Effect of Redispersible Polymer Powder Dosage on Putty

Redispersible polymer powder (RDP) is an important organic additive, widely used in building dry-mixed mortar, tile adhesive, putty powder, self-leveling floor and other products. It is made by spray drying of polymer emulsion, which can be redispersed in water to form a stable emulsion, giving the material good flexibility, adhesion and crack resistance. In putty, the amount of RDP has a significant effect on its construction properties, mechanical properties, water resistance, weather resistance and other aspects.

Effect of RDP Dosage on Putty Construction Performance

The construction performance of putty mainly includes workability, smoothness, scraping feel and anti-sagging. Adding an appropriate amount of RDP can significantly improve the scraping performance of putty, making it smoother and more delicate, and enhancing its adhesion to the base surface. At the same time, RDP can improve the anti-sagging performance of putty, ensure uniform coating thickness on the wall, and reduce the rework rate during construction.

However, if the amount of RDP is too little, the construction performance of putty will be limited, and it is still easy to have problems such as roughness, powder loss, and sagging. When the amount is too much, the polymer content in the putty is too high, which will cause the scraping to be soft, the drying to be slow, and even the phenomenon of sticking to the knife and the coating to be sticky, affecting work efficiency. Therefore, in terms of construction performance, the amount should be reasonably adjusted according to the product positioning and construction environment.

The effect of RDP dosage on the bonding strength of putty

RDP can form a continuous organic polymer film during the drying and film formation of putty, and together with inorganic gelling materials (such as cement, lime calcium, gypsum, etc.), it forms a composite gelling system. This system can significantly improve the bonding strength of putty, so that it can form a good mechanical bite and chemical bonding with the base layer (such as cement wall, brick wall, gypsum board).

With the increase of RDP dosage, the dry bonding strength and wet bonding strength of putty are significantly improved, but after reaching a certain threshold, the improvement of bonding strength tends to be flat, and even shows a downward trend. This is because excessive polymer powder will dilute the bonding strength of inorganic gelling materials and may cause the cohesion of the material to decrease. Therefore, it is ideal to control it within the recommended range (generally 2%-5% of the total dry powder).

The effect of RDP dosage on the crack resistance and flexibility of putty

RDP can enhance the flexibility and deformation ability of putty and reduce the risk of cracking caused by temperature changes, shrinkage of the base layer, etc. An appropriate amount of polymer forms a flexible film in the putty, which helps to absorb stress and improve crack resistance, especially suitable for exterior wall putty and high-performance putty.

However, too high a polymer content may cause the putty to be too soft and the strength to decrease, affecting the polishing and finishing of the putty in the later stage. Therefore, while pursuing crack resistance and flexibility, it is also necessary to weigh its effect on strength and surface hardness.

The effect of RDP dosage on the water resistance and weather resistance of putty

RDP improves the water resistance and alkali resistance of putty by forming a hydrophobic polymer film. Appropriate addition can effectively prevent putty from powdering, hollowing or peeling in a humid environment. For interior and exterior wall putties, especially those exposed to rain or high humidity, improving water resistance is particularly critical.

However, if the amount of RDP is insufficient, the putty coating is easily damaged by water penetration, reducing the service life; if excessive amount is added, the putty may have problems such as slow drying and sticky surface. Reasonable use of RDP can greatly improve the weather resistance of putty, making it more adaptable to various environmental changes.

Redispersible polymer powder plays a vital role in putty, and its amount is directly related to the performance of the product. Too little will not significantly improve the performance, and too much will easily lead to side effects. Therefore, RDP should be optimized according to product requirements based on sufficient testing. It is usually recommended that the amount be between 2% and 5%, and it should be flexibly adjusted according to the type of putty (interior wall/exterior wall, primer/leveling/surface layer) to take into account construction, adhesion, flexibility and durability, and achieve a balance between performance and cost.