Preparation method of microencapsulated gradient halogen-free flame retardant system

The invention relates to a preparation method of a microencapsulated gradient halogen-free flame retardant system. The preparation method comprises the steps of: mixing a phosphorus-series flame retardant with an inorganic flame retardant according to a certain ratio to obtain a microencapsulated halogen-free flame retardant, then carrying out surface modification on a charring agent, and then mixing the microencapsulated halogen-free flame retardant, a phosphorus-containing organic flame retardant and surface-modified charring agent according to a certain ratio to obtain the microencapsulated gradient halogen-free flame retardant system. By using the system, distributed gradient flame retarding is realized, the flame retardancy of a polymer material is greatly improved, the defect that compatibility between the flame retardant and the polymer is poor is solved, the migration of the halogen-free flame retardant from the polymer matrix under high-temperature and moisture conditions is significantly reduced, and the long-term storage of a flame-retardant polymer material is facilitated. The method has the characteristics of simple process, convenience for operation, environmental friendliness, and lower cost. The obtained flame retardant system has good flame retarding effect and wide application field.