Low‐Smoke, Halogen‐Free LLDPE / EVA Composites With Enhanced Flame Retardancy via Flake Ca–Mg Carbonate and Expandable Graphite

ABSTRACT Developing efficient, halogen‐free fireproof polymers with low environmental impact remains challenging due to high loading requirements of traditional inorganic fillers and the resulting mechanical defects they cause. In this study, a combined flame‐retardant system comprising expandable graphite (EG) and flake Ca–Mg complex‐phase carbonate (FCM) was incorporated into LLDPE/EVA blends. FCM is composed of 4MgCO 3 ·Mg(OH) 2 ·4H 2 O and CaCO 3 . The thermal decomposition releases MgO, CO 2 , and H 2 O, which are conducive to char reinforcement and dilution of combustible gases. The composite containing 3 wt% EG and 35 wt% FCM (LE‐3EG‐35FCM) achieved a UL‐94 V‐0 rating with an LOI of 24.8%, and maintained tensile strength above the threshold required for industrial applications. CCT results showed that the peak heat release rate, total heat release, and total smoke production of LE‐3EG‐35FCM decreased by 39.2%, 33.8%, and 77%, respectively, as compared with the composite containing 3 wt% EG (LE‐3EG). SEM, Raman, and XPS analyses revealed that EG and FCM act in combination to form a continuous and highly graphitized char layer, effectively inhibiting heat transfer, volatile release, and flame propagation. Thus, the EG/FCM system provides an efficient, eco‐friendly, and mechanically acceptable strategy to enhance the flame resistance of LLDPE/EVA composites, with potential applications in halogen‐free and low‐smoke cable materials.