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

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.