Material Analysis
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PSU Internal Stress Difficult to Eliminate
Problem Phenomenon
PSU products have large internal stress after molding; cracks appear during storage or use; stress marks are visible on transparent parts; solvent contact accelerates cracking.
Cause Analysis
PSU melt cools relatively quickly and molecular chains are rigid, making the internal stress generated during molding difficult to eliminate; high-viscosity melt orientation freezes; rapid cooling and excessive holding pressure aggravate stress accumulation.
Solution
①Increase mold temperature to 150~180°C to slow stress freezing; ②Apply moderate holding pressure to avoid over-compaction; ③Anneal after molding to release stress; ④Eliminate sharp corners in the structure.
Key Takeaway
Internal stress management is the fate of rigid, fast-cooling materials like PSU; high mold temperature and annealing are the two pillars; stress cracking verification must simulate the actual environment.; After confirming effectiveness, solidify the parameters and practices into the work instructions to prevent recurrence
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