Increasing 3D elongation potential in fixed blank forming via fiber curlation

Abstract

Wood-fiber-based packaging materials offer only limited formability in 3D, which is an obstacle to their usability for complex 3D shapes. Although the requirements of good formability differ for the different forming processes, paperboard with a high elongation capability in 3D forming processes is often desirable. In this study, paperboard elongation in 3D tray forming (fixed blank process) was succesfully increased by curlation treatment of bleached birch kraft pulp and bleached pine kraft pulp fibers, and by the use of a dry strength agent (starch) which was used to produce a high level of bonding. The clearest correlations observed with the 3D elongation were for fiber curl and in plane elongation of paperboard. Instead, the correlation with tensile strength and tensile index was poor. These key correlations agreed with the elongation potential of fiber concept, previously presented for in plane elongation situation and suggested to apply for 3D elongation situation as well. Graphical abstract