Modeling and Measuring the Bending Stiffness of Flexible Packaging Materials, 2001 Polymers Laminations & Coatings Conference Proceedings

Jakob Lange, Chantal Pelletier and Yves Wyser--Bending stiffness is an important property of flexible laminates, controlling machinability as well as performance in applications such as stand-up pouches. This work addresses the bending stiffness of thin films and laminates through a combined experimental and modelling approach. Different techniques for experimentally determining the bending stiffness have been evaluated. A cantilever test was found to give reliable data for all kinds of materials. A 3-point bending test proved to be sensitive to miss-alignment, whereas a bending-under-own-weight test generally gave too low values of stiffness. A model, predicting the bending stiffness of multi-layer laminates from the elastic modulus of the constituents, was used to show that thin layers such as adhesives, print and barrier coatings can have a large influence on the bending stiffness, and that the influence often goes against what would be intuitively expected.