Development of a functional prototype for recovery of recycled expanded polystyrene via extrusion

Abstract

Expanded polystyrene (EPS) is composed of 98% air and 2% polystyrene (PS). EPS parts are made up of PS beads that contain a blowing agent, typically pentane, entrapped into their interior, allowing them to expand and form a honeycomb-similar cellular structure. The expandable PS beads allow for efficient storage and transportation while also providing control over density in separate steps (pre-expansion and molding). EPS's low density, excellent strength-to-weight ratio and thermal stability make it widely used in insulation and packaging applications. However, despite its utility, EPS often has a short service life, necessitating effective recycling methods. The prevailing method involves shredding and extrusion into recycled PS granulates, a downcycling process. This study explores the feasibility of extruding recycled EPS in the presence of a blowing agent, aiming to produce recycled EPS granulates. A theoretical design for a mechanical prototype suitable to extrude recycled EPS is being developed. In parallel, the optimization of EPS compaction at different temperatures and heating times aiming to improve the extrusion process is being studied. Although the practical implementation of this prototype remains to be carried out, this work sets the groundwork for a potential closed-loop recycling process for EPS. By recycling EPS back into its original form, instead of down-cycling it into PS, this process aligns with the European Green Deal's objectives of promoting resource circularity and reducing the use of virgin feed-stocks.