Abstract:As a halogen-free flame retardant, Octaphenylcyclotetrasiloxane (P4) was synthesized by using Diphenyldimethoxysilane, was extruded with polycarbonate (PC) in proportion to gain the halogen-free flame retardant PC. The flame retardant PC samples were evaluated through limit oxygen index (LOI) test, UL-94 vertical combustion test (VBT), scanning electron microscope (SEM), thermogravimetic analysis (TGA), melt index (MI) test and mechanical property test. The results showed that P4 has an obvious flame retardancy effect on the PC and the flame retardancy level increased gradually. P4 is dispersed uniformly in PC and PC degraded to some extent wile char layer residues of PC became denser as the content of P4 increased. Besides, the thermal stability of PC increased to some extent and its carbon yield rose obviously in air when the content of P4 reached to a high level. The MFR of PC increased a little indicating the molecular weight declined to some extent. Furthermore, its tensile strength and impact strength declined obviously when added low content of octaphenylcyclotetrasiloxane while the two strength changed little when content of octaphenylcyclotetrasiloxane reached 4%. Meanwhile, the bending strength declined little as the content of octaphenylcyclotetrasiloxane increased.