Microrecycling of the metal-polymer-laminated packaging materials via thermal disengagement technology

Polymer-laminated metals are widely used in the packaging industries due to their flexibility of applications, superior properties, and relatively lower cost. Despite the advantages accomplished by the polymer-metal multilayer packaging materials, the recycling is a very difficult task due to the complexities of multimaterial intrinsic behaviors during the processing of cast-off materials. This study represents an innovative and sustainable way of recycling polymer-laminated aluminum packaging (PLAP) materials (postconsumer food packaging) into high-quality aluminum and a potential source of high-energy hydrocarbon gases and particulate carbon coproducts. Both sides of the aluminum foil of the packaging were laminated by two different polymers (polyethylene terephthalate, and polypropylene). Volatiles from the PLAP materials were eliminated by the thermal disengagement technology at 400-650 degrees C (5-30 min) with and without an inert gas supply. The volatiles evaporated from the PLAP materials were about 32%, and the rest 68% were aluminum (similar to 65%) and carbon (similar to 3%) from the decomposition of the polymers. The oxidation behavior of the surface of the recycled aluminum was studied by XRD, XPS, and elementary mapping, and a nanoscale oxidized surface was found in both inert and air atmospheric TD. The purity of the aluminum was measured above 98% by two different methods (LIBS and ICP-MS). The gaseous products released in TD were detected as high energy-carrying hydrocarbon, CO2, CO, H-2, H2O, and few other gases observed by real-time monitoring. The clean gases released in TD might be utilized upon reforming into CH4 or H-2 by further processing or as it turns out might be utilized as a source of heat energy for other applications. Carbon found from the decomposition of the hydrocarbons can be another useful element of this study. This recycling process offers an economically and environmentally feasible recycling strategy for a complex multilayer polymer-metal packaging waste.