Material Drying
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Defects Caused by Insufficient Drying Before Processing of High-Density Polyethylene High-Density Polyethylene
Problem Phenomenon
Silver streaks, bubbles, and rough surfaces appear on the product surface, and the mechanical properties decline.
The consequences of insufficient drying cover multiple defect types and are a common problem in plastics processing.
Cause Analysis
（1）The raw material absorbs moisture (although high-density polyethylene has low water absorption, it still absorbs water with long-term exposure)
（2）The drying temperature is too low or the drying time is insufficient
（3）The drying equipment is faulty or the dehumidification capacity is insufficient
（4）The dried raw material is placed in a humid environment for too long and absorbs moisture again
（5）The regrind is not dried or is insufficiently dried
Solution
（1）Use a dehumidifying dryer, with a drying temperature of 60-80°C and a time of 2-4h
（2）Control the moisture content after drying below 0.02% (high-density polyethylene)
（3）Keep the dried raw material sealed, cover the hopper, and limit the exposure to air to no more than 2h
（4）Dry the regrind the same as the new material
（5）Control the workshop environment humidity below 60%
Key Takeaway
Insufficient drying is a common root cause of processing defects, and a complete drying system and moisture content detection system need to be established.
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