Nitrile rubber/peroxide treatment transformed recycled polyethylene into mechanically improved materials

Abstract The recycled high‐density polyethylene (rHDPE) feedstock containing calcium carbonate (CaCO3) mineral was obtained from post‐consumer single‐use grocery bags. This feedstock is transformed into new composite materials with improved mechanical properties using a high‐shear compounding process. The rHDPE/CaCO3 feedstock is injected into the high‐shear polymer mixer and blended with acrylonitrile‐butadiene copolymer or nitrile rubber (up to 10 wt%) and crosslinked with dicumyl peroxide. The resultant materials exhibit high mechanical performance, with a maximum tensile strength of 20.3 MPa, stiffness of 1262 MPa, and impact strength of 63 kJ/m2. These mechanical properties are profoundly higher than those of neat rHDPE feedstock. Notably, the post‐consumer plastic bags contain a high amount of CaCO3 mineral of approximately 30 wt% (13 vol%), impacting the materials' mechanical properties with additives such as nitrile rubber. In addition, the materials' melt‐rheology, viscoelastic, and phase morphology are analyzed. The melt‐rheological characteristics indicate that the materials' complex viscosity and storage modulus are frequency‐dependent, demonstrating the thermoplastic nature of the composite materials and the possibility of thermomechanical recyclability of the materials. However, treating rHDPE/nitrile rubber blends with peroxide creates resistance to the melt‐flow of the materials.