High Impact, Heat-Resistant, and Chemically Recyclable PEF Copolyester for Sustainable Transparent Packaging

Poly(ethylene 2,5-furandicarboxylate) (PEF) is a type of biobased polyester with a high gas barrier, which has the potential to replace polyethylene terephthalate (PET). In view of the poor toughness of PEF, an innovative attempt was made to install a small amount of 2,5-thiophenedicarboxylic acid (TDCA) into the PEF backbone and synthesize the poly(ethylene furandicarboxylate-co-thiophenedicarboxylate) (PEFS-n) copolyester. The obtained PEFS-n demonstrates thermal stability and glass transition temperature (T_g) comparable to that of PEF. Additionally, the tensile properties of PEFS-n exhibit appreciable enhancements. The impact strength of PEFS-n exhibited a markedly higher value than that of PEF, particularly in the case of PEFS-5, which displays a 138% increase in impact strength. Concurrently, PEFS-n exhibits enhanced barrier characteristics (oxygen, carbon dioxide, and water) than PET, in addition to outstanding solvent resistance and transparency. After 4 h of hydrolysis in alkaline solutions at 80 °C, subsequently simply washing and filtering, more than 90% of FDCA monomer could be recovered. This work provides a direction for high impact and heat-resistant green packaging, as sustainable alternatives to PET.