Study on Preparation and Properties of Graphene Oxide/Bismaleimide-triazine Resin Composites

Author:Li Peng Bo

Supervisor:li tie hu

Database:Doctor

Degree Year:2018

Download:7

Pages:138

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Bismaleimide-triazine(BT)resin is a thermosetting resin formed by copolymerization of bismaleimide resin and cyanate ester resin.BT resin combines the excellent properties of bismaleimide resin and cyanate resin,which is wildly applied in many related industries such as printed circuit boards,semiconductors aerospace materials,due to its low moisture absorption,good thermal resistance,low dielectric constant and dielectric loss tangent.However,the cured BT resin is brittle because of its high cross-linking density.Graphene oxide(GO)possess unique two-dimensional molecular structure and excellent mechanical,electrical and thermal properties,which is believed as an ideal reinforced material for composite.In this work,GO was prepared by Hummers method,and 0,0-diallylbisphenol A functionalized graphene oxide(DBA-GO)was synthesized via the modification of GO by0,0-diallylbisphenol A(DBA).Subsequently,GO,DBA-GO and graphene oxide/carboxylic multi-walled carbon nanotubes(GO/MWCNTs-COOH)was used as the reinforcer to modify the BT resin.The influences of the variety and content of the reinforced material on the properties of the composites were investigated.The GO was prepared by Hummers method,and its dispersion in aqueous solution was studied systematically.The scanning electron microscopy research shows that the carbon-oxygen ratio of GO is 1.314,which indicating high degree of oxidation.The results of Raman analysis further indicates that the conjugate ordered structure ofπelectrons is destroyed during the oxidation of graphite,the defects and functional groups are introduced.The dispersion of GO in the aqueous solution varies with the pH of the solution.The carboxyl functional groups on the GO surface can ionize at higher pH of the solution,GO sheets has good dispersion because the strong electrostatic repulsion between the GO sheets.The ionizing phenomenon of the carboxyl functional groups on the GO surface is almost never occurred at lower pH of the solution,the van der Waals force is the main role between the GO sheets,which resulted in the agglomeration and the decreased dispersion.Two dissociation constant of GO are 6.85 and 2.55 respectively,which resulted in the carboxyl groups and special structure of GO respectively.X-Ray diffraction analysis showes the interplanar distance of GO is 0.789 nm.The scanning electron microscopy images show that the average particle size distributions of graphene obtained by reduction GO with metal Al is in the range of 110-130 nm.The kinetic parameters of curing reaction of GO/BT system were studied by non-isothermal differential scanning calorimetry(DSC).The results show that the addition of GO could reduce the initial crosslinking curing temperature and the activation energy of curing reaction.The influence of GO content on the performance of GO/BT composite was investigated.Results show that the impact and flexural strengths of the composite improved with addition of 0.8 wt%GO,which could be attribute to the existence of GO,GO in the composite can inhibit the crack propagation during the fracture process.Meanwhile,the deformation and flaking off the composite can be restrained by the presence of GO during the friction test,therefore,GO/BT composites exhibit lower friction coefficient and wear rate than BT matrix,it is worth noting that the wear rate is decreased by 77.6%.Moreover,the addition of GO can reduce the dielectric constant and dielectric loss;improve the thermal stability and moisture resistance of the composite.DBA-GO was synthesized by modification of GO with DBA.Subsequently,the resultant DBA-GO was incorporated into BT to prepare composites.The influence of DBA-GO content on the curing kinetics,mechanical,tribological,dielectric,thermal and water resistant properties of DBA-GO/BT composites was investigated.Results show that DBA-GO can play a positive role in promoting the curing reaction of BT resin.The impact and flexural strengths of the composite are increased by 39.9%and 34.0%with addition of 0.9wt%DBA-GO,respectively.The mechanical properties of DBA-GO/BT composite are superior to that of GO/BT composite,which can be understood from the better dispersion of DBA-GO in the matrix.Moreover,DBA groups in the molecule of DBA-GO can react with BT resin.As a result,the interfacial bonding strength between the two phases was increased,which can distribute stresses during the fracture process.The lowest friction coefficient and wear rate of the composite are 0.30 and 5.2×10-7mm3/(N·m)when the DBA-GO content are 1.2 wt%and0.9 wt%,respectively.The dielectric properties of the composite are improved by the addition of DBA-GO,the dielectric constant and the dielectric loss are stable in the range of 1-50 MHz.The increases in thermal stability and moisture resistance of the composite can be attributed to the"bend effect"and good barrier effect of DBA-GO,respectively.GO/MWCNTs-COOH/BT resin composites were prepared.The curing kinetics of GO/MWCNTs-COOH/BT system and the influence of GO/MWCNTs-COOH content on the performance of composites were investigated.The results show that the curing reaction of BT resin can be catalyzing by GO/MWCNTs-COOH.The addition of GO/MWCNTs-COOH is beneficial to improve the mechanical and tribological properties of composites.The mechanical and tribological properties of composites are optimized with 0.9 wt%GO/MWCNTs-COOH.The impact and flexural strengths of the corresponding composites are higher than that of GO/BT composites.The dielectric constant and Dielectric loss of composite is higher than that of BT resin,which is caused by the conductivity of MWCNTs-COOH.The thermal stability of composite has also been improved because the interfacial bonding between fillers and matrix can limit the movement of the molecular chain.The water absorption of composite is lower than that of BT resin with addition small amount of fillers,and with the increase of fillers content,the water absorption of composite is higher than that of BT resin.