Foam-laid extensible paper for improved extensibility and press-forming performance

This study was motivated by the recent raising interest for the sustainable plastic-free dry 3D formable materials. 3D forming processes are capable to produce large unit quantities, but the process conditions for packaging applications have been typically very demanding for cellulose-based materials. This study covers some of the key factors affecting the extensibility of cellulose fibre-based materials and presents a laboratory-scale development study of a press-formable material concept. The investigation focused on comparisons of two refining concepts for bleached softwood kraft (BSK) pulp and two sheet forming concepts, namely water-laid and foam-laid forming. Additionally, influence of thermoplastic additives on the extensibility and 3D forming performance were investigated. In-plane compaction was applied with Expanda® laboratory device. Performance of the materials was evaluated by tensile tests and depth of the 3D formed shapes. In this study, in-plane compaction at first in cross-machine direction (CD) and then in machine direction (MD) led to over 30% elongation with BSK-based laboratory sheets containing latex as a binder and foaming agent. In addition to high elongation, optimal strength was needed for the best press-forming performances. In-plane compaction was the most significant factor regarding the elongation, but it also decreased the strength of the materials. Similar press-forming performance was found with two materials with either highly anisotropic or more isotropic elongation. The elongation anisotropy was created by one-way and two-way in-plane compactions. The results indicate that a reasonable performance for BSK-based materials for 3D forming applications can be reached using the presented concept.