How to Adjust the Formula for Flexible PU Foam Foaming in Winter?

Winter foaming can lead to the following issues:

1. Streak Marks: When foaming, the surface may show streaks. In severe cases, the material overlaps can cause deep breaks.

2. Premature Material Surge: During foaming, the material may surge forward aggressively. This can create subsurface flow, where unfoamed material pushes forward and breaks the foam, sometimes affecting the sides of the flexible PU foam.

3. Top Cover Cracks: Insufficient gelation and low temperatures slow down the reaction, leading to delayed gelation.

4. Slow Drying of Surface: Slow post-curing of the surface can affect cutting. Severe slow drying can also cause fogging issues.

5. White Streaks in Foam: These are the result of material overlap and can cause the foam to tear easily. Severe cases may have streaks through the entire foam layer, often within the first 10 cm from the bottom. Streak marks and material filling are potential causes of these streaks.

6. Low Material Temperature: Based on experience, foams with more powder, more methane, or black pigment are significantly affected by low material temperatures.

Therefore, it is crucial to adjust the formula for foaming in winter. Foams with more methane are prone to the first three issues.

Formula Adjustments:

1. Heat the Components: Heat the ammonia, tin, silicon, and water components.

2. Heat the PPG, POP, TDI, and stone powder components.

3. Increase TDI in Some Formulas: For example, when adding stone powder, assess whether to increase TDI. If the foam's stability is poor, consider adding TDI.

4. Add Ammonia: This is a common adjustment method. When premature material surge occurs, prioritize adding ammonia.

5. Add Water and Reduce MC: This is an important method to adjust the reaction speed. If slow surface drying is severe, prioritize adding water and reducing MC. This increases the internal heat of the foam, accelerating post-curing.

6. Install Heating Lamps in the Foaming Molds: This is also crucial. Turn on the heating lamps about 15 minutes in advance.

7. Wrap the Machine Head with Electric Heating Tape: This is important because if the machine head is not wrapped, the foaming reaction will accelerate in the first two minutes, causing the foam height to decrease and the shape to incline upward. By adding electric heating tape and preheating to around 27-28°C (close to the material temperature), the reaction speed will remain consistent at startup.