The role of HPMC in reducing cracking of gypsum and plaster

Gypsum and plaster materials are widely used in construction. However, they are prone to cracking during the hardening process due to factors such as water loss, shrinkage, and base deformation, which affects the decorative effect and service life. Hydroxypropyl methylcellulose (HPMC), as a high-performance building additive, can significantly improve the construction performance of gypsum and plaster materials and reduce cracking.

1. Basic properties of HPMC

HPMC is a water-soluble polymer with good thickening, water retention, lubrication, film-forming and bonding properties. In building materials, HPMC is mainly used to improve construction performance, enhance water retention, and improve rheological properties. Its role in reducing cracking mainly comes from the following characteristics:

Water retention: HPMC can reduce the rapid evaporation of water, delay the hardening time, and increase the hydration degree of gypsum and plaster materials.

Thickening: HPMC provides appropriate viscosity, so that the material is evenly distributed, reduces segregation, and enhances overall uniformity.

Lubricity: HPMC improves the smoothness of construction, making the material easier to apply and level, and reducing internal stress accumulation.

2. The role of HPMC in reducing cracking of gypsum and plaster

The role of HPMC in preventing cracking of gypsum and plaster materials is mainly reflected in the following aspects:

2.1 Improving the water retention of materials and reducing shrinkage cracks

The cracking of gypsum and plaster materials is mainly caused by shrinkage, that is, the volume shrinkage caused by excessive evaporation of water. HPMC releases water slowly in the material through its efficient water retention, ensuring full hydration and reducing shrinkage cracks caused by early water loss. Especially in high temperature or dry environment, the water retention capacity of HPMC is particularly critical, which can effectively reduce micro cracks caused by rapid drying.

2.2 Enhance the shrinkage resistance of materials

HPMC gives gypsum and plaster materials better toughness, enabling them to adapt to the slight deformation of the substrate and reduce cracks caused by stress concentration. In addition, because HPMC can form a uniform polymer network structure, the internal bonding of the material is tighter, further reducing the risk of cracking.

2.3 Improve construction performance and reduce cracking caused by human operation

During the construction process, the application, leveling and thickness control of materials will affect the final quality of the finished product. HPMC makes gypsum and plaster materials have better lubricity and operability, so that construction workers can apply materials more evenly, avoiding uneven stress caused by uneven local thickness or insufficient mixing, which may cause cracking. In addition, the thickening effect of HPMC makes the material have good anti-sagging properties, avoiding cracking problems caused by excessive local thickness.

2.4 Improve adhesion and reduce interface cracks

Insufficient bonding between gypsum and plaster layers and the substrate will cause interface cracks. HPMC enhances the adhesion of the material, allowing it to better adhere to the surface of the base layer, reducing delamination, hollowing and cracking caused by excessive water absorption of the base layer or insufficient bonding. In addition, the film-forming properties of HPMC form a protective film on the surface of the material, further enhancing the bonding effect.

2.5 Refine the pore structure and improve crack resistance

HPMC can improve the pore structure in cement and gypsum-based materials, reduce the formation of large pores and capillaries, and thus improve the density and uniformity of the material. The optimization of the pore structure helps to reduce shrinkage deformation and cracks. In addition, uniform pore distribution can also improve the impermeability of the material and reduce shrinkage problems caused by water loss.

3. The anti-cracking effect of HPMC in different application scenarios

The anti-cracking effect of HPMC is different in different construction environments and application scenarios. The following are several main application scenarios and their functions:

Indoor plastering: In indoor environments, HPMC improves water retention and construction properties to keep the plaster layer uniformly hydrated and reduce cracking problems caused by excessive water loss.

Exterior wall gypsum leveling layer: The exterior wall gypsum layer is easily affected by wind, sun and temperature changes. HPMC enhances toughness and shrinkage resistance to enable the gypsum layer to better adapt to environmental changes and reduce temperature stress cracks.

Gypsum-based self-leveling floor: In floor applications, HPMC ensures the uniformity and crack resistance of the floor and reduces the formation of cracks by optimizing fluidity and improving adhesion.

As an important construction admixture, HPMC plays a significant role in preventing cracks in gypsum and plastering materials. It mainly reduces cracking problems caused by factors such as shrinkage, water absorption of the base layer, and construction defects by improving water retention, enhancing shrinkage resistance, improving construction performance, improving adhesion, and optimizing pore structure. In practical applications, the reasonable selection of HPMC viscosity and dosage, combined with the adjustment of the construction environment, can maximize its anti-cracking effect and improve the durability and construction quality of gypsum and plastering materials.