Hemicellulose-based latex coatings for oil and hydrocarbon barriers in fibre packaging

This study investigates galactoglucomannan (GGM)-based latices as sustainable, ionic-surfactant-free barrier coatings for paperboard substrates. GGM was chemically modified with allyl glycidyl ether (AGE) to introduce polymerisable double bonds, followed by free-radical copolymerisation with butyl acrylate (BA) to produce stable latex dispersions. Two GGM-based latices with different molecular weights—low molecular weight (LM-L) and high molecular weight (HM-L)—were synthesised and benchmarked against a commercial latex (C-L). The coated paperboards were evaluated for surface wettability, water vapour transmission rate (WVTR), grease resistance, and n-heptane vapour barrier performance. LM-L coatings exhibited pronounced hydrophobicity, with water contact angles above 90°, and demonstrated excellent resistance to olive oil penetration, maintaining integrity for more than seven days. In contrast, HM-L coatings provided superior barrier performance against n-heptane vapour, with permeation values remaining below the detection limit. Both GGM-based coatings showed strong resistance to grease and hydrocarbons. However, limitations were observed in water resistance and mechanical durability, particularly under creasing conditions. Overall, the results demonstrate the potential of GGM-based latices as bio-based alternatives to fossil-derived synthetic coatings for semi-permeable packaging applications requiring resistance to grease and hydrocarbon vapours, while providing moderate water vapour barrier properties.