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

Abstract

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

Dielectric properties of polyamide 12-chromium (III) oxide nanocomposites

“…This was shown for the introduction of nanosized oxide F 3 O 4 into polyurethane [7]. We obtained similar results for the preparation of 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 [8]. It was suggested that the introduction of new fracture mechanisms, rigidity augmentation, and pronounced filler-filler interactions were responsible for the observed behavior instead of filler-polymer interactions [9][10][11][12].…”

“…However, T g of the composite with 0.1 wt.% of Cr 2 O 3 is very similar (if not identical) to the T g of the pure polymer, but their Young's modulus is similar to moduli for other composites and is much smaller than that of pure PA12 [8], so the decrease in the moduli upon the introduction of the nanoparticles are not only due to a plasticizing effect. The softening of polymer matrix associated with local mobility (β-relaxation) is probably more important.…”

“…PA12/Cr 2 O 3 nanocomposites were synthesized according [8]. Dielectric measurements were performed using an Alpha Analyzer combined with a Quatro Temperature Control system unit that provides temperature stability of 0.1…”