Related effects of various indicators of polyether polyols on foam products-Hydroxyl value

Generally, polyol compounds have high functionality and high hydroxyl value, so the foam prepared has high hardness, good mechanical and physical properties, and good temperature resistance.However, the miscibility with other components such as isocyanate is poor.
The reaction of hydroxyl compounds with isocyanates is one of the most common and basic reactions in polyurethane synthesis.With the same hydroxyl content, the reaction rate with a large degree of functionality is large, and the viscosity of the reactant increases quickly.Under the same functional degree, the high activity of polyether with high hydroxyl value and the reactivity of TDI are strengthened, and the low activity of polyether with low hydroxyl value and the reactivity of TDI are weakened.As the two main reactions in the foaming process: the reactivity of TDI and water is equivalent to its reaction with secondary alcohol, so fluctuations in the hydroxyl value of polyether will destroy the reaction balance between TDI and polyether and water during foaming.If the hydroxyl value is high, the reactivity of TDI and polyether is enhanced, and the main reaction is enhanced.If the hydroxyl value is low, the reaction between TDI and water is enhanced, causing the main reaction speed to fail to keep up with the foaming reaction speed, which can easily cause the phenomenon of bubble collapse.
Fluctuations in the hydroxyl value of polyether have a greater impact on foam products. The hydroxyl value of polyether directly affects the amount of TDI added. If the hydroxyl value is high, the amount of TDI will increase. If the user does not adjust the amount of TDI, it is equivalent to adding too little TDI, resulting in foam cracks, poor resilience, poor strength, and increased compression permanent deformation.Conversely, it is equivalent to adding too much TDI, which will cause the foam to form large pores and closed pores, increase hardness, and cause heartburn after a long maturation time.