Hydroxypropyl Methylcellulose (HPMC) is a commonly used water-soluble polymer widely used in building materials, especially cement-based tile adhesives. The unique chemical properties and physical properties of HPMC make it play a vital role in improving the adhesion, construction performance, and durability of tile adhesives.
(1) Basic knowledge of HPMC
1. Chemical structure of HPMC
HPMC is a cellulose derivative obtained by chemically modifying natural cellulose. Its structure is mainly formed by methoxy (-OCH₃) and hydroxypropoxy (-CH₂CHOHCH₃) groups replacing some hydroxyl groups on the cellulose chain. This structure gives HPMC good solubility and hydration ability.
2. Physical properties of HPMC
Solubility: HPMC can dissolve in cold water to form a transparent colloidal solution and has good hydration and thickening ability.
Thermogelation: HPMC solution will form a gel when heated and return to a liquid state after cooling.
Surface activity: HPMC has good surface activity in solution, which helps to form a stable bubble structure.
These unique physical and chemical properties make HPMC an ideal material for modifying cement-based tile adhesives.
(2) Mechanism of HPMC enhancing the performance of cement-based tile adhesives
1. Improve water retention
Principle: HPMC forms a viscous network structure in the solution, which can effectively lock in moisture. This water retention ability is due to the large number of hydrophilic groups (such as hydroxyl groups) in the HPMC molecules, which can absorb and retain a large amount of moisture.
Improve adhesion: Cement-based tile adhesives require moisture to participate in the hydration reaction during the hardening process. HPMC maintains the presence of moisture, allowing the cement to fully hydrate, thereby improving the adhesion of the adhesive.
Extend open time: Water retention prevents the adhesive from drying quickly during construction, extending the adjustment time for tile laying.
2. Improve construction performance
Principle: HPMC has a good thickening effect, and its molecules can form a network-like structure in aqueous solution, thereby increasing the viscosity of the solution.
Improve anti-sagging property: The thickened slurry has better anti-sagging property during the construction process, so that the tiles can stay stably in the predetermined position during the paving process and will not slide down due to gravity.
Improve fluidity: The appropriate viscosity makes the adhesive easy to apply and spread during construction, and at the same time has good operability, reducing the difficulty of construction.
3. Enhance durability
Principle: HPMC enhances the water retention and adhesion of the adhesive, thereby improving the durability of the cement-based tile adhesive.
Improve bonding strength: The fully hydrated cement substrate provides stronger adhesion and is not prone to falling off or cracking during long-term use.
Enhance crack resistance: Good water retention avoids large-scale shrinkage of the adhesive during the drying process, thereby reducing the cracking problem caused by shrinkage.
(3) Experimental data support
1. Water retention experiment
Studies have shown that the water retention rate of cement-based tile adhesives with the addition of HPMC is significantly improved. For example, adding 0.2% HPMC to the adhesive can increase the water retention rate from 70% to 95%. This improvement is crucial to improving the bonding strength and durability of the adhesive.
2. Viscosity test
The amount of HPMC added has a significant effect on viscosity. Adding 0.3% HPMC to cement-based tile adhesive can increase the viscosity several times, ensuring that the adhesive has good anti-sagging performance and construction performance.
3. Bond strength test
Through comparative experiments, it was found that the bonding strength between tiles and substrates of adhesives containing HPMC is significantly better than that of adhesives without HPMC. For example, after adding 0.5% HPMC, the bonding strength can be increased by about 30%.
(4) Application examples
1. Laying of floor tiles and wall tiles
In the actual laying of floor tiles and wall tiles, HPMC-enhanced cement-based tile adhesives showed better construction performance and lasting bonding. During the construction process, the adhesive is not easy to lose water quickly, ensuring the smoothness of construction and the flatness of the tiles.
2. External wall insulation system
HPMC-enhanced adhesives are also widely used in external wall insulation systems. Its excellent water retention and adhesion ensure a strong bond between the insulation board and the wall, thereby improving the durability and stability of the external wall insulation system.
The application of HPMC in cement-based tile adhesives significantly improves the performance of the adhesive. By improving water retention, enhancing construction performance and improving durability, HPMC makes cement-based tile adhesives more suitable for modern construction needs. With the development of technology and the increasing demand for high-performance building materials, the application prospects of HPMC will be broader.
Post time: Jun-26-2024