Benchmarking barrier coatings for paper packaging: From biopolymers and nanomaterials to bionanocomposites

The growing demand for sustainable packaging has accelerated research on bio-based coatings for paper substrates, aiming to replace petroleum-derived barriers while maintaining functional performance. This review critically examines recent advances in biopolymers, nanomaterials and bionanocomposite coatings developed to improve paper's resistance to water, water vapour, oils/greases and gases. Particular attention is given to how material chemistry, coating architecture and processing conditions shape barrier functionality, supported by benchmark comparisons that place reported values within a consistent performance framework. The analysis highlights the selective strengths and persistent limitations of individual biopolymers and nanomaterials and shows how their integration into bionanocomposite structures enables broader and more balanced protection, including several formulations capable of triple- and quadruple-barrier performance. Persistent challenges, including formulation stability, drying behaviour, coating, scalability, and end-of-life performance are discussed in the context of their impact on industrial adoption. By assembling the literature into a unified barrier-performance landscape, this review provides a clear perspective on current capabilities and identifies the materials that will guide the development of robust, multifunctional coatings for next-generation paper packaging.