Application of Hydroxypropyl Methyl Cellulose in Building Coatings

Hydroxypropyl methylcellulose (HPMC) and methylcellulose (MC) are high-performance water-soluble ethers, acting as retarders, 

water-retaining agents, thickeners and binders in building coatings.

I. Roles of Hydroxypropyl Methylcellulose in Building Materials

1. Workability—Plasticity

Adding HPMC significantly enhances the workability of plaster. Mortar without HPMC is loose and prone to water loss. In contrast, HPMC - added mortar exhibits an 

“oily” texture, enabling full wall joints and a smooth surface. It also ensures ceramic tiles or bricks adhere firmly to the base and extends the working time, facilitating large-scale construction projects.

2. Water Retention—Strength

Cement or gypsum-based products rely on hydration reactions to gel. Water transforms silicates in cement into complex hydrates and converts anhydrous

 calcium sulfate and calcium sulfate hemihydrate in industrial gypsum into calcium sulfate dehydrate, imparting strength. Without sufficient water, these reactions 

cannot occur, resulting in weak or non-existent strength. Surfaces in contact with these materials often absorb water, hindering complete hydration and

reducing bond strength. HPMC’s primary function is to improve water retention, significantly boosting the bond and shear strength of building materials. 

Its water-retention capacity improves with increased viscosity.

3. Bonding

HPMC remarkably enhances the bonding of cement mortar, plaster, and binders, especially by increasing the initial bond force. This ensures that ceramic tiles 

remain in place during installation and that plaster adheres firmly to walls, and bricks bond tightly with mortar. However, the amount of HPMC added must be 

carefully controlled. Excessive use can make the paste sticky, complicating construction, and may cause hollow defects in plaster and caulking materials.

II. Building Materials Able to Use Hydroxypropyl Methylcellulose

1. Cement Mortar

In cement mortar, HPMC is crucial for water retention, preventing brick - induced dehydration and improving bond strength. Proper use enhances bending 

and shear strength, but excessive addition reduces compressive strength.

2. Ceramic Tile Adhesive

Ceramic tile adhesives face water absorption from both the base layer and tiles. HPMC’s water - retaining property ensures strong adhesive performance despite varying tile qualities.

3. Plaster

Adding a small amount of HPMC significantly improves plaster’s workability, plasticity and initial viscosity. Its water - retention also boosts the cured plaster’s bond strength.

Name: Molly.Wang

E-Mail:molly.wang@jtdf-rdp.com

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