Comparative Study on Flame Retardancy, Thermal, and Mechanical Properties of Glass Fiber Reinforced Polyester Composites with Ammonium Polyphosphate, Expandable Graphite, and Aluminum Tri-hydroxide

The aim of this study is to enhance the flame retardant property of the glass fiber reinforced polyester composites by using intumescent flame retardants such as ammonium polyphosphate (APP) and/or expandable graphite (EG) in addition to aluminum tri-hydroxide (ATH). Flame retardant properties of the composites were tested by limiting oxygen index and UL-94 tests. Chemical characterization of the materials was done using Fourier transform infrared spectroscopy. Mechanical properties were evaluated by tensile test, and surface morphology analysis was performed by using stereomicroscope and scanning electron microscope. Thermal properties of the composites were characterized by thermogravimetry/differential thermal analyzer. The results showed that the flame retardancy of the composites was significantly improved by the addition of intumescent flame retardants with no considerable adverse effect on the mechanical properties. Thermal analysis data revealed that intumescent flame retardants increased the char yields of the composites. Also, the APP containing formulations yielded lower weight loss rates. To our knowledge, this is the first study investigating the flame retardancy, thermal, and mechanical properties of glass fiber reinforced polyester composite comprising ATH, APP, and EG in dual- or triple-flame retardant formulations.