Processability of Different Polymer Fractions Recovered from Mixed Wastes and Determination of Material Properties for Recycling.

Selina Möllnitz,Renato Sarc,Ivica Duretek,Roland Pomberger,Gerald Schmidt,Michael Feuchter

doi:10.3390/polym13030457

Abstract

To achieve future recycling targets and CO2 and waste reduction, the transfer of plastic contained in mixed waste from thermal recovery to mechanical recycling is a promising option. This requires extensive knowledge of the necessary processing depth of mixed wastes to enrich plastics and their processability in polymer processing machines. Also, the selection of a suitable processing method and product application area requires appropriate material behaviour. This paper investigates these aspects for a commercial processed, mixed waste, and two different mixed polyolefin fractions. The wastes are processed at different depths (e.g., washed/not washed, sorted into polyethylene, polypropylene, polyethylene terephthalate, polystyrene/unsorted) and then either homogenised in the extruder in advance or processed heterogeneously in the compression moulding process into plates. The produced recyclates in plate form are then subjected to mechanical, thermal, and rheological characterisation. Most investigated materials could be processed with simple compression moulding. The results show that an upstream washing process improves the achievable material properties, but homogenisation does not necessarily lead to an improvement. It was also found that a higher treatment depth (recovery of plastic types) is not necessary. The investigations show that plastic waste recovery with simple treatment from mixed, contaminated wastes into at least downcycling products is possible.

Highlights

The waste management industry often talks about “plastics” as if it were a single material, but this is not the case
The investigation method is divided into three areas: A.) Mechanical pre-processing of the input materials; B.) Polymer processing consisting of material homogenisation, a compression moulding process, and test specimen preparation; and C.) Material characterisation with thermal, mechanical, and rheological material testing
The mechanical pre-processing consists of a drum screen for the separation of fine material (

Summary

Introduction

The waste management industry often talks about “plastics” as if it were a single material, but this is not the case. Each plastic type is designed with specific characteristics that make it ideal for its intended application. Whatever their application was, at the end of their service life, plastic materials are necessary resources that should first be recycled (upstream/downstream), and only when this is no longer technically possible and economically feasible, they should be used as an alternative energy source in energy recovery facilities [1,2,3]. The main areas of PET application are the production of fibres for the textile industry, moulding compounds, hollow bodies, and films, primarily for the packaging sector. Standard PS is mainly used to produce dimensionally stable food and other packaging products, e.g., cups, trays, caps, closures, boxes, and films. Expanded PS (EPS) and extruded PS (XPS) are frequently used as insulation material for thermal insulation or impact sound insulation

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