Preparation and properties of hybrid epoxy/hydro-terminated polybutadiene/modified MMT nanocomposites

The effects of hydroxyl-terminated polybutadiene (HTPB) number average molecular weight (\( \overline{{\boldsymbol{M\fancyscript{n}}}} \)) and preparation temperature on montmorillonite (MMT) intercalation/exfoliation behavior were investigated. X-ray diffraction and Fourier transform infrared spectroscopy results indicated that 40 to 80°C were the preferred temperatures to obtain nanostructured HTPB/MMT. The higher \( \overline{{\boldsymbol{M\fancyscript{n}}}} \) (> 2800) of HTPB led to a more exfoliated nanostructure than lower \( \overline{{\boldsymbol{M\fancyscript{n}}}} \) as proven by transmission electron microscopy. The tensile strength, tensile modulus, and elongation at break of nanostructured HTPB/MMT/EP ternary composites were higher than those of the HTPB/EP binary blend, which was due to the HTPB/MMT hybrid structure. The effect of increasing molecular weight on impact strength in the ternary system was less than that in the binary system. The HTPB/MMT/epoxy hybrid composites with low concentration could improve the impact strength, which was due to the superposition effect of organic/inorganic nanostructures. In hybrid HTPB/MMT/epoxy composite system, the toughening was attributed to the slow crack growth and fast crack growth, and the dissipated energy of pulling or debonding nanoclay out from the matrix also contributed.