| The study on flame retardant polymer composite is one of the hotspots. Flame retardant is an indispensable additive for flame-retardant polymer, which can improve fire retardance and self-extinguishing of combustible polymer. In general, it is difficult to get good flame retardancy and mechanical properties with one-component flame-retardant, so the study on compound flame-retardant, representing the major development of flame retardant polymer, has great significance.First, the suitable technology of synthesis of di-isooctyl pyrophosphate and themoplastic phenolic resin was determined by orthogonal test in this paper. The themoplastic phenolic resin was modified by di-isooctyl pyrophosphate, and reaction time, reaction temperature and the PH value were studied. The activation index of Al(OH)3 and Mg(OH)2 treated by stearic acid was discussed, and the suitable technology was determined. The results showed that di-isooctyl pyrophosphate had been bounded to the themoplastic phenolic resin, Al(OH)3/Mg(OH)2 had been activated by stearic acidSecondly, the study on the flame retardant, mechanical properties, dispersion and rheological properties of Al(OH)3/Mg(OH)2/LLDPE and modified phenolic resin/LLDPE was carried out. The results showed that synergistic effect of flame retardant between Al(OH)3 and Mg(OH)2 was optimal as the mass ratio of Al(OH)3 to Mg(OH)2 was 1: 3. While dosage of modified phenolic resin was 25phr, the comprehensive properties of LLDPE composite were best.The various properties of modifiedphenolic resin/Al(OH)3/Mg(OH)2/LLDPE composite were analyzed on the basis of above research, synergistic effect were studied among three kinds of flame retardant. We concluded that the suitable formula of compound flame retardant is as follow: the mass ratio of modified phenolic resin to Al(OH)3 to Mg(OH)2 is 5:2:6. The oxygen index is 39 and the comprehensive properties were reasonable for LLDPE composite filled with the compound flame retardant.Lastly, flame retardant cable compound was prepared by LLDPE filled with modified phenolic resin/Al(OH)3/Mg(OH)2(mass ratio of the compound flame retardant to LLDPE is 65:100). Properties of the flame retardant cable compound were as follow: oxygen index was 32, tensile strength was 15.0Mpa, elongation at break was 370%. The main performance indicators reached or even exceed those of domestic same kind of products. The research will provide scientific basis for the development of novel and high efficient flame retardant polymer composite in the application aspects.
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