Lascala, 3D printing, additive manufacturing

Taking 3D printing to the next level

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At the beginning of 2018, IMT Lille Douai unveiled an additive manufacturing platform dedicated to manufacturing large-scale parts: LASCALA. This equipment is a worldwide innovation.  Its capacity to use any type of polymer even enables it to print 3D composite parts measuring several meters. The scientific challenge has been successfully met and has opened up a whole new realm of possibilities for manufacturers.

 

Do you think you know what a 3D printer is like? With LASCALA*, the additive manufacturing platform, you are in for a surprise. Forget a printhead measuring a few square centimeters sliding along a rod the length of a school ruler. With its 6-axis industrial robot spanning over 2 m and a maximum load capacity of 150 kg, LASCALA is no desktop 3D printer. Located in the facilities of IMT Lille Douai, the printer is destined to take polymer-based additive manufacturing to the next level of its industrial potential. Up until now this design technique was only available for small-scale plastic parts of a few cubic centimeters. With LASCALA, the 3D-printed parts could reach dimensions of several meters and be fiber-reinforced.

The platform has been functional since January 2018 and is a major innovation in the sector. Using a 6-axis robot alone significantly distinguishes LASCALA from the solutions implemented on other additive manufacturing systems. The logical choice would have been to use a traditional construction with a gantry and printhead moving along it. In other words, reproducing a larger scale of what already exists. Yet the robotic arm introduces the advantage of 7 degrees of freedom: 6 axes of rotation and 1 plane of movement. The printhead attached to its end can therefore rotate in every direction and move in every direction in space.

https://www.youtube.com/watch?v=7WH9iQg3yFU

Another convincing argument: long-term, this system is more technologically advantageous. “Usually a 3D printer superimposes planar layers,” explains Jérémie Soulestin, a researcher in materials science at IMT Lille Douai in charge of LASCALA. This causes a staircase effect on the edges of the parts: when a smaller layer is added to another, they form a step.  “With the robot, we will be able to develop curved layers, which will limit this effect,” he continues. This new construction method using curved layers has a positive effect on the aesthetic aspect as well as on the parts’ mechanical properties.

The move towards 3D printing for composites

While LASCALA is the first platform of its kind, the team at IMT Lille Douai is not the only one to have attempted large-scale 3D printing. Local Motors, for example, was the first company to offer a car—named Strati— made of polymer materials entirely produced using 3D printing. Yet none of the attempts to date have developed machines flexible enough to deposit any type of polymer material in any direction. Most of the time, the manufacturer of the 3D printer even limits the materials that are compatible with the 3D-printing process. LASCALA, on the other hand, offers free-form design in terms of the choice of plastic materials. “This argument and the idea of not being limited by this constraint are what convinced us to develop our own machine,” Jérémie Soulestin explains.

La Strati de Local Motors, un roadster prototype d’impression 3D de grande taille. Son aspect met en évidence l’un des problèmes à résoudre pour la fabrication additive de cette dimension : les effets d’escalier.

The Strati by Local Motors, a roadster prototype produced using large-scale 3D printing. Its appearance highlights one of the problems to solve in additive manufacturing at this scale: the staircase effect.

And because they were now the masters of the machine they designed, the researchers were able to take their original idea a step further. The printhead contains an extrusion device: “an endless screw in a heated barrel pushes the material through a nozzle that deposits a melted filament,” the researcher explains. The shape of the nozzle can be adapted to deposit the filament in different ways and enables to improve the part quality. In addition, two materials can be deposited within the same melted filament, thus creating a material with a polymer core and an outer skin made of another plastic.

Finally, the researchers insisted on designing a platform that would be adapted to the industrial uses of the future. The printhead is therefore capable of depositing fiber-reinforced polymers. LASCALA can therefore use 3D-printing to produce composite materials with short, chopped fibers and even with continuous fibers.  This special feature makes the platform worthy of being presented at the largest annual global meeting in the field of composites: the JEC World show, which will be held from March 6-8 in Paris.  The equipment’s capabilities cannot help but attract manufacturers. “We knew that the aeronautics sector would be interested, but we were surprised the automotive sector contacted us so quickly,” says Jeremie Soulestin. LASCALA will still need nearly a year to transition from “functional” to fully “operational”. One year of optimization before this technical innovation begins producing impressive projects that will prepare the manufacturing processes of the future.

 

*LASCALA, LArge SCALe plAstics & composites 3D printing, receives support from the Hauts-de-France Region and is co-funded by the European Union

Also read on I’MTech:

Additive manufacturing, a process for the industry of the future

 

Photomécanique Jean-José Orteu

What is photomechanics?

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How can we measure the deformation of a stratospheric balloon composed only of an envelope a few micrometers thick? It is impossible to attach a sensor to it because this would distort the envelope’s behavior… Photomechanics, which refers to measurement methods using images and computer analysis, makes it possible to measure this deformation or a material’s temperature without making any contact. Jean-José Orteu, a researcher in artificial vision for photomechanics, control and monitoring at IMT Mines Albi, explains the principles behind photomechanical methods, which are used in the aeronautics, automotive and nuclear industries.

 

What is photomechanics?

Jean-José Orteu: We can define photomechanics as the application of optical measurements to experimental mechanics and, more specifically, the study of the behavior of materials and structures. The techniques that have been developed are used to measure materials’ deformation or temperature.

Photomechanics is a relatively young discipline, roughly 30 years old. It is based on around ten different measurement techniques that can be applied to both a nanoscale and the dimensions of an airplane and to both static and dynamic systems. Among these different techniques, two are primarily used: the digital image correlation (DIC) method for measuring deformations, and the infrared thermography method for measuring temperatures.

 

How are these two techniques implemented?

JJO: For the DIC, we position one or several cameras in front of a material: only one for a planar material that undergoes in-plane deformation and several for the measurement of a three-dimensional material. The cameras film the material as it is deformed under the effect of mechanical stress and/or heat. Once the images are taken, the deformation of the material is calculated based on the deformation of the images obtained: if the material is deformed, so is the image.  This deformation is measured using computer processing and is extrapolated to the material.

This is referred to as the white light method because the material is lit by an incoherent light from standard lighting. Other more complex photomechanical techniques require the use of a laser to light the material: these are referred to as interferometric methods.  They are useful for very fine measurements of displacements in the micrometer or nanometer range.

The second most frequently used technique in photomechanics is infrared thermography, which is used to measure temperatures. This uses the same process as the DIC technique, with the initial acquisition of infrared images followed by the computer processing of these images to determine the temperature of the observed material. Calculating a temperature using an image is no easy task. The material’s thermo-optical properties must be taken into account as well as the measuring environment.

With all of these techniques, we can analyze the dynamic evolution of the distortion or temperature. The material is therefore analyzed both spatially and temporally.

photomécanique Jean-José Orteu

photomechanics, Jean-José Orteu

Stereo-DIC measurement of the deformation field of a sheet of metal shaped using incremental forming

 

What type of camera is used for these measurement methods?

JJO: While camera resolution influences the quality and precision of the measurements, a traditional camera can already obtain good results. However, to study very fast phenomena, such as the impact of a bird in flight on an aircraft fuselage, very fast cameras are needed, which can take 10,000, 100,000 or even 1,000,000 images per second! In addition, for temperature measurements, infrared-sensitive cameras must be used.

 

What is the value of optical measurements as compared to other measurement methods?

JJO: Traditionally, a strain gauge is used to measure the deformation of a material. A strain gauge is a sensor that is glued or welded to the surface of the material to provide an isolated indication of its deformation. This gauge must be as nonintrusive as possible and must not alter the object’s behavior. The same problem exists for temperature measurements. Traditional techniques use a thermocouple, a temperature sensor that is also welded to the surface of the material. When the sensors are very small compared to the material, they are nonintrusive and therefore do not pose a problem. Yet for some applications, the use of contact sensors is impossible. For example, at IMT Mines Albi we worked on the deformation of a parachute when it inflates. But the canvas contained a lining only a few micrometers thick. A gauge would have been difficult to glue to it and would have greatly disrupted the material’s behavior. In this type of situation, photomechanics is indispensable, since no contact is required with the object.

Finally, both the gauge and the thermocouple offer only isolated information, only at the spot where the sensor is glued. You won’t get any information concerning a spot only ten centimeters away from the sensor. However, the problem in mechanics is that, most of the time, we do not know exactly where we will need information about deformation or the temperature. The risk is therefore that of not welding or gluing the sensors in the spots where the deformation or temperature measurement is the most relevant. The optical methods also offer field information: a deformation field or temperature field.  We can therefore view the material’s entire surface, including the areas where the deformation or temperature gradient is more significant.

 

Photomécanique Jean-José Orteu

Photomécanique Jean-José Orteu

phtomechanics

Top, a material instrumented with gauges (only 6 measurement points). Middle, the same material to which speckled paint has been added to implement the optical DIC technique. Bottom, the deformation field measured via DIC (hundreds of measurement points).

What are the limitations of photomechanics?

JJO: In the beginning, photomechanical methods based on the use of cameras could not measure surface deformations. But over the last five or six years, an entire segment of photomechanics has begun to focus on deformations within objects.  These new techniques require the use of specific sensors, tomographs. They make it possible to take X-ray images of the materials, which reveal core deformations after computer processing. The large volumes of data this technique generates raise big data issues.

In terms of temperature, the core measurement without contact is more complicated. We recently defended a thesis at IMT Mines Albi on a method that makes it possible to measure the temperature in a material’s core based on the fluorescence phenomenon. The results are very promising, but the research must be continued to obtain industrial applications.

In addition, despite its many advantages, photomechanics has not yet fully replaced strain gauges and thermocouples. In fact, optical measurement techniques have not yet been standardized. Typically, when measuring a deformation with a gauge, the method of measurement is standardized: what type of gauge is it?  How should it be attached to the material? A precise methodology must be followed. In photomechanics, whether in the choice of camera and its calibration and position, or the image processing in the second phase, everything is variable, and everyone creates his or her own method. In terms of certification, some industrial stakeholders therefore remain hesitant about the use of these methods.

There is also still work to be done in assessing measurement uncertainties. The image acquisition chain and processing procedure can be complex, and errors can distort the measurements in any stage. How can we ensure there are as few errors as possible? How can we assess measurement uncertainties? Research in this area is underway. The long-term goal is to be able to systematically provide a measurement field with a range of associated uncertainties. Today, this assessment remains complicated, especially for non-experts.

Nevertheless, despite these difficulties, the major industries that need to define the behavior of materials, such as the automotive, aeronautics and nuclear industries, all use photomechanics. And although progress must be made in assessing measurement uncertainties and establishing standardization, the results these optical methods achieve are often of better quality than those of traditional methods.

 

TechDay, fabrication additive, additive manufacturing

What are the latest innovations in additive manufacturing?

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Although additive manufacturing is already fully integrated into industrial processes, it is continuing to develop thanks to new advances in technology. The Additive Manufacturing Tech’Day, co-organized by IMT Mines Alès and Materiautech – Allizé-Plasturgie, brought together manufacturers and industry stakeholders for a look at new developments in equipment and material. José-Marie Lopez Cuesta, Director of the Materials Center at IMT Mines Alès, spoke with us about this event and the latest innovations in 3D printing.

 

What were the objectives of the Additive Manufacturing Tech’Day?

This event, which brought together nearly ninety people, was co-organized by IMT Mines Alès and Materiautech, which is network of institutions that organizes educational, technological and business activities on different plastic materials and processes for manufacturers and students. This provided an opportunity for several industry stakeholders to present their new developments in materials, tools and software through a series of conferences and demonstrations.

For us as researchers, the main objective of this tech day was to present our strategy in this area and build partnerships, particularly with manufacturers, with the aim of initiating projects.

 

What research projects are you currently working on in the area of additive manufacturing?

We have had the machines in the laboratory for a little over a year now, and we are beginning to launch projects. We just started a project focused primarily on engineering, for manufacturing an orthopedic brace, a medical corset. We also have a project in the initial development stages on SLS (Selective Laser Sintering) additive manufacturing technology, in partnership with a company based in Alès, and with potential funding from the region.

 

Has industry successfully taken advantage of 3D printing technologies?

Yes, absolutely. Today, 3D printing is seen as one of the major advanced manufacturing technologies.  It is developing very quickly, with the emergence of new machines and new materials. As a laboratory, we want to be a part of this development.

For manufacturers, the goal is to develop new products with original shapes that could not be formed using traditional processes, while ensuring that they are durable and possess the mechanical properties required for their use.

Although it was initially used for rapid prototyping, 3D printing is now being used in all industrial sectors, particularly in the aerospace and medical industries, due to the complexity of the parts they produce. In the medical industry, additive manufacturing is used to produce prostheses and orthoses, as well as intracorporeal medical devices such as stents, mesh inserted in the arteries to prevent clogging, and surgical screws. Manufacturing these parts requires the use of biocompatible and approved materials, an aspect mastered by certain companies, which produce these materials as polymer powders or wires adapted to additive manufacturing.

In the aeronautics industry, this technology is used especially for printing very specific parts, for example for satellites. It allows parts to be replaced, especially metallic parts produced using molding techniques, by lighter and more functional 3D-printed parts. These parts are redesigned based on the innovations made available through additive manufacturing, which means they can be produced using as little material as possible, resulting in lighter parts.

Finally, 3D printing is perfectly adapted to manufacturing complex replacement parts for older devices that are no longer on the market. We are moving towards production means that are increasingly customized and flexible.

 

In additive manufacturing, what are the latest innovations in materials?

Materials are being developed that are increasingly complex. Nano-composites, for example, which are plastic materials comprising nanometric particles, offer improved mechanical properties, heat resistance and permeability to gas. New bio-composites are also being developed. These materials are composed of bio-based components and have a lower environmental impact than synthetic polymers. Other new materials present new features, such as fireproofing. We are seeking to enter these areas based on the areas of expertise that are already present at the Materials Center of IMT Mines Alès.

 

Beyond new materials, are there any new machines that have introduced significant innovations?

In this field, innovations appear very quickly: new machines are constantly coming out on the market. Some are even able to print several types of materials at the same time, or parts with increasingly complex symmetry. We also see greater precision in the components, and improved surface conditions.

In addition, one of the main issues is the speed of execution: enormous progress has been made in printing objects at greater speeds. This progress is what made it possible for 3D printing to expand beyond rapid prototyping and start being used for manufacturing production parts. In the automotive industry, for example, additive manufacturing technologies are in direct competition with other production processes.

Finally, 3D printers are more and more affordable. You can find €2,000 or €3,000 machines on the market. You can easily acquire a 3D printer for home use or take a sharing economy approach and use the printer within a joint ownership property. Now anyone can manufacture their own parts, and repair or further develop devices.

Also read on I’MTech:

Additive manufacturing, a process for the industry of the future

composite materials

Composite Materials: the race to keep going faster

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In the world of materials, composites are currently undergoing a transformation that is just a significant as the plastics boom in the 1960s. To massively integrate these materials into high-volume production markets—automotive, aeronautics, rail, etc.—manufacturers must further reduce the time it takes to mold the parts. This complex goal is attainable by redesigning the materials’ composition and architecture, adapting the manufacturing processes used, and relying on new digital simulation tools.

 

“Fifteen years ago, we were happy when we could produce a complex part made of structural composites in five minutes,” recalls Patricia Krawczak, a materials researcher at IMT Lille Douai. In 2017, the requirements are more demanding. Many sectors are interested in the mechanical properties that composites have to offer, including the transportation industry. These new materials—which are more resistant, lighter, and more durable—pave the way for breakthrough products, and offer new economic opportunities. It is therefore necessary to be able to integrate them massively into markets with high-production volumes, such as the automotive industry. According to the Industry of the Future Alliance, the greatest industrial challenges currently facing composite materials are the reduction of molding cycle and manufacturing times, and the development of “high-speed” processes. For automotive parts, the target is set at around one minute.

Also read on I’MTech What is a composite material?

At the request of manufacturers, scientists are working to meet this challenge. To do so, the plastic resins used as the matrices to impregnate fiber reinforcements have already been modified for some time now. Researchers have switched from thermosetting resins—which harden when heated—to thermoplastic resins, which melt with heat and harden as the part returns to room temperature. “Cure times for thermosetting resins are fairly long, even though the suppliers of these matrices are making progress and working to reduce them,” explains Patricia Krawczak. However, thermoplastic resins can be shaped quickly, for example by using a hot-pressing process, stamping, or using injection technology on a fiber preform, without the need for any further curing. “In this respect, these resins can help reduce the cycle time,” the researcher explains.

 

A comprehensive “materials/process/products” approach

However, modifying the nature of the resin isn’t all that is required to reduce manufacturing time. In order for parts to feature high mechanical performance properties, defects, such as air bubbles trapped in the material, must be avoided at all costs. It is therefore necessary to ensure that the thermoplastic resin completely penetrates between the reinforcement fibers once it has become liquid through increased temperature. Yet these resins are known for being more viscous than thermosetting resins. Scientists must reduce the viscosity of these resins to gain a competitive edge and take advantage of the thermoplastics’ capacity to be shaped quickly. “We are working with chemists to develop polymers that retain the same properties once they become solid, while being more fluid at the processing temperature,” Patricia Krawczak explains.

Researchers in materials science can also adapt the architecture of the reinforcements. Within composite materials are fibers that form strands composed of filaments. They can be assembled–woven, braided or sewn–in different ways. “The way the reinforcement is formed affects the properties of the final composite material, as well as the permeability of the fiber preform, which therefore influences how the resin flows into the reinforcement,” Patricia Krawczak notes. In order to find the best structure, with the right balance between mechanical properties and sufficient permeability, the researcher’s team is also working with fiber reinforcement designers.

Another available means of action lies in the manufacturing process itself, particularly by adapting it to the specific characteristics of the materials that make up the composite itself: the polymer matrix and the reinforcement fiber. “Our team has developed fast hybrid processes that integrate several steps into a single molding operation, for example by combining resin transfer molding and compression molding, or thermoforming/stamping of local composite inserts and overmolding,” Patricia Krawczak explains. In addition to the shortened manufacturing cycle, this mix of processes significantly reduces the number of basic components that must be assembled to produce a complex part. This is a significant benefit for the plastic parts manufacturers that partner with IMT Lille Douai.

 

Optimization platform for new composite processes (POPCOM). Photo: IMT Lille Douai.

 

Digital technology helps identify optimal materials-process pairings

In practice, composite materials offer a very impressive range of “matrix polymer / fiber reinforcement / manufacturing process” combinations, which has been further increased by recent innovations from producers—chemists and textile manufacturers—and processors. To speed up the design of industrial parts, researchers develop virtual engineering chains. Using a technological platform equipped with prototype tools and demonstrators that represent industrial manufacturing processes, they analyze, identify and model impregnation mechanisms. They therefore complement and improve on the manufacturing numerical simulation tools.

“For example, a few years ago we worked with a highly reactive resin that had a gel time of one minute,” says Patricia Krawczak. “But at the time, the available simulation software did not take into account the spatial and temporal variations in the viscosity of these very fast-polymerizing resins. We therefore had to update the digital tool by incorporating a specific model combining thermokinetic reactions and flow”. It was then possible to properly simulate the impregnation of different types of reinforcements with this resin on geometrically complex automotive body parts. By conducting numerical tests, many more combinations have been explored. Researchers can work faster and identify the best configurations to optimize manufacturing technologies. They can therefore successfully reduce cycle times while still maintaining the level of quality and performance.

By studying the materials virtually, as well as the processes used, scientists can dare to explore methods that seem counter-intuitive. This was the case during a European project in which IMT Lille Douai partnered with manufacturers to reduce the molding cycle time for the floor structure of a motor vehicle. “By having our models integrate the way fiber fabrics are distorted during the draping procedure and the consequences this has on the local flow of resin, we were able to simulate a process. We proposed inlet points for the sequential injection of resin, distribution channels and vents at areas on the part that were not the most logical choices for manufacturers,” Patricia Krawczak recalls. But the numerical model had accurately predicted that the resin would impregnate the reinforcement faster and in a more homogeneous manner using this strategy. This result was then confirmed through full-scale experimental validations.

Today, the researchers continue to pursue this scientific approach—supported by industrial collaborations—to explore the potential of new materials and innovative processes. The digital tools are adapted to accurately simulate new technological alternatives and respond to the growing demand for natural fibers in composite materials. Due to their porous nature, they absorb part of the resin and swell. This phenomenon must therefore be included in the simulations, in hopes that this will lead to the discovery of new, more efficient scenarios. Cycle times are no longer improved by several minutes, like they were fifteen years ago; now they are improved by tens of seconds. This gain is still a considerable one in industries that can potentially produce thousands of composite parts each day.

Find out more about natural fiber-based high-performance composites:

Flax and hemp among tomorrow’s high-performance composite materials

 

Young Scientist Prize, julien bras, biomaterial

Julien Bras: nature is his playground

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Cellulose is one of the most abundant molecules in nature. At the nanoscale, its properties allow it to be used for promising applications in several fields. Julien Bras, a chemist at Grenoble INP, is working to further develop the use of this biomaterial. On November 21st he received the IMT-Académie des Sciences Young Scientist Prize at the official awards ceremony held in the Cupola of the Institut de France.

 

Why develop the use of biomass?

Julien Bras: When I was around 20, I realized that oil was a resource that would not last forever, and we would need to find new solutions. At that time, society was beginning to become aware of the problems of pollution in cities, especially due to plastics, as well as the dangers of global warming. So I thought we should propose something that would allow us to use the considerable renewable resources that nature has to offer. I therefore went to an engineering school in chemistry on developing the use of agro-resources, and then did a thesis for Ahlstrom on biomaterials.

What type of biomaterials do you work with?

JB: I work with just about all renewable materials, but especially with cellulose, which is a superstar in the world of natural materials. Nature produces hundreds of billions of tons of this polymer each year. For thousands of years, it has been used to make clothing, paper, etc. It is very well known and offers numerous possibilities. Although I work with all biomaterials, I am specialized in cellulose, and specifically its nanoscale properties.

What makes cellulose so interesting at the nanoscale?

JB: There are two major uses for cellulose at this scale. We can make cellulose nanocrystals, which have very interesting mechanical properties. They are much more solid than glass fibers, and can be used, for example, to reinforce plastics. And we can also design nanofibers, which are longer and more flexible than the crystals, which are easily tangled. This makes it possible to make very light, transparent systems covering a large surface. In one gram of nanofiber, the available surface area for exchange can reach up to two hundred square meters.

In which industry sectors do we find these forms of nanocellulose? 

JB: For now, few sectors really use them on a large scale. But it’s a material that is growing quickly. We do find nanocellulose in a few niche applications, such as composites, cosmetics, paper and packaging. Within my team, we are leading projects with a wide variety of sectors, to make car fenders, moisturizer, paint, and even bandages for the medical sector. This shows how interested manufacturers are in these biomaterials.

Speaking of applications, you helped create a start-up that uses cellulose

JB: Between 2009 and 2012, we participated in the European project Sunpap. The goal was to scale-up cellulose nanoparticles.  The thesis conducted as part of this project led us to file 2 patents for cellulose powders and functionalized nanocellulose. We then embarked on an adventure to create a start-up called Inofib. As one of the first companies in this field, the start-up significantly contributed to the industrial development of these biomaterials. Today, the company is focused on developing specific functionalization and applications for cellulose nanofibers. It is not seeking to compete with other major players in this field, who have since begun working on nanocellulose with European support, rather it seeks to differentiate itself through its expertise and the new functions it offers.

Can nanocellulose be used to design smart materials?  

JB: When I began my research, I was working separately on smart materials and nanocellulose. In particular, I worked with a manufacturer to develop conductive and transparent inks for high-quality materials, which led to the creation of another start-up: Poly-Ink. As things continued to progress, I decided to combine the two areas I was working on. Since 2013, I have been working on designing nanocellulose-based inks, which make it possible to create flexible, transparent and conductive layers to replace, for example, layers that are on the screens of mobile devices.

In the coming years, what areas of nanocellulose will you be focusing on?

JB: I would like to continue in this area of expertise by further advancing the solutions so that they can be produced. One of my current goals is to design them using green engineering processes, which limit the use of toxic solvents and are compatible with an environmental approach. Then I would like to increase their functions so that they can be used in more fields and with improved performance. I really want to show the interest of developing nanocellulose. I need to keep an open mind, so I can find new applications.

 

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Biography of Julien Bras

Julien Bras, 39, has been an associate research professor at Grenoble INP- Pagora since 2006, as well as deputy director of LGP2 (Paper Process Engineering Lab). He was previously an engineer in a company in the paper industry in France, Italy and Finland. For over 15 years, Julien Bras has been focusing his research on developing a new generation of high-performance cellulosic biomaterials and developing the use of these agro-resources.

The industrial aspect of his research is not restricted to his collaborations as it also extends to the 9 registered patents and in particular, the founding of two spin-offs to which Julien Bras contributed. One is specialized in producing conductive and transparent inks for the electronics industry (Poly-Ink), and the other is specialized in producing nanocellulose for the paper, composite and chemical industries (Inofib).

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laser femtoseconde, Femto Engineering

A new laser machining technique for industry

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Belles histoires, Bouton, CarnotFEMTO-Engineering, part of Carnot Télécom & Société numérique institute, offers manufacturers a new cutting and drilling technique for transparent materials. By using a femtosecond laser, experts can reach unrivalled levels of precision when manufacturing ultra-hard materials. Jean-Pierre Goedgebuer, director of FC’Innov (FEMTO-Engineering), explains how the technique works.

What is high aspect ratio precision machining and what is it used for?

Jean-Pierre Goedgebuer: precision machining is used in cutting, drilling and engraving materials. It allows various designs to be inscribed onto materials such as glass, steel or stainless steel. It’s a very widespread method in industry. Precision machining corresponds to a positioning and shaping technique for an extremely small scale, i.e. in the range of 2 microns (10-6 meters). The term “aspect ratio” for example is a reference to drilling. It corresponds to the relationship between the depth and the diameter. Therefore, an aspect ratio of 100 corresponds to a diameter 100 times smaller than its depth.

Cutting or drilling requires local destruction and mastery of the material. In order to achieve this, we supply energy from a laser. This emits heat when it comes into contact with the material.

 

What is femtosecond machining?

JPG: The term femtosecond [1] refers to the duration of the laser pulses, which last a few tens or hundreds of femtoseconds. The length of the pulse determines the length of the interaction between light and the material. The shorter it is, the fewer thermal exchanges there are with the material and therefore in principal, the less the material is destroyed.

In laser machining, we use short pulses (femtoseconds – 10-15 of a second) or longer pulses (nanoseconds – 10-9 of a second). The choice depends on the usage. For machining with no thermal effect, that is, where the material is not affected by the heat produced by the pulse, we tend to use femtosecond pulses, allowing us to find a good compromise between destruction of the material and how high the temperature is. These techniques are associated to light propagation models which allow us to simulate the impact of the properties of a material on the propagation of the light going through it.

 

The femtosecond machining technique generally uses Gaussian beams. The defining characteristic of your process is that it uses Bessel beams. What is the difference?

JPG: Gaussian laser beams are beams inside which the energy is spread in a Gaussian way. When they have raised energy levels, they produce non-linear effects when propagated in the materials. This means that they produce autofocusing effects, making their diameters non-constant and distorting their propagation. These effects can be detrimental to the quality of the machining of certain special kinds of glass.

In contrast, the Bessel laser beams, like what we use in our machining technique, allow us to avoid these non-linear effects. They therefore have the ability to maintain a constant diameter over a well-defined length. They act as very fine “laser needles”, measuring just a few hundred nanometers in diameter (a nanometer corresponds to approximately the size of an atom). Inside these “laser needles” is a very high concentration of energy. This generates an extremely localized plasma within the material, which causes the excision of the material. Furthermore, we can control the length of these “laser needles” in a very precise way. We use them to do very deep cutting or drilling (with an aspect ratio of up to 2,000) producing a precise, clean result with no thermal effects.

In order to start being able to use this new technology, we used a traditional femtosecond laser. What led to several patents being filed by the Institut FEMTO-ST, was finding out how to transform Gaussian beams into Bessel beams.

 

What is the point of this new technology?

JPG: There are two main reasons for it. As we’re dealing with “laser needles” which hold a high density of energy, it is possible to drill very hard materials which would pose a problem for traditional laser machining techniques. Thanks to the technique’s athermic nature, the material in question keeps its physicochemical properties intact; it does not change.

This machining method is used for transparent materials. Industrial demand is high as there are many products that require the machining of herder transparent materials. This is the case for example with smartphones, where the screens need to be made from special kinds of very durable, scratch-resistant glass. This is a big market and is a major focus for many laser manufacturers, particularly in Europe, the US and of course, Asia. There are several other uses however, including elsewhere in the biomedical field.

 

What’s next for this technique?

JPG: Our mission at FEMTO Engineering is to accentuate the research coming out of the Institut FEMTO-ST. In this context, we have partnerships with manufacturers with whom we are exploring how this new technology could respond to their needs in terms of very specific materials where traditional femtosecond machining doesn’t give satisfactory results. We are currently working on cutting new materials for smartphones, as well as polymers for medical use.

The primary research carried out by the Institut FEMTO-ST, is continuing to focus in particular on better understanding light-matter interaction mechanisms and plasma formation. This research was recently formally recognized by the ERC (European Research Council) which finances experimental projects that encourage scientific discovery. The aim is to really master the understanding of the physical properties of Bessel beam propagation which is something that has not been particularly studied on a scientific level before now.

[1] A femtosecond corresponds to one millionth of a billionth of a second. It’s the approximate duration of an electromagnetic wave. A femtosecond is to a second what a second is to the lifetime of the universe.

On the same topic:

FEMTO Engineering: a new component of the TSN Carnot institute

greentropism, spectroscopie

GreenTropism, the start-up making matter interact with light

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The start-up GreenTropism, specialists in spectroscopy, won an interest-free loan from the Fondation Mines-Télécom last June. It hopes to use this to reinforce its R&D and develop its sales team. Its technology is based on automatic learning and is intended for both industrial and academic use, offering application perspectives ranging from the environment to the IoT.

 

Is your sweater really cashmere? What is the protein and calorie content of your meal? Perhaps the answers to these questions come from one single field of study: Spectroscopy. Qualifying and quantifying material is at the heart of the mission of GreenTropism, a start-up incubated at Télécom SudParis. To do this, innovators use spectroscopy. “The discipline studies interactions between light and matter”, explains Anthony Boulanger, CEO of GreenTropism. “We all do spectroscopy without even knowing it, because our eyes actually work as spectrometers: they are light-sensitive and send out signals which are then analyzed by our brains. At GreenTropism, we play the role of the brain for classic spectrometers using spectral signatures, algorithms and machine learning.”

The old becoming the new

GreenTropism is based on two techniques implemented in the 1960’s: spectroscopy and machine learning. Getting to grips with the first of these requires an acute knowledge of what a photon is and how it interacts with matter. Depending on the kind of light rays used (i.e. X-rays, ultra-violet, visible, infrared, etc.) the spectral responses are not the same. According to what we are wanting to observe, the nature of a radiation type will be more or less suitable. Therefore, UV rays detect, amongst other things, organic molecules in aromatic cycles, whilst close infrared allows the assessment of water content, for example.

The machine learning element is managed by data scientists working hand in hand with geologists and biochemists from the R&D team at GreenTropism. “It’s important to fully understand the subject we are working on and not to simply process data”, specifies Anthony Boulanger. The start-up has been developing machine learning in the hope of processing several types of spectral data. “Early on, we set up an analysis lab within Irstea. Here, we assess samples with high-resolution spectrometers. This allows us to supplement our database and therefore create our own algorithms. In spectroscopy, there is great variation of data. These come from the environment (wood, compost, waste, water, etc.), from agriculture, from cosmetics, etc. We can study all types of organic matter”, explains the innovator.

GreenTropism’s knowledge goes even further than this. Their deep understanding of infrared, visible and UV radiation, as well as laser beams (LIBS, Raman), allows them to provide a platform for software and agnostic models. This means they are adjustable to various types of radiation and independent to the spectrometer used. Anthony Boulanger adds: “our system allows results to be obtained in real time, whereas traditional analyses in a lab can take several hours over several days.”

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A miniaturized spectrometer.

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A traditional spectrometer.

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Real-time analysis technology for all levels of expertise

“Our technology consists in a machine learning platform allowing for the creation of spectrum interpretation models. In other words, it’s software transforming a spectrum into a value which is of interest to a manufacturer that has already mastered spectrometry. This allows them to achieve an operational result since in this way they can control and improve the overall quality of their process”, explains the CEO of GreenTropism. By using a traditional spectrometer in association with the GreenTropism software, a manufacturer can verify the quality of the raw material at the time of its delivery and ensure that its specification is fulfilled for example. Continued analysis also ensures the monitoring of the entire production chain in real time and in a non-destructive way. The result is that all finished products, as well as those in the transformation process, are open to systematic analysis. In this case, the objective is to characterize the material of a product. It is used for example to dissociate materials or two essences of wood. GreenTropism also receives support from partnership with academics such as Irstea or Inrea. These partnerships allow them to extend their fields of expertise, whilst also deepening their understanding of matter.

GreenTropism technology is also aimed at novices wanting to instantly analyze samples. “In this case, we depend on our lab to construct a database in a proactive way, before putting the machine learning platform in place”, adds Anthony Boulanger. It is therefore a question of matter qualification. Obtaining details about the composition of an element such as the nutritional content of a food item is a direct application. “The needs linked to spectroscopy are still vague since we have been processing organic matter. We can measure the widespread parameters such as the level of ripeness of a piece of fruit, as well as other, more concrete details such as the quantity of glucose or saccharine a product contains.”

Towards the democratization of spectroscopy

The fields of application are vast: environment, industry, the list goes on. But GreenTropism technology also adapts to general public usage through the Internet of Things, mass market electrical technology and household electronic items. “The advantage of spectroscopy is that there is no need to create close contact between light and matter. This allows for potential combinations between daily life devices and spectrometers where the user doesn’t have to worry about technical aspects such as calibration for example. Imagine coffee machines that allow you to select the caffeine level in your drink. We could also monitor the health status of our plants through our smartphone”, explains Anthony Boulanger. This last usage would function like a camera. After a flash of light is emitted, the program will receive a spectral response. Rather than receiving a photograph, the user would for example find out the water level in their flower pot.

In order to make these functions possible, GreenTropism is working on the miniaturization of its spectrometers. “Today, spectrometers in labs are 100% reliable. A new, so-called ‘miniaturized’ generation (hand-held) is entering the market. However, these devices lack scientific publication about their reliability, casting doubt on their value. This is why we are working on making this technology reliable at a software level. This is a market which opens up a lot of doors for us, including one which leads to the general public”, Anthony Boulanger concludes.

CIRTES, pack&strat, INORI, packages

INORI packages industrial parts in under 5 minutes

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The INORI platform offers a 3D printing process for industrial parts and custom designs the packaging for these parts. Both patented innovations are central to the national and international marketing plan, made possible by the recent funds the platform raised of €1.5 million.

 

So, you’ve created a piece of art or technical component… but you’re afraid it won’t survive shipping? The solution to your problem is 100% French—and it’s called Pack&Strat®. The process offers layers of packaging that adapts to the shape of any object. The source of this innovation: Stratoconception, the patented process from the Research and Development team at CIRTES, which is also associated with the INORI platform (Innovation sur les Outillages Rapides Intelligents – Innovation in Fast Smart Tools, see box below).

What is the purpose behind INORI? To industrialize and market machine/software pairs for processes in the areas of plastics, advanced machining and additive manufacturing like Pack&Strat®. “We are an industry of the future platform, featuring all the ingredients the name implies: digital software, robots and machines,” explains Claude Barlier, the founder and president of INORI.

The platform currently enables the daily manufacturing of 3D packaging for 70 big-name companies. This includes Airbus, Baccarat, Bugatti, SECO Tools and La Poste. These last three companies installed the processes marketed by INORI in their own facilities. Let’s take a trip back to 1991 to learn how the platform has managed to win this share in the additive manufacturing market.

 

1991: Stratoconception sets the wheels in motion

It all started with research work carried out in the mid-1980s, and continued with the patent for the Stratoconception process, which was submitted by Claude Barlier in 1991. The process uses a layer-by-layer 3D printing procedure based on a digital file. The part that needs to be produced is automatically broken down into layers. These layers are calculated to ensure the part will withstand the future mechanical constraints it will be subject to. The layers are then “printed” by using a laser cutting system (or another cutting system) before being assembled.

Parts measuring several meters long can be produced this way. In addition, the diverse materials used by the platform (polymers, resins, wood, metal…) open the door to many different applications. “We have manufactured interior fittings for Airbus and others for Zodiac Aerospace, for boats. We create very elaborate technical parts and tools that enabled us to manufacture a full-size coach,” explains Claude Barlier. However, while the method for manufacturing the parts has been successful, there is still a problem when it comes to transporting the merchandise to the customer. “The parts were arriving damaged, which is when we had the idea of expanding our offering and creating 3D packaging adapted to each object,” the president of INORI recalls.

 

The patented Pack&Strat® process: tailor-made 3D packaging, unique in France

“We create a positive part. Our idea was to make its negative by creating its imprint using the digital file. That is the Pack&Strat® process,” Claude Barlier explains. It consists of software integrated into qualified cutting machines (cutter, milling…). The rest, you already know. The corresponding packaging is printed using the same process that produced the part. The result is a tailor-made cocoon. “We can package every possible and imaginable part by using its digital file or with a 3D scan of the object. The most successful solution uses cardboard. We cut layers out of this material and, in 5 minutes, we can package a part measuring 0.5 meters long,” Claude Barlier explains.

The platform features equipment that is adapted to printing packaging by unit and serial production. It is also committed to a sustainable development approach. It offers packaging made of cardboard, wood, cork, and other existing renewable sheet materials. “We made the decision not to follow the trend of consumables that consists in selling our captive materials in addition to our machines. Instead, we work with all the qualified industrial materials on the global market, which enables us to remain open,” Claude Barlier adds.

pack&strat, CIRTES, emballage, packages, INORI

Example of packaging produced with the Pack&Strat process– Credits: CIRTES

If the customers are satisfied with the two processes mentioned above, they can then buy and integrate the software offer or the machine/software duo. Marketing these processes is also a central concern for INORI as the platform moves forward. The platform recently raised €1.5 million from its shareholders. This will enable it to boost the national and international business activities and target the industrial parts and packaging sector.

 

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The INORI landscape

pack&strat, CIRTES, packages, INORI

Credits: CIRTES

The INORI platform is part of the VirtuReal (“from Virtual to Reality”) center in Saint-Dié-des-Vosges. CIRTES and InSIC (created by Mines Nancy, Mines Albi and CIRTES) are also part of this center. INORI was created in response to a national invitation to tender aimed at establishing innovation platforms. “The platform’s objective is to be complementary to INSIC and CIRTES and InSIC in terms of costs, means, and human, scientific and technical skill,” explains Arnaud Delamézière, the director of InSIC. The center’s entire platform covers an area of 8,000m². It houses industrial-sized equipment and pilot machines that make it possible to carry out pre-marketing trials for processes. Its current shareholders are La Caisse des Dépôts, La Caisse d’Epargne Lorraine Champagne Ardenne, CIRTES, InSIC. Fourteen SME manufacturers and key accounts are also shareholders. Visit of the platform here.[/box]

Piezoelectric, Cédric Samuel, IMT Lille Douai

Connected devices enter the piezoelectric generation

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Piezoelectric polymers may be key in the manufacturing of future generations of connected devices. Thanks to their capacity to generate electricity under mechanical stress, they could greatly reduce the energy consumption of intelligent sensors and make them autonomous. But in order to achieve this, researchers must be able to make these polymers compatible with classic production techniques in the plastics processing industry. All the possibilities are being considered, from 3D printing to bio-based materials.

 

Certain materials are able to generate an electric charge on their surface when deformed. This property, called piezoelectricity, has proven to be of particular interest in the field of connected devices. “Wearables”, which are intelligent devices worn on the body such as exercise trackers, are regularly subject to torsion, flexion and compression. By using piezoelectric materials in their design, there will be less need for batteries, reducing charging frequency and consequently increasing their autonomy. Piezoelectricity, although limited to ceramics since its discovery at the start of the 19th century, is gaining ground in the sector of polymers thanks to growing demand for flexible or transparent connected devices.

Nevertheless, these new plastics “will not compete with ceramics in their fields of application” warns Cédric Samuel, Materials Researcher at IMT Lille Douai (formerly Mines Douai and Télécom Lille). The coefficients that quantify the electricity produced by the piezoelectric effect are 15 times smaller for polymers than for ceramics: “30 picocoulombs per newton for the most efficient polymers, compared with 500 for ceramics” the scientist explained. But connected devices do not need high coefficients, since they only consume a small amount of energy. On the other hand, they require materials that are inexpensive to manufacture, a specification that would be met by piezoelectric polymers if researchers could make them compatible with classic production techniques in the plastics processing industry.

The researchers’ challenge – and it is a considerable one – lies in the processing and shaping of such materials. PVDF, which is currently the most efficient piezoelectric polymer, is far from easy to process. “Only a single type of PVDF crystal — the beta form — has piezoelectric properties,” Cédric Samuel explains. To obtain this form, PVDF must be deformed by more than 200% by stretching, at temperatures between 90 and 100°C. “This requires numerous processing and post-processing stages, which complicates the process and increases production cost” the researcher continued. Alternative options must be found in order to obtain a large-scale and inexpensive processing and shaping solution for piezoelectric PVDF.

PVDF crystals, a piezoelectric polymer with high potential

Researchers are exploring various other possibilities. Working with the University of Mons (Belgium) through a co-supervised PHD thesis, IMT Lille Douai is concentrating more particularly on polymer blends combining PVDF with another plastic: PMMA. This provides two advantages. Not only is PMMA less expensive than PVDF, but the combination allows a piezoelectric form of PVDF to be obtained directly through extrusion. Scientists thereby skip several stages of processing. “The downside is that it leads to a lower piezoelectric coefficient,” Cédric Samuel points out, before adding, “but then again, applications for piezoelectric polymers do not necessarily need huge coefficients.”

 

Piezoelectric polymers through 3D printing

Although polymer blends are an option worth studying to improve processing of piezoelectric PVDF, they are not the only possible solution. Through the Piezofab project, which involves the two Carnot institutes of the IMT (M.I.N.E.S Carnot institute and Télécom & Société numérique Carnot institute) alongside IMT Atlantique (formerly Mines Nantes and Télécom Bretagne) and IMT Lille Douai, researchers are aiming to create sensors and electric generators from piezoelectric polymers through 3D printing. “We seriously believe we can succeed, because we have sufficient background on polymer-based additive manufacturing thanks notably to the expertise of Jérémie Soulestin on the subject,” declares Cédric Samuel confidently.

Researchers at IMT Lille-Douai will endeavor to test the feasibility of the process. To do so, they will work on a modified form of PVDF supplied by their partner PiezoTech, a company which is part of the Arkema chemicals group. This PVDF has the specificity of directly crystalizing in the piezoelectric from when manufactured using 3D printing. Although the cost of the modified polymer is greater than that of its standard form, the manufacturing process could allow a serious reduction of the quantities used.

This inter-Carnot project will lead researchers to study the relevance of piezoelectric polymers for connected devices. IMT Atlantique’s task will be to incorporate piezoelectric polymers into radio transmitters and characterize their properties during use. “One of their greatest strengths is the integration of systems for specific applications, such as monitoring individual exercise” the researcher explained, referring to work carried out by Christian Person.

 

Piezoelectric materials can also be bio-based!

In the two previously-mentioned options currently being studied by Cédric Samuel and his colleagues, the common factor is PVDF. However, “PVDF is an engineering polymer, which remains expensive compared to the commodity polymers” he underlines, “ideally, we would like to be able to use the commodity polymers of plastics processes, and preferably bio-based if possible” he continued. To achieve this, IMT Lille Douai is directing a cross-border European project called Bioharv which associates academic partners in France and Belgium. The Universities of Mons, Lille and Valenciennes as well as Centexbel, a scientific center specialized in the textiles industry, are working alongside the graduate school.

 

Making prototypes using piezoelectric textile fibers.

 

The researchers are most interested in two bio-based polymers, or bioplastics: Polyamide 11 and Polylactic Acid (PLA). The first has proven piezoelectric properties, although a lot weaker than those of PVDF. For the latter, it is a question of proving whether it can in fact generate electric charges. “Certain scientific articles lead us to suppose that Polylactic acid is a promising option, but there has not yet been a clear demonstration of its piezoelectricity” Cédric Samuel explained. In order to do so, the scientists must obtain PLA in its semi-crystalline form. “It’s a stumbling block, as PLA is currently not easy to crystallize” the researcher went on.

The Bioharv project is organized in several stages, gradually developing increasingly effective generations of piezoelectric polymers. It reflects a dual regional research dynamic focusing on both new textiles and the use of natural resources for designing the materials of tomorrow. The stakes are high because the petrochemical industry will not always be able to meet an increasing demand for polymers. Since PLA is produced using agricultural resources, connected devices in the future may be able to be made using corn or potatoes, rather than oil.

 

Bioplastics, Mines Douai

Bioplastics: “still a long road to higher performance”

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As required by environmental transition, materials of the future must be “greener”. Bioplastics in particular have become a main focus of attention, and are often presented as the solution to the pollution caused by the plastics we use every day, which can take hundreds of years to decompose. Patricia Krawczak, a researcher at Mines Douai, studies these new polymers. Yet she issues this warning: our expectations must remain reasonable, because it will take time for bioplastics to become efficient and profitable… and not all of them are biodegradable.

 

Plastic materials are inextricably linked to our everyday lives. They are essential, and yet are often seen as a scourge of modern times. Their negative impact on the environment is often denounced, such as the millions of tons[1] of polymer waste disposed of in the oceans each year, negatively impacting marine biodiversity. Not to mention that producing these plastics requires hydrocarbons, and hence the use of fossil fuels. The scientific community is seeking to offer alternative solutions in response to this situation: “agro-based” or “bio-sourced” plastics made from natural materials of plant or animal origin, also referred to as bioplastics. At Mines Douai, this new “green” form of plastics processing is one of the key research areas of the TPCIM department directed by Patricia Krawczak.

“The current challenge is to develop bio-sourced polymers with higher added value, to set them apart from the widely-distributed plastics, called commodity plastics — such as polyolefins. The goal is to compete against technical plastics, or performance plastics, from the traditional, petrochemical derived process — such as polyamides and polycarbonates,” the materials researcher explains. These major polymer families Patricia Krawczak mentions are often used in key sectors, such as transportation (automotive, aeronautics, etc.), which are large-scale consumers of plastics. Yet entering these markets proves to be a difficult task, due to the demanding specifications.

Herein lies one of bioplastics’ greatest challenges: proving, if not their superiority, at least their equal performance compared to conventional polymers under strict operating conditions. Yet this is far from always the case. “For the time being, industrial-scale bio-sourced products are primarily used for applications in the low value-added packaging sector, such as  bags for supermarkets,” the scientist explains. The properties of the majority of these bioplastics are not yet adapted for producing vehicle components, such as under-the-hood automotive parts, which must be resistant to high temperatures and constant or repeated mechanical stress over time.

This is why much work remains to be done before certain attractive properties can be achieved, and explains the need to temper the excitement about bioplastics. Patricia Krawczak is very clear on this point: “We cannot yet compete with one hundred years of research in the field of petrochemical plastics processing. The road to high performance is still long for bio-sourced plastics.”

The “conventional” plastics industry has indeed been successful in developing a wide range of materials, able to meet the thermo-mechanical and physico-chemical demands of specific uses, and comply with strict application specifications. The range is much larger than what the few bioplastics currently being produced can offer. Not to mention the fact that these bioplastics sometimes have unattractive psychosensorial properties (smells, colors, transparency). A cloudy or yellowish appearance can make certain applications unacceptable, such as for food packaging or touchscreens; and the foul-smelling compounds generated during processing or during use can be disturbing.

However, this does not mean that bioplastics will be forever confined to markets for low value-added products. But hopes of quickly replacing all plastics from petroleum fractions with bioplastics should be tempered for the time being. However, a few examples do exist of bioplastics offering very good properties or even new functions, and are winning over plastics processing industrials and purchasers. This is the case for a bio-sourced polymer developed by Mitsubishi and marketed under the name of Durabio. Its impact resistance is comparable to that of conventional polycarbonate, as well having a high degree of transparency and excellent optical properties (resistance to UV yellowing) and surface properties (hardness, scratch and abrasion-resistance) that surpass its petroleum-based counterparts, and justify its price.

 

Bioplastics need to keep up with the pace!

One of the major hurdles to overcome — in addition to having the characteristics required to comply with application specifications — is that of the potential additional cost of using bioplastics. Bio-sourced polymers’ access to downstream markets is in fact subject to an inescapable condition: to remain competitive, manufacturers of plastic parts cannot consider investing in new production methods or substantially modifying their existing machinery. “It is therefore crucial to ensure that bioplastics can be integrated into current production lines, with technical performances, and production costs and speed that are compatible with market constraints,” Patricia Krawczak points out. Yet, this is not an easy task. Why? Because certain bio-sourced polymers are sensitive to thermal or thermomechanical degradation during the forming stages for manufactured products.

 

Mines Douai, Patricia Krawczak, Bioplastics

To bring bioplastics to maturity, researchers must make them compatible with current processes.

 

It is therefore up to bioplastics to adapt to the plastics processing procedures used to manufacture industrial parts, not the other way around. For the scientists, this means modifying the plastics’ behavior in liquid form, specifically by adding chemical additives. “A common example is starch, which cannot be processed in its raw state using conventional extrusion methods. It must be plasticized by adding water or polyols, with the aim of lowering the temperature at which it becomes liquid,” the researcher explains. Another approach being explored is mixing bio-sourced polymers to obtain a blend tailored to the specific characteristics required.

Once the appropriate formula has been developed, the work is not yet over. The possible migration of the various additives, or the potential changes to the morphology of the blends during the processing stage must also be controlled, to ensure optimal functional properties. In short, developing bioplastics requires a great deal of optimization.

 

Bio-sourced does not necessarily mean biodegradable

Once the bioplastics are perfectly adapted to current plastic processing procedures, and have become efficient and competitive, it is important to keep the initial goal in mind: reducing the environmental impact. However, green plastics processing is all too often wrongly associated with developing and processing biodegradable plastics. Patricia Krawczak reminds us that green polymers do not necessarily have this feature: “On the contrary, many applications in transportation (cars, airplanes) and construction require durable materials that can be used in the long-term without any form of deterioration.”

Since not all bioplastics are biodegradable, they must be recovered and recycled. And there is no guarantee we will be able to put them in our recycling bins at home. In France, these recycling bins currently only accept a limited number of specific plastics: polyethylene terephthalate, polyethylene and polypropylene. It may not be possible to recycle the new biopolymers using the same facilities. Studies must now be carried out to determine whether or not these biopolymers can be integrated into existing recycling facilities without any disruption, or to determine if new facilities will need to be created.

The problem is, the proportion of biopolymers in the total volume of the plastics produced and consumed in the global market represents only 0.5% of all different types (and an estimated 2% by 2020). “Establishing a recycling program generally requires the generation of a sufficient volume of waste to enable a sustainable economy to be built on the collection, sorting and reutilization procedures. At present, however, the amount of bioplastic waste is too small, and is too diverse,” Patricia Krawczak warns. However, initiatives are being developed to recycle small volumes of waste. This is one of the subjects being discussed by the Circular Economy & Innovation Chair (ECOCIRNOV) led by Mines Douai.

 

A promising future for green plastics?

Research aimed at removing the remaining obstacles is advancing, and the future looks promising for green plastics processing, as it is driven by application sectors with strong potential. In addition to transportation, the biomedical field is interested in biocompatible materials for creating controlled release systems for active ingredients. Patricia Krawczak’s team has worked on this subject in conjunction with a French research group on biomaterials from Nord Pas-de-Calais (Fédération Biomatériaux et Dispositifs Médicaux Fonctionnalisés du Nord Pas-de-Calais). The development of electroactive bio-sourced polymers suitable for 3D printing – the focus of research led by Jérémie Soulestin in one of Patricia Krawczak’s research groups – could also benefit the market for connected objects.

Finally, it is important to remember that polymers, along with fibers, constitute one of the two essential components required for producing composite materials. Chung-Hae Park, also a member of Patricia Krawczak’s team, is already working on the development of flax-based composites. He recently completed the proof of concept for the high-speed manufacturing of parts, with a cycle time of two minutes, close to automotive speeds (one part per minute). Success in offering biopolymers with suitable properties, reinforced with plant fibers, could therefore constitute another step towards developing completely bio-sourced structural composites. This class of materials could potentially have numerous high-performance applications.

 

[1] The United Nations Environment Program published a report in 2016 indicating that between 4.8 and 12.7 million tonnes of plastic were dumped in the world’s seas.