Material Drying
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Defects caused by insufficient drying before processing of low density polyethylene low density polyethylene
Fenómeno do problema
Silver streaks, bubbles, and rough surface appear on the product surface, and mechanical properties decrease.
The consequences of insufficient drying cover multiple defect types and are a common problem in plastics processing.
Análise das causas
(1) Raw material absorbs moisture (although low density polyethylene has low water absorption, long-term exposure still absorbs water)
(2) Drying temperature too low or drying time insufficient
(3) Drying equipment failure or insufficient dehumidification capacity
(4) Dried raw material placed too long in a humid environment and re-absorbs moisture
(5) Regrind not dried or insufficiently dried
Solução
(1) Use a dehumidifying dryer, drying temperature 60-80°C, time 2-4h
(2) Control moisture content after drying below 0.02% (low density polyethylene)
(3) Seal and store raw material after drying, cover the hopper, air exposure not exceeding 2h
(4) Dry regrind the same as virgin material
(5) Control workshop ambient humidity below 60%
Conclusão principal
Insufficient drying is a common source of processing defects; a complete drying system and moisture content inspection system needs to be established.
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