Composite films of nanofibrillated cellulose and O-acetyl galactoglucomannan (GGM) coated with succinic esters of GGM showing potential as barrier material in food packaging
Nanofibrillated cellulose (NFC)-Norway spruce O-acetyl-galactoglucomannan (GGM) composite films were coated either with a novel succinic ester of GGM or with native GGM. NFC films were made for reference. The succinic ester of GGM was synthesised at low (GGM-Su1) and high (GGM-Su2) degree of substitution to obtain different level of water repellence. GGM and its succinic esters had good affinity with NFC substrate. This made it possible to implement the barrier functionality on the NFC network with the adequate mechanical properties. The coatings further enhanced the already excellent oxygen permeability properties, achieving 0.1 [(cm3 µm)(m2 kPa d)] as the lowest value with the NFC-GGM film double-coated with GGM-Su2. The films demonstrated pronounced stiffness by adding GGM to the NFC, as well as coating of GGM-Su2 on the NFC-GGM films at 0–90 % relative humidity. The films turned out to be impenetrable with grease even at high temperatures. NFC-GGM film with GGM-Su2 coating exhibited hydrophobic characteristics according to the water contact angle measurements. It was shown that adding 5.5 wt% of GGM to a NFC film and further 5.4 wt% of coating of GGM-Su or GGM on the film may highly enhance the feasibility of the biocomposites to be used for food packaging to replace typical oil-based non-biodegradable plastics currently used.
KeywordsContact Angle Composite Film Atom Transfer Radical Polymerization Dynamic Mechanical Analysis Oxygen Permeability
This work was carried out in framework of the Future Biorefinery Project by the Finnish Funding Agency for Technology and Innovation and Fibic Ltd. This work was part of the activities of the Åbo Akademi Process Chemistry Centre and Bioregs graduate school. This work made use of Aalto University Bioeconomy Facilities. We thank the staff of Metla in Vantaa and Lappeenranta University of Technology for providing the filtrated GGM, Hanna Lindqvist of our laboratory and Maristiina Nurmi of the Laboratory of Paper Coating and Converting for the practical help. The consultation on the concept by Lars Berglund of KTH, is highly appreciated.
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