PIN FR effective in recycled polypropylene

An intumescent phosphorus-nitrogen PIN FR showed to be effective in both virgin and re-extruded PP (UL 94 V-0 3.2mm). Recycled PP was lab simulated by eight times re-extrusion at 210°C, so without any other polymers or contaminants likely to be found in real secondary PP streams. A PIN intumescent FR package of piperazine pyrophosphate and melamine polyphosphate (2:1) was added to virgin and to the re-extruded PP then fire and mechanical performance tested. Reduction in heat release rate was similar, but the PIN FR re-extruded PP showed a longer time to ignition, apparently resulting from denser char, maybe because of better dispersion of the FR due to lower viscosity of the re-extruded PP. The mechanical properties of the FR re-extruded PP were not compromised, other than a slight reduction in ductility. The authors conclude that multiple re-extruded polypropylene can be used in PIN flame retardant applications.

“Is Recycled Polypropylene Suitable for Flame-Retarded Applications?”, G. Bernagozzi, ACS Applied Polymer Materials 2026 https://doi.org/10.1021/acsapm.6c00885

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