Effect of the lignin type on the gas/UV barrier properties of lignin–polyethyleneimine based composite films

Abstract

In this work, the film forming abilities, gas barrier properties, and ultraviolet (UV) barrier properties of composite films composed of lignin derivatives and polyethyleneimine (PEI) were investigated. Three types of lignin derivatives were employed, namely SESC lignin (SESC) obtained by simultaneous enzymatic saccharification and comminution, along with lignosulfonate (LS) and soda lignin (Soda), which were obtained through pulping processes. All three lignin derivatives produced uniform films under appropriate conditions through the formation of polyion complexes (PICs) with PEI, which occurred via ionic interactions. The gas and UV barrier properties of the resulting films were tunable depending on the type of lignin derivative, the molecular weight of PEI, and the mixing ratio. Notably, the films composed of SESC and PEI exhibited excellent barrier properties while maintaining high transparency. Since these composite films can be produced in aqueous systems without the use of organic solvents, they offer potential for application in environmentally friendly packaging materials.