The influence of nanofillers migration on the mechanical property of PA6/chitosan nanocomposites

Blends of chitosan (CS) with polyamide 6 (PA6) were prepared via the solution casting technique using formic acid as the common solvent. Polyhedral oligomeric silsesquioxane (POSS), montmorillonite (PGN), and modified montmorillonite (TCN and TL) were incorporated into the polymer matrix. The dispersion state of the nanofillers in the polymer matrix was characterized by polarized optical microscopy (POM), attenuated total reflection Fourier transform infrared spectroscopy (FTIR-ATR), X-ray diffraction measurements (XRD) and transmission electron microscopy (TEM). It was shown that POSS could achieve the best dispersion state in the polymer matrix with only several tens of nanometers. The thermal and mechanical properties of the synthesized polymer nanocomposites were studied by differential scanning calorimetry (DSC) and an Instron single column material testing system. The morphology and element analysis of the cross-section of the sample film were characterized by scanning electron microscopy with energy dispersive X-ray (SEM/EDX) to further explain the mechanical property results. It was shown that CS tended to sediment during the solvent evaporation step whereas PA6 rich domains filled the upper zones of the samples. Interestingly, POSS preferred to migrate to the upper zone of the PA6 rich domain, while PGN, TCN and TL preferred to migrate to the CS rich domain. The migration of the nanofillers was found to be very important to improve the tensile strength of PA/CS blends.