In-situ Polymerization And Characterization Of Aminefunctionalized Graphene Oxide/Polyimide Composite Adhesive

Polyimide(PI)is a heterocyclic polymer whose molecular repeating units contain an imide group(-CO-NH-CO-).The commonly used fragrant PI molecule has very stable aromatic heterocyclic structure unit,which has good heat resistance,oxidation resistance,chemical stability and excellent mechanical properties,but its molecular chain structure has great rigidity,which will affect the practical application of PI adhesive properties.So it needs to be modified.As an important inorganic nanoparticle,oxidized graphene doped into the polymer can significantly improve the thermal and mechanical properties of polymers.By functionalizing the functional groups on the graphene oxide,it is possible to further expand the application range.After the inorganic nano-ions are doped into the polymer,the properties of the composites are largely affected by the dispersibility of the inorganic nano-ions.Therefore,the specific incorporation methods and pretreatment of inorganic nanoparticles are particularly important.First,the modified Hummers method was used to prepare graphene oxide(HGO).The IGO was prepared by optimizing the preparation method.In particular,the graphite was oxidized by the mixture of H2SO4 and H3PO4,the use of NaNO3 was abolished,and the temperature was controlled by oil bath.The oxidized graphene prepared by the two methods was characterized by FT-IR,UVvis,XRD,Raman,SEM,TEM and TGA respectively.The results show that the graphene oxide prepared by the optimized method has stronger ultraviolet absorption,the Raman ID/IG value increased by 28.7%,and thermal decomposition of functional groups more weight loss 7%.XRD showed that the distance d value increased by 5.5%.From the FT-IR spectra of FGO,it was found that ODA was aminated by ODA.Raman showed that the functionalization of ODA did not cause new structural defects to IGO.XRD showed that FGO had larger interplanar spacing(dFGO = 1.22 nm).Benzophenone-3,3',4,4'-tetracarboxylic dianhydride(BTDA)and 4,4'-diaminodiphenyl ether(ODA)were used as the monomer,and 4,4'-(4,4'-isopropylidenediphenyl-1,1'-diyldioxy)(BAPP)was used for copolymerization to improve the adhesion of polyamic acid(PAA)adhesives.The characteristic functional groups of PAA and PI were characterized by FT-IR.The proton hydrogen in the PAA molecular structure was analyzed by 1H-NMR and it was further verified that PAA was successfully prepared.The intrinsic viscosity [?] was 0.41 dl.g-1.XRD showed that the three kinds of PAA were amorphous and SEM showed that the PI section was smooth and flat.Three kinds of PAA have excellent thermal stability with initial decomposition temperature all above 500?.The imidization degree of polyamic acid was measured by infrared spectroscopy.The imidization degree of the three peaks(1374cm-1,1725cm-1 and 1775cm-1)at each temperature was studied by using the stretching vibration peak intensity of benzene ring as the standard.The ID values were calculated and graphs showing the degree of PAA imidization versus time and temperature were plotted,and the curing process of PAA was determined finally.It was found that when n(ODA): n(BAPP): n(BTDA)= 1: 2: 3,NMP was used as solvent,reaction time was 12 h and system solids content was 25%,the adhesive has a better shear strength value.The mFGO/PAA,FGO/PAA and IGO/PAA composite adhesive were prepared by direct blending and in-situ polymerization.XRD showed that the FGO was dispersed evenly in the polymer.It was found from the SEM that the in-situ polymerization had a better micro-morphology than the direct blending and 0.9% FGO/PI had the best dispersibility,interfacial compatibility and microcosmic morphology in the matrix.FGO intercalation in the polymer matrix weakened the interaction between molecules,resulting in the DSC curve of the composite material Tg temperature decreased to a certain extent.The thermal decomposition temperature of 0.9% FGO/PI is 510.7?,which is the highest decomposition temperature of all.mFGO/PI has the lowest shear strength value and FGO/PI has a higher shear strength value which 0.9% FGO/PI has the highest shear strength value of 15.1MPa.T-peel and 180 ° peel tests of FGO/PI showed that the highest peel strength values were 1.7N/mm and 2.3N/mm,respectively,when the doping amount was 0.9%.