Editorial-Innovative Separation and Quality Control Strategies Applied to Mixed Polyolefins Waste

The idea to write this Special Issue originated as I am involved in the running European FP7 Collaborative Project “Magnetic Sorting and Ultrasound Sensor Technologies for Production of High Purity Secondary Polyolefins from Waste (W2Plastics)” - Grant Agreement No. 212782, specifically addressed to develop a number of novel concepts and an innovative operative approach finalized for recovering high-purity polyolefins from complex wastes at low cost. Plastic waste recovery represents one of the key issues of recycling, not only from an environmental perspective, but also from a scientific-technical point of view. Plastic wastes, for their chemical physical attributes, represent, in fact, one of the most challenging materials to process in order to perform a correct separation of the different constituting polymers. The difficulties, influencing the separation-sorting strategies, being linked to several factors related both to polymers intrinsic characteristics (e.g. polymeric chain and structure) and utilized additives (e.g. fillers, pigments, etc.). Polyolefins represent a very important family of polymers, constituting more than a third of the total plastics consumption in Europe (EU). Complex wastes provide the vastest, presently unused potential resource of secondary polyolefins. In spite of that, polyolefins, such as polypropylene (PP), high density polyethylene (HDPE) and low density polyethylene (LDPE) are the least recycled plastic materials. Recycling technologies in this field need to be extremely powerful, since they must be relatively simple to be cost-effective, but also accurate enough to create high-purity products. In this Special Issue are thus reported procedures and solutions adopted to reach the previous mentioned goal embedding not only the logic of understanding: why it works (‘know-why’) but also how a certain goal can be accomplished (‘know-how’). A detailed knowledge of the market for streams of end-of-life products (supply side) and the market for recycled raw materials (demand side) are also always considered and evaluated to optimize the practical implementation of the logics inside the processing-recycling-chain.