Motivation

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Compacted polystyrene enriched waste fraction received by sorting of post-consumer waste.

The ResolVe project is dedicated to the chemical recycling of polystyrene. Polystyrene is a widely used polymer (see PlasticsEurope), that is used as a transparent, impact-modified (so-called HIPS) or foamed material in many applications. It can be found especially in packaging, in housings of household or electronic articles, but also as insulating material in the construction sector.

Similar to all other thermoplastic polymers such as polyethylene, polypropylene or polyethylene terephthalate, polystyrene can be mechanically recycled very well. For this purpose, in modern sorting facilities, polystyrene packaging material is collected as separate fractions (e.g. Germany: DKR 331 & 340).

However the demanding applications of polystyrene provide special challenges for mechanical recycling. In packaging with food or drinking water contact, there are high requirements on the purity of recyclates, which can be met only in closed systems, if at all. In further applications, polystyrene is valued for its outstanding colourability and gloss.

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Depolymerisation fills the gap between mechanical recycling and conventional incineration.

Chemical recycling provides the answer to these challenges, with polystyrene demonstrating its advantages: At high temperatures, it breaks down in a pyrolytic process into its smallest building blocks  – styrene monomer. The monomers may be purified with established procedures and reprocessed to high-quality styrenic polymers with properties similar to virgin materials.

Waste streams that do not allow for mechanical recycling (any more) may be used in a totally new approach, because impurities in the polymer are reliably separated in the pyrolysis and purification process.

The depolymerisation process of polystyrene that is investigated in the project ResolVe only requires a polystyrene-enriched feedstock. This allows the usage of cost- and resource-efficient sorting technologies, and still results in recyclates with the quality of virgin materials.