PIN FRs compatible with PP recycling

Polypropylene (PP) with PIN FR was re-extruded five times, maintaining fire performance and mechanical properties. The PIN FRs tested were 2:1 (by mass) piperazine pyrophosphate and melamine pyrophosphate, with a total loading of 21% in the polypropylene. After melt compounding then five injection moulding cycles, the materials retained processability and thermal stability. Fire performance of UL 94 V-0 (3.2 mm) was maintained after the five reprocessing cycles, and peak heat release rate, limited oxygen index and smoke release were not significantly changed, remaining 4 – 6 x better than neat polypropylene. Tensile strength, flexural strength and impact strength were not modified by the reprocessing of the FR-PP, but elongation at break was deteriorated beyond 2 processing cycles.

“Recyclability of Flame-Retardant Polypropylene: Property and Flame Retardancy Assessment”, G. Bernagozzi et al., Polymers 2026, 18, 845,  https://doi.org/10.3390/polym18070845