Paper and paperboard are widely used in various types of packaging. Paper-based packaging is a recyclable, biodegradable, renewable and sustainable product, which gives it certain advantages over most plastic-based packaging materials. Although paper-based packaging, in some areas, lacks attractiveness in terms of visual appearance, 3D forming is an important method for producing advanced shapes from paper and paperboard, suitable, for instance, for modified atmosphere packaging. That said, very little is known about the deformations experienced by paper-based materials in 3D forming. Understanding the role played by the mechanical properties of paper and paperboard in the 3D forming process is key to improving performance. This paper presents experimental results obtained using three different forming devices designed to be used with paper-based materials and links the formability data with specific mechanical properties of the paperboard samples. Paperboard properties that were found to correlate with formability were as follows: compressive strength and strain, tensile strain, paper-to-metal friction and out-of-plane stiffness. The requirements for formability are different for the fixed blank forming process and sliding blank forming process.

Fibre deformations have a significant effect on fibre strength and sheet properties. There is little information, however, on the kinds of deformations different types of treatments induce and how they affect the fibre strength. In the present study, first-thinning bleached pine kraft pulp was treated with three mechanical devices: a wing defibrator (high consistency treatment), an E-compactor (high consistency treatment) and a conventional Valley beater (low consistency treatment). The fibre properties were determined with a fibre analyser. The fibre cutting induced by the hydrochloric acid (HCl) treatment (‘cleavage index’) was used for the quantification of the fibre defects. The zero-span tensile strength of dry and wet paper was used to estimate the fibre strength. Each mechanical treatment induced fibre deformations in its own characteristic way. The wing defibrator induced fibre kinks and curl whereas the E-compactor, in addition to fibre cutting, favoured kinks. Low consistency Valley beating straightened the fibres and released fibre deformations. The fibre deformations, especially the number of kinks, correlated well with the wet zero-span tensile strength. The cleavage index had some correlation with the zero-span tensile strength, but the results indicated that the cleavage index may not be directly related to the mechanical defects in fibres but depend more on the chemical conditions on the fibre surface and the wall structure.

Tensile tests of individual bleached kraft pulp fibers and paper sheets of industrial origin were conducted in order to investigate the effect of refining and small-scale fiber deformations on the extensibility of fibers and paper. The shape of the tensile curves of most of the fibers was concave upward (i.e., increasing slope) and consisted of two or three phases suggesting that the fibrillar structure and disordered regions in the fiber wall were straightened out during straining. Only a few of the individual BSKP fiber tensile curves were apparently linear. Elongation of the individual kraft fibers varied from 8 to 32% and the average elongation was not increased by high consistency refining. Tensile test results of laboratory sheets made of the same BSKP pulp suggested that the fiber bonding not only governs paper strength, but also is highly relevant for the elongation of fiber networks. The key conclusion related to this investigation and freely dried sheets was that the increased network elongation and strength after refining is mainly due to increased inter-fiber bonding and a higher shrinkage tendency of the fiber network and not due to the increased elongation or strength of individual fibers.

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Ultra-low solid content gels were prepared by physically cross-linking TEMPO-oxidized cellulose nanofibrils (TEMPO-CNF) with the plant-cell-wall polysaccharide, mixed-linkage β-glucan (MLG).