Morphology and Mechanical Properties of Nanocomposites Fabricated from Organoclays and a Novolac Phenolic Resin via Melt Mixing

Nanocomposites of novolac phenolic resin with a series of organoclays based on sodium montmorillonite exchanged with various amine compatibilizers were fabricated via melt processing. The effects of the amine structure on the resulting morphology and physical properties were investigated by employing wide-angle X-ray scattering, transmission electron microscopy, viscosity measurement, flexural strength measurement, and Izod impact strength testing. All of the composites containing organoclay showed evidence of the intercalated state with a shift in the gallery spacing. The extent of silicate platelet intercalation was increased by (1) decreasing the number of long alkyl tails from two to one, (2) using methyl rather than polar hydroxyethyl groups or bulky groups such as 2-ethylhexyl or benzyl groups, and (3) using an equivalent amount of compatibilizer with the montmorillonite. Novo lac phenolic resin/organoclay nanocomposites cured with hexamethylenetetramine exhibited better flexural and Izod impact strength than the unmodified novolac phenolic resin. Nanocomposites with higher shifts in the platelet gallery height, i.e., higher platelet intercalation, showed better flexural and Izod impact strength.