Preparation of Stearic Acid Surface‐Functionalized Mg‐Al Layered Double Hydroxide and Its Regulation Mechanism on Structure and Properties of Polyethylene‐Based Composites

ABSTRACT Polyethylene (PE), a widely used polyolefin material, is limited in high‐safety applications due to low flame retardancy and thermal stability. To address this, stearic acid (SA) was used for surface graft modification of magnesium‐aluminum layered double hydroxide (LDH), constructing a low‐polarity organic functional layer to enhance interface compatibility with PE. SA‐LDH/PE flame‐retardant reinforced composites were successfully prepared. After modification, LDH hydrophobicity and dispersibility improved significantly, with water contact angle increasing from 11.7° to 146°. Composite surface hydrophobicity was also optimized, contact angle increasing from 67.38° to 78.3°. At a 10 wt% loading, composites show optimal performance: flexural modulus increased by 105% compared to pure PE, tensile properties enhanced, char residue to 5.34%, limiting oxygen index (LOI) rising from 17.4% to 23.5%. SA modification induces hydrophilic‐to‐hydrophobic transition in LDH, promoting uniform dispersion and efficient interfacial load transfer in PE matrix, facilitating stable char layer formation and improving thermal stability and flame retardancy. This study proposes a green efficient LDH modification strategy, providing an effective pathway for halogen‐free flame‐retardant polyolefins and theoretical support for high‐performance LDH dispersion and synergistic flame‐retardant enhancement.