Functional barrier and recyclable packaging materials through microfibrillated cellulose bilayer composite coatings

Abstract

Although microfibrillated cellulose (MFC) offers high barrier properties against air, oxygen, and oil, its limited water resistance restricts industrial applications. An innovative bilayer composite coating (BCC) has therefore been developed in response, consisting of a top layer providing water resistance and the MFC layer contributing to the gas & oil barrier and recyclability. The top coating integrates styrene-butadiene copolymer for its non-polar characteristics and nanoclay to create a hydrophobic surface that resists moisture with enhanced tortuosity. Scanning electron microscopy confirmed a stable interface between the paper substrate and the BCC. X-ray photoelectron spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) show that the BCC prevents intermixing between layers, enhancing barrier performance and fiber recovery with reduced stickies during recycling. The BCC significantly improved barrier properties, achieving a 56 % reduction in water vapor transmission rate, a ∼ 630-fold decrease in air permeability, an oil & grease resistance of kit rating 12, and < 5 % weight gain from the hot oil test. These improvements highlight the efficacy of the BCC system for enhanced barrier and recyclability, especially in stickies reduction. This research demonstrates that the strategic combination of conventional and novel MFC materials can provide sustainable packaging with functional barriers and recyclability for a circular economy.