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One of the major challenges in 4D printed Shape Memory Polymers (SMPs) is their slow response to thermal stimuli. Synthetic carbon fillers have been introduced to address this issue; however, their use comes with environmental concerns. On the other hand, Polylactic Acid (PLA) is commonly used for 3D/4D printing of SMPs, but it requires softening to achieve large deformations. This research paper introduces a sustainable solution through blending PLA with Polybutylene Adipate Terephthalate (PBAT) that not only addresses these challenges but also possesses environmental eco-friendliness due to PBAT's high biodegradability rate. PBAT with weight percentages of 15 %, 30 %, and 45 % is utilized to soften PLA, and their composites are successfully 4D printed. Mechanical properties, shape memory effects, morphology, and thermal behaviors are comprehensively investigated. The results show that blending PLA with 45 % PBAT weight results in excellent features such as 220 % elongation and 93 % shape recovery in just a few seconds. The other two PLA-PBAT blends achieve complete shape recovery in less than 8 s. The PLA-PBAT contains 15 % PBAT, in addition to high strength (40 MPa), has 17 % elongation. This, coupled with the low melting temperature of PBAT, drives the high shape recovery rate. Scanning electron microscopy images finally confirm the high printability of all three blends, with the PLA-PBAT composite containing 30 % PBAT exhibiting the best quality in layer interfaces and the least porosity.
Rahmatabadi et al. (Tue,) studied this question.