Bio-Based Coatings for Paper Applications

TLDR

Paper coatings traditionally rely on petroleum‑derived polymers for barrier and wettability, but their environmental drawbacks and limited recyclability have prompted interest in biopolymers, which face processing challenges that can be mitigated by blending with other biopolymers, plasticizers, and compatibilizers. This review surveys the barrier properties and processing of bio‑based polymers and their composites for paper coatings. The authors highlight recent nanotechnological advances, such as biopolymer nanoparticles, nanoclay, and nanocellulose, and the use of surface‑modified nanofillers combined with biopolymers to build hierarchical structures that improve hydrophobicity, barrier protection, and functionality.

Abstract

The barrier resistance and wettability of papers are commonly controlled by the application of petroleum-based derivatives such as polyethylene, waxes and/or fluor- derivatives as coating. While surface hydrophobicity is improved by employing these polymers, they have become disfavored due to limitations in fossil-oil resources, poor recyclability, and environmental concerns on generated waste with lack of biodegradation. Alternatively, biopolymers including polysaccharides, proteins, lipids and polyesters can be used to formulate new pathways for fully bio-based paper coatings. However, difficulties in processing of most biopolymers may arise due to hydrophilicity, crystallization behavior, brittleness or melt instabilities that hinder a full exploitation at industrial scale. Therefore, blending with other biopolymers, plasticizers and compatibilizers is advantageous to improve the coating performance. In this paper, an overview of barrier properties and processing of bio-based polymers and their composites as paper coating will be discussed. In particular, recent technical advances in nanotechnological routes for bio-based nano- composite coatings will be summarized, including the use of biopolymer nanoparticles, or nanofillers such as nanoclay and nanocellulose. The combination of biopolymers along with surface modification of nanofillers can be used to create hierarchical structures that enhance hydrophobicity, complete barrier protection and functionalities of coated papers.