Modified montmorillonite combined with intumescent flame retardants on the flame retardancy and thermal stability properties of unsaturated polyester resins

Modified montmorillonite-containing phytic acid (PA-MMT) has been prepared by acid treatment and then introduced into unsaturated polyester resin (UPR) with an intumescent flame retardant (IFRs). The flame retardancy and thermal degradation of UPR/IFRs/PA-MMT were evaluated by a limiting oxygen index (LOI) test, a vertical burning test (UL-94), a thermogravimetric analysis (TGA), and a cone calorimeter test (CCT). Besides, the mechanical properties were studied by a universal testing machine. The LOI value of UPR/IFRs/PA-MMT composites was increased to 29.2%. The CCT results indicated that the incorporation of PA-MMT and IFRs significantly improved the combustion behavior of UPR. The results of the mechanical properties indicated that 1.5 wt% loading of PA-MMT in UPR/IFRs showed the highest improvement in flexural strength and tensile strength. The flame-retardant mechanism of PA-MMT/IFRs was examined and discussed based on the results of combustion behavior and char analysis.