The Design and Chemical Recycling of Furan-based Polymers Towards a Sustainable Circular Plastic Economy

: (Alternative Format Thesis)

Abstract

With the growing awareness of multiple related environmental crises, greater scrutiny has been directed towards the source and end-of-life of plastics. The work detailed in this thesis aims to explore potential solutions to these issues. Biobased polymers can offer an alternative to contemporary fossil-based plastics. Furandicarboxylic acid (FDCA) is a biobased alternative to terephthalic acid (TPA). Several biobased alternatives have been synthesised using FDCA, offering a range of thermomechanical properties suitable for direct application in packaging materials.

This thesis explores the chemical recycling of PEF, a biobased alternative to PET. Various catalysts for this reaction have been investigated, and Zn(Pro)2 was found to be remarkably active, whilst being benign, colourless, stable, and inexpensive. This high activity promoted an exploration into reducing the catalyst loading of the depolymerisation, to align with the loading used in the polycondensation reactions, which is 30 ppm. This was successful, and, to the best of our knowledge, we report the lowest loading that has been demonstrated for PEF depolymerisation. Following this, a one-pot, closed-loop chemical recycling has been demonstrated using Zn(Pro)2 for both depolymerisation and repolymerisation. Furthermore, the Zn(Pro)2 embedded in the polymer chains has been reactivated to depolymerise the polymer; after three cycles, there was no evidence of catalyst degradation. With the scale of the industrial production of PEF increasing rapidly, mixed feedstocks of PEF and PET are inevitable. This could present challenges to the current polymer separation infrastructure; sequential depolymerisation could solve this problem. The sequential depolymerisation of PEF and PET was demonstrated using Zn(Pro)2 under the same conditions, using only catalyst selectivity.

In addition to PEF, other polymers were explored as biobased alternatives to PBAT, a biodegradable plastic derived from fossil fuels. The thermal and mechanical properties of these polymers have been examined and compared to those of industrial PBAT. Several were highlighted as having the greatest potential as a ‘drop-in’ replacement for PBAT. The end-of-life considerations of biobased polymers are vital for a sustainable circular plastic economy, whether that is biodegradability or cyclic chemical recycling. Significant work is needed to alleviate the environmental impact of plastics; bio-sourcing, biodegradability, and chemical recycling will all be necessary to achieve this.

Date of Award	22 Apr 2026
Original language	English
Awarding Institution	University of Bath
Supervisor	Matthew Davidson (Supervisor) & Matthew Jones (Supervisor)