Dimensional instabilities of polyester and polyolefin films as origin of delamination in laminated multilayer

Abstract

Polymer-metal multilayer films provide attractive barrier properties to air and water, provided by several films bonded together. Used in high temperature and humidity, the delamination is the most common degradation mechanism. This mode of failure is critical because it leads to premature loss of barrier properties. Therefore, delaminations limit the use of multilayer in these conditions. Delamination should result from interfacial shear stress, and plausibly from difference of shrinkage of the films, due to relaxation of internal stress. A method was developed for measuring the deformations of each individual film. The measurements indicate that the shrinkage is anisotropic and controls the decohesion in the multilayer.

Durability of Polymer Metal Multilayer: Focus on the Adhesive Chemical Degradation

“…The delamination in this polyolefin–polyester interface is strongly related to the shrinkage of the PP film. Indeed, a heat treatment of this film at 70°C during 192 days can induce a noticeable shrinkage of approximately −0.7% (Dubelley et al, 2017a). These authors showed that for such a shrinkage level, the PET/PU/PP interface was delaminated.…”

“…For example, delaminations of the PU adhesive layer at PET-Al/PU/PET-Al interfaces have been observed after only 1.5 years of aging at 65°C/75% RH (Brunner and Simmler, 2008). Other authors even evidenced debonding between PET and the sealing interface after 48 and 96 days of aging at 70°C/90% RH, respectively for PE and PP sealant materials (Garnier et al, 2011; Dubelley et al, 2017a). …”

“…Two main hypotheses have been formulated to explain the delamination occurring in thin multilayer systems: shear stresses resulting either from the difference in the hygrothermal expansion between the metal and the polymer (Simmler and Brunner, 2005) or by the shrinkage of the polymeric films (Dubelley et al, 2017a). Besides this purely mechanical assumption, it has also been suggested that the PU adhesive might also be degraded with a chemical hydrolysis weakening the interfaces, especially in moist environments (Simmler and Brunner, 2005; Brunner et al, 2006).…”