Abstract:
Microencapsulated Mg(OH)
2 (M-Mg(OH)
2) flame retardant with micro-sized Mg(OH)
2 particles as the core and cross-linking polyurea as the shell, was synthesized by in-situ polymerization. The obtained M-Mg(OH)
2 was incorporated into ethylene-vinyl acetate copolymer (EVA) and its flame retardant effect on EVA was studied. FTIR, SEM, thermal analysis and acid titration were used to investigate the properties of M-Mg(OH)
2. Limiting oxygen index (LOI) and vertical burning test (UL-94 VBT) were employed to study the flame retardancy of M-Mg(OH)
2/EVA composite and the effect of acid erosion on the flame retardancy of M-Mg(OH)
2/EVA composite. It shows that the surface of Mg(OH)
2 particles can be successfully encapsulated with cross-linking polyurea by in-situ polymerization and microencapsulated Mg(OH)
2 can be obtained. Compared with the pure Mg(OH)
2, the size of M-Mg(OH)
2 is larger, its thermal stability increases and the water solubility of M-Mg(OH)
2 decreases remarkably. The dispersion of M-Mg(OH)
2 in EVA matrix is more even than that of the pure Mg(OH)
2. The LOI of the M-Mg(OH)
2/EVA composite is always slightly larger than that of its Mg(OH)
2/EVA counterpart at identical loadings of flame retardant (FR). When the mass ratio of FR/EVA is less than 135:100, the VBT ratings of both composites are V-2. When the mass ratio of FR/EVA is between 135:100-150:100, the rating of the former is V-0, but the latter can only reach V-2 rating. When the mass ratio of FR/EVA surpasses 150:100, both composites can reach V-0 rating. In contrast with Mg(OH)
2/EVA composite, the acid resistance of the M-Mg(OH)
2/EVA composite increases substantially and it can be used in acid environment.