Studies On Preparation Of MWCNTs/Ep Composites And Their Performances

Epoxy (Ep) composites reinforced by multi-walled carbon nanotubes (MWCNTs) may combine the MWCNTs' exceptional mechanical and electrical properties with the Ep' anticorrosion, thermal stability and cohesiveness, and is considered to be one of the most promising research directions of application, but there are still some theoretical and experimental problems needed to be solved. In this thesis, the purification of the raw MWCNTs prepared by CVD method was investigated by adopting calcination and acid oxidation methods. The products of purification were characterized by TEM and XRD. It was found that the purification of MWCNTs could be improved obviously, if the HNO₃ concentration or temperature was increased. But the catalyst carrier α-Al₂O₃ could not be effectively removed, even if the concentrated HNO₃ or aqua regia was used. The effects of eight factors, such as epoxy resins, hardeners, toughening agents, and thinner, etc., on the preparation of Ep composites and their mechanical property and thermal stability were investigated by the orthogonal experimental method for the first time. The totally optimized conditions of preparation of Ep composites are that the epoxy resin is E-54, toughening agent is ZS-101, hardener is TY-300, solidifying temperature is 140℃, mixing time of Ep resin-toughening agent-hardener is 15 min, stiring time of Ep resin-toughening agent is 22 min, 660A added is 8wt%, solidifying time is 3h. MWCNTs/Ep composites were prepared under the optimized conditions, and then the mechanical and electrical properties, thermal stability were measured, and microstructure was characterized. It was concluded from the experimental results that the toughness and specific strength of MWCNTs/Ep composites were improved, the bulk resistivity decreased, the microstructure became much complex with the amount of MWCNTs added being increased. The bending strength of MWCNTs/Ep composites could be enhanced and the specific strength also be significantly increased, if the MWCNTs were first treated with the surfactant. With the measuring voltage of bulk resistance being increased, the bulk resistivity decreased. The thermal stability of MWCNTs/Ep composites was lightly higher than that of the Ep composites.