Preparation Of Properties Of Polyurethane/Carbon Nanotube Nanocomposites

Thermoplastic polyurethane(TPU) was a representative of elastomer polymers and it can be applied in many areas such as coating,adhesives,polymer moulding and medical,etc.Modified TPU composites with nanoparticles have exhibited the excellent properties.Since the discovery of carbon nanotubes(CNTs),they have been attracted considerable attentions by the scientific research workers because of their excellent mechanical,electrical,and other properties.Therefore,carbon nanotubes were one of the important candidates to modify TPU composites.In this study,the multiwalled carbon nanotube(MWNT)/TPU nanocomposite prepared by TPU matrix and MWNT fillers was analyzed in various properties.The work is summarized as following:1.Modification of MWNTMWNTs were modified using concentrated acid in order to graft the carboxyl onto the surface of nanofillers.FTIR and TEM confirmed the dispersion and the morphology of MWNTs and their dispersion,and interface interaction in polymer solution was effectively improved.2.Nanocomposites of MWNT-COOH/TPUThe nanocomposite was prepared via blending the solution of MWNT-COOH and TPU in DMAc and then solvent evaporation.SEM confirmed dispersion of MWNT in the TPU matrix.The degree of the hydrogen bonding in composites characterized by FTIR was increased,which was caused by MWNT-COOH and the decrease of the phase-separation.Compared with the pure TPU,the analysis of TGA,DMA and static mechanical indicated that both the mechanical and thermal properties were improved. The measurement of dynamic rheological behavior showed that there was the consistent change for complex viscosity(η~*),storage modulus(G') and loss modulus(G") as changing content of the MWNTs.It was related to the interaction among the MWNTs,the TPU and the solvent.3.MWNT-TDI/TPU nanocompositesMWNT-TDI was functionalized from MWNT-COOH by grafting 2,4-toluene diisocyanate(TDI) on its surface.SEM images indicated that MWNT-TDI can well disperse in TPU matrix.Mechanical properties of the MWNT-TDI/TPU composite were improved and the tensile strength increased by three times than that of pure TPU when content of the MWNT-TDI was 2%.Thermal properties obviously changed and it showed that the addition of MWNT-TDI has an influence on the hard segment of the TPU because side chain of the MWNT-TDI was similar to the hard segment. Dynamic rheology illuminated that complex viscosity(η~*) increased with the content of MWNT-TDI and has no obvious change in low frequency,along with the shear thinning at high frequency.The temperature was one of the important factors for complex viscosity(η~*).