ORIGINAL PAPER Microfibrillated cellulose foams obtained by a straightforward freeze–thawing–drying procedure Se ´bastien Josset . Lynn Hansen . Paola Orsolini . Michele Griffa . Olga Kuzior . Bernhard Weisse . Tanja Zimmermann . Thomas Geiger Received: 22 November 2016 / Accepted: 17 June 2017 / Published online: 21 June 2017 Ó Springer Science+Business Media B.V. 2017 Abstract Microfibrillated cellulose (MFC) is con- tinuously gaining attention due to its outstanding mechanical properties, in particular high strength-to- weight ratio. Recently, more and more studies target the production of porous materials, such as foams, out of this natural resource. Commonly, an energy- consuming freeze–drying method is utilized for pro- ducing pure MFC porous structures from water-based suspensions, which renders these products particularly unattractive for industry. Although alternatives for foam production have been proposed, using either modified MFC or with various additives, the freeze– drying step is still one of the most critical bottle-neck of MFC foam production upscaling. A novel straight- forward freeze–thawing–drying procedure assisted by the common additive urea was herein proposed. Such method allows the production of mechanically stable, lightweight MFC structures under low-cost ambient conditions drying. The influence of the cellulose fibril characteristics, the suspension formulation and the process parameters on the final foam properties have been studied in terms of porosity, density and mechanical properties. Keywords Microfibrillated cellulose  Ice-templating  Cellulose foam  Freeze–thawing  Porous structures Introduction In comparison to dense bulk materials, foams combine the advantages of having a light structure, an increased surface-to-weight ratio and being permeable for fluids Electronic supplementary material The online version of this article (doi:10.1007/s10570-017-1377-8) contains supple- mentary material, which is available to authorized users. S. Josset  L. Hansen  P. Orsolini  T. Zimmermann  T. Geiger (&) Applied Wood Materials, Swiss Federal Laboratories for Materials Science and Technology (Empa), Duebendorf, Switzerland e-mail: thomas.geiger@empa.ch M. Griffa Concrete/Construction Chemistry Laboratory, Center for X-Ray Analytics, Swiss Federal Laboratories for Materials Science and Technology (Empa), Duebendorf, Switzerland O. Kuzior Center for X-Ray Analytics, Swiss Federal Laboratories for Materials Science and Technology (Empa), Duebendorf, Switzerland B. Weisse Mechanical Systems Engineering, Swiss Federal Laboratories for Materials Science and Technology (Empa), Duebendorf, Switzerland 123 Cellulose (2017) 24:3825–3842 DOI 10.1007/s10570-017-1377-8