Furanoate thermoplastic elastomer copolymers with tunable Hard–Soft segment ratios for extrusion-based 3D rapid prototyping

Poly(ethylene 2,5-furandicarboxylate) (PEF) is a prospective substitute for its fossil-fuel counterpart poly(ethylene terephthalate). However, its high melting temperature and poor toughness have limited its industrial applications. The properties of PEF can be improved by copolymerization with long-chain aliphatic diols, 1,6-hexanediol (HD), 1,8-octanediol (OD), and 1,10-decanediol (DD). A two-step polycondensation yielded in copolymers with molecular weights ranging from 17 to 66 kg/mol. The thermal and mechanical properties of the copolymers could be tuned by adjusting the ratio of ethylene glycol (EG) to the long-chain diols (1:9, 3:7, 5:5, 7:3, 9:1). The melting temperatures (T m ) ranged from 94 to 139 °C for copolymers with 70 and 90 wt.% of long-chain diols; and the glass transition (T g ) temperature from -3 to 64 °C with increasing of EG content. Mechanical testing demonstrated a tunable stiffness affected by the hard (FDCA) vs soft (long-chain diols) segments ratios of the obtained copolymers. A copolymer with 70 wt.% decanediol exhibited ductile deformation with a strain of 420%, T g =2 °C, and T m =94 °C. While a copolymer with 70 wt.% hexanediol has a T g =36 °C and T m =139 °C, and exhibits a high degree of rubbery elasticity with elongation of 500% at room temperature. A copolymer with 70 wt.% hexanediol was 3D printed via Fused Granular Fabrication (FGF) into a dimensionally stable rubber spring with good layer adhesion, without delamination between the layers. Hence, the synthesized copolymers can form a bio-based and sustainable platform for next-generation engineering plastics used in additive manufacturing materials, replacing fossil-based thermoplastic polyurethanes.