Material Drying
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Defects caused by insufficient drying before processing of homopolymer polypropylene homopolymer polypropylene
Problem Phenomenon
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.
Cause Analysis
(1) Raw material absorbs moisture (although homopolymer polypropylene 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
Solution
(1) Use a dehumidifying dryer, drying temperature 60-80°C, time 2-4h
(2) Control moisture content after drying below 0.02% (homopolymer polypropylene)
(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%
Key Takeaway
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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