Putty is a base material widely used in building decoration projects, and its quality directly affects the service life and decorative effect of wall coating. Bonding strength and water resistance are important indicators for evaluating putty performance. Redispersible latex powder, as an organic polymer modified material, plays a key role in improving putty performance.
1. Mechanism of action of redispersible latex powder
Redispersible latex powder is a powder formed by spray drying of polymer emulsion. It can re-emulsify to form a stable polymer dispersion system after contacting water, which plays a role in enhancing the bonding strength and flexibility of putty. Its main functions include:
Improving bonding strength: Redispersible latex powder forms a polymer film during the drying process of putty, and synergizes with inorganic gelling materials to improve the interfacial bonding ability.
Enhancing water resistance: Latex powder forms a hydrophobic network in the putty structure, reducing water penetration and improving water resistance.
Improving flexibility: It can reduce the brittleness of putty, improve deformation ability, and reduce the risk of cracks.
2. Experimental study
Test materials
Base material: cement-based putty powder
Redispersible latex powder: ethylene-vinyl acetate (EVA) copolymer latex powder
Other additives: thickener, water retaining agent, filler, etc.
Test method
Putties with different redispersible latex powder dosages (0%, 2%, 5%, 8%, 10%) were prepared respectively, and their bonding strength and water resistance were tested. The bonding strength was determined by a pull-out test, and the water resistance test was evaluated by the strength retention rate after immersion in water for 24 hours.
3. Results and discussion
Effect of redispersible latex powder on bonding strength
The test results show that with the increase of RDP dosage, the bonding strength of putty shows a trend of first increasing and then stabilizing.
When the RDP dosage increases from 0% to 5%, the bonding strength of putty is significantly improved, because the polymer film formed by the RDP enhances the bonding force between the base material and the putty.
Continue to increase the RDP to more than 8%, the growth of bonding strength tends to be flat, and even slightly decreases at 10%, which may be because excessive RDP will affect the rigid structure of putty and reduce the interface strength.
Effect of redispersible latex powder on water resistance
The water resistance test results show that the amount of RDP has a significant effect on the water resistance of putty.
The bonding strength of putty without RDP decreased significantly after soaking in water, showing poor water resistance.
The addition of an appropriate amount of RDP (5%-8%) makes the putty form a dense organic-inorganic composite structure, improves water resistance, and significantly improves the strength retention rate after 24 hours of immersion.
However, when the RDP content exceeds 8%, the improvement of water resistance decreases, which may be because too much organic components reduce the anti-hydrolysis ability of putty.
The following conclusions can be drawn from experimental research:
An appropriate amount of redispersible latex powder (5%-8%) can significantly improve the bonding strength and water resistance of putty.
Excessive use of RDP (>8%) may affect the rigid structure of putty, resulting in a slowdown or even decrease in the improvement of bonding strength and water resistance.
The optimal dosage needs to be optimized according to the specific application scenario of putty to achieve the best balance between performance and cost.
Post time: Mar-26-2025