Why is Redispersible Polymer Powder (RDP) commonly added to tile adhesives, thermal insulation mortars, repair mortars, and other dry-mix products? The key is that RDP not only improves the bond between mortar and the substrate, but also enhances the mortar's internal cohesion and flexibility. Why Doesn't Traditional Mortar Always Bond Strongly? Traditional cement mortar mainly relies on the hardened cement structure and mechanical interlocking with the substrate. However, cement mortar is relatively brittle. When exposed to temperature changes, drying shrinkage, or slight substrate movement, stress can build up and eventually cause cracking, hollowing, or even debonding. How Does RDP Improve Bonding Strength? After adding RDP, the bonding mechanism of the mortar changes. First, stronger interfacial bonding. Polymers improve contact between the mortar and substrate and enhance interfacial bonding, reducing reliance on mechanical interlocking alone. Second, higher internal...