Environmental assessment of discarded plastic caps as a honeycomb core: An eco-mechanical perspective

Abstract

The extensive disposal of plastic components into the environment requires an economically and ecologically feasible solution for the proper treatment or new uses for plastic waste. This study compares the environmental and mechanical performance of a sandwich panel based on disposed bottle caps core with different eco-friendly skins and adhesive. A cradle-to-gate life cycle assessment compares the environmental impacts of the manufacture of six-bottle cap panel designs with various skin (aluminum, recycled PET, and flax laminates) and adhesive types (epoxy vs. biopolymer) by calculating their ReCiPe midpoint impact indicators. An eco-mechanical indicator is additionally proposed to measure the efficiency of designs with greater strength/stiffness and less environmental footprint. The bio-based skin on the sandwich panel significantly reduces environmental damage between 32% and 87% compared to metallic skins. Recycled skin promotes the lowest impacts, while considerably reducing mechanical performance. The bio-based adhesive has emissions up to 15% lower than epoxy. The eco-mechanical balance showed up to 630% higher efficiency for bottle cap panel designs based on bio-based polymer, flax-based skins, and/or less adhesive depending on the mechanical response. Promising environmental performance with superior mechanical strength highlights the potential of bottle caps as an eco-friendly honeycomb for secondary construction and transport structures.