Material Analysis
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Dimensional change of EVA products during long-term storage
Problem Phenomenon
After 3 months of storage, EVA product dimensions change ±2-3%, exceeding the ±0.5% requirement
Cause Analysis
EVA physical aging relaxation causes continuous dimensional change; secondary crystallization slowly changes density and dimensions; low molecular substances slowly migrate changing local density
Solution
1) Annealing treatment at 80°C/4h before shipment to stabilize dimensions; 2) Select high molecular weight grade to reduce low molecular substances; 3) Slight crosslinking to reduce molecular chain mobility and inhibit aging; 4) Control storage environment temperature at 23±2°C to reduce temperature change influence
Key Takeaway
Dimensional change is caused by physical aging; annealing treatment and slight crosslinking are measures to stabilize dimensions
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