What is the mechanism of action of redispersible polymer powder?

The mechanism of action of redispersible polymer powders (RPP) involves their interaction with water and other components of mortar formulations, leading to improved performance and properties. Here’s a detailed explanation of the mechanism of action of RPP:

1. Redispersion in Water:
   • RPP are designed to disperse readily in water, forming stable colloidal suspensions or solutions. This redispersibility is essential for their incorporation into mortar formulations and subsequent hydration.
2. Film Formation:
   • Upon redispersion, RPP form a thin film or coating around cement particles and other components of the mortar matrix. This film acts as a binder, binding the particles together and improving cohesion within the mortar.
3. Adhesion:
   • The RPP film enhances the adhesion between mortar components (e.g., cement, aggregates) and substrate surfaces (e.g., concrete, masonry). This improved adhesion prevents delamination and ensures strong bonding between the mortar and the substrate.
4. Water Retention:
   • RPP have hydrophilic properties that enable them to absorb and retain water within the mortar matrix. This increased water retention prolongs the hydration of cementitious materials, resulting in better workability, extended open time, and improved adhesion.
5. Flexibility and Elasticity:
   • RPP impart flexibility and elasticity to the mortar matrix, making it more resistant to cracking and deformation. This flexibility allows the mortar to accommodate substrate movement and thermal expansion/contraction without compromising its integrity.
6. Improved Workability:
   • The presence of RPP improves the workability and consistency of mortar, making it easier to mix, apply, and spread. This enhanced workability allows for better coverage and more uniform application, reducing the likelihood of voids or gaps in the finished mortar.
7. Durability Enhancement:
   • RPP-modified mortars exhibit improved durability due to their enhanced resistance to weathering, chemical attack, and abrasion. The RPP film acts as a protective barrier, shielding the mortar from external aggressors and prolonging its service life.
8. Controlled Release of Additives:
   • RPP can encapsulate and release active ingredients or additives (e.g., plasticizers, accelerators) within the mortar matrix. This controlled release mechanism allows for tailored performance and customized formulations to meet specific application requirements.

the mechanism of action of redispersible polymer powders involves their redispersion in water, film formation, adhesion enhancement, water retention, flexibility improvement, workability enhancement, durability enhancement, and controlled release of additives. These mechanisms collectively contribute to the improved performance and properties of RPP-modified mortars in various construction applications.