Microstructure Engineering of Microalgae‐Based Bioplastics With Enhanced Mechanical Property and Compatibility in Flexible Polyurethane Foam

ABSTRACT Bioplastic with significantly enhanced mechanical properties, impact resistance, and compatibility can be obtained from spirulina powder by a facile and green conversion process. The conversion is proceeded through the molecular mechanism of the protein ɑ‐β transformation, which is induced by the extensive hydrogen bonding interactions and thermal stress. The morphology, microstructure, chemical composition, dispersability, and thermal properties of the bioplastic are characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), Fourier‐transformed infrared spectroscopy (FTIR), dynamic light‐scattering (DLS), thermogravimetric (TGA), and differential scanning calorimetric (DSC). Both the SEM and XRD results reveal an anisotropic extension of the spirulina powder after conversion, where microstructures with higher aspect ratios and more planar facets can be observed, indicating the formation of sufficient β‐phase in the spirulina protein. Moreover, a higher intensity of multimeric hydrogen bonding structure is observed for the bioplastic, which leads to a higher dispersability and compatibility. The bioplastic shows promising applications in high‐performance flexible polyurethane foams for impact protection, which significantly improves the tensile strength, compressive strength, impact energy absorption, and thermal stability of the flexible foam, revealing its great potential in the next‐generation eco‐friendly plastics.