Additive manufacturing of PETG-TPU blends for tunable shape memory effect and mechanical properties

• Using the toughness of TPU and the 3D-4D printing capabilities of PETG to synergistically adjust mechanical properties and shape memory • The effect of TPU weight fraction on the thermal, mechanical, morphological, and shape memory properties of 4D-printed PETG-TPU blends was investigated. • DMTA analysis showed that PETG and TPU are immiscible, indicated by two distinct Tg peaks, and that the Tg increased from 80.5 °C to 88 °C as TPU content rose. • Excellent shape memory behavior was exhibited by all PETG-TPU blends, with 100% shape fixity observed for PETG70-TPU30 and PETG50-TPU50, while fixity decreased to 83.33% at 70% TPU. • Shape recovery was enhanced with higher PETG content, with PETG70-TPU30 achieving the fastest recovery rate, suitable for rapid-response applications. With the emergence of 4D printing, a new era has begun in additive manufacturing, where shape memory polymers transformed the static nature of printed samples into dynamic structures by their ability to change configurations under external stimuli. Polyethylene Terephthalate Glycol (PETG) is known as one of the best-performing shape memory polymers with excellent printability. However, its brittleness after printing has limited its use in advanced high-tech applications that require flexibility, such as smart wearable devices, stimuli-responsive artificial muscles, and smart textiles. On the other hand, Thermoplastic Polyurethane (TPU) is an excellent candidate to address this limitation because of its great flexibility. This study investigates blends of PETG and TPU to address these limitations and tune the final properties. Three PETG-TPU blends containing 30%, 50%, and 70% TPU were prepared, printed and compared with pure printed PETG. Their mechanical properties, printability, and shape memory behavior were evaluated using DMTA, SEM, tensile testing, and shape recovery tests. The results showed that as TPU content increased, tensile strength decreased (from 42.82 MPa for pure PETG to 13.92 MPa for the PETG50-TPU50 blend), while elongation at break significantly increased (from 7.9% for pure PETG to 945% for the PETG30-TPU70 blend). All samples demonstrated excellent shape memory properties. Both PETG70-TPU30 and PETG50-TPU50 exhibited a shape fixity ratio of 100%, but PETG70-TPU30 showed a slightly better shape recovery ratio of 95.56%. Notably, PETG70-TPU30 recovered in just 9 seconds, indicating superior performance ideal for applications requiring fast response times.