Epoxy resin-layered silicate nanocomposites (ER-LSN) were successfully synthesized using pre-intercalated novolac resin-layered silicate nanocomposites (NR-LSN) as epoxy hardeners to develop novel formulations for copper-clad laminate sheets (CCLS) with enhanced properties. We used melt, melt-ultrasonic, solution, and solution-ultrasonic intercalation methods to prepare NR-LSN with different kinds of novolac resins including phenolic novolac (PN), bisphenol-A novolac (BN) and phenolic aralkyl novolac, so-called Xylok (XK). We employed different kinds of montmorillonites (MMT that were organically modified with benzyl dimethyl octadecyl ammonium and bis(2-hydroxy-ethyl)methyl tallow ammonium. It was confirmed that the synthesized NR-LSN and ER-LSN were intercalated or exfoliated, and exhibited stable structure owing to the effective action of high-intensity ultrasound. These materials showed significantly improved thermal and mechanical properties suitable for halogen-free CCLS with highly reliable performance. (C) 2004 Society of Plastics Engineers.