Influence of the Addition of Spirulina Cyanobacterium ( <i>Arthrospira platensis</i> ) Biomass on the Thermal and Mechanical Properties of Polymer Composites

The incorporation of bio‐based additives into polymers offers potential sustainability benefits, providing a more environmentally friendly alternative for applications in bioplastics and composites. However, the comparative effects of microalgae or Spirulina in polypropylene (PP) versus ethylene vinyl acetate (EVA) at fixed loadings without compatibilizers remain largely unknown. This study evaluates the influence of incorporating the biomass Arthrospira platensis (Spirulina) on the properties of two different polymer matrices: PP and EVA. The composites were prepared using an internal mixer as a torque rheometer, followed by compression molding to produce test specimens. Morphological and dispersion analyses were conducted using scanning electron microscopy (SEM) and optical microscopy. Mechanical properties were assessed through bending tests (ASTM D790) and toughness tests (ASTM D5045), and thermal characterization was performed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). In the EVA, poor adhesion was observed between the Spirulina biomass and the polymer matrix, resulting in modest reductions in stiffness without significant compromise of the mechanical properties compared to the neat polymer, suggesting that Spirulina may act primarily as a filler. In the PP, better dispersion and adhesion of the biomass to the polymer matrix were observed. A 53% reduction in elasticity (Young’s modulus) was observed; however, no rupture occurred in the specimens containing Spirulina during the toughness tests, indicating its effectiveness in enhancing the toughness of the matrix, highlighting the feasibility of using its biomass as an additive in polymer matrices, with implications for the development of sustainable materials.