HPMC in wall putty and its role

1. Overview of HPMC

HPMC (Hydroxypropyl Methyl Cellulose) is a non-ionic cellulose ether widely used in building materials, coatings, medicine, food and other fields. In the construction industry, HPMC is mainly used in cement mortar, tile adhesive, putty powder, gypsum products, etc., to thicken, retain water, lubricate and improve construction performance.

Putty powder is an important material for wall construction. It is mainly used for wall leveling to provide a good base layer for better adhesion of paint or wallpaper. HPMC, as an important additive in putty powder, can greatly improve its construction performance and final quality.

2. The main role of HPMC in putty powder

(1) Enhance water retention

HPMC has a strong ability to absorb and retain water. It can retain moisture after the putty is applied and prevent the moisture from evaporating too quickly.

Extend the open time: construction workers have more time to apply and trim, improving construction efficiency.

Preventing too fast drying: Avoid cracking and powdering of the wall due to rapid water loss, and ensure the strength and adhesion of the putty layer.

(2) Improving construction rheology and lubricity

HPMC can significantly improve the rheological properties of putty, making it easier to spread and apply putty, reducing construction resistance, making putty easier to scrape, improving construction smoothness, and reducing labor intensity of workers.

Preventing putty from falling off, bubbling or peeling during construction, and improving construction quality.

(3) Improving adhesion

HPMC can also enhance the adhesion between the putty layer and the wall, making the putty more firmly attached to the base layer, reducing the risk of falling off or cracking, and ensuring that the wall surface is flat and durable.

(4) Preventing stratification and precipitation

After the putty powder is added with water and stirred, HPMC improves the uniformity of the putty slurry through thickening, prevents the precipitation of solid particles, and maintains the stability of the putty mixture, thereby improving construction consistency.

3. Selection and dosage of HPMC

(1) Viscosity selection

The viscosity of HPMC is an important indicator that affects the performance of putty powder. Generally speaking:

Low viscosity (400-20,000 mPa·s): good fluidity, suitable for putty with high construction requirements.

Medium viscosity (20,000-60,000 mPa·s): suitable for general putty formula, taking into account water retention and construction performance.

High viscosity (60,000-100,000 mPa·s): suitable for putty that requires strong water retention, such as walls used in high temperature and dry environments.

(2) HPMC addition amount

Generally, the amount of HPMC added to putty powder is about 0.1%~0.5%. The specific formula needs to be adjusted according to the putty type and construction requirements:

Excessive: may cause the putty powder to over-thicken, making it difficult to scrape, and prolong the drying time.

Insufficient: may cause the putty to crack, fall off or reduce adhesion.

4. Factors affecting the performance of HPMC

The quality and performance of HPMC will be affected by the following factors:

Degree of substitution (DS) and molar substitution (MS): determine the solubility, water retention and thickening of HPMC.

Purity: High-purity HPMC solution is clearer, has fewer impurities, and will not affect the color and performance of putty.

Particle size: Fine and uniform HPMC is easy to disperse, improving solubility and construction effect.

HPMC plays a key role in wall putty in enhancing water retention, improving adhesion, improving construction properties and stabilizing slurry. Correctly selecting the viscosity and dosage of HPMC can effectively improve the quality of putty, reduce construction defects, and make the wall smoother, stronger and more durable.