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Technology for improving the recycling of plastics and composites

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Plastics and composites aren’t recycled as often as we might wish, as a result of a lack of facilities, the right technologies not yet existing or not being profitable, or hazardous waste deposits. IMT Nord Europe have been working in partnership with manufacturers to develop and improve the available technologies.

Plastics and composites get a lot of bad press, but it is hard to do without them for many objects we use every day, including our cars. In order to minimise their polluting effect, they must be recycled, but this is complicated from both a technological and an economic perspective. Two researchers from IMT Nord Europe are seeking to improve processes with a view towards industrialisation.

In order to recycle plastic, outlets have to be found for these recycled materials. One of the main stumbling blocks is the presence of pollutants, including volatile organic compounds (VOCs), which can produce unpleasant and even toxic odours. There are also very strict standards governing the emission of VOCs and odours in vehicle passenger compartments. Marie-France Lacrampe, a researcher at IMT Nord Europe, is working on a solution which is striking in its simplicity: water-assisted extrusion.

Eliminating odours

Extrusion is a process traditionally used to manufacture objects made from plastic, involving pushing a doughy material through a die of the desired cross-section. Water is injected into the extruder and the steam washes the plastic, extracting the majority of any VOCs. “A few changes need to be made to the extruder”, explains Marie-France Lacrampe. Professor Lacrampe is working alongside three industrial partners and another laboratory, with the industrial pilot expected to be operational within two years.

In order to further improve this process, the researcher intends to combine water with supercritical CO2 – pressurised CO2 which becomes a highly effective solvent. The advantage is that it removes different molecules from those removed using water.

Process organisation and eco-design

Efficient recycling normally starts with designing materials which are easy to recycle. This is particularly true when it comes to food packaging, which is often made using several different materials (cartons, thermoformed tubs or re-heatable pouches, for example). “The ideal solution is to mix compatible polymers which can then be integrated into existing recycling processes”, explains Marie-France Lacrampe.

When it comes to recycling, it’s not just a question of the technology used, but how the whole process is organised. Waste must be used as locally as possible in order to cut transport and logistics costs, requiring intelligent analysis and handling of flows.

“If we want to boost recycling rates then we have to tackle what we don’t know how to do. This is particularly true for small quantities (hazardous waste deposits) and materials which we are unable to recycle or aren’t very good at recycling such as opaque PET (the plastic used to make milk bottles, for example). We are working on recycling small quantities through additive manufacturing, the industrial version of 3D printing, extruding them again with additives so that they be reused.” 

Composites – rarely recycled

If recycling plastics isn’t always easy, just imagine what it must be like for composites, materials which are generally comprised of glass or carbon fibre and a polymer matrix. A modern aircraft such as the Airbus A350 is half-made of composites, which are used in whole sectors of industry, from transport (not just aircraft, but also cars, boats and bikes) to electronics, leisure and wind power.

Once they have reached the end of their life, composites are primarily burned in order to produce energy, which isn’t ideal from either an environmental or an economic point of view. “Solutions are being developed in the aeronautics sector to recover carbon fibres”, points out Mylène Lagardère, who is also a researcher at IMT Nord Europe. “It is mostly carbon-based composites which are used in aeronautics, which are more “noble”, making them easier to recycle.” Technology for recycling fibreglass composite does exist, but it is not yet profitable.

Developing more affordable methods

There are two possible processes for recovering fibres: a chemical process in which the matrix is dissolved in a solvent (allowing the matrix to be reused) and a thermal process in which the matrix is damaged. Matrices themselves are either thermoplastic, meaning they can be melted, or thermosetting, meaning they are damaged when heated. As a result, as Mylène Lagardère explains, “each fibre-matrix combination is processed differently,  with a different process for each product.” This is what makes recycling composites so complicated. The purer the material, the easier it is to recycle.

As we can see, improving recycling is essential, and research into this subject is rightly being prioritised. “Our aim is to develop methods which are both simple and affordable”, explains Mylène Lagardère. “Our basis is the industrial problem: if we have a deposit of materials with certain properties, then we can recover a recycled material with such properties.” The issue is that, during recycling, the properties of the material always deteriorate, as the fibres are shortened.

The recycling of composites is still very much in its infancy, but a few processes are starting to emerge,  whether in water sports, where the association APER – funded by an eco-tax on new crafts – dismantles abandoned boats, or in the wind power industry. The automobile industry is also having to adapt, with legislation requiring recycled materials to be used in the production of new vehicles.

Cécile Michaut

Large quantities of composites for recycling on the horizon?

10 million tonnes of composites are produced each year worldwide, and the market is continuing to grow at a rate of 5% year on year. But recycling is set to really accelerate: composites whihe arrived on the market 20 to 30 years ago are now reaching the end of their lives. 50,000 tonnes of wind turbine rotors will need to be recycled between 2021 and 2022. In 2023, 25,000 boats, three-quarters made from composites, are to be dismantled. 4,000 railway carriages are also awaiting dismantling. Although resources remain limited (15,000 tonnes of production waste and 7,000 tonnes of materials at end of life in 2017), significant growth is anticipated. Processes mut develop and organise in order to become sustainable.

Also read on I’MTech

“We must work now to recycle composites”
Recycling carbon fibre composites: a difficult task

Corenstock Chair: a Trial Cylinder for the Heating Industry

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As 2021 begins, IMT and elm.leblanc launched the Corenstock Industrial Chair to address issues in energy and digital transition in the domestic heating industry. What is the objective? Within four years, to present a demonstrator for the hot water tank of the future: more resistant, efficient and durable. Behind this prototype lies the development of new economic models for the global transformation of the industry.

The principle of Corenstock Chair (Lifecycle design & systemic approach for energy efficiency of water heating and storage devices), launched in early 2021, is to consider an equipment of the everyday-life to be optimized and used as a model for the transformation of an entire industry. The objective is to present within four years a demonstrator for an innovative hot water tank, more energy efficient, more sustainable and more connected to its users. The project is however not limited to the design of a new domestic hot water tank: it covers the transition problematics of the heating industry as a whole. In line with new business models development, the underlying interest is to redefine the dedicated design methodologies, to generalize sustainable production and end-of-life recovery to implement new economic balances.

The Chair lead by IMT is co-funded in equal parts by the ANR (French Research National Agency) and elm.leblanc, a company specialized in the production of water heaters and boilers. The project relies on the complementary skills of the academic and industrial partners. “We are exploring two key avenues: on the one hand, technological innovation, involving design, materials and smart controls issues” says Mylène Lagardère, a researcher at IMT Lille Douai. She holds the Corenstock Chair, which is jointly coordinated with Xavier Boucher, a researcher at Mines Saint-Etienne. He is responsible for the operational management of the Chair and adds:  “on the other hand, we are working on innovation capabilities, decision-making support for new design methods and the transformation of the production chain together with the company organization”. The two researchers mention that they have “established a trusting and long-term partnership with elm.leblanc, with the goal of pursuing future projects in this area”.

What would be the tank of the future?

“The goal is to improve the energy efficiency of a product that everyone owns at home,” says Mylène Lagardère. Moreover, this equipment is crucial for various thermal systems; whether gas, oil or electricity is used as a source of energy, all of us need to store domestic hot water. To find ways to improve thermal performances, or to select materials to make the cylinder as efficient as possible, involves a significant amount and diversity of research actions. The Chair will thus benefit from the recruiting of 5 PhD students, 4 post-docs and 3 engineers.

Product durability is one of the main areas for improvement. In this sense, predictive maintenance is promising. The use of smart sensors is essential, both to better evaluate the tank performances and to foresee necessary repairs before it breaks down. Mylène Lagardère specifies that the objective is to have “the best compromise between each component, each function of the tank, while taking into account its integration in the environment and the management of the end-of-use”.

Behind the project’s targeted product, general reflection on the entire product life cycle is emerging and address the resources needed for its production, the product durability or the management valorization at the end of use. The project advancements on the improvement of the value chain are expected to be generalized to the entire industry :“The work conducted on the hot water storage tank tank is the entry point for more general work on the economic model itself,” says Xavier Boucher, and these questions are completely integrated in the Corenstock Chair program.

Evolution of the industry

Xavier Boucher emphasizes that “these hot water storage tanks are at the heart of a variable system and a transformation of this sector involves industrial actors at different levels, including the customers as well the maintenance providers”. As a result, the relations to the customers will naturally be modified. The two researchers mention: “this is part of a fairly strong phase of transition in the industries business. It is no longer simply a matter of selling a hot water storage tank, but of including the tank in a multi-actor performance contract.”

From the point of view of companies, they now need to develop customer loyalty and sustainability. “These different levers are necessary to establish a win-win relationship between the customer and the manufacturer,” says Xavier Boucher. Intelligent management offers opportunities to improve energy costs, reduce maintenance costs, and ultimately reduce the final energetic bill. This also reduces for manufacturing and maintenance internal costs.

Mylène Lagardère reports that they aim “to enlighten decision-makers on their economic transformation, particularly through the research for more sustainable indicators”. Her colleague from Saint-Etienne adds “virtualization proves to be a key tool in planning this transition”. The Corenstock Chair assumes the role of simulator of this transformation by observing the behavior of users and various partners. The project combines several routes of innovation, whether aiming towards digital, networking or what is known as digital servicing. This is a strategy converging towards a long-term customer relationship through digital services. “The challenge lies in the evolution of value creation mechanisms,” says Mylène Lagardère.

The Chair is also driven by the dissemination of the results generated and knowledge acquired towards students and future engineers in the field, but also towards the technical and innovation staff of elm.leblanc through professional trainings. Xavier Boucher notes “there are two aspects of training: short modules to increase professional skills, and a specialized master’s degree to integrate more largely the solutions into the industrial framework.” One of the objectives of the specialized master’s degree is to mutualize the skills of each school to encourage interaction between the different expertise domains required.

“Generally speaking, the Chair cannot be simply reduced to technological innovation. On the contrary it covers a global reflection on what the industry of the future is” says Xavier Boucher. This includes facilitating collaboration and opening among different sectors: industrial, technological, and economic. This collaboration is essential to ensure that these transformations are a lasting part of tomorrow’s industry. “The Chair marks what elm.leblanc is building with IMT: a new way of approaching these innovation processes, through a strong collaboration and a relationship of trust to increase the capacity for innovation,” concludes Xavier Boucher.

Tiphaine Claveau.