A comparative study of methods for porosity determination of cellulose based porous materials

Cellulose based foams and aerogels are gaining interest as an alternative to petroleum derived materials. The characterization of the internal void fraction, or porosity, of these materials is an essential parameter in assessing their potential for practical applications. The physical nature of these materials includes a web-like pore morphology, high compressibility, and significant roughness of both the internal and external surfaces. These issues cause the determination of porosity using standard methods to be unreliable. In this study, low density cellulose nanofibrils foams were generated, and pore volume and pore size results were compared using mercury porosimetry, Barrett–Joyner–Halenda (BJH) gas sorption, image analysis, and geometric methods. A new simple silicone oil saturation-based method to measure the porosity of these materials was also presented. Utilizing this method, the porosity of cellulose based foams and aerogels have been determined with improved accuracy compared to the existing standard methods.