Biocomposites based on plasticized starch: thermal, mechanical and morphological characterization

In this research, a composite material based on thermoplastic starch (TPS) obtained from pich seeds (Enterolobium cyclocarpum) filled with solid particles of their own shell (PP) was elaborated and fully characterized by different techniques such as DSC, TGA, FTIR, tensile test and SEM. All composites showed good dispersion of the shell particles within the matrix. Particles size and concentration effect over the mechanical, morphologic and thermic properties were studied. Calorimetric characterization by DSC exhibited an increment in ΔH_f as PP concentration was increased, while TGA analysis shown thermal events associated to decomposition of hemicellulose followed by cellulose and finally lignin components. Pich TPS/PP composite material FTIR spectrum clearly displayed absorption bands corresponding to amylose and amylopectin, cellulose, hemicellulose and lignin organic groups. SEM analysis identified average diameters in shell particles (PP) around 1180 μm, 600 μm and 425 μm. Higher mechanical properties corresponding to maximum stress (σ_max) and elastic modulus (E) were obtained for composites manufactured with particle size of 600 µm and 5% concentration. These results are consistent with the static mechanical behaviour, which vary according to the filler content. It is shown that the addition of PP fillers improves the thermal resistance and mechanical properties of these biocomposites.