Cryogenic mechanical behaviors of MMT/epoxy nanocomposites

Montmorillonite/epoxy (MMT/epoxy) nanocomposites were prepared by incorporating the organo-MMT slurry modified by acidified 2,4,6-tris-(dimethylaminomethyl) phenol (DMP-30) into the mixture of diglycidyl ether of bisphenol-A (DGEBA) and PU modified bisphenol-A using methyltetrahydrophthalic anhydride (MeTHPA) as the curing agent. X-ray diffraction (XRD) results showed that the nanocomposites at the 1 wt% MMT content exhibited no observable peaks in the range of 2-10 degrees (2 theta), indicating that most of the organo-MMT particles in the nanocomposites were exfoliated. The dispersion and exfoliation of organo-MMT in the nanocomposites were also observed using transmission electron microscopy (TEM). Mechanical behaviors of MMT/epoxy nanocomposites at both room temperature (RT) and liquid nitrogen temperature (77 K) were investigated in terms of tensile and impact properties. The strength and modulus of the nanocomposites were significantly higher at 77 K than at RT and these observations were explained in terms of the interfacial adhesion and constituent properties at 77 K and RT. The fracture surfaces of neat epoxy and MMT/epoxy nanocomposites were examined using scanning electron microscopy (SEM). Finally, the dependence of the glass transition temperature on the organo-MMT content was examined by differential scanning calorimetry (DSC). (C) 2007 Elsevier Ltd. All rights reserved.