Sustainable materials like paperboard can substitute for crude oil-based polymers in packaging applications and, by doing that, reduce the negative environmental impacts caused by plastic waste. For a broader application in the packaging industry, the forming of paperboard needs to overcome its limited forming behaviour and barrier properties. The presented work aims to influence the forming behaviour of uncoated and polyethylene terephthalate (PET)-coated paperboard with additives like water, gelatin and soap. Furthermore, the differences in the mechanical behaviour of coated and uncoated materials are investigated. For the studies, tensile, bulge and forming tests were combined with different optical measurement methods. The investigations showed that the overall forming behaviour is affected by the mentioned additives and can be improved. Additionally, the interaction of the coating and substrate paper is investigated under different load conditions.
An increased demand for sustainable materials has led to intensive research in the field of three-dimensional paperboard forming. To date, this work has focused on forming processes with shape-giving tools. However, individual shapes are often required, especially for large-format products. Incremental forming can be used in metal processing for small batches. In this article, the technology of incremental forming is transferred to paperboard. The results showed that elevated moisture content and a superimposed counter pressure significantly increased the forming limits. In addition, the use of polymer layers increased the shape accuracy. An extended understanding of the underlying mechanisms was achieved by analyzing the forming behavior. In uniaxial and biaxial characterization tests the influence of the moisture content on the forming behavior was investigated with conditions relevant for incremental forming. It was found that the bulge test is suitable to determine the most suitable moisture content regarding the forming limits and the spring back behavior in incremental forming. In addition, it was observed that the bearable elongations during the incremental forming of paperboard are significantly higher than in the established characterization tests. The reason for this is a compression of the fiber network during forming.
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