Properties and characterization of hydrophobized microfibrillated cellulose |
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Authors: | Martin Andresen Leena-Sisko Johansson Bjørn Steinar Tanem Per Stenius |
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Affiliation: | (1) Ugelstad Laboratory, Department of Chemical Engineering, Norwegian University of Science and Technology, N-7491 Trondheim, Norway;(2) Center for Chemical Analysis, Helsinki University of Technology, P.O. Box 6100, FIN-02015 HUT, Espoo, Finland;(3) SINTEF Materials and Chemistry, N-7465 Trondheim, Norway |
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Abstract: | Microfibrillated cellulose (MFC) obtained by disintegration of bleached softwood sulphite pulp in a homogenizer, was hydrophobically modified by surface silylation with chlorodimethyl isopropylsilane (CDMIPS). The silylated MFC was characterized by Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), transmission electron spectroscopy (TEM), X-ray photoelectron spectroscopy (XPS) and white light interferometry (WLI). The degree of surface substitution (DSS) was determined using Si concentrations from XPS survey scans, as well as deconvoluted peaks in high-resolution C1s XPS spectra. The DSS values obtained by the two methods were found to be in good agreement. MFC with DSS between 0.6 and 1 could be dispersed in a non-flocculating manner into non-polar solvents, TEM observations showing that the material had kept its initial morphological integrity. However, when CDMIPS in excess of 5 mol CDMIPS/glucose unit in the MFC was used, partial solubilization of the MFC occurred, resulting in a drop in the observed DSS and a loss of the microfibrillar character of the material. The wetting properties of films cast from suspension of the silylated MFC were also investigated. The contact angles of water on the films increased with increasing DSS of the MFC, approaching the contact angles observed on super hydrophobic surfaces for the MFC with the highest degree of substitution. This is believed to originate from a combination of low surface energy and surface microstructure in the films. |
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Keywords: | Atomic force microscopy (AFM) Degree of surface substitution (DSS) Fourier transform infrared spectroscopy (FT-IR) Microfibrillated cellulose (MFC) Surface silylation Transmission electron spectroscopy (TEM) Wetting properties White light interferometry (WLI) X-ray photoelectron spectroscopy (XPS) |
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