Developing structure-property-performance relationships in recycled polymer thermoplastics to help enable the increased recycling of plastic waste

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In recent years, the issue of plastic pollution climbed further and further up the agendas of political parties, NGOs, charities and market leading businesses. Sustainability is more important than ever, and the so called 'war on plastic pollution' is at an all-time high, evidenced by the growing amount of governing legislature released on the issue, most notably the introduction of a plastic packaging tax in April 2022 by the UK government. A number of sectors rely heavily on the use of polymer thermoplastics including the automotive, food and beverage, construction, agriculture and consumer goods industries. With such a heavy reliance on these materials in day to day life, it is unrealistic to expect a complete, permanent shift away from the use of plastics in the short term. It is therefore vital to develop other waste management avenues. Currently, mechanical recycling offers the most viable and large scale solution to solve the issue of consumer plastic waste. With people choosing to make more environmentally minded choices in day to day life, the requirement of a circular plastics economy is more applicable than ever before. However, this progression requires in depth knowledge of how the incorporation of recycled plastic affects plastic product quality but also how products containing recycled material perform across their whole life-cycle. This research is critical in ensuring that the circular plastics initiative is achievable but also acts as a long term solution to the problem of plastic waste. The plastics which undergo recycling do not just include post-consumer plastic packaging but as this is the largest sector for polymer thermoplastics, research in this field holds the most immediate importance. Achieving high quality and performance of products made from high weight percentage recycled plastic is key in convincing the world to swap to recycled materials. Industry demands consistency and a high quality of material feedstock to ensure a high standard of final product - hence the current high demand on virgin plastics derived from fossil fuels. In order to meet these demands, the research carried out on recycled polymer thermoplastics is key in highlighting how the recycling process affects the structure and properties of materials. In depth information on how plastic materials change and perform following multiple recycling cycles is currently limited and extensive work in the field is required to help achieve a circular economy. This PhD research aims to develop a robust understanding of the link between structure, property and performance of polymer thermoplastics following extensive mechanical recycling. An understanding of these structure-property-performance relationships will help to drive the informed design of materials made from an entirely recycled feedstock. Currently, the issue of increasing recycled content in materials is only limited by the perceived 'lower quality' product that is presented. By changing this perception through research into how the performance of recycled material can be improved, the issue of heavy reliance on virgin plastic polymer is addressed. By providing informed design based research, industrial suppliers and manufacturers can consult this information during product design to ensure high concentrations of recycled material are included, facilitating a more widespread incorporation of recycled plastics into the consumer market.