20. Fracture Mechanics Characterisation of Low-Adhesive Stretch Films

Polymeric stretch films are wrapped around a packaging unit to keep it bundled and safe for transportation and storage. To maintain the generated retention forces and prevent a peel-off of the film, adhesive interactions between the film layers are required. Fracture mechanics investigations have been done in order to characterise the autohesive (cling) properties of the linear low density polyethylene/α-olefin copolymer based stretch wrap films. Resistance against initiation and stable peel front propagation across the interface of the cold-welded peel films are supposed to indicate detailed adhesive interactions. Next to the energy release rate G _IC that considers all kind of deformations during the peel process, the adhesive energy release rate G _aIC was determined using the standard peel cling test for polymeric stretch films according to ASTM D 5458. As a function of the peeling angle, an independence of G _aIC between 10° and 90° could be observed for the investigated stretch films. The crack resistance curve concept was applied and crack initiation values could be determined next to stable crack propagation. The results might indicate multiple adhesive interactions due to the surface morphology and viscoelastic behaviour of the investigated films. In accordance to the calculated crack initiation, a physical crack initiation could be observed.