Development of sustainable food packaging through the integration of the polyolefin crosslinking control technique in multilayer film technology

Food packaging is the main cause for the huge volumes of plastic waste that often cannot be recycled and that are destined for landfills or released into the environment . The development of sophisticated technologies, such as the production of multilayer films by co-extrusion of different polymers, has allowed the design of technical films for food packaging with specific properties for each food able to perform different functions, such as food protection, as required by food safety and increasing their shelf life. However, this development has reduced the possibilities of mechanical and chemical recycling of plastic waste deriving from food packaging because the technical films are made up of layers of different polymers that are difficult to separate . Due to the difficulties in separating different polyolefins and the chemical incompatibility between different polyolefins, in particular between polyethylene (PE) and polypropylene (iPP), the products deriving from recycling mixtures of PE and iPP show worse properties than those of the original components . To improve the properties of products deriving from the secondary recycling of plastic waste, and consequently increase the recycling percentages, a strategy has been developed which involves the introduction of a certain degree of crosslinking with the formation of chemical bonds between the macromolecules which allows to reduce the thickness of the polymeric films without modifying their barrier and food protection properties. On the one hand, this strategy significantly reduces the volume of plastic waste derived from food packaging and, on the other hand, significantly increases the chances of mechanical recycling of the films themselves, without causing downcycling. A study of the strategies to produce polymeric films that integrates the controlled crosslinking technique of polyolefins in the industrial technology of multilayer film production by coextrusion is presented. This technology not only improve the properties of the films by reducing their thickness but also, improve the possibility of recycling and environmental sustainability of the packaging. Specifically, the optimal degree of crosslinking and of the minimum thickness of the various layers will be evaluated from the analysis of the physical and mechanical properties of crosslinked multilayer films and fine-tuning of the industrial production of recyclable multilayer films that can replace the current products used for food packaging, after passing the recyclability tests.