Material Drying
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Product Defects Caused by Excessive Moisture Content of Block Copolymer Polypropylene Raw Material
Problem Phenomenon
Silver streaks and bubbles appear on the product surface, voids are generated inside, and the mechanical properties decline.
Excessive moisture content of the raw material is the common root cause of multiple defects, manifested in both product appearance and performance.
Cause Analysis
（1）The raw material is improperly stored and absorbs moisture; although block copolymer polypropylene has low water absorption, it still absorbs water with 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 environmental 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, with a drying temperature of 60-80°C for block copolymer polypropylene and a drying time of 2-4h
（2）Use the dried raw material in time, install a heat preservation cover on the hopper, and limit the residence in the hopper to no more than 2h
（3）Control the workshop environment humidity below 60%
（4）The regrind must be dried before use, with the same drying parameters as 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 and use moisture-proof packaging
Key Takeaway
Excessive moisture content of the raw material is solved by sufficient drying, and a complete drying and storage management system needs to be established.
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