A Catalyst-Free Polyester Vitrimer via Synergistically Blending High- and Low-Viscosity PET: Enhanced Creep Resistance, Reprocessability, Foamability, and Mechanical Properties

Poly(ethylene terephthalate) (PET) is the most widely produced polyester. To achieve its low-energy and green processing, recycling, and develop sustainable foams with a high expansion ratio (ϕ) for saving raw materials and lowering heat loss, this study reported on the production of catalyst-free PET vitrimers with controlled viscoelasticity, low relaxation activation energy, and CO 2 foaming properties with a high ϕ, by synergistically blending high and low-viscosity PET and performing a melt reaction with tetraglycidyl 4,4’-diaminodiphenylmethane (TGDDM) within a few minutes. The entire process of preparing the vitrimers and foams was safe and environmentally friendly, eliminating the need for metal catalysts and solvents. The PET vitrimer foamed by environmentally friendly CO 2 achieved a foaming ϕ of up to 39-fold and still maintained a 22-fold ϕ after reprocessing. This work proposes a promising and environmentally friendly strategy to synergistically regulate the gel content, viscoelasticity, and crystallization temperature of PET vitrimers from a raw material perspective, realizing PET vitrimer foams with a high ϕ, which potentially have wide application in thermal insulation and lightweight fields.