Recycling of polyethylene: Tribology assessment

Abstract

Use of recycled polymers is heavily application restricted based on mechanical-property-dependant requirements, which often result in downcycling into low-value products. Exploration of new applications for recycled polymers, and more ambitiously upcycling, falls to clever design, understanding of application-specific requirements, and differences between various grades of the same polymer. This constitutes a shift from an individual component exposed to external influences, to a component within a system acted upon by other known components and results in different design requirements. The higher-value system-specific opportunities of various reprocessed PE-HDs for use in the field of tribology were assessed. Reprocessed PE-HD exhibits differences of up to 20% in melt flow and mechanical properties compared to virgin PE-HD and may not be suitable for many engineering applications. It is, however, comparable to PE-UHMW based on tribological system-specific requirements alone (coefficient of friction < 0.1). Use of reprocessed PE-HD in this field constitutes upcycling due to the high value of the resulting products and the expansion of recycled material to new applications. Such expansion will be critical to meet ambitious new EU targets and legislation on use of recycled material, with existing applications for recycled materials highly limited and already saturated.