Novel polyamide 12/chromium (III) oxide nanoparticles composites: Melting behavior and complex isothermal crystallization kinetics

Polymer nanocomposites based on PA12 filled with different loading (0.1−10 wt%) of nanosized (average grain size of about 1−5 nm) chromium(III) oxide were prepared by in situ polymerization, and their mechanical and thermal properties were investigated. A homogeneous dispersion of Cr₂O₃ nanoparticles in the polyamide matrix was achieved at the level of isolated particles as a result of amphoteric nature of chromium (III) oxide. However, it was found that the tensile modulus and yield stress of the nanocomposites decrease. The reason for this is a change in the crystallization type of PA12due to the Cr₂O₃ nanoparticles (from α to γ type of crystal phase). The crystallization kinetic of PA12 matrix has been successfully studied and described using a two‐parameter Avrami model for isothermal crystallization. It is shown that nanosized chromium(III) oxide dioes not change the nucleation mechanism. The addition of Cr₂O₃ nanoparticles also does not have a significant effect on crystallization rate and energetic and kinetic parameters of crystallization. The presence of nanofillers in PA12 matrix decreases their crystallinity from 63 to 51%. Hence, the mechanical properties of nanocomposites can be influenced not only by the type and dispersion of nanofillers but also by their effect on the crystal structure and degree of crystallinity of the polymer matrix. POLYM. COMPOS., 36:999–1005, 2015. © 2015 Society of Plastics Engineers