Multi-Walled Carbon Nanotubes Encapsulated With Polyurethane And Its Nanpcomposites

Multi-walled carbon nanotubes (MWCNTs) were first acid treated with concentrated HNO₃/H₂SO₄ (1:1, v/v) to generate hydroxyl. Fourier transform infrared spectrometer (FTIR) and X-ray photoelectron spectroscope (XPS) were used to confirm the formation of hydroxyl groups on the surface of MWCNTs.Poly (acryloyl chloride) (PAC1) was employed to enhance the surface of MWCNTs. PAC1 was esterified by hydroxyl groups on the surface of MWCNTs to obtain an encapsulation of MWCNTs. The numerous acryloyl chloride groups on the outer layer were esterified with a proper amount of ethylene glycol, thus multi-hydroxyl functionalized MWCNTs were obtained. The chemical structure of multi-hydroxyl functionalized MWCNTs was identified by FTIR, the morphology was observed by transmission electron microscope (TEM).In the presence of multi-hydroxyl functionalized MWCNTs, a polyurethane layer was formed in situ by condensation polymerization of 4,4'-methylenebis(phenylisocyanate) and 1,4-butanediol. The formation of polyurethane layer on MWCNTs was confirmed by FTIR and XPS. The morphology of encapsulated MWCNTs was observed by TEM and scanning electron microscope (SEM). Thermo gravimetric analysis showed the grafted polymer fraction was up to 90%.MWCNTs/PU nanocomposite films were prepared through solvent evaporation method. In an attempt to examine the reinforcing effect of PU encapsulated MWCNTs in PU matrix, mechanical properties of nanocomposites were measured by stress-strain test and Dynamic mechanical thermal analysis (DMTA). An increase in tensile strength by 60.6% and improvement in modulus by 6.3% over neat PU was observed.