What hidden issues can incomplete foaming reaction during PU sandwich panel production cause?

Incomplete foaming means the isocyanate and polyol have not fully reacted. Residual isocyanate groups react with atmospheric moisture to form polyurea and CO₂ bubbles, leading to “post-foaming expansion” or powdering during service. Symptoms include: 1) Local surface bulging; 2) Unreacted liquid exudation on cut surfaces; 3) >30% reduction in core compressive strength; 4) Persistent strong odor. Detection method: place a core sample in an 80°C oven for 48 hours; if mass loss exceeds 3% or volume expansion occurs, the reaction is incomplete. Prevention requires controlling raw material temperature (22–25°C), mixing head speed, and production line speed matching.

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What hidden issues can incomplete foaming reaction during PU sandwich panel production cause?

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