Polyurethane nanocomposites reinforced with surface modified halloysite nanotubes

The physical properties of polyurethane (PU) reinforced with surface modified halloysite nanotubes (HNTs) were investigated. The HNTs were modified with two different surface modifiers: n-octadecyltrimethoxysilane (OTMS) and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPS). The external surface modifiers were introduced through a chemical vapor adsorption (CVA) process. The dynamic light scattering of HNTs dispersed solution indicates that the OTMS-modified HNTs (O-HNTs) are dispersed in THF better than unmodified one. The modified HNTs were mixed with PU resin by solution blending. The PU/O-HNTs nanocomposites show significant improvements in tensile and thermal properties. At 0.5 wt% O-HNTs, the nanocomposite shows large increase in tensile strength and modulus, and 30% increase in elongation at break with respect to the unfilled PU. The simultaneous improvement in modulus, strength, and ductility is attributed to the interaction between the welldispersed O-HNTs and the PU matrix. The application of modified HNTs for flame retardant nanocomposite was done by loading bisphenol-A bis(diphenyl phosphate) (BDP) into the hydrophobically modified lumen of HNTs. The exterior surface was subsequently modified with AEAPS using a CVA process. The AEAPS-modified HNTs containing BDP show improved flame retardant performance without sacrificing the mechanical properties.