Upcycling of Saline Lake Magnesium into Functionalized Si-MgO for Synergistic Fire-Safe PVC: A Waste-to-Wealth Strategy Coupling Catalytic Charring and Physical Insulation

Abstract

Abstract：PVC is easy to burn and release smoke, and traditional flame retardants will reduce its mechanical properties.Based on this, a halogen-free synergistic flame retardant system with low addition amount, high efficiency and good flame retardancy and mechanical properties was developed.Silane modified MgO (Si-MgO) was prepared by surface modification of MgO with γ-aminopropyltriethoxysilane.Acidified EG (A-EG) was obtained by acidizing EG with mixed acid. PVC composites were prepared by mixing Si-MgO and A-EG in different proportions.When the addition amount is 5 wt % and the mass ratio of Si-MgO to A-EG is 2 : 3, it has the best comprehensive performance, the LOI reaches 28.67 %, and passes the UL-94 V-1 test; CCT test showed that the HRR, THR and SPR were reduced by (30.99 %), (31.68 %) and (71.96 %), respectively, compared with pure PVC. The smoke density test showed that the Ds was reduced by 91.8 %, and the mechanical properties were retained.The flame retardant mechanism is as follows:A-EG is expanded by heat to form a porous carbon layer skeleton, and Si-MgO catalyzes the crosslinking of PVC to form an amorphous carbon filler. The two synergistically construct a dense barrier-catalytic composite carbon layer to isolate the transmission of mass and heat, imprison smoke particles, and achieve synergistic flame retardant and smoke suppression.In this study, the Si-MgO/A-EG synergistic flame retardant system was successfully constructed through the synergistic strategy of interface modification and component compounding.Highlights1. Incomplete KH-550 grafting on MgO (contact angle: 26.5°→89°) preserves active sites for catalysis while improving dispersion.2.A "flow-filling" synergistic mechanism is proposed: amorphous carbon from Si-MgO infiltrates and densifies the A-EG porous skeleton.3.The composite exhibits dramatically reduced fire hazards: HRR ↓30.99%, THR ↓31.68%, SPR ↓71.96%, TSR ↓94.25%, COPR ↓73.72%, CO 2 PR ↓36.82%.4.Upcycling of saline lake magnesium into high-performance flame retardants embodies a waste-to-wealth strategy.5.Simultaneous enhancement of flame retardancy and toughness retention is achieved.