News Coatings Technologies
Hyperbranched polyesters combine PET recycling and flame retardancy
Researchers have developed hyperbranched polyester powder coatings that integrate PET-derived polyols with bio-based building blocks. The resulting system combines self-healing behaviour with effective flame retardancy, offering a sustainable route for repairable and fire-safe powder coatings.
Polyester powder coatings are widely valued for their VOC-free processing, yet they still struggle to combine sustainable raw material sourcing with in-service reparability and fire safety. A new study presents a “recycled plus renewable” design strategy that addresses these limitations by combining a tetrafunctional polyol (THETA) obtained from PET upcycling with renewable chemicals to produce flame-retardant and self-healable polyester powder coatings.
The researchers synthesised hyperbranched polyesters (HBPEs) rich in free hydroxyl and carboxyl groups, using THETA together with succinic acid and a phosphorus-containing diacid derived from itaconic acid. A resveratrol-based tri-epoxy was developed as the curing component, producing crosslinked networks that exhibit transesterification-enabled vitrimeric behaviour.
Event Tip: EC Conference Frontiers in Wood Coatings
The EC Conference Frontiers in Wood Coatings, formerly the Wood Coatings Congress, has established itself as the international reference platform for scientific and technical exchange in the field of wood coatings. Over the course of two intensive days in Amsterdam, the conference will bring together stakeholders from across the value chain — from resin and additive producers to leading research institutes, coating manufacturers, and end-use industries — to discuss the latest advances in formulations, application processes, and sustainable solutions.
Stable processing and self-healing performance
The powder resin system showed stable behaviour throughout melt-compounding, powder production, spraying and curing, remaining well within the typical powder processing window. The cured coatings demonstrated thermally triggered network rearrangement, enabling scratch self-healing without compromising the integrity of the crosslinked structure.
The phosphorus-containing architecture delivered synergistic flame retardancy by combining gas-phase quenching with condensed-phase char formation. Enhanced thermal protection was confirmed on steel plates, medium-density fibreboard and basswood plywood. The findings show that recycled carbon sources from PET and renewable feedstocks can be successfully integrated into a single coating network, offering a validated pathway towards systematic synergy between sustainable raw materials, self-healing and fire safety in polyester powder coatings.
Source: Gu, S. et al., PET-upcycled and biobased hyperbranched polyesters for self-healable and flame-retardant powder coatings. Green Chemistry (2026).
