Foaming behaviour of cellulose pulp fibre-surfactant systems used for novel production of fibre-based materials

Work performed in the mid 1970s reports on the use of foam as a replacement for water in the paper making process. After several decades of inactivity in this area, the ever increasing need for more versatile and cost-efficient production methods capable of handling a variety of raw materials (e.g. nanoparticles, nanocellulose, flexible fibres over 25 mm-long) for the production of new types of products, has resulted in a renewed interest in the foam-based process for paper making applications. The work presented here deals with the foaming properties of the wood-pulp fibre dispersions, focusing on an aspect overlooked in the early studies, namely the role of surfactants, their structure and concentration on the properties of foams produced from fibre dispersions. The mechanical properties of the resulting hand-made paper sheets are also investigated. Suitable surfactants were selected based on their reported good foaming properties, compatibility with common paper making additives, availability on an industrial scale as well as environmental safety. The results from foamability and foam stability studies confirmed that the foaming properties of these systems are the result of a complex interplay of physico-chemical interactions between surfactants, fibres and other additives, where non-equilibrium phenomena play a major role. Properties of the resulting paper handsheets, such as mechanical strength and water adsorption, were found to vary significantly depending on the nature of the surfactants used, systems containing non-charged surfactants of the alkyl polyglucoside type displaying the best performance.