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Open AccessArticle

The Hydrophobicity of Lignocellulosic Fiber Network Can Be Enhanced with Suberin Fatty Acids

1
Production Systems, Natural Resources Institute Finland, Latokartanonkaari 9, FI-00790 Helsinki, Finland
2
Laboratory of Paper Coating and Converting, Center for Functional Materials, Åbo Akademi University, Porthaninkatu 3, FI-20500 Turku, Finland
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Oy Separation Research Ab, Porthaninkatu 3, FI-20500 Turku, Finland
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Department of Food and Nutrition, Faculty of Agriculture and Forestry, University of Helsinki, Agnes Sjöbergin katu 2, FI-00014 Helsinki, Finland
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Laboratory of Wood and Paper Chemistry, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Porthaninkatu 3, FI-20500 Turku, Finland
*
Author to whom correspondence should be addressed.
Academic Editor: Francisco J. Barba
Molecules 2019, 24(23), 4391; https://doi.org/10.3390/molecules24234391
Received: 1 November 2019 / Revised: 27 November 2019 / Accepted: 29 November 2019 / Published: 1 December 2019
(This article belongs to the Special Issue Recovery of Phytochemicals from Forest Materials)
Suberin fatty acids were extracted from outer bark of Silver birch (Betula pendula Roth.) using an isopropanolic sodium hydroxide solution. Laboratory sheets composed of lignocellulosic fiber networks were prepared from unbleached and unrefined softwood kraft pulp and further impregnated with suberin fatty acid monomers and cured with maleic anhydride in ethanol solution. The treatment resulted in hydrophobic surfaces, in which the contact angles remained over 120 degrees during the entire measurement. The fiber network also retained its water vapor permeability and enhanced fiber–fiber bonding resulted in improved tensile strength of the sheets. Scanning electron microscopy (SEM) images revealed that the curing agent, together with suberin fatty acids, was evenly distributed on the fiber surfaces and smoothing occurred over the wrinkled microfibrillar structure. High concentrations of the curing agent resulted in globular structures containing betulinol derivates as revealed with time-of-flight secondary ion mass spectrometry (ToF-SIMS). Also, the larger amount of suberin fatty acid monomers slightly impaired the optical properties of sheets. View Full-Text
Keywords: Birch outer bark; suberin fatty acids; lignocellulosic fiber network; hydrophobicity; contact angle; scanning electron microscope; time-of-flight secondary ion mass spectrometry Birch outer bark; suberin fatty acids; lignocellulosic fiber network; hydrophobicity; contact angle; scanning electron microscope; time-of-flight secondary ion mass spectrometry
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Korpinen, R.I.; Kilpeläinen, P.; Sarjala, T.; Nurmi, M.; Saloranta, P.; Holmbom, T.; Koivula, H.; Mikkonen, K.S.; Willför, S.; Saranpää, P.T. The Hydrophobicity of Lignocellulosic Fiber Network Can Be Enhanced with Suberin Fatty Acids. Molecules 2019, 24, 4391.

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