Preparation of modified ammonium polyphosphate blended aqueous boron phenolic resin and its application to insulating paper

The support material for cellulose-insulating paper is usually phenolic resin, which can no longer meet the mechanical characteristics, flame-retardant performance, and heat resistance requirements of insulating paper as the market evolves. In this article, the modified ammonium polyphosphate (APP) particles with excellent flame retardant and hydrophobic properties were prepared by the sol–gel method, which was applied to cellulose paper by compounding them with aqueous boron phenolic resin (BPF). The performance of the insulating paper had been significantly improved by evaluating the various properties of the paper, its breakage resistance and stiffness retention rates were 60.1% ~ 77.5% and 39.9% ~ 50.4%, respectively. With conductivity and breakdown voltage of 8.76 × 10 –14 ~ 1.01 × 10 –11 S/cm and 8.28 ~ 9.81 kW/mm, respectively. The introduction of Si elements on the surface of APP for surface coating improved the insulation performance of the insulating paper. According to the results of the cone calorimeter, the insulating paper fulfilled the UL-94 standard V-0 level with a maximum LOI value of 32.5%, which was a flame-retardant grade.