Synthesis of novolac‐based char former: Silicon‐containing phenolic resin and its synergistic action with magnesium hydroxide in polyamide‐6

Novel novolac‐based char former silicon‐containing phenolic resin (SCPR) was synthesized by the reaction of novolac with γ‐aminopropyltriethoxysilane in ethanol via a dehydration reaction, and the synthesized SCPR was characterized by Fourier transform infrared (FT‐IR) spectra, proton nuclear magnetic resonance (¹H NMR) spectroscopy, and thermogravimetric analysis (TGA). Serving as a synergist of magnesium hydroxide (MH) for the flame retardancy of polyamide 6 (PA6), it shows that the introduction of silicon in the structure of novolac molecule can greatly increase the charring performance of phenolic resin, and effectively eliminate the melt drips of PA6, thus improving the flame retardancy of the PA6. Compared with conventional novolac, the thermal oxidative stability of SCPR was obviously enhanced in the presence of MH due to the decrease of phenol hydroxide groups sensitive to oxidation, as well as the high energy Si–O bond introduced in the molecular structure. Copyright © 2010 John Wiley & Sons, Ltd.