Nanocomposites of novolac type phenolic resins and organoclays: The effects of the resin molecular weight and the amine salt structure on the morphology and the mechanical properties of the composites

Abstract

Nanocomposites of novolac-type phenolic resins having various molecular weights with a series of organoclays containing organic amine salts were prepared by melt processing. The effects of the molecular weight of novolac resin and the amine structure of organoclay on composite morphology and physical properties were examined. Composites containing organoclay exhibited the intercalated state with shifts in gallery spacing regardless of the molecular weight of novolac resin. The extent of silicate platelet intercalation increased as molecular weight of novolac resin increased and the number of long alkyl tails decreased from two to one. Novolac resin/organoclay composites cured with hexamethylenetetramine (HMTA) always exhibited better flexural and Izod impact strengths than the novolac resin cured with HMTA when the molecular weight of novolac resin was fixed. Among the nanocomposites prepared here using organoclays, those with higher platelet intercalation generally showed better flexural and Izod impact strengths. However, resin-coated sands prepared from organoclay containing one long alkyl tail exhibited only better flexural strength than that prepared from novolac resin.