Effects of polyurethane/functionalised carbon nanotube interfacial interactions on tensile and compressive properties – molecular dynamics simulations

In order to understand the enhancement mechanism of the interaction between functionalised carbon nanotubes and polymer matrix, and to investigate the effects of different functionalised carbon nanotubes on the properties of composites at the microscopic level, the models of pure polyurethane (PUR), carbon nanotubes/polyurethane (CNTs/PUR), hydroxyl-functionalised carbon nanotubes/polyurethane (CNTOH/PUR), and carboxyl-functionalised carbon nanotubes/polyurethane (CNTCOOH/PUR) systems were constructed, and molecular dynamics methods were used to simulate the effects of different functionalised carbon nanotubes on the mechanical properties of polyurethane composite systems. The effects of different functionalised carbon nanotubes on the properties of PUR composite systems were compared by analysing the properties of PUR and its composite systems in terms of free volume fraction (FFV), radial distribution function (RDF), binding energy, and density distribution of PUR around different functionalised carbon nanotubes. The effects of intermolecular interactions on the properties of the composite systems were elucidated at the microscopic level. The final simulation results show that the CNTCOOH/PUR composite system with added carboxylated CNTs has the highest tensile yield strength, compressive properties and modulus; the smallest free volume fraction; the strongest bonding energy between CNTCOOH and PUR matrix, the largest density distribution of PUR matrix around CNTCOOH, and the best interfacial interaction.