Solubility Parameter‐Guided Interfacial Design of Polyolefin Elastomer/Stearic Acid Modified Calcium Carbonate Composites for Enhanced Properties

ABSTRACT The compatibility between inorganic fillers and polymer matrices fundamentally determines the performance of polymer composites. This study proposes a novel theoretical framework that combines Hansen Solubility Parameters (HSPs) with chain entanglement theory to predict and explain the enhanced compatibility between stearic acid‐modified calcium carbonate (SA‐CaCO 3 ) and polyolefin elastomer (POE). Using HSP analysis, the solubility parameter of SA‐CaCO 3 (≈26) approaches POE (≈17) compared with that of CaCO 3 (≈48), indicating an improved thermodynamic affinity that favors interfacial chain interpenetration. The stearic acid long alkyl chains form a stearic acid coating layer on the CaCO 3 surface, enabling physical entanglement with POE molecular chains and creating a flexible interphase that facilitates efficient stress transfer. Experimentally, POE/SA‐CaCO 3 composites with 5 wt% SA‐CaCO 3 loading achieved a tensile strength of 19.35 ± 2.26 MPa, representing a 24% improvement over pure POE. The composites also exhibited superior electrical insulation (volume resistivity of (15.0 ± 0.45) × 10 16 Ω·cm), enhanced hydrophobicity (water contact angle of 106° ± 2°), and improved thermal stability (maximum decomposition temperature of 483.8°C). These findings demonstrate that HSP‐based compatibility prediction combined with molecular chain entanglement design provides a rational and effective strategy for optimizing filler‐matrix interfaces in polymer composites.