Preparation of <scp> SiO ₂ </scp> / <scp>MA</scp> Coated <scp>APP</scp> and Its Application in Flame Retardant and Foamed <scp>PPO</scp> / <scp>PS</scp> Blends

ABSTRACT This article reports the preparation of a multi‐layer core‐shell flame retardant (APP@SiO 2 @MA) using melamine (MA), ethyl silicate (TEOS), and γ‐(2,3‐epoxypropoxy) propyltrimethoxysilane (KH‐560) as raw materials, coated with ammonium polyphosphate (APP). Apply the flame retardant to PPO/PS composite materials to improve their flame retardant properties and investigate its effect on the foaming performance of PPO/PS composite materials. This article confirms the successful microencapsulation of APP by SiO 2 and MA through energy dispersive spectroscopy (EDS) analysis, X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) observation. The combustion performance of P samples and their foam samples was evaluated through thermogravimetric analysis (TG), limit oxygen index (LOI), and UL‐94 vertical combustion test, the residual carbon quality significantly increased from 17% of PPO/PS to 38%, and the maximum oxygen index increased from 22.9% to 30.5%. At 165°C and 3.5 MPa foaming conditions, the foaming ratio increased from 1.18 to 4.56 times, and the maximum oxygen index after foaming was 27.9%. This study provides a green and convenient method for the preparation of flame‐retardant PPO/PS bead foam materials, expanding the practical application of PPO/PS in industry.