Esterified lignin coating as water vapor and oxygen barrier for fiber-based packaging

Lignin, esterified with palmitic and lauric acid chloride, has been studied for the application as coating on fiber-based packaging material. The aim was to improve the barrier properties against water vapor and oxygen of paperboard. The esterification was followed by Fourier transform infrared spectroscopy, P-31 nuclear magnetic resonance spectroscopy, and gel permeation chromatography measurements. The lignin esters were applied on paperboard and formed a continuous film. The moisture barrier property of the coated paperboards was characterized by the water vapor transmission rate (WVTR). A significant decrease in WVTR was observed, for example, 40 g m(-2) (for 24 h) for a paperboard coated with 10.4 g m(-2) hardwood kraft lignin palmitate. The contact angle of water on the lignin ester coatings was high and stable. For all paperboard samples coated with lignin esters, a significant decrease in oxygen transmission rate was observed. Accordingly, lignin palmitate and laurate have a high potential as a barrier materials in packaging applications.