Cloudy with a slight expectation of sun – that sums up the present mood in the automotive industry. After the number of new approvals in Germany fell to its lowest level since 1985 last year, German auto manufacturers expect a steady recovery this year. 2.8 million new vehicles, seven percent more than in 2021, are expected to be added in Germany according to the Association of the Automotive Industry (VDA). That is not a record, but the downturn seems to have bottomed out. Such ambivalent reports are currently pervading the automotive world, for example as regards the subject of semiconductors.

The supply bottlenecks for these critical parts continue to make life difficult for the manufacturers – as well as for many suppliers – and repeatedly result in production outages. VW’s recent plans to cancel almost all the night shifts at its Wolfsburg plant in Germany after Easter caused quite a stir. However, some manufacturers were able to make use of supply difficulties. Volvo, for example, made a virtue of necessity and, last year, installed the scarce chips in particularly lucrative models, which paid off financially. Despite lower sales figures, the company thereby achieved a record revenue of 26.7 billion euros. It is also interesting that manufacturers such as Opel have given preference to their E-vehicle production in allocating the expensive electronic components, even though these vehicles generally have higher chip consumption. This indicates that the companies are particularly loathe to alienate those customers who are interested in electromobility.

What does all this mean for the plastics industry? In view of the tense situation, there is still no sign of clear skies, though there are a few tentative signs of a certain easing. It was also a smart move that the sector got on board with electromobility for quite some time (you can find some examples of this in our Automotive Special from page 10). This will pay off in the future.

Florian Streifinger [<a href="mailto:Florian.Streifinger@hanser.de">Florian.Streifinger@hanser.de</a>]

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Streifinger, Florian

Part 3 of the Series: Digitalization in Compounding

In the second part of the series the digitalization applied in injection molding was presented with examples. The quality of the granulates used, produced in the upstream compounding process, is an important influencing factor via the viscosity. Can consistent granulate quality be achieved through the use of digitalization in compounding? Does comprehensive data recording bring with it further use cases, and what special attention must be paid to a continuous process? The Eastern Switzerland University of Applied Sciences presents the first results of internal projects.

The collection of data along the entire value chain including different processes (here compounding and injection molding) can help to establish correlations between component properties and the data information from both production processes. This information can also be used to reduce fluctuations in compounding, thereby improving the injection molding process. Monitoring this data allows anomalies in the process to be detected in an early stage, such as varying melt temperatures or torque pickups. If these anomalies can be reduced, cost- and time-intensive quality checks at incoming goods can be partially dispensed.

A fundamental requirement is to consider and analyze the compounding process. In line with the use case framework from part 1 and the process concept for digitalization presented in part 2 of this series, the first step is to define six possible use cases with high potential for data acquisition during compounding.

For the consideration of coupled processes, the use case “Direct improvement of product quality/process stability” is of relevance. For this reason, it is first considered which process information can be supplied and which are necessary for the use case.

The Challenge of Data Acquisition during Compounding

In contrast to the discontinuous injection molding, compounding is a continuous process. The data can therefore not be directly assigned to a single part via a cycle but must be continuously recorded and then assigned to different material batches. The challenge here is to assign the recorded process data to the granules produced in such a way that they can be referred to during further processing. Among other things, this interferes with the modeling between the parameters of the compounding process and the quality data of the produced granules. However, it is very possible to constantly monitor the process and thus detect anomalies (process fluctuations) at an early stage.

A compounding line can basically be divided into four subassemblies, storage and finished granules are also considered, as in Figures 1 and 2.

Depending on the process control and the number of liquid and solid additives added, the process varies in complexity. Here, each component provides important process information for the process, which is shown in Figure 3. The data information is color-coded according to the following groups: temperatures (red), pressures (blue), speeds (orange) and torques (green).

The aim now is to record and evaluate this information from the compounder and its peripheral devices as well as additional sensors. However, standardized interfaces such as Euromap and OPC UA are rarely used for compounding plants, which makes data recording more laborious. As shown in Figure 3, a compounding plant consists of many peripheral units from different companies, which are often only combined with main functions (on, off and enable) centered in one control system. Because the manufacturers usually use their own controls and interfaces, data recording is made much more difficult. According to this, often no data for energy consumption and the exact operating data of the peripheral units can be tapped. In practice, this leads to isolated solutions that do not allow overall recording, evaluation, and optimization.

A central data acquisition system will be set up at the Institute of Materials Technology and Plastics Processing (IWK), which will acquire the data from Figure 3, combine them and store them using a common time stamp. The choice of the sampling frequency of the individual signals is crucial here. In contrast to injection molding, this usually does not have to be high frequency in compounding, since the processes are often run-in and do not change at short notice. Nevertheless, it must be possible to detect short-term process fluctuations and form suitable characteristic values with a minimal loss of information. The storage space required for the data also plays a decisive role here.

Experimental Setup and First Use  of the Data Acquisition

The ZSK-26 compounder at the IWK is equipped with a Siemens S7 controller, which can be well integrated into the data recording. Individual peripheral units have new types of controls and standard interfaces; these can often be integrated directly into the data recording system without major additional expense. For other units, without common interfaces, individual solutions must be worked out in each case. Additional sensors, installed in the compounder or in various peripheral units, can be integrated directly into the data recording. For this purpose, an I/O system is used in which analog and digital current interfaces can be connected and recorded via specific terminals.

It must also be possible to assign further data from upstream and downstream processes that are not recorded in real time to the data recorded in the process. The upstream processes include for example material drying and the downstream processes include granule properties, such as viscosity measurement in the laboratory. For the upstream processes, this is not a simple issue, which is why the concrete implementation is still a target to reach. For the downstream processes, the information can be added batch by batch to the previously stored data.

The data acquisition system that has been set up is already being used for research projects at the IWK. A central major topic for the future is to optimize the energy efficiency of the compounding plant, however, this can only be reached, when the networking of the entire plant is considered.

Further topics are the improvement of process understanding when adding water-based liquid-dosed fillers and the monitoring of process stability. In one project, important findings were obtained by combining the signals from built-in sensors and parameters of the compounder and peripherals. In addition, a deeper understanding of the project made it possible to identify the critical point when adding liquid fillers.

The knowledge gained in compounding can also be used for extrusion. Correlation with the end product is easier here. Because in extrusion the recorded data can be assigned to the extrudate, for example, via the linear meters of the profile.

Alex Ramsauer (left) and Prof. Daniel Schwendemann from IWK take a critical look at the data analysis.

Table 1. Possible use cases for the compounding process.

Fig. 1. The compounding plant at the IWK in Rapperswil, Switzerland, was the basis for the internal research project on digitalization.

Fig. 2. Main process steps during compounding.

Fig. 3. Overview of the main influencing variables of the compounding process – simplified and divided into process steps.

Name - Hauptartikel

The following authors work at the Institute of Materials Engineering and Plastics Processing (IWK) at the University of Applied Sciences of Eastern Switzerland (OST) in Rapperswil, Switzerland:

<ul><li>Prof. Daniel Schwendemann is head of the compounding and extrusion department.</li><li>Jasper Hollender, M.Sc., is project manager at the compounding and extrusion department.</li><li>Prof. Dr.-Ing. Frank Ehrig is an institute’s director.</li><li>Curdin Wick, M.Sc., is head of the injection molding/PU department.</li><li>Prof. Dr. Roman Hänggi is a partner at the Institute for Product Design, Development and Construction (IPEK) and Professor for Production Management at OST.</li></ul>

This series of articles consists of three parts. Part 1 “<a href="https://en.kunststoffe.de/a/specialistarticle/implementation-of-industry-40-in-injecti-346591" target="_blank">Implementation of Industry 4.0 in ‧Injection Molding and Compounding</a>” appeared in Kunststoffe international 7/2021, part 2 “<a href="https://en.kunststoffe.de/a/specialistarticle/on-the-way-to-the-smart-injection-moldin-354863" target="_blank">On the Way to the Smart Injection Molding Factory</a>” in issue 9/2021.

Extrusion

Kunststoffverarbeitung: Verfahren

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Industrie 4.0 für die Kunststoffverarbeitung

Industrie 4.0

Compoundieren

Kunststoff-Aufbereitung

Atmospheric Plasma Technology as the Key to More Resource Conservation

The use of recyclates confronts companies with new requirements in the processing, bonding, printing and labeling of materials and components. Atmospheric plasma technology, in which Plasmatreat GmbH has specialized, has established itself as a key technology: it often makes the use of recycled plastics possible in the first place – and also proves to be the means of choice on the way to more environmentally friendly, more resource-efficient production processes.

Responsible use of resources is a serious corporate goal for more and more companies that is right at the top of the agenda. In plastics processing, the use of recyclates as a supplement and alternative to new goods plays a decisive role in the commitment to environmental and climate protection. However, with the switch to materials with a proportion of recyclates or even to pure recycled plastics, companies are facing new challenges. Because when preparing materials for reuse, it depends on purity of type: if this is ensured, plastics can generally be melted down and used again to manufacture a wide variety of products. “In many cases, however, this is not entirely possible. Plastics such as polypropylene and polyethylene in particular cannot be separated according to type using traditional methods, as they are chemically only slightly different,” explains Dr. Alexander Knospe, Head of Innovations and Patents at Plasmatreat. But even minor changes to the material can affect the entire manufacturing process.

This is where Plasmatreat’s competence comes into play: the company specializes in the use of atmospheric plasma technology in industrial production. When plasma comes into contact with materials, their surface properties change, for example from hydrophobic to hydrophilic. Plasmatreat has developed various solutions for surface treatment that are used in controlled and reproducible processes for almost all materials:

<ul><li>Fine cleaning with Openair-Plasma removes contaminations from the substrates.</li><li>Plasma activation increases the surface energy and improves the subsequent adhesion of adhesives and paints.</li><li>The PlasmaPlus process uses nano-coating to create functionalized surfaces with defined properties, such as an anti-corrosion coating or an adhesion promoter layer.</li></ul>

Numerous industries are already using the power of plasma for a wide variety of processes. When using recycled plastics, plasma technology is once again of particular importance: due to the fact that the separation is not always 100 % pure, plastics are created in the recycling process that have (slightly) different properties than new goods, for example in terms of the quality of the surface.

This has a negative effect on processes such as bonding, printing, painting, labeling, applying seals and more. “Plasmatreat offers efficient solution options with various plasma applications. These simplify the further processing of recycled plastics, for example through targeted activation of the plastic or through the application of a nano-layer that provides the surface with additional properties. In this way, we are expanding the possible uses of recyclates, using only electricity and compressed air ourselves and thus contributing to more environmental and climate protection,” explains Lukas Buske, Head of Plasma Applications at Plasmatreat.

Flawless, Long-Lasting UV Digital Printing on Recycling Cups

Plasmatreat demonstrates what this can look like in practice in cooperation with injection molding machine manufacturer Arburg, among others: at the Digital Edition of Hannover Messe 2021, Arburg demonstrated how a freshly injection molded drinking cup with a wrinkled look made of recycled polypropylene (PP) can be printed using UV digital printing without the use of additional adhesion promoters. After removal from the injection mold, the recycling cup is subjected to an Openair-Plasma treatment that effectively activates the printing surface (Fig. 1).

The plasma activation ensures that the surface energy of the non-polar plastic increases significantly. This enables full-surface wetting of the printing surface in UV digital printing and creates the prerequisite for good adhesion of the solvent-free printing inks to the substrate, such as the recycled PP used here (Fig. 2). The result is a brilliant, sharp print image that is permanently resistant to abrasion and moisture.

In the project described, which Arburg realized as part of the R-Cycle initiative, this is important not only for visual reasons but also for practical ones: during production, the recycling cup is given a “digital passport” and is printed with DM codes that are easily legible even after prolonged use thanks to plasma treatment. The material information for recycling stored in the R-Cycle database can be called up via a DMC. These make the cup a recyclable material again after use and support a sustainable recycling economy.

Solid Connection in 3D Printing of Metal and Recycled Plastic

Another joint project was dedicated to 3D printing with a high-strength sustainable plastic. At the Fakuma 2021, the companies involved – Plasmatreat, the plastics specialist Akro-Plastic and Yizumi Germany, manufacturer of 3D printers for industrial applications – presented the production of a 3D component from a bio-based and carbon fiber-reinforced polyamide on a metal carrier. In the printing process, a stainless steel sheet coated with a plasma-polymerized adhesion promoter served as the substrate (Fig. 3).

In this case, the PlasmaPlus technology from Plasmatreat was used: depending on the application, specific additives are added to the plasma via a special nozzle head; these are stimulated by the plasma. Their reactivity is thereby increased significantly. In this way, the substances can accumulate on the material surface during the plasma coating and bind firmly. The result is a layer with functional surface properties that can be individually tailored to the process. In the example described, a PT-Bond nano-layer is deposited on the sheet metal, which creates a firm connection between the metal carrier and the first layer of the plastic melt, i.e. between normally incompatible materials. With this process, users will benefit in the future from expanded fields of application for 3D-printed components and the opportunity to use more sustainable materials.

The Automotive Industry Relies on Dashboards with Recycled Content

The use of recycled plastics has long since arrived in the automotive industry, with its high quality and strict requirements for suppliers. Many manufacturers require defined recycling quotas in their specifications. The suppliers are faced with the challenge of reliably implementing these requirements. Plasma technology has already proven itself in various ways here. When it comes to interior design, numerous vehicle manufacturers already use recycling materials to a certain extent, for example in the production of plastic instrument panels.

Various manufacturers use the plasma technology from Plasmatreat for surface pretreatment: pretreatment with plasma makes non-polar (recycling) plastics susceptible to adhesion processes and ensures that the different, sometimes even incompatible materials are firmly bonded, for example when laminating dashboards made from recycled plastics materials with powder-sintered molded skins made of soft plastic (Fig. 4).

More Environmentally Friendly Processes and Raw Material Savings

However, it is not only through the improved use of recycled plastics that plasma technology supports industry in its efforts for more environmental and climate protection. It also helps to replace environmentally harmful processes with less harmful ones. Well-known manufacturers, for example from the automotive industry, use plasma pretreatment as an alternative to the traditionally used surface treatment (Fig. 5).

Plasma technology helps manufacturers achieve significant CO2 savings: while the flame is applied with propane or methane gas, for example, plasma nozzles are operated with electricity and compressed air. If you now use green energy, the plasma treatment takes place in a CO2-neutral manner. But even if a conventional electricity mix is used, the CO2 balance in relation to the treated area is at most a fifth of the emissions that occur in the event of a flame. Lukas Buske adds: “Plasma technology also makes environmentally harmful chemicals, such as the commonly  use of primers for bonding, superfluous. That also improves the environmental balance.”

The example of dashboard production also shows that plasma technology can score with more efficient processes and raw material savings. The flame application process requires that all areas of the components that are not to be adhered to later be covered with thermally stable masks. With the use of Openair-Plasma (Title figure), this work step is completely eliminated, as the plasma jet works in a location-selective manner and follows the component geometry with millimeter precision.

In addition, very little heat is generated during plasma treatment. As a result, the treated components remain dimensionally stable and undamaged even if they are designed with overall thinner walls. The environment and manufacturers also benefit from the material savings that this makes possible. The automotive industry in particular, in its striving for lightweight construction, can thus – with weight-optimized and at the same time resilient components – reduce the overall weight of the vehicles and thus the fuel consumption.

Plasma Technology Drives Sustainable Developments

The examples presented show how plasma technology supports companies not only with powerful and efficient processes, but also in their efforts to conserve resources. The current possibilities of plasma technology, however, are only the beginning – at Plasmatreat and in several research institutions, further projects are in the starting blocks, which should also become series solutions.

Dr. Alexander Knospe, Head of Innovations and Patents at Plasmatreat, leads back with his outlook to the starting point of this article, recycling plastics: “Due to the large quantities of plastics used, polypropylene and polyethylene in particular play an important role in material recycling. As described, a pure separation during recycling is challenging and sometimes not economical due to the similar material properties. Today, up to 10 wt. % of cost-intensive additives are added to ensure the mixing of the materials in the extruder and to achieve acceptable material properties – thus recycling the valuable material but adding substances that produced CO2 emissions and significantly increase the material price.”

Current research that is being carried out at the Institute for Plastics Processing (IKV) at RWTH Aachen University, Germany, as part of the AiF project “Melt Functionalization” should make this superfluous in the future. Functionalization of the plastic melt with the help of atmospheric pressure plasma directly in the extruder could increase the compatibility of the materials by incorporating functional groups into the polymer chains. Knospe concludes: “Then in the future, for example, mixtures of PE and PP films would no longer have to be separated with great effort.”

When using Openair-Plasma, the plasma jet works in a location-selective manner and follows the component geometry with millimeter precision. During the plasma treatment, very little heat is generated, so that the treated components remain dimensionally stable.

Fig. 1. The injection-molded recycling cup is treated with Openair-Plasma to increase the surface energy of the non-polar plastic.

Fig. 2. A high surface energy is decisive for the wetting of the printing ink in UV digital printing and creates the prerequisite for good adhesion of the solvent-free printing inks.

Fig. 3. Thanks to the adhesive layer, which is applied to the metal carrier using the PlasmaPlus process, the pen holder made of carbon fiber-reinforced, bio-based polyamide holds on to the surface.

Fig. 4. The pretreatment with plasma makes non-polar plastics susceptible to adhesion processes and ensures a firm connection of the different, sometimes even incompatible materials, for example when laminating dashboards made of recycled materials with powder-sintered molded skins made of soft plastic.

Fig. 5. Activating the surface with plasma technology increases the surface energy and  improves the adhesion of adhesives and paints, even with plastic parts made from recycled material.

Plasmatreat - Hauptartikel

Anne-Laureen Lauven is Head of Marketing at Plasmatreat GmbH, Steinhagen, Germany; <a href="mailto:al.lauven@plasmatreat.com">al.lauven@plasmatreat.com</a>

Plasmatreat GmbH is an international leader in the development and manufacture of atmospheric plasma systems for the pretreatment of material surfaces. Whether plastic, metal, glass or paper – the industrial use of plasma technology modifies the properties of the surface in favor of the process requirements. Openair-Plasma technology is used in automated and continuous manufacturing processes in almost all industries. Examples of this are the automotive, electronics, transport, packaging, consumer goods or textile industries. However, the technological, cost and environmental advantages of plasma technology are also used in medical technology and in the field of renewable energies.

The Plasmatreat Group has technology centers in Germany, the USA, Canada, China and Japan and, with its worldwide sales and service network, is represented by subsidiaries and sales partners in over 30 countries.

<a href="https://www.plasmatreat.com/" target="_blank">www.plasmatreat.com</a>

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Kreislaufwirtschaft

Irradiation Crosslinking Replaces High-Performance Plastics with Cheaper Polymers

The conditions in electric vehicles place high demands on the materials used. Therefore, automakers and suppliers must resort to expensive, high-performance plastics. For many applications, cost-effective alternatives are plastics whose properties have been greatly improved by means of treatment with high-energy electron beams.

Between 1970 and 2010, the amount of plastics in total vehicle weight increased continuously: from about 6 % in 1970 to some 16 % in 2010. During the same period, average automobile tare weight increased from 1100 to 1400 kg [1]. Both developments are mainly due to the fact that automobiles have become safer and more comfortable. For example, polymer foams were widely used to fill empty spaces in the vehicle body to reduce the accident effects of overturning or side impacts [2]. The introduction of electronic safety systems, but also the increasing popularity of air conditioning and infotainment systems resulted in the stricter  use of printed circuit boards  with a high plastic content [3]. In addition, plastics were increasingly used as synthetic leather and deco foil, which lend the vehicle a premium quality appearance.

Meanwhile, the automotive industry is in transition: primarily because of tighter emission limits as well as state funding, electric vehicle sales are booming. In spite of improvements, the limited driving range of battery electric vehicles without recharging is still the main disadvantage. One of the proposed solutions involves the replacement of metals in the vehicle body with lighter plastic materials. Because less weight helps to save energy, thereby increasing the vehicle’s driving range.

According to analysts, the increased use of plastics has other advantages apart from lightweight construction: it permits automakers to lower productions costs, promote modular assembly methods, and improve the aerodynamic properties of the car body [4].

Particular Challenges in  Electric Vehicles

In the past, the vehicle’s interior was the main field of use for plastics. But now, the focus is on applications near the drive train, the battery, and on the body (Fig. 1). In these locations, however, temperatures and mechanical loads are often much higher. Therefore, the materials must meet new requirements:

<ul><li> In certain applications, they must withstand temperatures of more than 150 °C.</li><li> Because electric currents play a particularly important role in electric vehicles, the materials must provide good insulation.</li><li> The plastics used should maintain the above properties during the vehicle’s entire lifetime, i.e. they must be durable and age-resistant.</li><li>They must exhibit high mechanical strength and toughness. Among other things, this also means that with fiber composite plastics (FCP), the bond between the polymer matrix and fibers must be particularly good.</li></ul>

In order to meet these demands, automakers and component suppliers therefore frequently resort to high-performance plastics such as polysulfones (PSU, PES, PPSU), polyphenylene sulfide (PPS) and polyether ether ketone (PEEK) (Fig. 2). However, these materials have a serious drawback: they are expensive [5]. Moreover, their processing involves higher costs and energy consumption than for engineering plastics. The reason for this is that processing is usually done at high temperatures. Typical are injection temperatures of 300 to 400 °C, and mold temperatures of 125 to 210 °C. Furthermore, special injection molding machines and molds are necessary.

Cost-Effective Alternatives with Irradiation Crosslinking

One way out of this dilemma is provided by the irradiation of engineering plastics such as polyamides (PA) and polybutylene terephthalate (PBT) [5]. Compared with high-performance plastics, the material costs are lower by a factor between 2 and 10. The processing temperature during injection molding of e.g. irradiation crosslinkable PA is at least 100 °C lower than that of high-performance plastics. Mold temperature is between 60 and 100 °C.

Irradiation crosslinking is always done after the component has been shaped. The manufacturer uses injection molding, extrusion, or blow molding as before. Consequently, there is no need to purchase new machines or molds. The plastic component can be manufactured with the usual production method, and with optimum speed. In summary, not only the material costs, but also the processing costs for components made of irradiated engineering plastics are lower than those for high-performance plastic components.

Irradiation crosslinking raises the characteristic properties of suitable engineering plastics to a higher level, enabling them to be used in conditions that they could not withstand otherwise (Fig. 3, page 16). This effect is achieved by high-energy irradiation, e.g. gamma or beta rays, whereby they first cause homolytical splitting of chemical bonds in the polymer’s molecules. This creates instable fragments with a single electron, so-called free radicals. When neighboring free radicals react with each other, covalent bonds are formed, resulting in a three-dimensional, highly stable network.

But not all plastics are suitable for irradiation crosslinking, as a corresponding reactivity must be present. Not suitable are e.g. polycarbonate (PC) and acrylonitrile butadiene styrene copolymers (ABS). Many of the engineering plastics (Fig. 2) that come into question for use in electric vehicles require crosslinking agents: such polymers include PA6, PA11, PA12, PA66, PBT, and thermoplastic elastomers based on urethane (TPE-U). In modified form, these materials are already available on the market. Many polyolefins and their copolymers, for example thermoplastic copolyester elastomers (TPE-E), ethylene vinyl acetate copolymers (EVAC), ethylene propylene diene rubbers (EPDM), and the standard plastic polyethylene (PE) manage without crosslinking agents. Radiation crosslinking is always done at room temperature. The results of irradiation are easily reproducible.

The Added Value of  Radiation Crosslinking

The effect of radiation crosslinking on polyamides has been investigated in depth [6–8]. They are versatile in use, and easy to process. However, in an  untreated state they reach their limits at high temperatures and if durability is required under heavy mechanical loading, e.g. due to friction.

Irradiation with electrons changes the behavior of PA under thermal influence. For example, the glass transition temperature of PA66 increases from 81 to 97 °C. Decisive however, is that the storage modulus of non-crosslinked PA66 decreases rapidly at about 240 °C: the material starts to melt. Not so with irradiated PA66. In the plastic’s amorphous areas, the crosslinked locations hold the polymers together, which is why the material exhibits a 120-fold higher storage modulus at this temperature than non-crosslinked  PA66. Up to a temperature of 360 °C, residual stiffness hardly changes. Consequently, treatment of PA66 with electron beams leads to increased thermal stability. The same effect is also observed with other materials (Fig. 4).

Similarly, the mechanical characteristics of PA are improved by irradiation (Table 1, page 15). This is also the case with glass fiber-reinforced types. For example, the elastic modulus of PA6-GF30 increases from 6220 to 6780 N/mm2 parallel to the injection direction, and yield stress from 108 to 121 N/mm2. Simultaneously, elongation at break drops from 2.8 to 2.5 % (Table 2, page 15). The increased strength at room temperature is due to the better bond between fiber and matrix. This is underlined by investigations on fracture surfaces of irradiated and non-irradiated FRP. The fracture surface of a non-irradiated PA6-GF30 sample exhibits smooth, almost bare glass fibers, while matrix remnants are visible on the fibers in the irradiated sample as an indication of better bonding between the two components (Fig. 5).

Crosslinking with electron beams creates additional positive tribological effects:

<ul><li>Creep tendency of e.g. PA6-GF30 is reduced by up to 70 %.</li><li> Wear coefficient of e.g. PA66 is reduced by up to 60 to 70 %.</li><li>Dimensional stability is improved due to a lower thermal expansion coefficient.</li></ul>

But higher performance due to irradiation is not limited to PA. Also well proven is the positive effect of irradiation crosslinking, e.g. with PBT, PE, EVAC, TPE, and other thermoplastics [5,  9].

Crosslinked engineering plastics can be used for different purposes in electric vehicles (Fig. 1). Some of these components, such as gear drives as well as from the fixing and connecting field (clips) are also found in vehicles with IC engines, where they are already in series use. Others, especially for the requirements of electric vehicles, are still in the development stage. This applies in particular for battery housings as well as separators and power cables near the battery. The BGS Beta-Gamma-Service company, one of the pioneers in the treatment with beta and gamma rays, is presently conducting corresponding research projects with automakers and suppliers.

[1] Rouilloux, G., Znojek, B.: Plastics. The Future for Automakers and Chemical Companies, ATKearney Report (2012).

[2] Paulino, M., Teixeira-Dias, F.: On the Use of Polyurethane Foam Paddings to Improve Passive Safety in Crashworthiness Applications. In Polyurethane, Intech. Rijeka (2012), pp. 337 - 354

[3]. Cucchiella, F., D‘Adamo, I., Rosa, P., Tezi, S.: Scrap automotive electronics: A mini-review of current management practices. Waste Management and Research, (2016) 34 (1), pp. 3 - 10

[4 ] <a href="https://www.plasticstoday.com/automotive-and-mobility/six-trends-impacting-global-automotive-plastics-market-new-decade" target="_blank">https://www.plasticstoday.com/automotive-and-mobility/six-trends-impacting-global-automotive-plastics-market-new-decade</a>.

[5] Rausch, J. Danek, M., Strahlenvernetzung Thermoplastischer Kunststoffe: Eine Alternative zu Hochleistungskunststoffen, Vortrag, BGS Irradiation Service Days (2021).

[6] Brocka, Z.; Ehrenstein, G.W.: Strahlenvernetzung von Polyamid zur Verbesserung des tribologischen Verhaltens, Zeitschrift Kunststofftechnik/Journal of Plastics Technology 2 (2006) 5, p.1

[7] Brocka-Krzeminska, Z.: Werkstoff- und Einsatzpotential strahlenvernetzter Thermoplaste, Dissertation, Universität Erlangen-Nürnberg, 2008

[8] Müller, T., Schmidt, T., Schaffrath, A., Blum.T.: Strahlenmodifizierte Kunststoffseilscheiben in Seiltrieben, Logistics Journal: Proceedings (2016)

[9] Ostrowiki, A., Danek, M., Manas, M., Holik, Z., Mizera, A., Reznicek, M..: Radiation Crosslinking – way to improve the properties of polymers <a href="http://Plasticportal.eu" target="_blank">Plasticportal.eu</a> (2015).

Table 1. Comparison of mechanical characteristics of non-irradiated and irradiated PA66 (at room temperature / 120 °C).

Table 2. Comparison of mechanical characteristics for non-irradiated and irradiated PA6-GF30 (parallel / transverse to injection direction). 

Fig. 1. Crosslinked engineering plastics can be used for many different applications in electric vehicles.

Fig. 2. Standard polymers as well as engineering plastics and high-performance polymers  can be crosslinked. The process permits treatment of the polymers highlighted in green. 

Fig. 3. Trend lines due to irradiation crosslinking for different  material properties. Of particular interest for use in electric vehicles are the resulting higher thermal stability and chemical resistance.

Fig. 4. Treatment significantly increases the short-term thermal stability of glass fiber-reinforced plastics – the increase is particularly large with PA6. 

Fig. 5. Fracture surfaces from tensile tests with non-irradiated (left) and irradiated PA6-GF30 (right) under the scanning electron microscope:  the matrix remnants on the glass fibers of the irradiated sample indicate the better bond between fibers and matrix polymer.

KUint 2-22_BGS - Hauptartikel

Dr. Michal Daněk has been working as Key Account Manager for irradiation crosslinking at BGS Beta-Gamma-Service GmbH & Co. KG in the CEE region since 2005; <a href="mailto:danek@bgs.eu">danek@bgs.eu</a>

Wilhelm Schneider has been working as Key Account Manager for irradiation crosslinking at BGS since 2021; <a href="mailto:schneider@bgs.eu">schneider@bgs.eu</a>

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Thermoplaste

Technische Kunststoffe

Strahlenvernetzung

Hochleistungskunststoffe

PEEK and Epoxy Provide Efficient Insulation for High Voltage E-Motor

The rising voltages in electric vehicles are creating higher requirements on insulation materials. This is why PEEK is increasingly used for this purpose. A problem with this high-performance polymer used to be its adhesion to the secondary insulation material. An epoxy resin now promises to solve the issue.

In an effort to increase battery electric vehicle range and decrease the battery charging time, automotive OEMs and tier suppliers have begun to adopt high voltage systems ranging from 800 to 1200 V. These systems require special insulation materials to meet the high requirements in the high-voltage range. With KetaSpire, plastics manufacturer Solvay has introduced an appropriate polyetherether ketone (PEEK) for magnet wire insulation in electric vehicles (Fig. 1).

Key drivers for using PEEK-insulated magnet wire above all include the material’s resistance in high voltage environments with typical partial discharge inception voltage values of 1600 to1700 V at 150 μm. With a lower level of defects versus pure enamel solutions, the material is also very reliable. In addition, the use of PEEK can raise the efficiency of high-voltage systems. Utilizing the extrusion-based PEEK materials developed by Solvay together with hairpin technology, various OEMs have been able to increase their copper slot fill by over 10 % (Fig. 2).

A remaining challenge for e-motor designers has been to identify suitable secondary insulations with perfect adhesion to PEEK magnet wire and PEEK slot liner insulation materials.

Epic Resins company developed ProPreg E240, a single component epoxy secondary insulation specifically designed to increase the adhesion to PEEK while also being compatible with other common insulation materials such as polyamide imide (PAI). ProPreg E240 provides the industry‘s highest adhesion in a variety of applications including: wire to wire, wire to aramid paper, aramid-paper to steel, and wire to PEEK slot insulation. The development work eventually resulted in an epoxy resin capable of penetrating the tight conductor spacings of efficient high copper slot fill factor applications. Currently, 5000 hour thermal testing is underway, targeting a temperature rating of 240 °C to match the thermal ratings of PEEK.

One of the first optimization steps was to adjust ProPreg E240 to the mechanical properties of PEEK products such as Solvay‘s KetaSpire KT-880 and Ajedium slot insulation. By matching the thermal transitional properties, Epic Resins was able to minimize differences in coefficient of thermal expansion which had resulted in failures of brittle polyester resins used in the market today. Another challenge was to ensure that the epoxy resin could be used in existing trickle processing equipment with minimal changes. The material should also offer potential to reduce cure and process times.

Once the ProPreg E240 formulation had been finalized, Epic Resins worked closely with Solvay to generate the required adhesion and compatibility data. To determine the adhesion strength between the epoxy resin and PEEK, Solvay developed a 180-degree peel test method (Fig. 3).

The peel test benchmarked a standard e-motor polyester secondary insulation alongside the epoxy resin. Two tests were performed. One using a KetaSpire PEEK magnet wire grade and the other using Ajedium PEEK slot liners. In both cases, a significant increase in adhesion was observed. The relative peel force between the KetaSpire PEEK material and the ProgPreg epoxy resin was two times higher than the adhesion between PEEK and the standard e-motor polyester (Fig. 4). Similarly, adhesion between the epoxy resin and the PEEK slot liner also showed great improvement.

In addition to the adhesion between PEEK and the epoxy secondary insulation, compatibility data is being developed on the adhesion of PEEK coated wire and ProgPreg E240 after 2000 hours of exposure to automatic transmission fluid (ATF) at 150 °C (Table 1). ATF is commonly used as a fluid to cool the e-motor windings. Present results show that PEEK and the epoxy resin maintain their adhesion strength when exposed to ATF for up to 1500 hours. In both cases, the polymer coating only separated from the copper wire, whereas the bond between the epoxy resin and the polymer remained intact. The results indicate that the adhesion strength of ProPreg E240 is greater than the tensile strength of the polymer coating and of the polymer copper bond strength.

Adapting to meet the changing needs of electric vehicle is where innovation and collaboration becomes a game changer for suppliers and material manufacturers. The successful joint efforts between Epic Resins and Solvay demonstrate what can be achieved through collaboration. Epic Resins’ new ProPreg E240 secondary insulation and Solvay‘s KetaSpire PEEK magnet wire grade and Ajedium PEEK slot liners show significant improvement in adhesion over conventional standard e-motor secondary insulations.

Due to higher voltages, manufacturers are increasingly using PEEK as insulation material for electric motors.

Fig 2.. Multi-layer and mono-layer magnet wire design with PEEK: the copper fill factor can clearly be raised if the enamel wire layer is eliminated. 

Fig. 3. Adhesion test method by Solvay for PEEK film and secondary insulation materials. The test clearly showed the better adhesion between PEEK and the ProPreg epoxy resin in comparison to PEEK  and a standard polyester material for electric motors.  

Fig. 4. Peel force test results: The adhesion between PEEK and the epoxy resin is more than twice as strong as with PEEK and a standard polyester.

Table 1. Adhesion strength of PEEK and ProPreg E240 after 1500 hours of ATF exposure (test method: IEC 60133).

Fig. 1. PEEK magnet wire insulations are becoming increasingly popular in the high-voltage range. They are very resistant and can withstand high temperatures and voltages. This ensures higher reliability compared to the use of enameled wires.

KUint2-22_Solvay - Hauptartikel

<ul><li>Brian Baleno is Head of Marketing Transportation at Solvay.</li><li>Deedee Smith works as Marketing Manager Transportation for Solvay.</li><li>Mohammad Qasim Shaikh is ADL Project Engineer at Solvay.</li><li>Kayla Brown works as Marketing Coordinator for Epic Resins.</li><li>Jeffrey Southworth is Technical Sales Representative at Epic Resins.</li></ul>

Elektromotoren

Antriebe

Polyetherketon

Electric, Environmentally Friendly, Thermoplastic

Improving the Performance of Electric Vehicles with the Right Materials

Electric-vehicle makers looking for fresh impetus are turning to thermoplastics, as these can be used to  improve the safety, performance and sustainability of the vehicles. Initial application areas for manufacturers can be found in a multitude of components ranging from battery cases to busbars, cooling lines and seals. Things become very interesting when material suppliers offer support in the form of CAE and injection molding analyses.

Few materials offer as much scope as thermoplastics for improving the design of electric vehicles. Engineering thermoplastics are increasingly proving to be the best solution to complex issues arising in electromobility, such as safety, rapid charging, durability and sustainability. Their ability to adhere to metal, for example, facilitates overmolding. They offer low coefficients of thermal expansion (CTE), thermal and electrical conductivity, and EMI shielding.

The role played by these plastics in battery systems is important. A long battery life is crucial for gaining the confidence of consumers and boosting their willingness to buy electric vehicles. The majority of drivers still hesitate to buy them because they consider the charging times to be long. This perception has spurred intensive work on the development of ultra-rapid charging systems. The high-energy-density batteries which these require are very challenging in respect of thermal management, especially in the case of compact, powerful electric motors that generate high torque. For a long service life, the operating and charging temperatures should not stray outside the range 15 to 60 °C. High temperatures are harmful to battery health, shorten its service life, and run the risk of thermal runaway and fire.

Protecting Batteries with Hybrid Plastic-Metal Solution

Battery systems also need to be protected against extreme cold, however. Modern cooling plate systems have a metal-on-metal design that easily leads to excessive heat dissipation and thus to excessive battery cooling. This reduces battery performance and shortens the vehicles’ range. Some original equipment manufacturers (OEMs) try to prevent this by separating the base plate and battery housing with a 10 mm-thick layer of expanded polypropylene (EPP) foam, but doing so pushes up costs and complicates manufacturing.

One possible alternative is a hybrid cooling plate. This is a more cost-efficient and reliable way of protecting against extreme temperatures. It consists of an aluminum base plate chemically bonded to a channel plate made of injection-molded thermoplastic, with integrated inlet and outlet valves and fluid channels. The strong chemical bond between the plates represents a major advance here. It is achieved by a specialty polyamide (PA) that was recently launched by DuPont, a plastics supplier, and provides effective protection against coolant leakage. The combination of plastic and metal prevents high heat dissipation and thus excessive battery cooling.

Extensive simulations at DuPont show that, after 12 hours’ exposure to -30 °C under no load, the cell temperature has dropped to -22 °C in a metal-on-metal cooling plate, but to just -5 °C in the hybrid version. This 17 °C improvement leads to better performance and a longer life. Auto-makers are also attracted by the shorter assembly times and lower overall system costs of the hybrid cold plate. And, because it can also be injection molded, functional integration of clips, flow guides, quick-fit connectors and other items is possible.

Thermoplastics can also be used to protect other high-voltage components of rapid-charging systems. They are ideal, e.g., for isolating transformers, charging connectors and plugs, wires and cables, as well as for surface protection. Crastin FR684NH1 OR168, an orange-colored polybutylene terephthalate (PBT), was developed for this purpose by DuPont. Its stable dielectric properties across all the usual temperatures encountered in these applications and its resistance to hydrolysis render it ideal for the production of durable high-voltage components.

The use of thermoplastics can also open up improvements in the field of busbars. These seemingly simple components, usually made of aluminum, transmit high voltages between battery components. However, manufacturers have identified the need for enhanced protection against thermal runaway.

The usual test requirement for busbars is to withstand five minutes’ exposure to heat at 500 °C. In addition, they must also pass shock tests at alternating temperatures of -40 and 150 °C for 1000 hours. Standard thermoplastics are unable to cope with such extreme temperature fluctuations. DuPont has developed special grades, including flame-resistant variants, which can be used for overmolding aluminum parts for enhancing thermal management and can even accommodate such high loads (Fig. 1).

Overmolding of Metal Parts: Avoiding Cracks and Loose Coatings

Even under the most favorable conditions, it is difficult to overmold metal parts with thermoplastics and still achieve stable long-term performance. The different coefficients of thermal expansion lead to differential shrinkage, which can give rise to cracks and even detachment of the coating. The overmolding of busbars specifically for electric vehicle batteries and motors present further challenges. The thermoplastics employed need to be highly resistant to both creep and hydrolysis. Weld line strength, too, is critical.

To overcome these challenges, DuPont relies in particular on computer-aided engineering (CAE). This slashes the number of trial-and-error tests needed and uses models to study the influence exerted by the glass fiber alignment on the stiffness and the CTE.