Composting a Sticky Problem: Synthesis and Degradation of Isosorbide-Derived Hot-Melt Adhesive

초록

Highlights •A novel biodegradable hot-melt adhesive (PCISC) was synthesized from biomass.•PCISC shows high adhesion (5.2 MPa), outperforming conventional HMAs.•PCISC exhibits remarkable biodegradability in compost and sewage sludge.•Isosorbide (ISB) moiety is identified as a key component for strong adhesion.•The adhesive achieves maximum strength with a short curing time (5 min). The accumulation of nondegradable plastics in the environment exacerbates the severity of plastic pollution, and adhesives such as hot melts are no exception. In multilayer plastic products, hot-melt layers are inserted between plastic films to provide functionality and adhesion: however, these adhesives reduce the overall degradability of the product and adversely affect the physical and chemical biodegradation process, even if the underlying substrate is biodegradable. Given the wide range of its industrial applications, transitioning from petroleum-based hot-melt adhesive components to biomass-based alternatives that maintain adequate mechanical properties is essential. In this context, we introduce a novel biodegradable hot-melt adhesive system based on poly(1,4-cyclohexanedimethylene-co-isosorbide succinate-co-citrate) (PCISC), a complex polyester derived from isosorbide. This system incorporates biomass-derived monomers and demonstrates a high adhesion of 5.2 MPa, similar to that of conventional hot-melt adhesives. The structure of the PCISC with such a high adhesion is evaluated through rheological analysis, and the transition of the adhesive component upon curing is identified using two-dimensional correlation spectroscopy. The high adhesion is the result of a combination of factors, including the mobility of flexible components (1,4-cyclohexanedimethanol and succinic acid), the formation of a 3D network through crosslinking of rigid components (citric acid), and partial charge interactions between the oxygen-containing moieties in isosorbide and the substrate. Degradation and composting experiments using biodegradable poly(lactic acid) as a substrate demonstrate the potential of the PCISC as a successful alternative to conventional hot-melt adhesives.

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