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

近年来，塑料污染问题越来越多地上升到政党、非政府组织、慈善机构和市场领先企业的议程上。可持续发展比以往任何时候都更加重要，所谓的“打击塑料污染的战争”正处于历史最高水平，这一点从越来越多的立法机构在这个问题上公布就是明证，最引人注目的是英国政府在2022年4月引入了塑料包装税。许多部门严重依赖聚合物热塑性塑料的使用，包括汽车、食品和饮料、建筑、农业和消费品行业。在日常生活中如此严重地依赖这些材料，指望在短期内完全、永久地放弃使用塑料是不现实的。因此，开发其他废物管理途径至关重要。目前，机械回收为解决消费塑料垃圾问题提供了最可行和最大规模的解决方案。随着人们在日常生活中选择更环保的选择，循环塑料经济的要求比以往任何时候都更适用。然而，这一进展需要深入了解加入回收塑料如何影响塑料产品质量，以及含有回收材料的产品在整个生命周期中的表现。这项研究对于确保循环塑料倡议是可实现的至关重要，同时也是塑料废物问题的长期解决办法。回收的塑料不仅包括消费后的塑料包装，而且由于这是聚合物热塑性塑料的最大部门，这一领域的研究具有最直接的重要性。实现高质量和高性能的由高重量百分比的再生塑料制成的产品，是说服世界改用再生材料的关键。行业要求原料的一致性和高质量，以确保最终产品的高标准-因此目前对从化石燃料中提取的原始塑料的需求很高。为了满足这些需求，对回收聚合物热塑性塑料的研究是突出回收过程如何影响材料结构和性能的关键。关于塑料材料在多次循环后如何变化和性能的深入信息目前有限，需要在该领域开展广泛的工作，以帮助实现循环经济。这项博士研究的目的是深入了解聚合物热塑性塑料在广泛的机械回收后的结构、性能和性能之间的联系。了解这些结构-性能-性能关系将有助于推动由完全回收的原料制成的材料的知情设计。目前，增加材料中可回收含量的问题仅限于被认为质量较低的产品。通过研究如何改善回收材料的性能来改变这种看法，解决了严重依赖原始塑料聚合物的问题。通过提供基于设计的知情研究，工业供应商和制造商可以在产品设计过程中参考这些信息，以确保产品中包含高浓度的回收材料，从而促进回收塑料更广泛地进入消费市场。

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.