Abstract
New bio-based packaging materials are highly interesting for replacing conventional fossil based products for a more sustainable society. Water-stable cellulose fiber foams have been produced in a simple one-batch foam-forming process with drying under ambient conditions. The cellulose fiber foams have a low density (33–66 kg/m3) and can inhibit microbial growth; two highly valuable features for insulating packaging materials, especially in combination with stability in water. Cationic chitosan and/or polyvinylamine have been added during the foam-forming process to give the foams water-stability and antimicrobial properties. The structural and mechanical properties of the cellulose fiber foams have been studied and the antimicrobial properties have been evaluated with respect to both Escherichia coli, a common model bacteria and Aspergillus brasiliensis, a sporulating mold. The cellulose foams containing chitosan had both good water-stability and good antibacterial and antifungal properties, while the foams containing PVAm did disintegrate in water and did not inhibit fungal growth when nutrients were added to the foam, showing that it is possible to produce a bio-based foam material with the desired characters. This can be an interesting low-density packaging material for protection from both mechanical and microbial damage without using any toxic compounds.
Highlights
Interest in cellulose-based packaging materials is steadily growing as we are trying to replace petroleum-based plastics with materials from renewable resources (Makaremi et al 2017; Svagan et al 2011)
Several research studies have reported that it is possible to cross-link chitosan with the cellulose in cotton textiles using citric acid (CA), to obtain a fabric that inhibits bacterial and fungal growth (Alonso et al 2009; El-Tahlawy et al 2005)
The cationic chitosan provides both antibacterial and antifungal properties, and it can be seen as a contact-active antimicrobial component as the chitosan is not leached from the foam during washing
Summary
Interest in cellulose-based packaging materials is steadily growing as we are trying to replace petroleum-based plastics with materials from renewable resources (Makaremi et al 2017; Svagan et al 2011). Shock adsorbing materials with low density, e.g. polystyrene foam, are often used for protection and insulation of sensitive products. Bio-based alternatives for low-density packaging materials are needed to replace the fossil based ones. Foam forming of papers was first developed in the 1960s to reduce the amount of pulp fibers needed compared to traditional wet-forming of paper products (Bernardin 1969; Chung 1974). With the development of cellulose nanofibril (CNF) production, research into highly porous biobased foam materials has exploded (De France et al 2017). From an economic and industrial point of view, it would be a great advantage to be able to create foam packaging materials directly from cellulose pulp fibers, rather than advanced CNF foams
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