Polyurethane Powder in Redispersible Polymer Powders
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Solution Overview
Problem
Redispersible polymer powders used in construction applications face performance issues such as low mortar density, increased set time, limited adhesion after water immersion, and high costs for achieving good impact resistance, particularly in cementitious compositions like external thermal insulation systems.
Innovation Solution
Incorporating powdered polyurethane foam or elastomer as an inner additive in redispersible polymer powders, such as styrene-butadiene or vinyl acetate-ethylene copolymers, to create a water-redispersible polymer powder composite that improves adhesion, reduces set time, and enhances impact resistance while maintaining workability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If carboxylated latex is used in redispersible polymer powder, then adhesion is improved, but mortar density becomes very low and set time increases
Solution Approach 1:
The patent combines carboxylated latex with powdered polyurethane foam to create a composite redispersible polymer powder. The carboxylated latex provides adhesion through its carboxylic acid groups that form bonds with cement, while the polyurethane foam particles contribute to mortar density and maintain workability, thus resolving the contradiction between adhesion and density
2Strength
If carboxylated latex is used in redispersible polymer powder, then adhesion is improved, but set time increases
Solution Approach 1:
The composite formulation combines carboxylated latex with powdered polyurethane foam in specific proportions. The carboxylated latex component provides the necessary adhesion through chemical bonding with cement, while the polyurethane foam component does not interfere with the setting mechanism and helps maintain appropriate set time by contributing to the overall rheology without retarding setting
3Ease of manufacture
If vinyl acetate polymer is used in redispersible polymer powder, then cost is reduced, but adhesion after water immersion is very limited
Solution Approach 1:
The patent creates a composite where vinyl acetate polymer provides cost-effectiveness and basic film-forming properties, while powdered polyurethane foam contributes to water resistance and enhanced adhesion after water immersion. The polyurethane component forms a hydrophobic barrier that prevents water penetration, thereby maintaining adhesion strength even after prolonged water exposure
4Strength
If polymer dosage is increased to obtain good impact resistance, then impact resistance is improved, but cost increases significantly
Solution Approach 1:
The composite redispersible polymer powder combines vinyl acetate polymer with powdered polyurethane foam, where the polyurethane component provides enhanced impact resistance at lower dosages. The foam particles create a more flexible and resilient matrix that absorbs impact energy more effectively, allowing for reduced overall polymer dosage while maintaining or improving impact resistance performance
Solution Approach 2:
The invention changes the compositional parameters by introducing powdered polyurethane foam with specific physical properties (cell structure, density, elasticity) into the redispersible polymer powder formulation. This parameter change enables achieving better impact resistance at lower dosages compared to conventional single-polymer systems
Data Source
AI summary
A powdered polyurethane, preferably a powdered recycled polyurethane rigid foam is co-dried with a water insoluble film-forming polymer to obtain a redispersible polymer powder composite for use in hydraulic binders or cementitious compositions to improve performance of cementitious compositions or mortar, in applications such as cement based the adhesives (CBTA), or external thermal insulating composite systems (ETICS).