Halogen-free synergistic composite flame retardant and preparation method thereof

The invention relates to the technical fields of light industrial and chemical materials, and in particular relates to a halogen-free synergistic composite flame retardant and a preparation method thereof. The halogen-free synergistic composite flame retardant is formed by performing an in-situ compounding chemical reaction on an anion intercalation-modified layered double hydroxide (LDH) and phosphonitrilic chloride trimer through a silane coupling agent, and has a layered structure. The preparation method of the halogen-free synergistic composite flame retardant comprises the following steps: step 1, preparing the anion intercalation-modified layered double hydroxide; and step 2, preparing the halogen-free synergistic composite flame retardant. The halogen-free synergistic composite flame retardant provided by the invention has more excellent flame-retardant and smoke suppressing comprehensive properties compared with the LDH or the phosphonitrilic chloride trimer; the flame retardant has very good compatib