Comparing HFFR formulations containing two different PFR types reveals that Tign and Ea values are independent of PFR types. Based on the addition levels, the results show that PFR 1 is more effective as a flame retardant than PFR 2, and addition of Paxymer® proved to be an effective synergist for both types of PFR additives, reducing their addition levels significantly. The onset temperature and the %-char were also determined for some of the model formulations using TGA measurements, and the results are summarized in Table below. The results show that all formulations showing V0 have comparatively higher Onset temperatures compared to virgin PP except BG582, where we have measured a slight decrease in the onset temperature. This may be due to the earlier initiation of thermal degradation, as mentioned in our discussions above, at higher concentration of PFR 1 compared to BG586 where both the lower concentration of PFR 1 and the presence of Paxymer® synergist may favour the thermal stability of the material. However, for PFR 2 we measure an increase in the onset temperature for both the formulations, no matter of concentrations. This also shows that fire retarding properties are very specific and may differ from one PFR additive to other and are therefore required to be measured. All HFFR formulations show high char contents that vary with the type and addition levels of PFR. However, we could not observe any systematic correlation between the onset temperature and the char contents with UL-94V classifications. This may be due to the differences in the fire retarding parameters for different PFR types.