Abstract: Low-cost and low brominated flame-retardant polypropylene (PP) composites were prepared by a complex of phosphorus-nitrogen intumescent flame retardant (SR201A) and bromine-antimony flame retardant, and the effect of flame-retardant agents on combustion performance and mechanical properties of flame-retardant PP were investigated. The combustion behavior and mechanical properties of PP were evaluated by vertical burning experiments, limiting oxygen index, cone calorimeter measurement, thermogravimetric analysis and mechanical measurements. The results indicated that composite achieved a classification of UL 94 V-2 in the vertical burring test when 20 wt % of complex flame retardants was added, and their limiting oxygen index reached 31.4 %. The cone calorimeter testing results confirmed that there was a synergistic effect derived from the complex flame retardant agent systems, which could effectively promote the formation of residual char during the combustion of PP composites. In addition, the tensile and flexural strength of flame-retardant polypropylene composites was higher than those of pure PP resin.

Key words: polypropylene, phosphorus-nitrogen complex intumescent flame retardant, bromine-antimony flame retardant, synergist