The Effect of Mixing Time and Speed on Polyurethane Foam

Stirring is also a form of increasing energy of foam system, and the stirring situation has a great impact on the performance of foam cell size and other properties. The uneven mixture will cause local proportioning imbalance, and even lead to sub weight cracking, foam collapse, core burning, etc. of the foam system in serious cases.
Generally speaking, insufficient stirring (too slow or too short a time) can roughen the pore structure and make it difficult for the pore wall film to break through, resulting in the formation of closed pores; If stirring excessively (too fast or for too long), it can cause the system to have too fine bubbles, and even cause cracking in severe cases.
Mastering the appropriate stirring speed and time is also important for achieving successful foaming.
In a low-pressure continuous foaming machine, stirring also plays a role in dispersing the incoming air. If the stirring speed is too low, it is not enough to disperse the incoming air, resulting in the formation of large bubbles.
The commonly used stirring speed for continuous foaming machines is 2000-6000r/min, and the stirring speed for box foaming agents is 800-1500r/min. The appropriate mixing speed depends on various factors such as the size of the mixer type, flow rate (or material), etc.