Depolymerisering

Depolymerisering is the chemical or biological process by which polymer chains are cleaved into shorter segments, typically monomers or oligomers. It is the reverse of polymerization and is central to chemical recycling and material recovery. Depolymerisering can occur under various conditions and through different mechanisms, including thermal cleavage, hydrolysis, or solvolysis, often catalyzed by acids, bases, or solid catalysts. Enzymatic depolymerisering has gained prominence for certain polymers, using hydrolase enzymes such as PETase and MHETase to break polyethylene terephthalate into terephthalic acid and ethylene glycol.

In practice, depolymerisering aims to recover high-purity monomers that can be repolymerized, enabling closed-loop recycling. Polymers with cleavable linkages, such as polyesters, polyamides, and polyurethanes, are particularly amenable, whereas non-povalent or heavily crosslinked plastics pose challenges. PET, polystyrene, and some polyesters have been demonstrated to depolymerize under laboratory or industrial conditions into their constituent monomers or valuable intermediates.

Challenges include energy requirements, selectivity, catalyst development, and purification of the recovered monomers. The environmental and economic viability of depolymerisering depends on achieving high yields with minimal impurities and low energy input, as well as integration with upstream waste sorting.

Depolymerisering also occurs in nature through biodegradation, where enzymes and microorganisms cleave polymer chains, contributing to the decomposition of synthetic and natural polymers in the environment.