Strain‐Induced Failure Mechanisms of Silicon Oxide PECVD Barrier Coating Systems on PET: Experimental Analysis and Simulation of Crack‐Mediated Permeation

Silicon oxide barrier coatings deposited by plasma‐enhanced chemical vapor deposition offer recyclability advantages for flexible packaging but face mechanical durability challenges. PECVD coating systems on PET substrates were subjected to uniaxial tensile strain up to 5%. Water vapor transmission measurements showed complete barrier failure at 5% strain (single loading) and 3% strain (cyclic loading). Electron microscopy revealed cracks accounting for only 0.8–3.7% of surface area, indicating that sub‐resolution defects contribute significantly to permeation. Simulations demonstrated that crack offset patterns reduce permeation by up to 81% through tortuous path effects, though systematically underestimated measured values. These findings establish critical strain thresholds for barrier functionality and highlight the need for improved coating architectures balancing mechanical durability with recyclability requirements for sustainable packaging applications.