Material recycling of post-consumer flexible polyethylene packaging waste

Licentiatavhandling, 2022

The mechanical and thermal properties of recycled post-consumer flexible polyethylene packaging waste was studied, using material collected and sorted on a large-scale from two sources. Unwashed, laboratory-scale washed, industrial-scale washed, and industrial-scale washed and melt-compounded (industrially recycled) materials were used. The unwashed and washed flakes were melt-compounded on a laboratory scale with a twin-screw extruder using two different temperature profiles and two screw configurations. The pellets were then injection moulded.

Washing reduced the polymer molecular mass and the melt viscosity, making the material susceptible to further degradation during melt-compounding and more so at a higher temperature. The Young’s modulus and tensile strength were affected by the washing but not by the compounding temperature or screw configuration, while the elongation-at-break were affected somewhat both by the washing and compounding temperature but not by the screw configuration. The moulded samples made of unwashed, laboratory-washed and industrial-washed materials had a stiffness, a tensile strength and an elongation-at-break as expected of conventional polyethylene grades available. The industrially recycled samples, however, had a lower stiffness, a slightly higher tensile strength and a significantly greater elongation-at-break. This significantly different mechanical properties of the industrially recycled material were probably due to the melt-filtration and possibly also to the additives in industrial melt-compounding. The overall results indicated that post-consumer flexible packaging waste had useful properties for further applications in new products, such as for non-food packaging.