Production & Quality
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PC Internal Bubbles
Problem Phenomenon
Round bubbles are visible inside transparent PC parts, mostly in thick-wall areas, affecting appearance, light transmission and strength, optical parts are directly rejected.
Cause Analysis
Water in the raw material vaporizing into bubbles is the first cause; insufficient holding pressure in thick-wall areas forms vacuum bubbles; air entrainment during filling also forms bubbles; the three mechanisms look similar in appearance but their treatment directions are completely different, they need to be distinguished by location and morphology (water-content bubbles are often accompanied by silver streaks).
Solution
①First verify and strengthen drying to eliminate the moisture factor; ②For thick-wall parts increase holding pressure and time to eliminate vacuum bubbles; ③Appropriately reduce the melt temperature to reduce volatiles; ④Improve mold venting to avoid air entrainment; ⑤Structurally reduce material in thick-wall areas.
Key Takeaway
PC bubbles are investigated by the three-way method of 'water, vacuum, entrained air': first verify drying, then look at holding pressure, and finally check venting; transparent parts have zero tolerance for bubbles, and drying verification is the first and most important checkpoint.
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