Thermoforming
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Chill marks in PP/TPO '2079851475616104458
Problem Phenomenon
Shiny chill mark lines or haze spots appear where the surface of PP/TPO thermoformed parts contacts the plug or mold surface.
Cause Analysis
The hot sheet contacts the overly cold plug or mold surface before stretching is complete, is quenched prematurely, and the surface replication is poor, leaving stress marks; too low mold or plug temperature is the direct cause.
Solution
①Preheat the mold to a reasonable temperature; ②heat the plug or switch to a low-thermal-conductivity material; ③slow the plug descent speed so that contact occurs after stretching is sufficient; ④check whether the workshop airflow blows directly on the sheet; ⑤balance the temperature of each heating zone.
Key Takeaway
A chill mark is the mark left by 'touching a cold surface too early': raise the mold/plug temperature and postpone the contact timing, and the problem disappears; this is a typical temperature management problem, not a material problem.
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