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.