The Preparation Of Polyether Imide And The Properties Of Its Nanocomposites

Polyetherimide (PEI) is widely used in the industrial field for their excellent mechanical properties and heat resistance. However, their application in the field of heat conduction, such as heat exchanger and radiator, was seriously limited, owing to their low thermal conductivity. And because of the high insulation of PEI, the electrostatic charge generated on the surface of PEI could not lead away by PEI, as a result, it is likely to cause materials'damage. Therefore, in order to broaden the application of PEI in the thermal field while avoiding the damage caused by static electricity, PEI is desired to have thermal conductive and antistatic modification.Firstly, we adopted the four-steps method to synthesize bisphenol A dianhydride (BPADA). Bisphenol A was reacted with sodium hydroxide and transferred to bisphenol A sodium salt, then bisphenol A sodium salt reacted with N-methyl-4-nitro phthalates formyl imine under the action of A phase transfer catalyst, and bisphenol A diether and dipeptide imide (BEPI) was obtained and it would be experienced hydrolysis? acidification and dehydration anhydride and BPADA was synthesized.Secondly, in this paper, the azide polyacrylic acid (APAA) was grafted onto the surface of multi-walled carbon nanotubes (MWCNTs) through the reaction between the sidewall of MWCNTs and the nitrenes generated by azide groups under high temperature. Then, p-phenylene diamine (PPD) was conjuncted on the surface of MWCNTs by the reaction of p-phenylene diamine and carboxyl groups in APAA. Thus, PPD functionalized MWCNTs(MWCNTs@PPD) were prepared and the structural morphology of the carbon nanotubes was characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (Raman), elemental analysis (EA),, scanning electron microscopy (SEM), thermo-gravimetric (TGA) and high-resolution transmission electron microscopy (HRTEM). The test results revealed the success of surface modification of MWCNTs, and showed that the polymer was coated uniformly on the surface of MWCNTs and the amount was increased with the increase of azide degree and the degree of polymerization.Lastly, MWCNTs@PPD was introduced into the in situ polymerization of PEI with the monomer BPADA and PPD, the thermal conductive and antistatic PEI was obtained. The results of dynamic mechanical analysis of MWCNTs@PPD/PEI composites showed that the storage modulus was increased and the Tan delta was decreased due to the introduction of MWCNTs@PPD. And the storage modulus was improved and the Tan delta got reduced as the loading of MWCNTs@PPD increase. Compared with pristine MWCNTs, MWCNTs@PPD had better dispersion in PEI matrix, and the the volume electric conductivity and thermal conductivity of MWCNTs@PPD/PEI were all higher than those in pristine MWCNTs/PEI. The volume electric conductivity of the percolation threshold was 6.4×10-8 S/cm when the loading of MWCNTs@PPD was 1.0wt%, and when the content of MWCNTs@PPD was 4.0wt%, the thermal conductivity of nanocomposites could rise to 0.43W/(m·K), whereas at this content, the thermal conductivity of pristine MWCNTs/PEI composites was only 0.37W/(m·K).