MENG Xiangfei , SHI Hu , WANG Jihua , WANG Yongliang , HAN Zhidong

(1. School of Materials Science and Engineering, Harbin University of Science and Technology, Harbin 150040, Heilongjiang, China; 2. Key Laboratory of Engineering Dielectrics and Its Application, Ministry of Education,
Harbin University of Science and Technology, Harbin 150040, Heilongjiang, China)

Abstract: In this paper, graphite nanoplatelets (GNP) are used as synergists to compound with intumescent flame retardants (ammonium polyphosphate and pentaerythritol). The synergistic effect and flame retardant mechanism of GNP in halogen-free flame retardant polystyrene were investigated. The polystyrene composites were prepared by powder-composite method, and the amount of the intumescent flame retardant was 25wt.%. The effects of different GNP levels (0, 0.5wt.%, 1.0wt.%, 2.0wt.%) on the flame retardancy of composites were investigated. The flame retardant composites were characterized by limiting oxygen index (LOI) and vertical combustion. The effect of GNP on the morphology of carbon layer was studied by scanning electron microscopy. The effect of GNP on the heat release rate of the composite was investigated by a cone calorimeter. When the amount of flame retardant in PS/IFR composite exceeded 25wt.%, the flame retardancy of the composite material was significantly improved. When the amount of the flame retardant reached 30wt.%, the limiting oxygen index reached 37.3, and the vertical combustion reached V-0. GNP can significantly reduce the amount of intumescent flame retardant. For GNP/IFR/PS composite, when 24.5wt.% IFR and 0.5wt.% GNP were used, the limiting oxygen index reached 36, and the vertical burning reached V-0. The mechanism of GNP on flame retardancy was discussed. The results showed that GNP can promote the compaction of the char layer during combustion and the heat release rate was reduced, which brings a better synergistic flame retardant effect.
Key words: graphite nanoplatelets; flame retardant; polystyrene; intumescent flame retardant