PIN FRs for recycled polyethylene

PIN FRs zirconium phosphate and ATH improved mechanical and fire performance of post-consumer recycled rHDPE. The recycled high-density polyethylene (rHDPE) was supplied from a Brazil recycler. Layered zirconium phosphate (ZrP) was synthesised in the laboratory and aluminium hydroxide (ATH) was purchased as such. To optimise dispersion, specimens (125 x 12 x 3 mm) containing 10% PIN FR were extruded after first extruding masterbatches of rHDPE with 20% FR., Tests compared neat rHDPE with 10% ZrP, 10% ATH and 5% ZrP+5% ATH. Analysis showed that the reprocessing of the rHDPE led to some oxidative degradation. The PIN FRs showed some molecular reaction with the rHDPE, increased rHDPE stiffness and tensile strength was maintained. ASTM D635 fire testing showed increased burning rates with the PIN FR addition but much longer times to dripping (nearly 7x longer) and with ZrP+ATH burning drips extinguished. The authors conclude that the PIN FRs increased flame retardancy, with synergy between zirconium phosphate and the ATH shown by increased char formation.

“Post-consumer high density polyethylene / zirconium phosphate and aluminum hydroxide composites: Assessment of physico-mechanical and flame retardancy properties”, G. Albitres et al., J. Composite Materials 2024, Vol. 58(4) 489–503, https://doi.org/10.1177/00219983231226278