Oxygen and oil barrier properties of microfibrillated cellulose films and coatings |
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Authors: | Christian Aulin Mikael Gällstedt Tom Lindström |
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Institution: | (1) BIM Kemi AB, Box 3102, 443 03 Stenkullen, Sweden;(2) Department of Fibre and Polymer Technology, School of Chemical Science and Engineering, The Royal Institute of Technology, 100 44 Stockholm, Sweden;(3) Innventia AB, Box 5604, 114 86 Stockholm, Sweden |
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Abstract: | The preparation of carboxymethylated microfibrillated cellulose (MFC) films by dispersion-casting from aqueous dispersions
and by surface coating on base papers is described. The oxygen permeability of MFC films were studied at different relative
humidity (RH). At low RH (0%), the MFC films showed very low oxygen permeability as compared with films prepared from plasticized
starch, whey protein and arabinoxylan and values in the same range as that of conventional synthetic films, e.g., ethylene
vinyl alcohol. At higher RH’s, the oxygen permeability increased exponentially, presumably due to the plasticizing and swelling
of the carboxymethylated nanofibers by water molecules. The effect of moisture on the barrier and mechanical properties of
the films was further studied using water vapor sorption isotherms and by humidity scans in dynamic mechanical analysis. The
influences of the degree of nanofibrillation/dispersion on the microstructure and optical properties of the films were evaluated
by field-emission scanning electron microscopy (FE-SEM) and light transmittance measurements, respectively. FE-SEM micrographs
showed that the MFC films consisted of randomly assembled nanofibers with a thickness of 5–10 nm, although some larger aggregates
were also formed. The use of MFC as surface coating on various base papers considerably reduced the air permeability. Environmental
scanning electron microscopy (E-SEM) micrographs indicated that the MFC layer reduced sheet porosity, i.e., the dense structure
formed by the nanofibers resulted in superior oil barrier properties. |
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