Design of new bioresourcepackaging from wood hydrolysates

Abstract: Hemicelluloses are a large group of polysaccharides that have recently attracted considerable attention in many industrial fields due to their abundance and renewability. They are non-edible and possess very good oxygen-barrier properties.Wood hydrolysates are hemicellulose-rich liquids extracted in aqueous solution from the hydrothermal treatment of wood. Nevertheless few industrial applications have been explored for this group of polysaccharides. This thesis presents methods for utilizing wood hydrolysates with primary upgrading as a key material for making oxygen-barrier films with a considerable potential for the food packaging industry.Softwood hydrolysates from wood chips and the fiberboard industry have been hydrothermally treated and upgraded via ultra-filtration and dia-filtration using different cut-offs.  Films produced directly from wood hydrolysates were fragile, hence three types of components were chosen to blend with the wood hydrolysates in order to reinforce the matrix: carboxymethyl cellulose (CMC) and microfibrillated cellulose (MFC) have been blended with softwood hydrolysates originally from wood chips (SW), and poly L-lactide (PLLA) with softwood hydrolysates from a fiberboard mill (Masonite AB) referred to as MSW.MSW was functionalized with L-lactide oligomers through a ring-opening polymerization mediated grafting-from reaction. The graft copolymer was designed to act as a compatibilizer in MSW/PLLA blend films. The PLLA addition improved the tensile behavior of the MSW/PLLA matrix and this effect was further enhanced by the addition of minor amounts of the synthesized compatibilizer which has only a minor influence on the oxygen-barrier property. With addition of only 1% (w/w), a 400% increase in the ductility of the PLLA/MSW was observed.Free-standing films of SW with different cut-offs were made with CMC and MFC as co-component and oxygen permeability values as low as 0.35 cm3µm day-1m-2kPa-1 was achieved using 10 kDa cut-off softwood hydrolysate, referred to as SW10, which made these films ready to compete with most of the petroleum-based polymers such as PET and PVOH for the packaging industry. Keywords: Wood hydrolysate, oxygen permeability, ring-opening polymerization (ROP), CMC, MFC, food packaging.