The Study Of The Prepartion Of MWNT/PET Nanocomposite With Very Low Content Of MWNT Via In Situ Polymerization And The Effect Of MWNT Networks For The Properties Of Matrix

Because of the excellent mechanical and electrical properties of carbon nanotubes, the polymer/CNTs have been widly studied all over the world. Compared to the usual fillings, the polymer/CNTs nanocomposites prepared by melting, solution and in situ method with a very small quantity of CNTs can achieve a remarkably enhancement in the properties of mechanical, electrical and calorifics and etc. So the potential of this nanocomposite in the high technology will be great in the future.In our study, two-steps method was used to solve the problem that MWNT was hard to disperse and imcompatible with the polymer. The MWNT could be purified and functionalized with this method, and the dispersion of MWNT in the monomer was improved. By in situ polymerization, PET/carbon nanotube nanocomposites with very low content of MWNT (0.005～0.01wt%) were prepared in the auto reactor. The effect of MWNT dispersion, the structure of MWNT network and the crystallization and mechanical preperty the composites were characterized by FT-IR, SEM, DSC, DMA and mechanical testing.With the two-steps method, the a amount of—COOH and—OH groups in the surface of MWNT could be increased evidently as well as the impurities can eliminated from the as-received MWNT. Because of the H-bond between groups and solvent, the MWNT-COOH could be stably dispersed in the H₂O and EG for a long time.With the in situ method, MWNT-COOH were well dispersed in the PET, and formed the network structure throughout the matrix. The network structure became more dense and consecutive with the content of MWNT—COOH increasing, but the dispersion was poorer. As the good nucleator, MWNT—COOH can dramatically improved the crystal temperature of PET and resulted in the relative intensity of double-melting peaks changed regularly with the content of MWNT—COOH increasing combined with the effect of the netword structure.The esterification of methanol and ester-exchange reactions with MWNT—COOH is viable. The wrapped function of the organic groups largely reduced the nucleating points. The crystallization was embarrassed by the formation of network structure.The mechanical property of composites were the best when added the MWNT -COOH. And when the content of MWNT-COOH is 0.05wt%, the mechanical property of the matrix appeared the maximum. If the content was more than 0.05wt%, the mechanical property descend obviously, because the aggregated MWNT conglomeration is the objection in the matrix.In conclusion, the PET/carbon nanotube nanocomposites can be successfully prepared bu in situ polymerization. The properties of the composites are improved dramatically with a very low content of MWNT. Because of the simply preparation technology and the low cost, this compound method has the potential for industrialization.