Low dielectric and flame‐retardant properties of thermosetting redistributed poly(phenylene oxide)

Abstract A curable low‐molecular‐weight poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) was prepared by the redistribution of regular PPO with maleic anhydride (MA) in toluene, using benzoyl peroxide as an initiator. The redistributed PPO (MA‐PPO), which contained alkene groups, was characterized by proton nuclear magnetic resonance and Fourier transform infrared spectroscopy. The redistributed PPO oligomers with reactive double bonds were cured with triallylisocyanurate (TAIC) and/or a phosphorus‐containing allyl‐functionalized monomer (allyl‐DOPO). Electrical properties of cured resins were studied by using a dielectric analyzer. The glass transition temperatures were measured by dynamic mechanical analysis. The flame retardancy was determined by the UL‐94 vertical test. The effects of curing accelerator and the amounts of TAIC and allyl‐DOPO incorporated into the network on the dielectric properties, glass transition temperature, and flame retardancy of the resulting systems were investigated. The results indicated that MA‐PPO cured with TAIC exhibited low dielectric constants (2.23–2.58 at 1 GHz) and dissipation factors (0.0034–0.0039 at 1 GHz) but had high glass transition temperatures (171–197°C) . The MA‐PPO/TAIC copolymerized with allyl‐DOPO could achieve a flame retardancy rating of UL‐94 V‐0 at about 1.35 wt % of phosphorus. The redistributed PPO/TAIC resins have potential applications in the fabrication of printed circuit boards. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers.