▎ 摘　　要

NOVELTY - Preparing polymethacrylimide (PMI) foam with wave-absorbing and flame-retardant performance comprises (i) mixing methacrylic acid (MAA) and methacrylonitrile (MAN), adding thickening agent, and preparing into first component, (ii) mixing and stirring crosslinking agent, nucleating agent, foaming agent, initiator and dispersing agent, and preparing into second component, (iii) grinding and mixing at least one wave absorbing agents to prepare fine and uniform granular mixture, and preparing third component, (iv) mixing flame retardant and flame retardant auxiliary reagent, and forming fourth component, (v) dissolving first component, adding third component, and forming brown uniform mixed solution, (vi) adding solution mixed solution to fourth component to mixed solution, and adding solid mixture to fourth component to mixed solution, (vii) adding mixed solution into second component to mixed solution, (viii) polymerizing mixed material solution, and (ix) processing prepolymer. USE - The foam is useful as sandwich material of aircraft e.g. unmanned aerial vehicle and manned aircraft. ADVANTAGE - The foam: has special properties e.g. anti-radar detection; is not easy to burn; and prevents the detection of radar waves and electromagnetic waves within a specific frequency range. DETAILED DESCRIPTION - Preparing polymethacrylimide (PMI) foam with wave-absorbing and flame-retardant performance comprises (i) uniformly mixing methacrylic acid (MAA) and methacrylonitrile (MAN), adding 0.01-20 pts. wt. thickening agent, stirring in a water bath or oil bath at 26-75°C, uniformly dispersing, dissolving for 5-72 hours to form a mixed solution with viscosity, and preparing into first component, (ii) taking crosslinking agent, nucleating agent, foaming agent, initiator and dispersing agent, uniformly mixing and stirring, dissolving into a uniform mixed solution, and preparing into second component, (iii) uniformly grinding and mixing at least one wave absorbing agents to prepare a fine and uniform granular mixture, and preparing third component, (iv) selecting 0.01-12 pts. wt. flame retardant and flame retardant auxiliary reagent, uniformly mixing and dispersing the solution reagent, uniformly mixing and dispersing the solid flame retardant or flame retardant auxiliary reagents to form fourth component, (v) uniformly dissolving first component, adding third component in 3-12 batches, and uniformly stirring and dispersing evenly to form a brown uniform mixed solution, (vi) adding solution mixed solution into fourth component into mixed solution prepared in the step (v) in 3-10 batches, continuously stirring and uniformly dispersing, then adding solid mixture into fourth component to the mixed solution in 3-8 batches, uniformly stirring and mixing, (vii) adding mixed solution into second component to mixed solution prepared in the step (vi) in 2-6 batches, and uniformly stirring and mixing to obtain a mixed material solution, (viii) polymerizing mixed material solution prepared in the step (vii), and demolding to obtain a prepolymer, and (ix) heating, foaming, pre-processing, cutting and processing prepolymer to obtain PMI foam.