Functionalized xylans in the production of xylan-coated paper laminates

Two functionalized xylans, namely a carboxymethyl xylan (CMX) and a 2-dodecenyl succinic anhydride-modified xylan (X-2-DSA) were, i) synthesized from beechwood xylan (BX) and characterized for their structural properties, thermal behaviour and molar mass and, ii) used in the production of paper/xylan laminates for food packaging. Films prepared from the functionalized xylans by solvent casting were applied onto paper employing the calendering moulding under pre-selected conditions in order to produce the laminates. The obtained laminates, as well as the starting base paper and the xylan-derived films, were characterized for their mechanical and barrier properties. The novel type of laminates demonstrated a synergistic effect with respect to its individual constituents, as the Young's modulus, tensile, tear and burst strengths of laminates were significantly improved in comparison to those of the starting paper or the xylan films. The xylan-coated paper laminates showed good moisture barrier properties, reducing up to 30-fold the water vapor permeability of the paper. At the same time, despite of fairly good oxygen barrier properties of the bio-based films from functionalized xylan, their application in paper laminates did not permit maintaining the same order of magnitude of oxygen transfer rates, which were, however, comparable to those reported for packaging papers coated by polyethylene films.