Material Drying
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Obvious dimensional increase of PA products after moisture absorption
Problem Phenomenon
The dimensions of PA products increase significantly after moisture absorption, exceeding the tolerance range, and the dimensional difference between the dry state and the humid state is large
Cause Analysis
（1）Polyamide (general-purpose nylon) has strong moisture absorption, the water absorption rate can reach 1.5-2.5%, and the molecular chain spacing increases and the volume expands after moisture absorption
（2）The product storage environment has high humidity and moisture absorption continues
（3）Used directly without moisture conditioning treatment
（4）Products with large wall thickness show more obvious moisture absorption
（5）The moisture absorption expansion amount is not considered during design
Solution
（1）Perform moisture conditioning treatment according to the use environment: condition to equilibrium moisture content under 65%RH, 80°C conditions
（2）Reserve moisture absorption expansion allowance during design (1.5-2.5%×1.5-2 times)
（3）Control the storage environment humidity
（4）Thin-walled products are less affected by moisture absorption
（5）Use low-moisture-absorption PA varieties
Key Takeaway
PA moisture absorption dimensional changes require moisture conditioning treatment and design reservation
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