Abstract:
Using micro Mg(OH)
2 (mMg(OH)
2), nano Mg(OH)
2 (nMg(OH)
2) and microencapsulated red phosphorus (MRP) as the halogen-free flame retardants and ethylene-vinyl acetate copolymer (EVA) as the polymer matrix, a series of Mg(OH)
2-MRP/EVA flame-retardant composites with different loadings of flame retardant were prepared by melt-compounding. The flame retardancy, mechanical and processing properties of the Mg(OH)
2-MRP/EVA composites were investigated by limiting oxygen index, vertical burning test, cone calorimetry, thermal analysis, SEM, tensile test and rheological analysis. The results indicate that both flame retardancy and smoke suppression of the nMg(OH)
2/EVA composite are better than that of the mMg(OH)
2/EVA composite at the same loading of Mg(OH)
2 flame retardant. However, the UL-94 rating of nMg(OH)
2/EVA and mMg(OH)
2/EVA composites can not reach V-0 rating when the Mg(OH)
2 loading is less than 60wt%. The flame retardant efficiency of Mg(OH)
2 is low by itself and there is remarkable synergism between nMg(OH)
2 and MRP on the flame retardancy of EVA. The loading of Mg(OH)
2 can be reduced considerably when nMg(OH)
2 and MRP are combined at proper ratio. Comparing with nMg(OH)
2/EVA composite, the nMg(OH)
2-MRP/EVA composite can produce a continuous and compact char residue layer on its surface, which serves as a barrier against fire and increases fire retardancy. The thermal degradation of nMg(OH)
2 has crucial influence on the fire behavior of the nMg(OH)
2-MRP/EVA composite. When nMg(OH)
2 is pre-pyrolyzed and added to the MRP/EVA composite, both flame retardancy and smoke suppression of the obtained nMg(OH)
2-MRP/EVA composite decline sharply. When the mass ratio of nMg(OH)
2:MRP:EVA is 40:10:100, the obtained nMg(OH)
2-MRP/EVA composite shows excellent flame retardant, mechanical and processing properties simultaneously, which can meet the demand of practical applications.
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