Thermally Induced Dynamic Interfacial‐Loading of Nanoparticle and Phase Morphology Evolution in Low‐Temperature Toughened PPR Nanocomposites

Despite achieving excellent low‐temperature toughness and rigidity–toughness balance through selective interfacial‐loading of nanoparticle in polypropylene‐based nanocomposites, the understanding of the mechanisms governing nanoparticle migration, phase morphology evolution, and the corresponding structure‐properties relationships remains limited. In this study, the dynamic interfacial‐loading of SiO 2 nanoparticle for random copolymer polypropylene (PPR)/ethylene propylene rubber (EPR)/SiO 2 nanocomposites via molten‐state annealing was investigated. Morphological and mechanical results revealed that the initial increment in stiffness for PPR/EPR/SiO 2 nanocomposites was mainly dominated by migration and aggregation of SiO 2 nanoparticle from inner phase to interface, while the subsequent decrease was primarily governed by phase coarsening. The rheological behavior of PPR/EPR/SiO 2 nanocomposites further confirmed these findings. Moreover, the molten‐state annealing had a negligible impact on the low‐temperature toughness of PPR/EPR/SiO 2 nanocomposites, which mainly originated from the effective suppression in phase coarsening of EPR domains through the interfacial‐loading of SiO 2 nanoparticle. Additionally, the structural recoverability of PPR/EPR/SiO 2 nanocomposites after long‐term high‐temperature annealing was verified, highlighting their excellent processability and reusability arising from the balance of thermally induced dynamic interfacial‐loading of nanoparticle and phase morphology evolution under melting‐blending. This work provides potential guidance for designing thermoplastic resin materials with optimal rigidity–toughness balance and reusability.