Microrecycling of multi-layered waste packaging to produce value-added aluminium

Abstract

Multi-layered waste packaging materials 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 multilayers packaging materials, recycling the waste in a traditional method is a very difficult task due to the complexities of multi-materials intrinsic behaviours during the processing of cast-off materials. In this study, a newly developed microrecycling technique (thermal disengagement technology, TDT) has been introduced and briefly demonstrated. Several outcomes are: (i) Polymer laminated Al packaging materials available from the local market was thermally disengaged by TDT into several useful products including ~98% pure Al, and graphitic C without any major emission (ii) laminated polymers in multi-layered packaging materials can be degraded into the graphitic C in an inert atmosphere. Degraded C can stay on Al surface to provide well protection against surface oxidation, (iii) TDT was utilised for different types of multilayer packaging materials consisting of multiple polymers and metallic contents (Al, Cu, & Fe) available in the local market. TDT is highly capable to recycle all different types of packaging materials irrespective to their inclusive materials. (iv) Al-containing packaging material was recycled in different media (air, nitrogen, & argon). Argon media was suitable to recycle Al into its original form and polymers into degraded graphitic C. Recycled Al was transformed into microparticles by non-traditional mechanical milling at cryogenic temperature (-196°C) created by liquid N2. Synthesised flake shaped, and micro-sized carbonaceous Al microparticles are contamination-free and thermally stable and can be useful in the fields of additive manufacturing, (v) A rapid transformation process was introduced where thermally disengaged Al from the TDT subsequently thermally transformed in an arc furnace at a very high temperature (~2000°C) in a short time period (~20s) in an inert and vacuum condition. As a result of this rapid transformation, ceramic reinforced Al alloy with an enhanced physical, microstructural, and mechanical properties was synthesised. The overall project of recycling polymer-metal multilayer packaging materials can be concluded with numerous green materials output along with some co-products and metallic alloys.