Synthesis and properties of polycyclic phosphonate resins using one-pot method under ultrasound irradiation

Novel polycyclic phosphonates were first synthesized from novolac phenol formaldehyde (PF) resins under ultrasound irradiation in the absence of phase transfer catalyst (PTC). Experimental results demonstrated that ultrasound can accelerate the cycle condensation of the novolac PF resin in good yield. The chemical structure of the synthesized polycyclics was characterized using Gel-permeation chromatography (GPC), Fourier transfer infrared (FTIR), 1H- and 31P-nuclear magnetic resonance (NMR). Thermal properties of these polycyclics were determined by TG/IR analysis. The results showed that the induced cyclical phosphonate resins can greatly inhibit the oxidative weight loss of the polycyclic phosphonates, leading to very high char yields at temperatures higher than 700 °C. The char yields remained still about 4 wt.% while the weight remaining of phosphonate-free phenol formaldehyde (PF) resin was almost 0% at 600 °C. This indicates that the synthesized polycyclic phosphonates could be the potential candidates as a flame retardant for the polymers such as polycarbonate, epoxy resin and poly(ethylene terephthalate) etc.