Preparation, characterization and properties of polycaprolactone diol-functionalized multi-walled carbon nanotube/thermoplastic polyurethane composite

Multi-walled carbon nanotubes (MWCNTs) were chemically functionalized to prepare thermoplastic polyurethane (PU) composites with enhanced properties. In order to achieve a high compatibility of functionalized MWCNTs with the PU matrix, polycaprolactone diol (PCL), as one of PU's monomers, was selectively grafted on the surface of MWCNTs (MWCNT-PCL), while carboxylic acid groups functionalized MWCNTs (MWCNT-COOH) and raw MWCNTs served as control. Both MWCNT-COOH and MWCNT-PCL improved the dispersion of MWCNTs in the PU matrix and interfacial bonding between them at 1 wt% loading fraction. The MWCNT-PCL/PU composite showed the greatest extent of improvement, where the tensile strength and modulus were 51.2% and 33.5% higher than those of pure PU respectively, without sacrificing the elongation at break. The considerable improvement in both mechanical properties and thermal stability of MWCNT-PCL/PU composite should result from the homogeneous dispersion of MWCNT-PCL in the PU matrix and strong interfacial bonding between them.