Study On The Structure And Properties Of Carbon Nanotubes Filled Polyurethane And Preparation Of Polyurethane/Carbon Nanotubes Nanocomposites

Carbon nanotubes have excellent mechanical strength, electrical and thermal conductivity and thermal stability, which is considered to be the optical filler for polymer materials. Carbon nanotubes is a hollow tubular material possessing high aspect ratio. Recently, many researches focus on the incorporation of carbon nanotubes in polymer materials. In this paper, polyurethane/multi-walled carbon nanotubes (PU/MWNT) nanocomposites were successfully fabricated through different compounding technology, the structure and properties of PU/MWNT nanocomposites were systematically investigated.Firstly, a melt blending process has been employed to prepare nanocomposites based on thermoplastic polyurethane (TPU) and MWNT. The content of MWNT filled in TPU was increased till 40phr (parts per hundreds of rubber).The morphological, structural and mechanical properties of the resulting TPU nanocomposites were systematically investigated using scanning electron microscope (SEM), transmission electron microscope (TEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), dynamic mechanical thermal analysis (DMTA) and tensile testing. The results indicated that the unmodified MWNT were dispersed finely and uniformly in the TPU matrix beyond expectation, and the microphase separation structures of the TPU nanocomposites were slightly affected by the presence of MWNT. The mechanical properties of the TPU nanocomposites containing various amounts of MWNT at both room temperature and 120℃were studied, which demonstrated that the modulus of TPU were greatly increased and the high temperature tensile strength of TPU was also prominently improved when MWNT content is higher. Moreover, the TPU nanocomposites exhibited improved thermal and electrical conductivities that might mean the TPU/MWNT nanocomposites have potential application as multi-functional materials.In addition flocculation method through annealing the nanocomposites at higher molding temperature has been adopted to improve the electrical conductivity of the nanocomposites. XRD experiment shows that the microphase separation structures of the TPU nanocomposites are affected by annealing heat treatment. Annealing heat treatment is in favor of increasing electrical conductivity of the nanocomposites and the percolation threshold value in electricity of the annealed TPU/MWNT nanocomposites is lower by contrast to the TPU/MWNT nanocomposites. Secondly, a spray drying approach has been adopted to prepare polyurethane (PU)/MWNT nanocomposites. Through the SEM observation, the unmodified MWNT were dispersed finely and uniformly in the PU matrix. XRD experiment indicates that the microphase separation structures of the PU nanocomposites were slightly affected by the presence of MWNT. In the electrical conductivity test, the electrical conductivity of the nanocomposites is gradually improved with increasing MWNT content as expected. The percolation threshold of the PU nanocomposites filled with MWNT is about 5vol %.In the final part, PU/MWNT composite fiber has been prepared by electrospinning, their structure and the electrical conductivity property have also been studied. SEM and TEM images show that the composite fibers have the diameter of nano scale and MWNT in the composite fibers have been aligned partly.