Recent Advancements towards Sustainability in Rotomoulding.

Rotational moulding is a unique low-shear process used to manufacture hollow parts. The process is an excellent process method for batch processing, minimal waste and stress-free parts. However, the process has drawbacks such as long cycle times, gas dependency and a limited palette of materials relative to other process methods. This review aimed to shed light on the current state-of-the-art research contributing towards sustainability in rotational moulding. The scope of this review broadly assessed all areas of the process such as material development, process adaptations and development, modelling, simulation and contributions towards applications carving a more sustainable society. The PRISMA literature review method was adopted, finding that the majority of publications focus on material development, specifically on the use of waste, fillers, fibres and composites as a way to improve sustainability. Significant focus on biocomposites and natural fibres highlighted the strong research interest, while recyclate studies appeared to be less explored to date. Other research paths are process modification, modelling and simulation, motivated to increase energy efficiency, reduction in scrap and attempts to reduce cycle time with models. An emerging research interest in rotational moulding is the contribution towards the hydrogen economy, particularly type IV hydrogen vessels.

Mechanical Performance of Rotationally Molded Multilayer mLDPE/Banana-Fiber Composites.

The incorporation of materials different from the polymer within the rotational molding process usually results in lowered mechanical properties, where impact strength is of particular concern. In order to overcome this issue, multilayer structures of virgin polyethylene (PE) and banana fiber composites were prepared to determine the impact of the different layers on the performance of the final part. Cycle time has been studied to identify the influence of the addition of fibers in the process. The tensile, flexural and impact properties have been analyzed, finding improvements in Young's modulus of up to 13%, although at the expense of significant decreases in impact strength. A reduction in the fiber size due to the pulverization process was observed, which affected the rheological and mechanical behavior of the composite. The beneficial effects of working in multiple layers have been demonstrated in this work, where composites with up to 5% of banana fiber have been produced in two-layer structures. Finally, the need to add neat polyethylene in the external layer is also highlighted as a way to counteract the reductions in mechanical properties, particularly for flexural elastic modulus and tensile strength, and this also helps with the drop in impact behavior to a lower extent.