Toughening Phthalonitrile And Research On The Electrical Conductivity Of Composite Material

As an important part of national science and technology development,new materials are regarded as one of the development project of high technology in the21st century.With the rapid development of high-tech industries,organic polymer and composite materials which is important parts in the field of new materials,have made great progress in the field of academic research and industrial application.At the same time,in order to meet the more stringent requirements,high performance-based polymer materials will become the inevitable trend of future development.Phthalonitrile resins are a unique class of high-performance thermosetting materials having a variety of potential uses in aerospace,ships,machinery,electronics and other fields,owing to their outstanding thermal stability,good chemical stability,excellent mechanical properties,superior moisture resistance,fire resistance,and good processability.Nitrile groups of phthalonitrile monomer with catalyst have addition polymerization,forming highly crosslinked polymer structure and there are no small molecular by-products during the process.In addition,phthalonitrile resins are widely used in the preparation of fiber reinforced composite materials because they have good adhesion on the fiber surface.However,the performances of bisphthalonitrile resins are limited by some disadvantages as follows:a small processing window and high processing temperatures.Owing to high crosslinking density,the fracture toughness of phthalonitrile resin is poor,which restricts it for many potential applications.The functionalization of bisphthalonitrile resins has not been abundant enough,and their application range needs to be expanded.In order to solve said problem,the dissertation focuses on the modification and functionalization of bisphthalonitrile resins.In this work,bisphthalonitrile resins were modified by a variety of methods,and their combination properties have been improved.Specific research contents are as follows:Biphenyl polyether sulfone with nitrile group and double bond?aPPSU-CN?is chosen to improve toughness of phthalonitrile resin.The introduction of flexible polymer chain segment t improves its internal network,at the same time,nitrile group on the aPPSU-CN can have cross-linking reaction with phthalonitrile oligomer,improving the interaction of two phase interface and perfecting the compatibility between thermoplastic filler and thermosetting matrix.The relative concentration of nitrile groups reduces in the toughened system due to the addition of aPPSU-CN,resulting to a decline of the crosslinking density in the system.But the double bond which has cross-linking reaction can counteract the impact of aPPSU-CN on the thermal stability.The char yield for the aPPSU-CN toughened systems varied slightly from 76%to 73%as seemed to be closer to the curing PAEK-CN.The elongation at break of resulting thermosets increases with the content of aPPSU-CN,which increases from 2.17 to 7.00%.The fracture energy increases from 4.00 to 52.34 kJ/m²with incorporation of 16 wt%aPPSU-CN into phthalonitrile.Our results suggested that adding aPPSU-CN into the system can increase the mechanical properties significantly and simultaneously maintain thermal properties.In order to develop the application of bisphthalonitrile resins in the conductive composite membrane materials field,the phthalonitrile resin/multi-walled carbon nanotubes?MWNTs?/graphene nanoplatelets?GnPs?conductive composite membranes was prepared by solution blending method.The combination of high aspect ratio of MWNTs and larger surface area of GnPs contribute to the synergistic effect of the hybrid samples and finally composite materials with three-dimensional structure have been gotten.In the mixture samples,when the CNTs:GnPs ratio is 9:1,composite materials showed best comprehensive performance.It is found that the temperature of weight loss at 5%(T_d5%)and the char-yield at 800^oC in N₂ slight decrease with the similar tendency reflecting in mechanical properties.But the electrical conductivity of the conductive composite membranes has improved.Mechanical performance of the composite membrane is better than the proportion of MWNTs and GnPs for 10:0,suggesting that MWNTs and GnPs have synergy effect.Results of scanning electron microscopy?SEM?illustrate the synergy between MWNTs and GnPs make the carbon nanomaterials disperse well.