Mechanical Strength and Water Resistance of Paperboard Coated with Long Chain Cellulose Esters

Long chain cellulose esters (LCCE) are bio-based materials, which are biodegradable, can be prepared from renewable materials, and have relatively good mechanical and barrier properties. In this study, we tested the feasibility of various LCCEs as a coating material for paperboard. Cellulose hexanoates (C6) and cellulose palmitates (C12) of various degrees of substitution were synthesized and tested as barriers. Coating of paperboard was performed by dissolving the LCCE to chloroform or acetone, and levelling the coating with wire bar coater to the surface of the paperboard. The coating gave hydrophobic surface to the paperboard, and significantly improved the water vapour barrier properties. Cellulose palmitate coatings were better water vapour barriers than cellulose hexanoate. However, polyethylene-coated paperboard had markedly lower water vapour transmission rate than LCCEs used in this study. The LCCE coatings slightly improved the tensile strength of the paperboard. In order to find out the suitability of LCCEs for extrusion coating, the thermal behaviour of LCCEs were also assessed. The cellulose hexanoate starts to degrade thermally at 280 degrees C and cellulose palmitate at temperature 320 degrees C. These materials do not have a clear melting point, but they behave as amorphous materials, and turn gradually to viscous form as temperature increases from 170 degrees C to 200 degrees C. This indicates possibilities to use them in extrusion coating, at least if the viscosity is improved with suitable additives. Copyright c 2011 John Wiley & Sons, Ltd.