Effects of flexing,optical density,and lamination on barrier and mechanical properties of metallized films and aluminum foil centered laminates prepared with polyethylene terephthalate and linear low density polyethylene

Flex barrier and optical density (OD) are two unique properties for metallized films and aluminum foil. This study investigated the effect of flexing on barrier properties of a laminate comprising metallized films and aluminum foil, as well as OD and adhesive lamination process on the overall multilayer laminate performance. Three (3) barrier layers, namely aluminum foil, metallized polyethylene terephthalate (met OPET) film with a high OD, and standard metallized PET film(met OPET), were laminated with the same printing layer OPET and sealing layer linear low density polyethylene (LLDPE), into OPET/adhesive/foil/adhesive/LLDPE and OPET/adhesive/met OPET/adhesive/LLDPE structures. The oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) were measured before and after flexing. The aluminum foil centered laminate had an excellent oxygen barrier after the 20-cycle flexing test and failed to retain its oxygen barrier after the 270-cycle flexing. Compared to the aluminum foil centered laminate, the metallized film centered laminates were less affected by the flexing on the oxygen barrier. For all laminates, the water vapor barrier was less severely affected by flexing than the oxygen barrier. This study suggests that the ASTMF392 Gelbo D (20- cycle flexing) can determine if aluminum foil and metallized film centered laminates are resistant to flex-formed pinhole failures. A higher OD, a thicker film thickness and lamination process improved laminate’s actual barrier, resulting in lower measured transmission rates versus that predicted using Henry's solubility law and Fick's diffusion law. The laminate’s water vapor transmission rate is 55–74% lower than predicted. The oxygen transmission rate is 15–31% lower than predicted.