Properties of lightweight fibrous structures made by a novel foam forming technique

We describe a novel method for the production of lightweight fibrous structures of densities as low as 8.8 kg m^{- 3}. The method is based on the use of liquid foam as a carrier medium for dispersed Kraft fibres. Different to the process of foam forming, where the quick removal of the foam results in the formation of thin fibrous sheets, our samples are allowed to slowly drain and dry until all foam has disappeared. This procedure results in bulk samples whose height (up to 25 mm) and density are controlled by initial fibre concentration and liquid fraction of the foam. Above a minimum density, the compression modulus of elasticity of the samples increases linearly with density. Furthermore, we show compressive strength of the structures being controlled via the initial liquid fraction of the foam, making this an important process parameter for the fabrication of such structures. Graphical abstract: [Figure not available: see fulltext.].