Fully Bio‐Based <scp>TPUs</scp> From <scp>PLA</scp>/<scp>PTMC</scp>: Tunable Strength and Degradation Profiles

ABSTRACT This study synthesizes a series of fully bio‐based thermoplastic polyurethanes (TPUs) using poly(lactic acid) (PLA‐OH) and poly(trimethylene carbonate) (PTMC‐OH) as blended soft segments, L‐lysine ethyl ester diisocyanate (LDI) as the hard segment, and 1,4‐butanediol (BDO) as a chain extender. By systematically modulating the PLA‐OH/PTMC‐OH molar ratio (9:1–6:4) and isocyanate‐to‐polyol stoichiometry (1.1:1–1.4:1), precise control over the mechanical, thermal, and degradation properties of the TPUs was achieved. Increasing PTMC‐OH content enhanced flexibility, with elongation at break increasing, whereas tensile strength decreased, due to the influence of flexible carbonate bonds. Conversely, elevating the isocyanate‐to‐polyol ratio strengthened the interactions of the hard segments, improving tensile strength but reducing elongation at break. Thermal analysis showed that higher PTMC‐OH content lowered the glass transition temperature (Tg), whereas increased isocyanate/polyol ratios enhanced thermal stability. Degradation studies revealed a pH‐dependent hydrolysis rate, with the mass loss in alkaline conditions slowing down as PTMC‐OH content increased, due to the slower cleavage of carbonate bonds compared to ester bonds. This dual‐variable design strategy provides a sustainable approach to engineering biodegradable TPUs, suitable for applications ranging from high‐strength packaging to flexible medical devices, balancing environmental compatibility with tailored functional performance.