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bioplasticsMAGAZINE_1801

From Science and

From Science and Research Alginate barrier coating A promising biomaterial for the use in packaging concepts Alginate is a promising barrier coating for oxygen and grease. It is biobased and biodegradable. Furthermore, it allows new recycling strategies to be developed because alginate can be dissolved in water, i.e. in washing processes during recycling. The water based Alginate coatings are applied to a substrate via lacquering processes. They have a high grease resistance and very low oxygen permeability. However, the high sensitivity against humidity still limits an extensive application. Therefore, Verena Jost and Matthias Reinelt from the Fraunhofer Institute for Process Engineering and Packaging IVV (Freising, Germany) worked on this challenge and published a study with their results. In order to decrease the moisture sensitivity, a crosslinking of alginate with polyvalent ions was performed with the possibility for a scale-up to a continuous roll-to-roll application. Alginates are scaffolding polysaccharides produced by brown seaweeds (Fucophyceae, was Phaeophyceae, mainly Laminaria). They consist of the two monomers β-D-mannuronic acid and α-L-guluronic acid linked by a 1,4-glycosidic bonding. The crosslinking of alginate was performed by internal setting where inactivated, polyvalent ions (here Ca 2+ ) were added to the alginate formulation. A pH-shift then triggers the crosslinking. The Ca 2+ concentration was optimised for each of the three crosslinking agents. The researchers found that by an optimal crosslinked alginate, the final films had increased mechanical strength and flexibility. Additionally, the water vapour and oxygen permeability was reduced. Additionally, the scale-up of the crosslinked alginate formulation to a continuous lacquering pilot plant was performed proving the potential of this biopolymer for industrial processes. The used substrate films were made of the biopolymer PHBV and PET. In comparison to the uncoated samples, the alginate-coated substrates showed reduced permeabilities. When the alginate coating was additionally crosslinked, the permeabilities were further reduced. The oxygen permeability of non-crosslinked alginate films was 0.3 [cm³ (STP) 100µm m -2·d -1·bar -1 ] and the water vapour permeability was 71.1 [g 100µm·m -2·d -1·mbar -1 ]. The lowest measured oxygen permeability of cross-linked alginate was reduced by factor 3 to 0.1 [cm³ (STP) 100µm·m -2·d -1·bar -1 ] and the lowest water vapour permeability was also reduced by factor 3 to 26.2 [g 100µm·m -2·d -1·mbar -1 ]. These results show, that alginate is a promising biomaterial for the use in packaging concepts especially due to its extremely low permeabilities. Nonetheless, optimisation is necessary for implementation as widely used barrier material for which Fraunhofer IVV seeks industrial and academic partners. MT A comprehensive text on this research can be found at Journal of Applied Polymer Science, 2017: tinyurl.com/alginate-barrier (with cost) www.ivv.fraunhofer.de Figure 1: Alginate films (Source: Fraunhofer IVV) 50 bioplastics MAGAZINE [01/18] Vol. 13

Automotive Innovation. Technology. Sustainability. From equipment and trends to the people advancing plastics manufacturing, NPE2018: The Plastics Show has it covered. Be there to discover new ways to maximize efficiency, advance your operations and achieve success. REGISTER TODAY AT NPE.ORG MAY 7–11, 2018 | ORLANDO, FL, USA We’ve got it machined. melted. extruded. welded. compounded. blow molded. injection molded. covered. casted. fabricated. foamed. thermoformed. rotation molded. vacuum formed. cooled. heated. sealed. thermoset. packaged. transported. consumed. recycled. bioplastics MAGAZINE [01/18] Vol. 13 51

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