Flame-Retardant PP/SF Composites Synthesis

The two-step melt blending method was used for the preparation of PP/SF flame-retardant composites. SF and IFR were mixed with a PP matrix in a different order, as shown in Figure 1. After each melt blending step, the extruded strips were cut into pellets and dried for subsequent processing. In order to better distinguish each sample, the abbreviations of the composite materials prepared under different mixing processes were simply named as (PP/IFR)/SF, (PP/SF)/IFR, and PP/IFR/SF, where (PP/IFR)/SF indicates that the matrix and flame retardant were firstly melt blended, and then remixed with SF (as shown in Figure 1a). (PP/SF)/IFR indicates that the matrix and SF were firstly melt blended, and then remixed with IFR (as shown in Figure 1b). PP/IFR/SF indicates that PP, IFR, and SF were firstly melt blended, followed by a second blend (as shown in Figure 1c).