Material Drying
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EVOH barrier property decreases after moisture absorption
Problem Phenomenon
After EVOH is exposed to humidity >80%RH for 24h, OTR increases from 0.1 to 10cc/m²·24h
Cause Analysis
EVOH vinyl alcohol groups are strongly hydrophilic; after moisture absorption, hydrogen bonds are destroyed by water molecules and barrier properties drop sharply
Solution
1) Sandwich the EVOH layer between PE layers to prevent moisture absorption; 2) Increase EVOH layer thickness to 15-20μm to compensate moisture absorption loss; 3) Multi-layer coextrusion with EVOH not exposed on the outer layer; 4) Avoid long-term high-humidity exposure after package sealing
Key Takeaway
EVOH moisture absorption causing a sharp drop in barrier property is its inherent characteristic, requiring sandwich structure protection
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