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Bio-based flame-retardant coating with reduced moisture uptake
A Chinese research team has developed a purely bio-based coating system using phytic acid, whey protein, and chitosan, offering both strong flame-retardant properties and reduced hygroscopicity.
In pursuit of sustainable alternatives to conventional flame retardants, researchers combined phytic acid with whey protein and chitosan. The resulting bio-based coating was applied to poplar wood using a water evaporation lamination technique. Structural analysis revealed that whey protein underwent dual denaturation – both heat- and acid-induced – which modified its secondary structure and enhanced flame retardancy.
The treated veneer showed a 22.9 % increase in limiting oxygen index compared to the phytic acid control samples. The coating provided flame resistance in both the gas and condensed phases, significantly boosting overall performance.
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Chitosan film minimises hygroscopic defects
A chitosan top layer further reduced water uptake, with samples showing a 46.92 % inhibition rate of hygroscopic defects after 24 hours. This barrier effect also improved surface quality, facilitating the application of waterborne paints on treated wood. Combining sustainable raw materials with high flame resistance and low hygroscopicity, the system represents a promising strategy for bio-based protective coatings.
Source: Wang, Y. et al., Dual-denatured protein for phytate-based systems: Purely bio-based coating featuring high flame retardancy and low hygroscopicity. Prog. Org. Coat. 203, 109157 (2025).
