Plastics: Vilify or Deify?
Plastics are big business. Around 322 million tonnes of plastics are produced globally each year. In the UK, plastics manufacturing accounts for £25.5bn – 1.5% of GDP, and it’s the third largest manufacturing sector in the UK, ahead of the pharmaceutical, paper, nuclear and steel sectors.
However, the amount of plastic waste in the ecosystem has been much in the news recently, and as a result, this class of materials has received a lot of bad press. But is the criticism of these materials really justified, or is it how these materials are disposed of that is causing all the problems?
Modern plastics, or more accurately polymeric materials, have been in existence for over 150 years, having been invented in England by Alexander Parkes, giving us Parkesine. Since then, a huge variety of polymers have been developed to meet the needs of a growing number of applications, often with specialist mechanical, physical and chemical properties.
Along with specialist properties, polymers bring the benefits of light weight, low energy consumption manufacture, environmental stability, resource-efficiency, hygiene, shatter-resistance.
They are used in virtually every industry known to man, from electronics to food production, automotive to medical, agriculture to power generation. They improve fuel efficiency in cars, ensure safe transit of both clean and waste water, keep food fresh and enable life-saving surgery. There can be no denying that the world wouldn’t function as it does without plastics.
So what’s the problem? Perhaps it is down to the uncertainty around disposal and recycling. There are so many symbols embossed in plastics and different governments and local authorities have different policies around recycling. There’s no wonder people are confused. It is just easier to throw plastics away with the rest of your rubbish. And then stability of plastics becomes a problem as they don’t break down in the environment for a long time.
But recycling is a genuine option. Some feel that it is just a false promise so people feel good about themselves, but recycling is actually done. One of the biggest problems that exists is the country’s capacity for plastics recycling. In the UK we have can recycle 360,000 tonnes of plastics each year, yet the government claims that we recycle over 1 million tonnes of plastic. This is because so much is sent overseas for processing – it is therefore out of our hands and outside our control.
Moreover, new methods of treating waste plastics are being developed. For example, Recycling Technologies (www.recyclingtechnologies.co.uk) has developed a process based on thermal cracking that integrates with traditional mechanical recycling activities in order to tackle the hard-to-recycle plastic waste. They reckon that this process could increase current recycling rates by up to 90%.
The process of thermal cracking breaks down hard-to-recycle plastics, including things like crisp packets, films, and black trays to convert them back into the oil that they were originally made from. This oil is then fed back into the plastics industry thereby forming a circular economy.
There’s plenty of discussion around the what can be done with plastic waste, and far more that we can hope to cover in this post. Moreover, there’s not a clear answer to the question posed in the title of the article. Granted, plastics are causing environmental problems. However, there are people who are trying to repair the damage already caused, and mitigate against it getting worse.
You may be interested the following links:
Hatfield Memorial Lecture
December sees the 66th Hatfield Memorial Lecture take place in the Octagon in Sheffield. This year’s lecture, which takes place on Tuesday 11th December, will be given by Dr Jeffrey Wadsworth, former President and CEO of the Battelle Memorial Institute.
Dr Wadsworth’s presentation will be entitled ‘Connections and Pathways evolving from a Metallurgical Education at Sheffield University’. As an alumnus of the Department (BEng, PhD, DMet), he went on to join Stanford University, initially as a Postdoctoral Research Associate, then a Research Associate and finally a Lecturer.
From Stanford, his career took him to Lockheed Missiles & Space Company, The University of California and then to the Battelle Memorial Institute where he took on a number of different roles. He was President and CEO there from 2009 to 2018.
On 22nd August 1944, the University of Sheffield agreed to be the Trustees of a fund to establish a lecture series “as a memorial to the late Dr William Herbert Hatfield FRS and as a mark of appreciation of his distinguished work in connection with research into the qualities and uses of metals and allied branches of science”.
William H Hatfield (1882-1943) studied metallurgy at University College, Sheffield, under Professor John Arnold, who held the Chair of Metallurgy from 1889 until 1919. In 1902 Hatfield won the Mappin Medal and in 1913 was awarded the degree of Doctor of Metallurgy.
Author of numerous technical papers on many branches of metallurgy, in particular rust, cast iron and acid and heat-resistant steels, Hatfield succeeded Harry Brearley Director of the Firth-Brown Research Laboratories in 1916, where he developed several stainless steel compositions, including 18/8 stainless steel, and later joined the Board of Messrs Thomas Firth and John Brown Limited, and was a member of many scientific societies, including being elected Fellow of the Royal Society in 1935.
To book your free tickets for this event, please visit the website: www.sheffield.ac.uk/materials/hatfield
Student Visits to Industry
The first week in November is traditionally Skills Week for our First Years. As well as providing them with some of the essential skills they will need during their time at University, we arrange visits to a number of different organisation that utilise the skills of materials scientists and engineers.
This year, groups of students visited Arconic Forgings and Extrusion, British Steel, Guardian Glass and H.J. Enthoven and Sons. They heard from materials scientists and engineers working in industry and got to see inside manufacturing facilities. For many of them, this will be the first time they have come face to face with heavy industry, and get a picture of the types of career that may be open to them in the future.
Students visiting the Arconic Engines site in Derbyshire witnessed the production of some high-end aero engine and industrial gas turbine components developed for the next generation of quieter, more fuel-efficient aero engines and cleaner power generation.
The Scunthorpe site of British Steel is home to three manufacturing facilities: wire rod, rail and steel sections, all of which were included in the tour. Particular highlights were the continuous steel production process and the medium section mill.
Guardian Glass showed off both the float and lamination lines, informing students how glass is manufactured on an industrial scale.
At H.J. Enthoven students found out about how vehicle and industrial lead-acid batteries are recycled. Principally, H.J.Enthoven are lead smelters, but the majority of their lead comes from batteries. On top of extracting the lead, they are also able to recycle the plastic casing, and convert the sulphuric acid to gypsum which is used in agriculture and sugar production.
At all four sites, students engaged with highly knowledgeable engineers, asking questions which were answered in a way they could understand.
These visits are an essential part of a student’s journey, and often what they see will stay with them for the rest of their life – they can be really influential. You can often speak to people who are well and truly established in industry who still remember the first time they walked on the shop floor, be that as an apprentice, a student or during their first day on the job.
We would like to thank everyone involved at the host companies for making us very welcome and giving interesting and informative tours.
We are always keen to establish new industrial relationships. If you think that you can provide a fulfilling visit for a group of students, please contact Dr Plato Kapranos.
Next Generation Aerospace Materials
The materials used for high-temperature aero-engine components are typically manufactured from nickel-based (Ni-based) superalloys. This is because of their high-temperature stability, creep and fatigue resistance and reduced risk of degradation due to oxidation and corrosion.
However, new targets have been set for performance and environmental metrics for future aero engines which may push the properties of nickel-based superalloys to their limits.
Research being carried out by Professor Panos Tsakiropoulos is hoping to identify a new range of alloys that could outperform existing alloys, allowing engines to run with greater thermal and propulsive efficiencies.
The aerospace industry has set new property goals for new ultra-high temperature alloys. These must have:
- Room temperature fracture toughness above 20 MPa(m)½
- Less than 1% creep in 125 h at 1473 K and stress of >170 MPa
- Oxidation life at 1588 K equal to that of second generation nickel-based superalloys at 1423 K
- Short-term oxidation goal for uncoated material to survive under typical engine conditions with a loss of material less than 200 µm thickness in 10 h at 1643 K
- Long-term oxidation goal for a loss of material less than 25 µm thickness in 100 h at 1588 K
The materials under investigation are based on refractory metal intermetallic composites (RMICs), which offer a balance of the properties required in critical applications in future aero engines.
Niobium silicide based alloys (Nb-silicides) have been identified as a potential substitute for Ni-based superalloys, as they can surpass the fracture toughness and creep property goals for the new materials, and can be close to the oxidation goal. Moreover, the substitution of Nb silicide based aerofoils for Ni-based superalloy aerofoils could result in a reduction of rotor weight of more than 20%.
Professor Tsakiropoulos’s recent papers in Materials discuss the alloy design and selection, and alloying behaviour and properties of Nb5Si3 as an alternative to Ni-based superalloys. Read them here:
- On Nb Silicide Based Alloys: Alloy Design and Selection
- Alloying and Hardness of Eutectics with Nbss and Nb5Si3 in Nb-silicide Based Alloys
- Alloying and Properties of C14–NbCr2 and A15–Nb3X (X = Al, Ge, Si, Sn) in Nb–Silicide-Based Alloys
- On the Alloying and Properties of Tetragonal Nb5Si3 in Nb-Silicide Based Alloys
Professor Tsakiropoulos is Professor of Metallurgy and POSCO Chair in Iron and Steel Technology in the Department of Materials Science and Engineering at the University of Sheffield.
After graduating in Mining Engineering and Metallurgy at the National Technical University of Athens, he undertook postgraduate studies and research at the University of Sheffield. His first academic role was at the University of Surrey. He rejoined the University of Sheffield in 2006.
His research interests are in the design and development of alloys and composites for the aerospace, energy and transport industries via process-microstructure-property studies.
New Research Centres
Advanced Metals Processing is set to benefit from multi-million pounds of investment into three new advanced engineering research centres opened recently at the University of Sheffield, including the Royce Translational Centre (RTC) – part of the Department of Materials Science and Engineering.
The RTC is home to Royce@Sheffield and the metals research group of AMRC, the National Metals Technology Centre (NAMTEC). Royce@Sheffield is one of the ‘spokes’ of the Henry Royce Institute, the UK national institute for advanced materials, and its work at the RTC is accelerating the benefits to industry in the field of Advanced Metal Processing.
Northern Powerhouse Minister, Jake Berry MP, and Mayor of the Sheffield City Region, Dan Jarvis MP, officially opened the centres which aim to boost Sheffield City Region’s reputation as a hub for advanced engineering and industrial digital technologies.
Working with companies to help develop new technologies, the centres will use the transformational power of research to cut costs and lead times which will revolutionise industrial processes.
Read the full story here.
What’s the Matter?
So, you think you know your materials? Can you identify the picture above? Post your comments below, or Tweet us @msesheffield with the hashtag #WhatsTheMatter.
Last month’s picture was of solidified glass which had been poured through a grid when making Prince Rupert’s Drops.
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