Material Drying
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Excessive moisture content of general-purpose polyethylene raw material causing product defects
Problem Phenomenon
Silver streaks and bubbles appear on the product surface, voids are generated inside, and the mechanical properties decrease.
Excessive moisture content of the raw material is a common root cause of various defects, and is manifested in both the appearance and performance of the product.
Cause Analysis
（1）The raw material is improperly stored and absorbs moisture; although general-purpose polyethylene has low water absorption, it still absorbs water after long-term exposure
（2）The drying equipment is faulty or the drying process is improper, and the dehumidification is insufficient
（3）The hopper is left open for too long, and the dried raw material absorbs moisture again
（4）The ambient humidity is high, and the raw material absorbs water during conveying
（5）The regrind is used directly without drying
Solution
（1）Use a dehumidifying dryer, the drying temperature of general-purpose polyethylene is 60-80°C, and the drying time is 2-4h
（2）Use the raw material in time after drying, install a heat preservation cover on the hopper, and the residence in the hopper should not exceed 2h
（3）Control the workshop environment humidity below 60%
（4）The regrind must be dried before use, and the drying parameters are the same as those of the new material
（5）Regularly test the moisture content of the raw material and control it below 0.02%
（6）Store the raw material sealed, using moisture-proof packaging
Key Takeaway
Excessive moisture content of the raw material is solved by sufficient drying, and a sound drying and storage management system needs to be established.
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