Investigation of flame retardancy properties of polypropylene-colemanite and intumescent flame retardant additive blends

Polypropylene (PP) represents a considerable proportion of polyolefins (PO) used in different industrial applications such as automobile components, textiles, packaging, insulation, medical devices, various housewares, and household appliances due to its efficient cost, desirable mechanical, thermal and electrical properties, easy processability and recyclability. Because of its carbonaceous structure, PP is a highly flammable material with an LOI value of ۱۸ that presents a serious fire hazard. In this research, Intumescent flame retardant (IFR) and colemanite were added to polypropylene to compose ۳۰% of the total mass of the polymeric compounds, and the synergistic effect of colemanite with intumescent flame retardant (IFR) additive in PP was investigated by limiting oxygen index (LOI), glow wire test (GWT), UL-۹۴ test and mechanical properties measurements. The LOI, UL ۹۴ and glow wire test results showed that colemanite had a significant effect on flame retardancy and LOI value which can reach ۳۷.۶% with a loading amount of ۲ wt% colemanite at the total amount of flame retardant additives kept constant at ۳۰ wt%. Additionally, the PP/IFR compounds passed UL ۹۴ V۰ rating and both ۷۵۰ °C and ۸۵۰ °C glow wire tests with ۲-۸ wt% colemanite loading. According to Thermal gravimetric analyses (TGA), the results indicated that colemanite improved the thermal stability of PP/IFR compounds and also promoted the formation of the char layer. When colemanite mineral is added to polypropylene without an IFR system, it has no effect on the flame retardancy properties of polypropylene. When all properties have been taken into consideration, colemanite can be used up to ۴ wt% in IFR.