Trash into treasure: Chemical upcycling of poly(ɛ-caprolactone) waste plastic to plasticizer with excellent plasticizing performance and migration resistance

In recent years, with the increasingly serious environmental pollution, the achievement of a truly circular materials economy approach to sustainability has attracted the attention of scientists. In this paper, we proposed an approach that combined the chemical recycling of poly(ɛ-caprolactone) (PCL) plastic with the synthesis of a green plasticizer to promote the development of plastics' reutilization. An efficient alcoholysis strategy was employed to achieve the precise chain scission of PCL into short-chain PCL (sc-PCL), which was subsequently blended with polyvinyl chloride (PVC). The excellent compatibility of PVC/sc-PCL blend was characterized through differential scanning calorimetry (DSC) and solubility parameters. Thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) confirmed that the thermostability and plasticity of the plasticized PVC samples were superior to those of most commercial plasticizers' plasticized samples. Meanwhile, the exceptional extraction and migration resistance of PVC/sc-PCL implied that sc-PCL was capable to modify PVC as an ideal plasticizer. The flexible macromolecular structure of sc-PCL and the high percentage of polar ester groups made sc-PCL closely entangled with PVC, thus exhibiting excellent plasticizing properties. This trash into treasure strategy was also applicable to commercial PCL products, which will open up a new direction for chemical recycling of plastics as well as design and synthesis of green plasticizers.