Post-consumer high density polyethylene/zirconium phosphate and aluminum hydroxide composites: Assessment of physico-mechanical and flame retardancy properties

Regarding environmental preservation, the upcycling of plastics from petroleum source is a consistent alternative. This work intended to investigate melting extruded composites of post-consumer HDPE (rHDPE) filled with pristine zirconium phosphate (ZrP), aluminum hydroxide [Al(OH)3] and aluminum hydroxide modifying-zirconium phosphate [ZrPOct/Al(OH)3]. Physico-mechanical and flame retardancy were assessed. FTIR revealed that rHDPE brought some degree of oxidative degradation probably from its cleaning process and/or processing. By nuclear magnetic resonance at time domain, rHDPE showed three relaxation domains. Fillers induced the lowering of rHDPE relaxation time owing to polymer/filler by hydrogen bonds. Diffraction pattern of rHDPE/Al(OH)3 and rHDPE/ZrPOct/Al(OH)3 indicated better fillers' dispersion. Fillers changed rHDPE crystallinity degree and thermal stability but rheologic properties were invariable. For all composites, elastic modulus increased (up to 17%) indicating stiffening. Yield strength did not change but stress and strain at break decreased. For the composites, SEM/EDS showed better dispersion and distribution of ZrP and ZrPOct/Al(OH)3 particles. It was assumed that ZrP and ZrPOct/Al(OH)3 greatly increased the flame retardancy. The work corroborates the importance of polymers' upcycling, and it is in consonance with the objectives of 2030 Agenda released by United Nations.