Effect of ZB/APP on ceramifying properties of ceramifiable polyethylene composites at high temperatures

Abstract

Zinc borate/ammonium polyphosphate (ZB/APP) was added to polyethylene/wollastonite fiber (PE/WF) composite to further improve ceramifiable properties. The effect of ZB/APP on the mechanical properties, shape stability, and self‐supporting properties of residues was investigated. The residue formed at 1000°C had a flexural strength of 30.5 MPa for the PE composite with addition of ZB/APP, which showed a significant improvement compared to the corresponding values of PE/WF/ZB and PE/WF/APP. In terms of shape stability, the PE/WF/ZB/APP system exhibited better dimensional stability and maintained its original shape after heat treatment. The bending angles of PE/WF/ZB/APP composite after being fired at 1000°C were less than 15°. The ceramifying process was studied by XRD, FTIR, SEM, and TG. During the heat treatment process, a phosphate glassy phase containing PO43− groups was formed by the reaction between ZB and APP. And then glassy phase reacted with WF to generate hydroxyapatite (Ca5(PO4)3OH). The reaction between ZB and APP inhibited eutectic reactions between each other as well as with WF, thereby stabilizing the crystallinity of the residue at high temperature. Moreover, the viscosity of the phosphate glassy phase produced by their reaction was higher than that of the APP melt, which improved both the mechanical and self‐supporting properties of the residue.