LESSON 78: PRACTICAL SIGN OF EARLY POLYMERIZATION IN PU FOAM PRODUCTION PROCESS.

Early polymerization in polyurethane (PU) foam production occurs when the polymer structure forms too quickly before the foam has enough time to rise and expand properly. This causes the foam to become excessively tight, hard, or restricted during expansion. Common causes include excessive catalyst levels, especially tin catalyst, high isocyanate index, low water content, overly active amine catalysts, high chemical temperature, and poor formulation balance. Strong silicone stabilization can also make the foam gel too quickly. In practice, early polymerization often leads to high foam density, poor rise, tight or closed cells, internal stress, scorching, surface cracking, and reduced foam flow. The foam may appear “frozen” early during rising because the polymer network develops faster than gas generation and expansion.