Influence of ultra-low graphene nanoplatelet loadings on the thermal behavior and crystallization kinetics of PA6

Abstract

This study aims to investigate the influence of graphene nanoplatelet (GNP) content on the crystallization and melting behavior of polyamide 6 (PA6) nanocomposites produced via melt mixing and injection molding. Compositions containing 0.05 and 0.10 phr of GNP were prepared and characterized using differential scanning calorimetry (DSC), activation energy analysis through the Friedman isoconversional method, Sestak–Berggren–Sbirrazzuoli (SbC) kinetic modeling, and field emission scanning electron microscopy (FEG-SEM). The presence of GNP shifted crystallization to higher temperatures and reduced the activation energy for crystallization, confirming the nanofiller’s nucleating effect. Pseudo-Avrami and SbC modeling showed excellent agreement with experimental data, revealing that GNP modifies crystallization kinetics by reducing the Nakamura Kg index and altering the reaction orders for nucleation and growth. During melting, neat PA6 exhibited complex, multi-step behavior associated with its heterogeneous melting response, whereas the nanocomposites, particularly those with 0.10 phr GNP, exhibited smoother melting behavior and lower apparent kinetic barriers. These results suggest that GNP modifies the thermal history and crystallization/melting behaviour of PA6, although confirmation of specific crystalline phases or structural changes would require complementary techniques such as XRD or WAXD. SEM analysis showed GNP incorporation into the PA6 matrix with localized agglomeration. Overall, the incorporation of GNP alters the crystalline morphology, reduces kinetic barriers, and significantly affects the thermal behavior of PA6, providing valuable insight into processing optimization and the development of advanced PA6-based nanocomposites.