Enhancing the barrier properties of paper board by a novel lignin coating

In this study, commercially available softwood lignin was esterified with tall oil fatty acid (TOFA) and studied as barrier material in fibre-based packaging material. The lignin was esterified to different degrees of substitution and the chemical analyses of the resulting samples were carried out by FTIR, TMAH thermochemolysis GC-MS, P-31 NMR and SEC. After functionalization, the thermoplastic properties of the lignin were enhanced as shown by DSC. The novel thermoplastic lignin samples were applied with a bar coater forming an even coating on the paperboard substrate. The WVTR of the paperboard (840 g/m(2) x 24 h) could be reduced to 260 g/m(2) x 24 h with a TOFA lignin ester double coating of 3.9 g/m(2). Furthermore, a decrease in OTR value was observed for the TOFA lignin ester as well as the TOFA coated paperboard samples. In contrast to the TOFA coating, the modified lignin coatings exhibited a high and stable contact angle (80 degrees for 2 min). The coating material did not affect the tensile strength of the paper-board. According to the results, the demonstration of the conversion of lignin into a value added product has been shown. Furthermore, the novel coating material shows promising properties for the development as sustainable barrier material in fibre-based packaging material to replace oil-based barriers. (C) 2013 Elsevier B.V. All rights reserved.