CELLULOSE NANOFIBRILS AS FUNCTIONAL ADDITIVES IN BIO-BASED BARRIER COATINGS FOR PAPER PACKAGING

Abstract

Sustainable fiber-based packaging materials are primarily produced from renewable materials that have high recyclability. Nevertheless, to achieve barrier properties required for food packaging applications, paper and cardboards are often laminated or coated. Conventional barrier coatings that are currently in use are still mostly fossil-based, highlighting the need to develop sustainable coating solutions for fiber-based materials. Cellulose nanofibrils (CNF) that has large specific area and ability to form strong network structures via hydrogen bonding is a promising material for improvement of mechanical as well as barrier properties. While CNF can be obtained also from alternative biomass sources, in the SuperBark project we aim to produce CNF from bark and use it in bio-based coatings to achieve barrier properties for food packaging papers. To evaluate the bark-based CNF used in these kinds of applications, the barrier coating solutions with starch and bleached or unbleached bark-based CNF were developed and applied on three different base papers. Barrier properties of rod coated samples were evaluated regarding water vapour transition rate (WVTR) and grease resistance. Subsequent mechanical evaluation of the coated samples was performed. The research has confirmed that the starch coating increase barrier as well as mechanical properties on all three paper samples. However, the addition of bark-based CNF into starch coating increased the water vapour barrier at 85% relative humidity and was crucial to achieve the highest KIT 12 grease resistance and better mechanical properties on Paper 3.