Hydroxypropyl Methyl Cellulose (HPMC) is an important polymer material widely used in dry mixed mortar. The main function of HPMC is to improve the performance of mortar and improve the construction effect and durability.

1. Properties of HPMC
HPMC is a nonionic cellulose ether formed by replacing hydroxyl groups on cellulose with methyl and hydroxypropyl groups. Its molecular structure determines that it has the following properties:

Solubility: HPMC can dissolve in cold water to form a transparent colloidal solution.
Thickening: HPMC has a significant thickening effect and can increase the viscosity of liquids.
Film-forming properties: HPMC can form a tough transparent film on the surface and has a certain degree of water resistance.
Water retention: HPMC has good water retention properties and can significantly reduce water evaporation.
Stability: HPMC is stable to acids and bases and has stable performance within a wide pH range.

2. The mechanism of action of HPMC
In dry mixed mortar, HPMC mainly works through the following mechanisms:

Water-retaining effect: The water-retaining performance of HPMC prevents the water in the mortar from losing easily, extending the opening time of the mortar, which is beneficial to subsequent construction operations.
Lubricating effect: HPMC can improve the fluidity and operability of mortar, making it easier to construct.
Improve adhesion: HPMC can improve the adhesion between mortar and base material and enhance the adhesion of mortar.
Anti-crack effect: By improving the water retention of mortar, HPMC can prevent the rapid evaporation of water during the drying process, thereby reducing the occurrence of cracks.
Improve freeze-thaw resistance: HPMC can enhance the freeze-thaw resistance of mortar and adapt to the requirements of cold environments.

3. Application of HPMC in dry mixed mortar
HPMC is widely used in dry mixed mortar, mainly including the following aspects:

Masonry mortar: When used in masonry walls, HPMC can improve the water retention and adhesion of the mortar, making the masonry more stable.
Plastering mortar: When used for plastering, HPMC can improve the construction performance of the mortar and prevent the plaster layer from cracking and falling off.
Tile adhesive: Among tile adhesives, HPMC can improve adhesion and anti-slip properties to ensure that the tiles are firmly adhered.
Self-leveling mortar: HPMC can improve the fluidity and water retention of self-leveling mortar, giving it better construction performance.
Insulation mortar: In thermal insulation mortar, HPMC can enhance the water retention and adhesion of the mortar and improve the construction quality of the insulation layer.

4. Precautions for using HPMC
When using HPMC, you need to pay attention to the following points:

Dosage control: The dosage of HPMC should be controlled according to the specific mortar formula and construction requirements. Too much or too little will affect the performance of the mortar.
Stir evenly: HPMC should be stirred thoroughly before use to ensure that it is evenly dispersed in the mortar.
Cooperating with other additives: HPMC can be used with other additives, such as water reducing agent, early strength agent, etc., to further improve the performance of mortar.
Storage conditions: HPMC should be stored in a dry and ventilated environment to prevent moisture and deterioration.
Ambient temperature: The temperature of the construction environment has a certain impact on the performance of HPMC. The usage method and dosage should be adjusted according to the temperature.

As an important cellulose ether, HPMC plays a vital role in dry mixed mortar. By improving the water retention, adhesion and construction performance of the mortar, HPMC significantly improves the quality and durability of the mortar. In practical applications, HPMC needs to be used rationally according to specific circumstances to give full play to its advantages and ensure project quality.