Hydroxypropyl methylcellulose (HPMC), as a common cellulose ether, is increasingly used in building materials, especially in gypsum-based plaster and gypsum products. HPMC has good water solubility, thickening, water retention and film-forming properties, and therefore plays an important role in the production and application of gypsum products.

Basic properties of hydroxypropyl methylcellulose (HPMC)
HPMC is a non-ionic cellulose ether, named after the introduction of hydroxypropyl and methyl groups on the cellulose molecule. Its basic properties include:

Solubility: HPMC can dissolve rapidly in cold water to form a transparent or slightly turbid colloidal solution.
Thickening: HPMC has an excellent thickening effect and can increase the viscosity of the solution.
Water retention: HPMC can remain moist for a long time when water evaporates, preventing water from being lost too quickly.
Film-forming: HPMC can form a flexible and transparent film after drying.
These characteristics make HPMC an important additive in gypsum-based plaster and gypsum products.

Application of HPMC in gypsum-based plaster
Gypsum-based plaster is a commonly used interior and exterior wall decoration material in modern buildings, mainly composed of semi-hydrated gypsum, aggregates and various additives. The application of HPMC in gypsum-based plaster is mainly reflected in the following aspects:

Thickening effect: HPMC can significantly increase the viscosity of gypsum-based plaster, making the plaster more operable during construction and preventing sagging and sag.
Water retention effect: Due to the excellent water retention performance of HPMC, the evaporation rate of water in gypsum-based plaster can be effectively delayed, ensuring that the plaster has enough water to participate in the reaction during the coagulation and hardening process, thereby improving the strength and durability after hardening.
Improving construction performance: HPMC can improve the lubricity and fluidity of gypsum-based plaster, making it easier to spread and smooth during construction, reducing construction difficulty and improving construction efficiency.
Crack resistance: By increasing the flexibility of plaster, HPMC can effectively reduce cracking caused by shrinkage and increase the service life of the decorative layer.

Application of HPMC in gypsum products
In addition to its application in gypsum-based plaster, HPMC is also widely used in various gypsum products, such as gypsum board, gypsum lines, gypsum models, etc. In the production process of these products, the addition of HPMC can also bring significant effects:

Modification and thickening: Adding HPMC to gypsum slurry can improve its viscosity and thixotropy, make the slurry have better filling properties in the mold, reduce bubbles and defects, and improve the surface quality of the finished product.
Improve toughness and strength: The film structure formed by HPMC during the hardening process can increase the flexibility and impact resistance of gypsum products and reduce damage during transportation and installation.
Improve water retention: HPMC can maintain a moist state for a long time during the drying process of gypsum products, avoiding cracking and deformation caused by too fast drying.
Uniform molding: HPMC can make the gypsum slurry evenly distributed in the mold, improve the density and uniformity of the product, and ensure the dimensional accuracy and surface finish of the product.

The application of hydroxypropyl methylcellulose (HPMC) in gypsum-based plaster and gypsum products has significant advantages. By improving the thickening, water retention, film-forming and other properties, HPMC not only improves the construction operability and finished product quality, but also extends the service life of gypsum products. In the future research and development and application of building materials, HPMC, as an important functional additive, will continue to play its unique role and make greater contributions to the development of the construction industry.