This chemical-free and waterless treatment method has been developed to improve the durability and longevity of post-consumer polyethylene terephthalate (PET) textiles. This technology enables PET textiles to be reused multiple times by conducting the process at 230^oC for 8 hours, which results in a 200% increase in molecular weight and more than 98% decolourisation in a one-off. It allows PET fibres to be reused, recycled and redyed in a simple and inexpensive way by achieving decolourisation, molecular weight enhancement and durability improvement simultaneously in the textile treatment.