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From PeopleScience & Research Biocomposites research for packaging By Davide Bandera Laboratory for Biomaterials and Laboratory for Applied Wood Materials Swiss Federal Laboratories for Materials Science and Technology St. Gallen and Dübendorf, Switzerland Schematic of nacre’s structure (top) and Seashell (bottom) The Laboratory for Biomaterials at the Swiss Federal Laboratories for Materials Science and Technology (Empa) in St. Gallen, Switzerland, is actively searching for new solutions in the area of bio-based packaging materials. The goal is to expand and improve the range of applications of biopolymers in this field, focusing on those materials, which are accessible through more sustainable and efficient routes, rendering them suitable alternatives to more conventional oil-based packaging. In particular, their inspirational sources are natural inorganic-organic composites, like nacre, which is found in mother of pearl and other seashells. These systems are composed by relatively weak constituents, mainly inorganic platelets, proteins and polysaccharides, but their hierarchical arrangement imparts exceptional mechanical and barrier properties. The structure resembles that of an array of bricks glued together by the bio polymers. From the barrier viewpoint, it is clear that gases need to go through a rather long and tortuous path in order to pass them; mimicking similar constructions should allow for the preparation of materials displaying good barrier properties. The researchers tackle the issue by using biopolymers [like PLA, chitosan, etc.] and pristine or modified inorganic layered silicates. Biomimetic films from PLA and organically modified layered silicates have been prepared by blade coating in order to improve barrier properties of PLA. The resulting films, prepared at high layered silicate loadings, mostly preserved the natural PLA transparence. It was also found that the crystallization behavior of the PLA was not heavily influenced with up to 50% by wt. in content of layered silicate. The water vapor barrier was 10-fold enhanced in the bionanocomposite with comparison to the original PLA. Chitosan and layered silicate composites films were also developed. Usually, these materials display high mechanical strength but their ductility is low. The addition of an ionic liquid type of plasticizer to the mixture improved the ductility by a factor of two, even with a plasticizer amount that was a third compared to the one required with the commonly used glycerol. The oxygen barrier properties of these films had 6-fold enhancement compared to pristine chitosan. It is reasonable to foresee future industrial applications where multilayered systems, based on these naturally occurring polymers and layered silicates, can provide more environmentally friendly packaging solutions for food and other goods. In a collaborative industrial project funded by the Swiss Commission for Technology and Innovation [CTI], the scientists deal with the improvement of the barrier properties of paper materials for food packaging. In particular, the task is to develop a solution to the manufacture of PLA water-based dispersions used as coatings for paper and paperboard. The biopolymer- 44 bioplastics MAGAZINE [06/13] Vol. 8

From Science & Research Chitosan/Layered silicate film (cross section SEM picture) 5.00 um PLA water-based dispersion (SEM picture) 10 µm based coating has to provide better water vapor and oxygen barrier properties, but also comply with the strict industrial requirements of low viscosity and high solid content. To face this challenge we started from a solution of polymer and prepared the water based dispersion that contains also a layered silicate. An innovative formulation was obtained with relatively high solid content (up to 25%), rather homogeneous particle size distribution, low viscosity and capable of improving the water barrier properties of paper when applied to it. The solutions and knowledge of the Swiss research team sets them as ideal partners for industries which are looking for innovative biopolymer-based packaging applications. INTAREMA THE NEW DIMENSION OF PLASTIC RECYCLING TECHNOLOGY bioplastics MAGAZINE [06/13] Vol. 8 45

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