Can a halogen-free flame retardant system be chosen when manufacturing PP flame-retardant sheets?

The general production process of PP sheets includes: feeding materials; extrusion, using a single-screw extruder to extrude the material barrel; heating in four zones; evaporating the moisture contained in the PP raw materials and promptly discharging it through the exhaust holes set on the material barrel; and then extruding into a mold for molding and shaping into sheets. 

For halogen-free formulations, among the halogen-free additive flame retardants used for flame-retardant PP, intumescent flame retardants are commonly seen. When each component in the intumescent flame retardant is used alone, its flame-retardant effect on PP is not satisfactory. However, when they are used together, the flame retardancy of PP is significantly improved due to the increased char formation rate. And the addition amount of the halogen-free flame retardant system is generally relatively high. On the one hand, it is not convenient for a single-screw extruder to disperse the flame retardant, and on the other hand, too much addition amount will also affect other properties of the sheets. 

Therefore, in order to achieve better dispersibility and a better flame-retardant effect, it is still recommended to use flame-retardant master batches for PP sheets.