The effectiveness of defoamers for polyurethane is influenced by various factors, which directly affect the dispersibility, stability, and defoaming efficiency of the defoamer in the polyurethane system.

The chemical structure and active ingredients of defoamers determine their defoaming mechanism and effectiveness. For example, some defoamers destroy the foam film by reducing the surface tension of foam, while others realize defoaming by inhibiting the formation of foam. The compatibility of defoamers with polyurethane raw materials and other additives is a key factor affecting their effectiveness. If the compatibility is poor, it may lead to uneven dispersion of defoamers in the polyurethane system, thereby affecting the defoaming effect.

The pH value of polyurethane system has a significant impact on the effectiveness of defoamers. Generally speaking, defoamers can achieve optimal results within a suitable pH range (such as 6-9). Excessively high or low pH values may disrupt the stability or reduce the activity of defoamers. The change in temperature will affect the viscosity, reaction rate, and dispersibility of polyurethane defoamers. Under high temperature conditions, defoamers may be more prone to volatilization or decomposition, thereby affecting their effectiveness. The viscosity of polyurethane system can also affect the effectiveness of defoamers. A high viscosity system may make it difficult for defoamers to disperse, thereby reducing their defoaming efficiency.

The amount of defoamer added needs to be determined based on the specific situation and experimental results of the polyurethane system. Insufficient addition may not achieve the expected defoaming effect, while excessive addition may lead to increased costs and even affect product performance. It is crucial to choose the appropriate timing to add defoamers during the mixing or reaction process of polyurethane raw materials. Adding too early or too late may affect the effectiveness of defoamers. The choice of stirring method can also affect the dispersibility of defoamers in polyurethane systems. Proper stirring helps to evenly disperse defoamers in the system, thereby improving their defoaming effect.

Humidity has certain influence on the stability of foam during polyurethane foaming. When manufacturing polyurethane foam, if the ambient humidity is high, the moisture may react with the isocyanate inside the polyurethane to produce carbon dioxide, thus affecting the quality of foam. Although this mainly affects the polyurethane foaming process rather than directly targeting the effectiveness of defoamers, understanding the influence of humidity on polyurethane systems can help better control production conditions to improve defoaming effects.

Polyurethane systems may also contain various other additives, such as catalysts, stabilizers, pigments, etc. The interaction between these additives and defoamers may also affect the defoaming effect. For example, certain additives may alter the pH or viscosity of polyurethane systems, thereby affecting the stability and dispersibility of defoamers.

In summary, the effectiveness of defoamers for polyurethane is influenced by various factors such as the characteristics of the defoamer itself, the characteristics of the polyurethane system, usage methods and conditions, environmental factors, and the interaction with other additives. Therefore, when using defoamers, it is necessary to comprehensively consider these factors and adjust and optimize according to the actual situation to improve the defoaming effect.