Influence of antimony oxide on flammability of polypropylene/intumescent flame retardant system

摘要

An intumescent system consisting of ammonium polyphosphate (APP) as an acid source and blowing agent, pentaerythritol (PER) as a carbonific agent and antimony oxide (Sb_2O_3) as a synergistic agent was used in this work to enhance flame retardancy of polypropylene (FR-PP). Sb_2O_3 was incorporated into flame retardant formulation at different concentrations to investigate the synergistic mechanism of Sb_2O_3 with the flame retardant materials. The content of APP and PER was fixed at 25 wt% of total amounts of flame retardant-PP composite. The synergistic effects of Sb_2O_3 on novel intumescent flame retardant-PP composites were evaluated by limited oxygen index (LOI), vertical burning test (UL-94), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Results show that LOI is increased from 27.8 to 36.6% in the presence of Sb_2O_3 and meets the UL-94 V-0 standard at the loading of 2 wt% Sb_2O_3. The SEM, and FT-IR results indicated that Sb_2O_3 could react with APP and form the stable charred layer which can inhabit the oxygen and heat transfer.