Assessment of processibility and properties of raw post-consumer waste polyethylene in the rotational moulding process

Abstract

This paper presents work from an ongoing study into the use of post-consumer waste polymer in the rotational moulding process. Raw plastic recyclate, predominantly consisting of polyethylene, was processed into polymer powders containing an additive package suitable for rotational moulding, with and without the addition of a compatibiliser. Rheological studies on the materials showed very high viscosities at low shear rates in comparison with materials typically used in rotational moulding, which has significant implications for melt flow and bubble removal during the process. It was possible to mould the materials successfully, but poor surface finishes were achieved. Impact strength was drastically lower for recyclate mouldings compared with virgin material. Tensile strength of the recyclate mouldings was reduced compared to virgin polyethylene, but results indicated that optimising the processing conditions could lead to improvements. This work gives some baseline indicators to inform further planned work on optimising processing conditions and identifying viable material compositions.

Recent Advancements towards Sustainability in Rotomoulding

“…This appears to be dependent on the source of recyclate and extent of the mechanical recycling process. Pick et al [ 19 ] aimed to provide ‘baseline data’ on polyethylene from recycled rotomoulded tanks and mixed post-consumer (PCR) waste for comparison with virgin polyethylene [ 22 ]. A compatibiliser was reportedly used in an attempt to increase miscibility, and in this case, an ionomer of an ethylene acid copolymer was studied.…”

“…The authors believed that the most significant contributing factor was attributed to the presence of PP and lower melt flow PE grades. The large increase in viscosity at low shear rates was also thought to be a significant factor regarding performance when using PCR [ 19 ]. Cestari et al [ 20 ] reported a similar study to Pick et al [ 19 ], and in this study, the authors compared various polymer blends of fractional MFI rHDPEs sourced from post-consumer feedstock, bottles pipes and household waste (PCR).…”

“…The large increase in viscosity at low shear rates was also thought to be a significant factor regarding performance when using PCR [ 19 ]. Cestari et al [ 20 ] reported a similar study to Pick et al [ 19 ], and in this study, the authors compared various polymer blends of fractional MFI rHDPEs sourced from post-consumer feedstock, bottles pipes and household waste (PCR). Fundamentally, they studied and compared the performance of compression moulded plaques and rotomoulded samples without the presence of a compatibiliser [ 20 ].…”

Recent Developments in Inorganic Composites in Rotational Molding

“…Several attempts have been made to introduce recycled resources in rotomolded parts as a way not only to increase the range of materials available but also to advance through the development of more sustainable solutions. Some authors have tried rotomolding recycled PLA fractions, where it is vital to control the process accurately to reduce polymer degradation [ 2 ] or post-consumer plastic residues [ 3 ]. The last study highlights the difficulties of obtaining relatively pure fractions of the PE, leading to the obtaining of parts with reduced mechanical properties.…”

Use of Ricinus communis shredded material as filler in rotational molded parts to improve the bio-disintegration behavior

“…Polylactic acid (PLA) is one of the most studied alternatives [2][3][4][5][6] due to its recyclability, good mechanical properties, and biodegradability under certain conditions. In order to improve the process sustainability, some authors have proposed using recycled materials from post-consumer plastics [7] or recycled PLA fractions [8]. Other authors have also suggested introducing natural fibers to improve rotomolded parts' properties.…”