HPMC (Hydroxypropyl Methylcellulose) for putty is a commonly used building additive. It is a white powdery substance and belongs to non - ionic cellulose ethers. It is made from natural cellulose through chemical modification and has good water solubility.

In putty, HPMC plays the following important roles:

• Improving construction performance: It can increase the consistency and thixotropy of putty, making the putty smoother and fuller during troweling, without dragging the trowel or dropping the paste, improving construction efficiency and the experience of construction workers.

• Enhancing water retention: Effectively locks in moisture and delays water evaporation, preventing the putty from cracking and powdering due to rapid water loss, ensuring that the cement or hydrated lime and other cementitious materials fully hydrate, making the wall more compact, non - hollow, and improving the quality and service life of the putty product.

• Increasing adhesion: Enhances the adhesion between the putty and the substrate, avoiding problems such as hollowing and peeling, and has good adaptability to a variety of substrate materials.

• Reducing shrinkage: Reduces the shrinkage rate of the putty during the drying and curing process, helping to prevent crack formation.

• Preventing sagging: Improves the sag - resistance of the putty, making it suitable for the construction of vertical walls.