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Oxygen and oil barrier properties of microfibrillated cellulose films and coatings
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
2010 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 17, no 3, 559-574 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2010. Vol. 17, no 3, 559-574 p.
Keyword [en]
National Category
Paper, Pulp and Fiber Technology
URN: urn:nbn:se:kth:diva-13666DOI: 10.1007/s10570-009-9393-yISI: 000277637100008ScopusID: 2-s2.0-77952430889OAI: diva2:326513
QC 20100623Available from: 2010-06-23 Created: 2010-06-23 Last updated: 2011-01-04Bibliographically approved
In thesis
1. Novel oil resistant cellulosic materials
Open this publication in new window or tab >>Novel oil resistant cellulosic materials
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this study has been to prepare and characterise oil resistant cellulosic materials, ranging from model surfaces to papers and aerogels. The cellulosic materials were made oil resistant by chemical and topographic modifications, based on surface energy, surface roughness and barrier approaches. Detailed wetting studies of the prepared cellulosic materials were made using contact angle measurements and standardised penetration tests with different alkanes and oil mixtures.

A significant part of the activities were devoted to the development of model cellulosic surfaces with different degrees of crystalline ordering for the wetting studies. Crystalline cellulose I, II and amorphous cellulose surfaces were prepared by spin-coating of cellulose nanocrystal or microfibrillated cellulose (MFC) dispersions, with Langmuir-Schaefer (LS) films or by a layer-by-layer (LbL) deposition technique. The formation of multilayers consisting of polyethyleneimine (PEI)/anionic MFC or cationic MFC/anionic MFC was further studied and optimized in terms of total layer thickness and adsorbed amount by combining Dual Polarization Interferometry (DPI) or Stagnation Point Adsorption Reflectrometry (SPAR) with a Quartz Crystal Microbalance with Dissipation (QCM-D).

The smooth cellulosic surfaces prepared had different molecular and mesostructure properties and different surface energies as shown by X-ray diffraction, Atomic Force Microscopy (AFM) imaging, ellipsometry measurements and contact angle measurements.

The cellulose model surfaces were found to be ideal for detailed wetting studies, and after the surface has been coated or covalently modified with various amounts of fluorosurfactants, the fluorinated cellulose films were used to follow the spreading mechanisms of different oil mixtures. The viscosity and surface tension of the oil mixtures, as well as the dispersive surface energy of the cellulose surfaces, were found to be essential parameters governing the spreading kinetics. A strong correlation was found between the surface concentration of fluorine, the dispersive surface energy and the measured contact angle of the oil mixtures.

Silicon surfaces possessing structural porous characteristics were fabricated by a plasma etching process. The structured silicon surfaces were coated with sulfate-stabilized cellulose I nanocrystals using the LbL technique. These artificial intrinsically oleophilic cellulose surfaces were made highly oleophobic when coated with a thin layer of fluorinated silanes. By comparison with flat cellulose surfaces, which are oleophilic, it is demonstrated that the surface energy and the surface texture are essential factors preventing oil from spreading on the surface and, thus, inducing the observed macroscopic oleophobic properties.

The use of the MFC for surface coating on base papers demonstrated very promising characteristics as packaging materials. Environmental-Scanning Electron Microscopy (E-SEM) micrographs indicated that the MFC layer reduced the sheet porosity, i.e. the dense structure formed by the nanofibers resulted in superior oil barrier properties. Attempts were made to link the procedure for preparation of the MFC dispersions to the resulting microstructure of the coatings, and film porosity and the film moisture content to the resulting permeability properties.

Finally, MFC aerogels were successfully prepared by freeze-drying. The surface texture of the porous aerogels was carefully controlled by adjusting the concentration of the MFC dispersion used for the freeze-drying. The different scales of roughness of the MFC aerogels were utilised, together with the very low surface energy created by fluorination of the aerogel, to induce highly oleophobic properties.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. ix, 55 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2009:57
oleophobic, MFC, cellulose, oil resistant, contact angle, XPS, SEM
National Category
Paper, Pulp and Fiber Technology
urn:nbn:se:kth:diva-11494 (URN)978-91-7415-476-4 (ISBN)
Public defence
2009-12-04, F3, Lindstedtvägen 26, KTH, Stockholm, 10:00 (English)
QC 20100623Available from: 2009-11-17 Created: 2009-11-17 Last updated: 2012-03-13Bibliographically approved

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