Material Drying
4 조회수
PA6 Silver Streaks from Insufficient Drying
문제 현상
Fan-shaped silver-white streaks appeared on the surface of PA6 products, spreading outward from the gate; appearance parts were directly scrapped, often accompanied by tiny bubbles.
원인 분석
PA6 contains polar amide groups and has strong hygroscopicity; moisture-containing particles are heated in the barrel, moisture vaporizes and fills with the melt, leaving silver streaks on the cavity surface; insufficient drying, dryer dew point not meeting the standard, or secondary moisture absorption after drying are the main causes, and the moisture content allowed for PA6 is extremely low.
해결 방법
①Dehumidification drying at 80℃ for 4~6 hours, reducing moisture content to below 0.2%;②dryer dew point monitoring (recommended below -20℃);③seal after drying to prevent secondary moisture absorption and use up within a time limit;④verify moisture content by the Karl Fischer method when necessary;⑤appropriately reduce speed and increase back pressure for venting.
핵심 요약
PA6 silver streaks = 'drying is the first suspect': verify moisture before adjusting the machine; PA6 absorbs moisture quickly and has a strict window, drying is both an appearance gate and a performance gate, and moisture content verification must be included in the startup SOP and cannot rely on feeling.
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