High efficiency value-added bulk recycling of polymers by solid state shear milling

Lead Research Organisation: University of Bradford
Department Name: School of Engineering and Informatics

Abstract

Over 300 million tonnes of plastic is produced annually and this is expected to double over the next 20 years. Plastics have become vital materials in many aspects of everyday life but the generation of plastics solid waste (PSW) is becoming an increasing problem, for example 8 million tonnes of plastic waste finds its way into the oceans each year, having a huge impact on marine ecosystems. Some relatively clean and easy to separate types of waste plastics can be recycled economically, such as drinks bottles, and levels of recycling are increasing but many polymeric materials are much more difficult to recycle, for example composites containing different materials of polymers which cannot be re-melted such as rubber tyres and printed circuit boards. As such there is an urgent need worldwide to develop new technically and economically feasible methods to recycle these types of materials. This aligns with the concept of a circular economy which seeks to keep products and materials in use and design out waste and pollution.

Our joint UK-China team aims to develop an industrial scale continuous process to successfully recycle and re-manufacture currently difficult to recycle bulk waste streams, with high efficiency. A continuous milling process will be developed to break down solid polymeric waste into fine powders with controlled properties, which can then be reprocessed into value-added products. We will perform experiments to understand the mechanisms of the milling process and how these can be opitimised for particular waste streams. We will characterise the materials produced and examine different ways of turning these powders into useful, value-added products.

We combine unique skills and strengths of our Chinese and UK groups to address key issues facing both of our countries - effectively reducing the significant amount of plastic waste with efficient routes to re-use. This proposal builds on the highly successful research collaborations over the last decade between the world-class research laboratories of the Polymer IRC at Bradford and Sichuan University State Key Laboratory for Polymer Materials Engineering (SKLPME), an important and international award-winning part of our RCUK Bradford Science Bridges China platform.

Planned Impact

This programme focuses on the global issue of solutions for bulk difficult to recycle waste polymers. We aim to develop a recycling process which will convert waste materials into fine powders, and then to re-use these materials in new value-added products. As such there will be a clear national and international societal benefit in reducing the amount of waste plastic and an associated environmental benefit through reduction in the amount of waste which will be disposed of by landfill or leaked into waterways and oceans. This aligns well with the strategic priorities of the UK and China governments, evidence by recent legislation.

Our project aims to make high value added products from controlled manufacturing routes which exploit our underpinning scientific knowledge in a resource efficient manner, by significantly enhancing the properties or functionality of specific polymers, creating added value. The proposal aligns strongly with the Circular Economy agenda, which aims to promote recycling and re-use and move away from the traditional make-use-dispose economic model. This approach is now of first order importance in both the UK and China. There will be direct benefit to the UK and China economies, initially through our collaborator companies in the UK and China, who will be involved in the later stages of the programme to help bring the technology to full scale. More widely there will be an economic benefit to the recycling industry with the introduction of a new technology which will broaden the type and amount of waste polymer materials which can be recycled. There will be an associated benefit to machinery manufacturers and processors, through the introduction of a new manufacturing route.

There will also be a wider benefit to public perception related to polymers and how they are used. Polymers are too good to waste - they are chemically rich and made predominantly from oil which a rich source of energy but one which around 90% of is burned. It makes little sense to scrap polymers having invested energy in making these important and highly useful materials. We aim to disseminate the findings of our research widely through both scientific and general media (for example our research has previously been highlighted on Chinese television channel CCTV) in order to promote the recycling initiative.

Through the scientific underpinning of the research carried out within the programme, there will be direct benefits to the associated scientific and academic community. Research groups working in the fields of polymer recycling and waste management will benefit from understanding of the solid shear milling technology. The wider polymer research community will benefit from improved understand of the types of blended and composite materials which can be formed form recycled fine powders. Groups working in other fields such as the food and pharmaceutical industries will also benefit from exposure to the solid state shear milling, leading to new applications of the technology.

Publications

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Description One key finding from this award is that recycled natural rubber from shock absorbers was successfully combined with recyled cable waste to produce new thermoplastic vulcanisates (TPVs) - a material combining conventional plastic and rubber. This recycled formulation was found to have comparable properties to a virgin TPV material, which could provide a potential market from thermoset rubbers. A second key finding has been that we have been able to measure how the S3M recycling process breaks the crosslinks in the rubber and produces radicals at the ends of the broken chains. This is key to understanding and optimising the recycling step.
Exploitation Route Polymer recyclers could utilise the S3M process to recycle rubber and other difficult to recycle crosslinked polymers. We are actively discussing ongoing projects with collaborative partners.
Sectors Manufacturing, including Industrial Biotechology,Other

 
Description Royal Society Newton Advanced Fellowship
Amount £111,000 (GBP)
Funding ID NA150222 
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 08/2015 
End 08/2018
 
Description Joint International Laboratory for Polymer Micro Processing 
Organisation Sichuan University
Country China 
Sector Academic/University 
PI Contribution Establishment of a micro moulding facility in Sichuan, to mirror the (more extensive) facilities in Bradford, to develop further our collaborative research. Joint IP for conducting polymer products.
Collaborator Contribution Materials engineering expertise, including polymer nano composite products, especially for electrically conducting products. Joint IP for conducting polymer products.
Impact Joint publications. Joint IP
Start Year 2010
 
Description State Key Laboratories for Polymer Materials and Engineering, Sichuan University, China 
Organisation Sichuan University
Country China 
Sector Academic/University 
PI Contribution Our research team has longstanding links with the SKLPME at Sichuan. The current project is a joint UK-China funding award from EPSRC to investige plastics recycling using a novel solid state shear milling process. The contributions made by Bradford will be to develop new uses for the recycled polymeric materials and to better understand the mecahnics of the recycling process and its effect on material properties.
Collaborator Contribution SKLPME contributes to the current project as the inventors of the S3M process. Recycled materials are produced in China and samples sent to the UK for analysis and processing. SKLPME has well over a decade's experience in using S3M to engineer the properties of various materials.
Impact A number of jointly authored journal papers have been published between the two groups
 
Description PPS Presentation Hadj Benkreira 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact A conference presentation delivered by Professor Hadj Benkreira (S21-122-Acoustic and Thermal Insulation Materials from Elastomeric Waste Residues) at the Polymer Processing Society's Annual Conference in Turkey (May 26-30, 2019). The focus of the presentation was on recycling of waste residues into insulation materials using a novel extrusion process. The presentation also discussed recycling by solid state shear milling and addressed the possibiliy of materials from this waste stream being incorporated into insulation products. The talk was attended by academic and industrial researcher from around the world. Questions and discussion followed the talk.
Year(s) Of Engagement Activity 2019
URL http://www.pps-35.org/en/
 
Description Quoted in the press release by the British Plastics Federation for polymer recycling 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact promotion of the value of plastics materials in society, adding information to the debate about plastics waste.
Year(s) Of Engagement Activity 2019