Researchers in France have developed a method for recycling polyester waste that actively resists conventional processing. The technique heats mixed waste to 270°C, activating residual manufacturing catalysts to create structures accessible to the same enzymes used for PET bottle recycling.
- The approach transforms rigid crystalline polyester structures that previously blocked enzyme access into recyclable materials.
- The method processes unsortable automotive textiles, sportswear fabrics, and mixed synthetic waste without preliminary separation.
- Hernan Garate from École Supérieure de Physique et Chimie Industrielles, Paris is the lead author.
KEY TAKEAWAY: The research team proves that intentionally mixing recalcitrant polyester waste delivers superior recycling outcomes compared to sorting approaches. The method challenges fundamental assumptions about plastic processing by demonstrating that controlled blending at high temperatures creates enzyme-accessible structures from previously unrecyclable materials.
WHAT'S AT STAKE: The textile industry faces mounting regulatory pressure over synthetic waste streams that actively resist current recycling technologies. Polyester waste from fashion, automotive components, and household products represents millions of tonnes annually destined for landfills due to insurmountable sorting costs and material properties that block enzymatic breakdown.
- Mixed polyester textiles contain incompatible additives like dyes and plasticisers that make separation economically prohibitive.
- Crystalline polymer structures in materials like PBT pack too tightly for enzyme penetration and chemical breakdown.
- Global synthetic textile recycling rates remain below 1% despite growing environmental mandates and consumer pressure.
THE TRIGGER: The study, published in Proceedings of the National Academy of Sciences, demonstrates that heating mixed polyester waste to 270°C activates antimony trioxide catalysts embedded during original manufacturing. This triggers transesterification reactions creating random copolymer networks with structures vulnerable to enzymatic attack.
- Residual manufacturing catalysts eliminate the need for additional chemical processing agents during breakdown.
- Vitrimerisation using epoxy cross-linking agents prevents rapid crystallisation in enzyme-resistant materials like PBT.
- Ice-bath cooling produces polymer structures that standard PET bottle recycling enzymes can effectively depolymerise.
- The process generates high-purity monomeric building blocks suitable for manufacturing new polyester products.
BY THE NUMBERS: The research team tested the method on various polyester waste combinations with striking results across different material types.
- Pure PET nonwoven waste achieved 20% enzymatic depolymerisation under conventional processing.
- Pure PBT waste managed only 1% breakdown using traditional enzyme treatment methods.
- Mixed PET and PBT waste streams reached 90% depolymerisation efficiency using the new technique.
- High-quality monomeric building blocks suitable for manufacturing new polyester products were recovered.
STRATEGIC SUBTEXT: This development addresses critical bottlenecks in circular economy implementation for synthetic textiles. By eliminating sorting infrastructure requirements whilst improving processing efficiency, the method could make textile recycling industrially competitive with virgin material production, fundamentally altering waste management economics across the fashion and automotive sectors.
