Interfacial Engineering of Polyvinyl Chloride/Molybdenum Trioxide Doped Magnesium Hydroxide Composite via Chain‐Length Tunable Si‐P Polyether Modifiers: Synergistic Enhancement of Mechanical Properties and Flame Retardancy

To enhance the interfacial compatibility and fire safety of polyvinyl chloride (PVC)/molybdenum trioxide‐doped magnesium hydroxide (MO@MH) composites, three chain‐length‐varied silicon‐phosphorus polyether modifiers (ABP 200 , ABP 1000 , and ABP 2000 ) were synthesized and characterized. Magnesium‐molybdenum‐silicon‐phosphorus multicomponent flame retardants (MO@MHABP) were subsequently prepared via wet modification. The chain‐length‐dependent mechanical behavior of PVC composites was systematically evaluated through combined experimental characterization and molecular dynamics (MD) simulations. Static mechanical tests revealed that yield strength, tensile strength, and impact strength of PVC/MO@MH composite were all improved by inducing ABP modifiers, with the shortest‐chain ABP 200 showing optimal enhancement. Dynamic mechanical analysis revealed increased storage/loss modulus and glass transition temperatures for PVC/MO@MHABP, indicating restricted chain mobility. Interface interaction models (Turcsányi equation and Kubát model) combined with MD simulations demonstrated that the shortest‐chain modifier (ABP 200 ) enhanced interfacial adhesion through the strongest Cl–NH interactions (supported by the most negative Δ E values). Cone calorimetry tests indicated that ABP modification decreased the heat release rate and total heat release of PVC/MO@MH composites but did not significantly improve smoke suppression. This study provides valuable insights into interfacial regulation and performance optimization in PVC composites.