Material Drying
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Product defects caused by moisture content of homopolymer polypropylene raw material exceeding standard
Problem Phenomenon
Silver streaks and bubbles appear on the product surface, voids form inside, and mechanical properties decrease.
Raw material moisture content exceeding standard is a common source of multiple defects, manifested in both product appearance and performance.
Cause Analysis
(1) Raw material improperly stored and absorbs moisture; although homopolymer polypropylene has low water absorption, long-term exposure still absorbs water
(2) Drying equipment failure or improper drying process, insufficient dehumidification
(3) Hopper left open too long, dried raw material re-absorbs moisture
(4) High ambient humidity, raw material absorbs water during conveying
(5) Regrind used directly without drying
Solution
(1) Use a dehumidifying dryer; homopolymer polypropylene drying temperature 60-80°C, drying time 2-4h
(2) Use dried raw material promptly, install insulation cover on the hopper, residence in hopper not exceeding 2h
(3) Control workshop ambient humidity below 60%
(4) Regrind must be dried before use, drying parameters same as virgin material
(5) Regularly test raw material moisture content, control below 0.02%
(6) Seal and store raw material, use moisture-proof packaging
Key Takeaway
Raw material moisture content exceeding standard is solved by full drying; a complete drying and storage management system needs to be established.
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