Abstract
The molecular mechanisms behind the interactions between fibres in fibrous networks, and their link to paper/network strength, have long been under intense scientific investigations and scientific debate (Wågberg and Annergren 1997, Lindström et al. 2005; Hirn and Schennach 2017) but still there is no unified view on how the strength of fibre/fibre joints and network strength can be linked to different molecular mechanisms (Wohlert et al. 2022). Historically the interaction between cellulose-rich fibre surfaces was ascribed to hydrogen bonding and elaborate models were developed for linking mechanical properties of fibrous networks to the H-bonding between the surfaces (Nissan and Batten Jr 1997). This is however an oversimplification for several reasons. First of all, the H-bonds are very specific, which means that they are short-ranged and not implicitly additive over the material volumes engaged in the contact region between the fibres. Secondly the molecular interactions in the fibre/fibre contact zones are actively participating in the formation of the fibre joints, i.e. in the making of the fibre/fibre joints. The interactions in the wet state will hence affect the dimensions of the wet and dry contact zones and they will also create built-in stresses in the zones of contact in the dried fibre/fibre joint. The dry mechanical properties of the fibrous networks, i.e. the breaking of the joints and the fibres, will then be controlled by the molecular contact zone, the interactions in the contact zone, and also outside the molecular contact zone but within the molecular interactions range, the number of molecular contacts/network volume and the individual fibre strength.
Download PDF