▎ 摘　　要

NOVELTY - Preparing multi-layer flame-retardant composite material involves dispersing N,N-dimethylformamide and graphene oxide ultrasonically at 20-40 degrees C for 20-40 minutes, adding intumescent flame retardant, ultrasonically dispersing it at 20-40 degrees C for 20-40 minutes, and subjecting it to centrifugation, washing and drying to obtain modified flame retardant I. The N,N-dimethylformamide and graphene oxide are dispersed ultrasonically at 20-40 degrees C for 20-40 minutes, intumescent flame retardant is added and ultrasonically dispersed at 20-40 degrees C for 20-40 minutes, dicyclohexylcarbodiimide is added and mechanically stirred for 22-24 hours at 40-60 degrees C in water bath, and then centrifuged, cleaned and dried to obtain modified flame retardant II. The intumescent flame retardant and polybutylene terephthalate are dried at 70-90 degrees C for 8-12 hours, mixed in different mass ratios, modified flame retardant I and II, liquid paraffin and antioxidant are added at same time. USE - Method for preparing multi-layer flame-retardant composite material. ADVANTAGE - The method enables to prepare multi-layer flame-retardant composite material, which has simple and easy to control process, improves flame-retardant performance and mechanical property, and effectively solves problem that materials are easy to melt and drip and mechanical property is reduced. DETAILED DESCRIPTION - Preparing multi-layer flame-retardant composite material involves dispersing N,N-dimethylformamide and graphene oxide ultrasonically at 20-40 degrees C for 20-40 minutes, adding intumescent flame retardant, ultrasonically dispersing it at 20-40 degrees C for 20-40 minutes, and subjecting it to centrifugation, washing and drying to obtain modified flame retardant I. The N,N-dimethylformamide and graphene oxide are dispersed ultrasonically at 20-40 degrees C for 20-40 minutes, intumescent flame retardant is added and ultrasonically dispersed at 20-40 degrees C for 20-40 minutes, dicyclohexylcarbodiimide is added and mechanically stirred for 22-24 hours at 40-60 degrees C in water bath, and then centrifuged, cleaned and dried to obtain modified flame retardant II. The intumescent flame retardant and polybutylene terephthalate are dried at 70-90 degrees C for 8-12 hours, mixed in different mass ratios, modified flame retardant I and II, liquid paraffin and antioxidant are added at same time, extruded and granulated through a co-rotating twin-screw extruder, dried and subjected to injection molding to obtain final product.