Preparation and characterization of thermoplastic starch and cellulose nanofibers as green nanocomposites: Extrusion processing

Abstract

This research was aimed at studying the preparation of thermoplastic starch (TPS) from cornstarch flour using twin screw extrusion. Also, the effects of the addition of cellulose nanofibers (CNFs) as reinforcement, on TPS nanocomposite films properties were evaluated. Nanocomposites with 0.5, 1.0 and 1.5wt% of CNFs content were prepared. The chemical structure of starch, TPS and TPS/CNFs were characterized by Fourier-transform infrared spectroscopy (FT-IR) and X-ray diffraction. The mechanical properties, morphological structure, and thermal stability of neat thermoplastic starch and their nanocomposites were investigated by scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and water absorption (WA) test. Results showed that it was possible to improve the WA, thermal, and mechanical properties of TPS with the addition of CNFs due to its good dispersion and the interaction of CNFs with the TPS matrix. The storage modulus, loss modulus, and the tan δ peak position of TPS/CNF nanocomposites improved in comparison with the TPS matrix. These findings confirmed the enhancement of mechanical properties of TPS/CNF nanocomposites. In addition, TGA and DSC results showed that increasing CNF content improves the thermal stability of TPS-based nanocomposites. SEM images showed that CNFs dispersion within the TPS matrix was uniform and the surfaces of TPS/CNF films were smooth. The WA of the TPS/CNF composites moderately decreased with the addition of CNFs. Finally, the results obtained clearly showed the advantages of reinforcing TPS with CNFs, a natural, cheap and abundant green nanocomposite.

Keywords: Cellulose nanofibers; Nanocomposite; Thermogravimetric analysis; Thermoplastic starch.