Preparation And Properties Of MWCNTs/PES-MBAE Composites

Bismaleimide is a kind of advanced resin matrix that has the advantages of high thermostability,good processability and insulativity,but the application of BMI is restricted by its brittleness.To achieve the goal of improving toughness without reduce other properties,polymer matrix(MBAE)was prepared by reactive diluent which contained diallyl bisphenol A(BBA)and bisphenol-A diallyl ether(BBE)with 4,4'-diamino diphenyl methane bismaleimide(MBMI);Polyether sulfone(PES)and MWCNTs as modifiers were used to prepare MWCNTs/PES-MBAE composite was through in-situ polymerization method.Contrast the effect of toughening composite materials that added acid-MWCNTs and SCE-MWCNTs,and analysis the differences between these composites.The infrared spectrum characteristic peaks of MWCNTs were studied by Fourier Transform Infrared Spectroscopy(FT-IR),the results show that two methods both have the effect of purification because the free hydroxyl in 3727 cm^-1of pure MWCNTs disappeared after modify.The characteristic peaks at 3448 cm^-1and1635 cm^-1were appeared after acidizing,indicating the existence of-COOH.The characteristic peak of-OH appeared near 3450 cm^-1means surface of MWCNTs combined with ethanol molecules after supercritical treatment.Transmission Electron Microscope(TEM)results showed that the modified MWCNTs were kept large length to diameter ratio,no winding between tubes;The best time of acidification treatment is 2 h and surface turned to rough,but supercritical tube wall kept smooth after processing.Microstructure and phase structure of the composite were observed by Scanning Electron Microscope(SEM)and Atomic Force Microscope(AFM).PES presented as two-phase structure in MBAE matrix,and PES resins evenly dispersed in polymer matrix with“honeycomb”shape.Material changed from typical brittle fracture to ductile fracture after joining PES and MWCNTs.Interfacial interaction among PES,acid-MWCNTs and the resin matrix was strong and the modifying agent dispersed in matrix evenly.Supercritical MWCNTs in the curing of the Interfacial compatibility is poor.Results of heat resistance of composites showed that the thermal decomposition temperature would decline when MBAE matrix mixed with PES,but MWCNTs can enhance the thermal stability of composite materials.The change of dielectric constant for composite was not remarkable in low frequency area,when the frequency was more than 10⁴Hz they decreased obviously.Dielectric loss of composites increased slightly,but they were less than 1×10^-3,this could be used as a conventional insulation materials.Results of mechanical properties of acid-MWCNTs/PES-MBAE and SCE-MWCNTs/PES-MBAE composites were different and showed that the impact strength and bending strength were both changed with the content of acid-MWCNTs and showed a trend of first increases and then decreases,increased by 74%and 53%,respectively,when the content of acid-MWCNTs was 0.02 wt%,while the mechanical results of SCE-MWCNTs/PES-MBAE composites showed a downward trend with the content increase of SCE-MWCNTs.