How does retort processing actually change the adhesive bond strength?Retort causes three things to happen. First, heat softens the adhesive layer, reducing its internal cohesion. Second, moisture penetrates the edges of the laminate and hydrolyzes certain adhesive chemistries (especially polyester-based polyurethanes). Third, different materials expand at different rates — aluminum foil expands very little, while polypropylene expands significantly. That thermal expansion mismatch creates shear stress at the interface. A well-formulated retort-grade adhesive will lose only 10–25% of its initial bond strength after retort. A poor adhesive can lose 70% or more.https://www.sinstarsl.com/bond-strength-in-retort-packaging-can-solvent-free-qualify