NOVELTY - Preparing copolymer foam comprises (1) adding silicon hydroxyapatite powder in a three mouth flask and then adding water, adding acicular wollastonite, water and methyl methacrylate, stirring the mixture, adding monomer and water soluble initiator to react and then filtering and drying, (2) adding acrylonitrile, treated acicular wollastonite, thickening agent, initiator, foaming agent, cross linker, monomer, density control agent, nucleating agent and then mixing to obtain uniform solution and (3) pouring the resulting solution into a rubber strip sandwiched between two parallel glass plates.    USE - The foam is useful as used as filling material or core material in aerospace field, high speed train, wind power field, marine field and medical field.    ADVANTAGE - The foam is useful as used as filling material or core material in aerospace field, high speed train, wind power field, marine field and medical field.    DETAILED DESCRIPTION - Preparing copolymer foam comprises (1) adding silicon hydroxyapatite powder in a three mouth flask and then adding water, adding 100 pts. wt. of acicular wollastonite, 80 parts of water and 20 pts. wt. of methyl methacrylate, stirring the mixture at 70-75 degrees C, adding monomer and 0.6-0.7% of water soluble initiator to react and then filtering and drying in a 120 degrees C oven, (2) adding 40-60 pts. wt. of acrylonitrile, 40-60 pts. wt. of treated acicular wollastonite, 1-30 pts. wt. of thickening agent, 1-30 pts. wt. of initiator, 0.05-0.6 pts. wt. of foaming agent, 1-16 pts. wt. of cross linker, 1-12 pts. wt. of monomer, 0.1-3 pts. wt. of density control agent, 0.3-18 pts. wt. of nucleating agent and then mixing to obtain uniform solution, (3) pouring the resulting solution into a rubber strip sandwiched between two parallel glass plates, carrying out polymerization at 30-70 degrees C water bath for 10-70 hours to form a methacrylic acid/acrylonitrile copolymer plate, (4) carrying out copolymerization at 80-180 degrees C for 10 hours and then prefoaming at 180-230 degrees C for 100-200 minutes and (5) foaming the obtained product at 100-200 degrees C for 1-5 hours and then cooling to room temperature.