Novel Carbon Nanotubes/Polymers Containing Phthalazinone Moieties Composites

Polymer containing phthalazinone moieties is a novel amorphous high performance thermoplastic with outstanding high temperature stability, good solubility in some organic solvents and integrative properties. As a result, all of these make it a very ideal alternative of matrix for advanced composites potentially used in some harsh environmental conditions. Carbon nanotubes (CNT), possess remarkable electrical and mechanical properties coupled with good chemical stability due to their unique nanostructures, which allows them to be applied to many high technology fields ranging from microelectronics to aerospace. In recent years, combining CNT and polymers to produce functional composite materials with superior properties has attracted great interest. These strategies mainly include the use of CNT as conductive fillers in insulating polymer matrices and as reinforcements in structural materials. In this work, taking advantages of high performances of CNT and polymers containing phthalazinone moieties, we prepared functional nanocomposites. The effects of the processing methods and the functionalized MWNT on the structures and properties of the composites have been researched. Additionally, the microwave absorbing properties of the CNT/polymer containing phthalazinone moieties composites were exploringly investigated.Firstly, two types of matrix, poly (phthalazinone ether sulfone ketone)s (PPESK) and polyamide with phthalazinone (PPEA), were blended with multiwalled carbon nanotubes (MWNT) to produce MWNT/polymer nanocomposites by solution-mixing and in situ polymerization method, respectively. The morphologies and structures of the composites were characterized by Fourier transform infrared (FT-IR), Raman spectroscopy and scanning electron microscope (SEM). Moreover the tensile properties, electrical conductivity and thermal stability of the composites were investigated. The results show that introducing MWNT into matrix decreases the value of electrical resistivity and the transition of the electrical resistivity indicates a typical percolation behavior. The tensile properties and thermal stability of the composites were obviously improved too. Compared the various processing methods, the composites via in situ polymerization have sufficient dispersion of MWNT and excellent interfacial adhesion between filler and matrix, which results in better electrical and tensile properties.Then, by chemical modification, the MWNT were successfully functionalized with phthalazinone-containing diamine (DHPZDA) groups that have similar chemical structure to matrix by the amidation reaction. Two types of matrix, PPESK and PPEA, were blended with functionalized MWNT to produce nanocomposites by solution-mixing method, respectively. The structures of the functionalized MWNT and composites were characterized by FT-IR, Raman spectroscopy, SEM, transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The results show that the reacted DHPZDA are covalently attached to the MWNT surfaces by strong interaction. The functionalized MWNT/polymer has more sufficient dispersion of MWNT and better interfacial adhesion between filler and matrix, indicates better electrical conductivity and tensile properties, compared with unmodified MWNT/polymer composites.Lastly, nickel-coated MWNT (Ni-MWNT) were prepared by electroless deposition, and the morphologies and components of Ni-MWNT were characterized by SEM and energy dispersive spectroscopy (EDS). It can be seen that the nickel were successfully coated onto the surface of MWNT with ultrasonic vibrations by electroless deposition. Additionally, two types of fillers, MWNT and Ni-MWNT, were blended with PPESK by the solution-mixing method, respectively. The electrical conductivity shows that Ni-MWNT/PPESK composites have relatively lower electrical resistivity values than MWNT/PPESK composites, and in both cases the decrease of electrical resistivity indicates a similar percolation transition behavior in the same MWNT content region. The microwave absorbing properties of MWNT/PPESK and Ni-MWNT/PPESK composites were investigated. Ni-MWNT/PPESK composite has the wider frequency region of the reflection loss (RL) less than -10 dB and the lower minimum value of RL compared with MWNT/PPESK, which can be attributed to the improved dielectric and magnetic properties of the fillers. For MWNT/PPESK composites, in the testing MWNT concentration range, the correlation coefficient values are close to 1 and there is a close to linear dependence between the microwave absorbing and electric properties. For Ni-MWNT/PPESK composites, the microwave absorbing and electric properties have a behavior of unrelated quantities. When Ni-MWNT were added in PPESK, the mechanical and high temperature stability properties of the composites are more enhanced, which facilitates the formation of the microwave absorbing composites with good integrative properties.