Interplay Between Dispersion, Nucleation, and Crystallization in HDPE/Graphene Nanocomposites Processed Under Thermokinetic Conditions

ABSTRACT

This study investigates the interplay between dispersion, nucleation, and crystallization kinetics in HDPE/graphene nanoplatelet (GNP) nanocomposites processed under solid‐state thermokinetic conditions (10–240 min, 0.1 and 1 wt% GNP). This processing route imposes much higher shear rates and submelting temperatures than conventional melt blending. SEM analysis revealed progressive GNP fragmentation, from ~2.4to ~0.5–0.8 μm with increasing processing time. Rheological results showed a transition from reinforcement to lubrication behavior, with viscosity increasing at short times and later decreasing. DSC results indicated enhanced heterogeneous nucleation, with the onset crystallization temperature increasing by ~5°C and supercooling decreasing from ~10°C for HDPE to ~4°C–6°C for the nanocomposites. At longer times, a high‐temperature shoulder (~120°C) emerged, indicating a secondary nucleation pathway. The SbC–Sbirrazzuoli model provided excellent fitting ( F _exp  = 1.00 <  F _crit  = 1.96), but the Avrami and Nakamura models failed to capture the multistep kinetics, highlighting the inadequacy of single‐mechanism assumptions for nanocomposite systems. Activation energy analysis showed a transition from nucleation‐controlled (−620 to −500 kJ mol ⁻¹ ) to diffusion‐controlled crystallization (−300 to −450 kJ mol ⁻¹ ). Graphene induces multistep crystallization through the interplay between heterogeneous nucleation and restricted chain mobility. The proposed kinetic–mechanistic framework establishes relationships between processing conditions, crystallization kinetics, and microstructure, providing a physically based interpretation of the crystallization behavior of HDPE/GNP nanocomposites.