Synthesis, flame-retardancy testing, and preliminary mechanism studies of nonhalogenated aromatic boronic acids: A new class of condensed-phase polymer flame-retardant additives for acrylonitrile-butadiene-styrene and polycarbonate

This study describes the syntheses and thermal properties of aromatic boron ic acids and their use as flame retardants. The possible flame-retardancy m echanisms are also discussed. The materials were synthesized from aromatic bromides using one of two procedures. The first procedure involved traditio nal approaches to boronic acids, using lithium-halogen exchange and quenchi ng with trimethylborate followed by hydrolysis. The second procedure used a nickel catalyst and a dialkoxy borane to generate aromatic dialkoxyboronat es that were converted to boronic acids by acid hydrolysis, The thermal pro perties of these aromatic boronic acids were studied using differential sca nning calorimetry (DSC) and thermal gravimetric analysis (TGA). These mater ials were blended into acrylonitrile-butadiene-styrene (ABS) and polycar bo nate (PC) resins and tested for ignition resistance, using the UL-94 flame test. A 10 wt % loading of 1,4-beezeenedboronic acid in polycarbonate gave a UL-94 V-0 result. This same diboronic acid showed flame retardancy and ch ar formation in ABS, but this result was not quantifiable by the UL-94 test . Burn times for the ABS samples often exceeded 5 min, thereby showing unus ual resistance to consumption by fire. (C) 2000 John Wiley & Sons, Inc.