Synthesis and Properties of Boron-Containing Oligomers Based on Hydroquinone and Boric Acid

Abstract

By polyesterification of boric acid with hydroquinone in o-xylene with azeotropic distillation of water, polyesters of hydroquinone and boric acid are obtained. By adding equimolar amounts of phenol to the reaction between boric acid and hydroquinone, a mixed polyester of hydroquinone, phenol and boric acid is obtained. From the ratio of the integral intensity of phenol protons to hydroquinone protons, it was found that the addition of phenol to the hydroquinone polydiester and boric acid occurs by 80%. The synthesized polyesters reacted with formaldehyde using o-xylene as a solvent and a boron trifluoride etherate catalyst. By the method of end groups it was determined that all the compounds obtained have a small molecular weight and belong to the class of oligomers. The structure of the synthesized oligomers was confirmed by elemental analysis, IR and NMR (1H, 13C) spectroscopy. All compounds obtained have a good adhesion to glass, wood and metal. The thermal destruction of samples in a flow of nitrogen at 900 °C was studied, the residual mass for polyesters is from 49 to 53%, for polymethylene ester - from 18.5 to 31%. The residual mass during thermo-oxidative degradation in an air flow at 600 ° C for polyesters is from 62 to 65%, for polymethylene ester from 37 to 44%. The reaction of the modification of synthesized oligomers with a sulfur curing system and epoxy resin was studied. The maximum content of insoluble gel fraction when cured by sulfuric system at a temperature of 220 °C reaches 94% for polymethylene diester hydroquinone and boric acid, the minimum is 68% for the polytriester of hydroquinone and boric acid. The maximum content of insoluble gel fraction when cured with epoxy resin at a temperature of 150 °C for polyesters is in the range 52 - 66 %, for polymethylene ester 50 - 61%.