In‐situ preparation of modified‐halloysite/thermoset nanocomposites via thiol‐epoxy click chemistry

Abstract

AbstractIn the current study, thermoset nanocomposites including halloysite nanotubes (HNTs) have been prepared through thiol‐epoxy click reaction at ambient conditions. Naturally available HNTs are first modified separately by epoxy and thiol groups and used as nanofillers in a mixture of trimethylolpropane triglycidyl ether and trimethylolpropane tris(3‐mercaptopropionate) ranging from 0 to 5 wt%. Fourier transformed infrared (FT‐IR) spectroscopy has been used to observe the characteristic bands of the pure and modified halloysite, neat thermoset, and HNT/thermoset nanocomposites. Thermal properties of epoxide‐modified and thiol‐modified halloysite nanotubes and also final thermoset nanocomposites have been investigated using thermogravimetric analysis (TGA) by comparing pure halloysite and neat thermoset, respectively. The dispersion of HNT nanotubes in thermoset matrix has been examined with scanning electron microscopy (SEM). In addition to the agglomerated/non‐agglomerated distribution, the present of HNT has been proved by EDX. The effect of HNT‐Epoxide and HNT‐Thiol loadings on mechanical properties has been examined by tensile test. All nanocomposites were found to exhibit better tensile strength than that of neat thermoset, called as reference sample. The most enhanced mechanical properties have been detected in the nanocomposite with 3% modified‐HNTs by weight because of the best dispersion, which promotes effective interactions between the nanotubes and thermoset matrix. Tensile strength of thermoset nanocomposites increased by 43% and 62%, while elongation at break increased by 58% and 149% when 3 wt% HNT‐Epoxide and 3 wt% HNT‐Thiol were added to the matrix, respectively. Further increase of HNT added to the matrix causes agglomeration of nanotubes and thus deterioration of mechanical properties.Highlights Pure HNT was modified and successfully converted into HNT‐Epoxide and HNT‐Thiol. In‐situ preparation of thermoset nanocomposites with modified‐HNTs was effectively achieved via thiol‐epoxy click chemistry. Mechanical properties increased significantly with both HNT‐Epoxide and HNT‐Thiol loading ratio up to 3 wt%. The presence and agglomerated/non‐agglomerated dispersion of modified‐HNTs in the thermoset matrix were verified by SEM–EDX analysis.