The Role of Redispersible Polymer Powder in Putty Powder

Redispersible Polymer Powder (RDP) is a key additive in building putty production. It has unique physical and chemical properties that offer multiple solutions to improve putty performance. Made through spray drying, RDP is a polymer dispersion. When mixed with water, it can re-form a stable liquid—just like the original emulsion. This reversible feature makes it a core component for modifying inorganic cementitious materials.

How It Works

When putty powder is mixed with water, RDP goes through a dynamic change: from tiny particles to a continuous film.

At first, RDP particles spread evenly in the cement paste. As cement starts to hydrate, the liquid fills with calcium hydroxide. Then, polymer particles begin to settle on the surface of cement gel and unhydrated cement particles.

As water in the mix decreases (either absorbed by the base material or evaporated), these RDP particles pack tightly in small pores. Finally, they dry and join together to form a continuous polymer film.

This film, combined with the hard structure from cement hydration, creates a strong "composite network." The cement provides a rigid frame, while the polymer film adds flexible connections. Together, they greatly boost the putty’s ability to resist cracks, reducing damage from base material movement or environmental stress.

How It Improves Putty Performance

Better Bond Strength

RDP lets you control bond strength precisely. With the right formula, it can maximize bond strength using the least amount of RDP. It also avoids problems from overly high strength. For example, in external wall insulation systems, the putty (as a transition layer) must be less strong than the rendering mortar. If not, the interface could crack.

Easier to Work With

RDP makes putty easier to handle and shape. It improves scratch resistance and flexibility, while reducing shrinkage as the putty dries. This means the putty stays easy to use during application and remains stable once dry.

Longer Lifespan

RDP enhances weather resistance and durability:

• The polymer film blocks moisture, making the putty more water-resistant.

• It handles high alkalinity (common in cement), so it works well with cement-based materials.

• Better wear resistance extends how long the putty layer lasts.

Plus, RDP helps the putty hold water longer and extends its "open time"—giving workers more time to apply it.

Balancing Performance in Use

In practice, RDP dosage needs to follow a "flexibility rule": the putty must be more flexible than the base material. This helps it adapt when the base moves.