Testing and Predicting Impact Puncture Resistance of Multilayer Flexible Packaging Films

摘要

The resistance of films to high speed punctures, such as those that occur during filling operations on vertical-form-fill-seal packing lines, is difficult to measure and predict from laboratory tests. New test methods and computer modeling capability are described that correlate well with drop tests, promising to shorten development time for improving package performance. The creation of pinholes by snack crackers during filling operations is chosen as the initial focus of the study. High speed video is used to understand what happens to the cracker and film during a puncture event. From this study, a high-speed reverse-impact puncture test with a needle probe is developed that mimics the puncture event. The ultimate work to puncture the film is found to correlate with puncture resistance. Test results on seven coextruded barrier films show that the new test is able to quantitatively rank the performance of the films, give results that correlate with known structure variables, and provide input into model development. The reverse impact test results also agree with drop impact tests performed with bullets. An explicit nonlinear finite element model capable of predicting the impact puncture resistance of multilayer flexible packages is developed. The model explicitly considers each layer so that the contribution of the film structure can be determined. Initial results show excellent agreement between the model predictions and the multilayer barrier film test results. Future work will explore the role of material selection, layer placement and interlayer adhesion on puncture resistance, and ultimately lead to better performing packages.