsum mortar. High viscosity methyl cellulose ethers help to improve the water retention, anti-sagging and adhesion of mortar, thereby improving its physical properties and workability. However, too high a viscosity may cause the mortar to have a reduced fluidity and make construction difficult. Therefore, in practical applications, it is necessary to select methyl cellulose ether with a suitable viscosity according to specific construction requirements to achieve the best use effect.