Solvent Retention
Retention of organic printing or adhesive solvents within the dried layers of a flexible laminate or paperboard package leads to contamination issues and bond degradation. Residual solvent trapping occurs when high production line speeds or inadequate dryer temperatures prevent complete evaporation of solvents before the web is wound or laminated. The trapped molecules remain sealed inside the structure, where they can slowly migrate through the packaging layers over time.
This migration can contaminate the packaged product, causing off-gases, unpleasant odors, and taste changes.
Structural Damage
Trapped solvents act as unwanted plasticizers in the adhesive layer, weakening the polymeric network and reducing overall bond strength. As residual solvent trapping persists, the cohesive strength of the laminating adhesive declines, which can lead to blistering or delamination under mechanical stress. This softening can also lower the thermal resistance of the laminate, causing failures during hot-filling or heat-sealing processes.
Monitoring residual solvent levels using gas chromatography is essential for quality assurance in packaging production.
Dryer Optimization
Increasing air velocity and optimizing the temperature zones in the drying ovens ensures that the solvent is fully removed before lamination. This adjustment prevents the trapped compounds from destabilizing the packaging structure or contaminating the contents.
