Shape memory PLA/TPU blend using high-speed thermo-kinetic mixing

Official URL: https://dx.doi.org/10.1021/acsomega.4c04338

In this study, a thorough examination of the chemical, thermal, and mechanical characteristics, as well as shape memory behavior at low temperatures, of blends consisting of polylactic acid (PLA) and polyurethane (TPU) is conducted. The research involves the preparation of PLA/TPU mixtures with varying concentrations of TPU using a high-speed thermo-kinetic mixing approach. Chemical, morphological, and thermal analyses were conducted on pure PLA, TPU, and PLA/TPU mixtures by using Fourier Transform Infrared (FTIR), X-ray diffraction pattern spectroscopy (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). Mechanical properties were assessed through tensile and three-point bending tests. The achievement of a uniform mixture is confirmed through SEM images, reduction in the glass transition temperature according to DSC and DMA, and an improvement in mechanical properties compared to results documented in the literature, implying a more effective mixing method for the compounds. To assess the practical applicability of this blend, an investigation into the shape memory properties of the mixture when deformed at low temperatures, i.e., cold programming) is carried out. Gray relational analysis (GRA) is employed to identify the optimal TPU content for the mixture, considering both mechanical and shape memory properties. The results indicate that a mixture with a 20% volume fraction of TPU exhibits mechanical properties comparable to those of pure PLA, along with sufficient flexibility at room temperature and notable shape recovery properties.