Structure And Properties Of High Impact Strength Bismaleimide Resin Interleaved With Low Content Of Polybenzimidazole Film And Its Hybrid

Bismaleimide（BMI）,having excellent heat resistance,electrical insulation,wave permeability,radiation resistance,flame resistance,weather resistance and dimensional stability,and the process similar to epoxy resin,is widely used in aviation,aerospace,machinery,electronics and other industrial areas of advanced composite resin matrix,high temperature insulation materials and adhesives since it was developed in 1969 by the French company Rhone Poulenc company successfully.However,the cured BMI exhibits low fracture toughness,low impact resistance forthe high crosslinking density,so,cracks always occur within the resin matrix,which which reduces the service life and limits the application field of materials.Results show that high temperature thermoplastic components can significantly improve the impact resistance of thermosetting resin matrix,but high content of the traditional thermoplastic particles is needed for the significant improvement in impact resitance,and also,the processability of thermosetting resins may be decreased.The use of low concentration of thermoplastic film intervleaved thermosetting resin shows significantly improved impact resistancewithout sacrificing the processability.High temperature thermoplastic polybenzimidazole（PBI）exihibits excellent heat resistance,flame resistance,mechanical properties and dielectric properties.In this paper,considering the low impact strength of of BMI thermosetting resin and the advantage of film intercalation technology to improve the toughness of thermosetting resin materials,PBI film and amine-functionalized aligned carbon nanotube bundles（ACNTB）contained polybenzimidazole（PBI-ACNTB-NH₂）hybrid film were used to interleave BMI resin plates.The effects of the interleaf layers of PBI and PBI-ACNTB-NH₂ hybrid films on the mechanical properties（impact strength,fracture toughness,flexural strength and flexural modulus）,thermal stability,flame retardancy and dielectric properties were investigated.The main research contents are as follows:First,PBI film was prepared by solvent casting method.PBI dissolved in N,N’-dimethylacetamide.Then different layers（0,2,3,4 and 5）of PBI films were interleaved into BMI/DBA prepolymer plate.The results show that the impact strength and fracture toughness of BMI/DBA resin system are 247%and 39%higher than that of BMI/DBA resin system,without sacrificing the flexural strength and modulus.The main reason for the increase of mechanical properties is that PBI film with excellent impact resistance can effectively arrest the crack and the good interface adhesion between the PBI film and BMI/DBA matrix.PBI film interleaved BMI/DBA resin has better thermal property and lower dielectric constant than BMI/DBA resin.PBI film interleaved BMI/DBA displays significant improvement in flame retardancy for the fire blocking barrier of PBI film.When the same amount of PBI is introduced,PBI film is more effective in increasing the impact strength and flame retardancy of BMI/DBA than PBI particles,mainly owing to its arresting all cracks within matrix,larger area thermal and fire blocking barrier in a specified direction,respectively.Second,amine-functionalized aligned carbon nanotube bundles（ACNTB）（ACNTB-NH₂）was prepared,and PBI hybrid films with different contents（5,10 and 15%）of ACNTB-NH₂ were prepared.Results show that PBI hybrid films with 5%ACNTB-NH₂（PBI-5%ACNTB-NH₂）exihibits better comprehensive performance for the good dispersivity of ACNTB-NH₂.PBI-5%ACNTB-NH₂ film interleaved BMI/DBA resin system was fabricated,and the infulences of the hybrid film on the structure and property of BMI/DBA were discussed.The BMI/DBA interleaved with 5-layer PBI-ACNTB-NH₂film shows 279%and 45%higher in impact strength and fracture toughness than BMI/DBA,and BMI/DBA interleaved with 4-layer PBI-ACNTB-NH₂ film shows the optimal flexural strength and modulus,which are 33%and 21%higher than that of BMI/DBA respectively.BMI/DBA interleaved with 5-layer PBI-ACNTB-NH₂ film shows the best flame retardancy properties,the peak heat release rate（PHRR）and the time to ignition（TTI）are 56.5%lower and 90%higher than that of BMI/DBA respectively.PBI-5%ACNTB-NH₂ interleaved BMI/DBA shows better mechanical property,thermal property and flame retardancy than PBI film interleaved BMI/DBA.