The transformation from the combustion to the electric engine entails several imponderabilities for the plastics industry. In part, electric drives have completely different material requirements which are becoming specifically evident with the increasing use of appropriate vehicles.

In electric vehicles, the change in engine technology also entails new requirements for the plastic materials used

Flame Retardancy, Heat and Tracking Resistance of Electric Vehicles

Elektromotoren

Antriebe

Kfz-Elektronik

Elektronik

Elektromobilität

Mobilität

Kunststoffe

Photonik

Optik

Polyamide

Kunststoff Werkstoffe

Thermoplaste

Elektronische Bauelemente

Leistungselektronik

Technische Kunststoffe

Hochleistungskunststoffe

Drivers of Electromobility

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.

Thermoplastics play an important role in the batteries of electric vehicles. They help to keep battery temperatures in the optimal range for a long service life and high performance. 

16:9

Improving the Performance of Electric Vehicles with the Right Materials

Electric, Environmentally Friendly, Thermoplastic

With the change from internal combustion engines to hybrid and electric vehicles, peak operating temperatures have dropped from 135 °C to 110 °C. At the same time, the number of operating hours compared to combustion engines has increased nine-fold. This has an influence on material selection.

A Comparison of PA66 and PPA for Electric Vehicles

Higher Performance in Water

Electrical architecture in an E-car is significantly more challenging than for conventionally powered vehicles. Particularly for insulation of high-voltage (HV) components, the demands on the materials used are increasing. With specially-tailored materials for electric vehicles, challenges in automotive high-voltage technology can be overcome.

Insulation of high-voltage components in electric vehicles makes high demands on the materials used

Polyamide Specialties for Electromobility

Automotive

Kunststoff

Bauwesen

Baustoffe

High Voltage in Cars

The Chinese automotive manufacturer Geely will in the future use a polyamide 6 (PA6) from Lanxess for front-end (FE) carriers in its vehicles.

The front-end carrier for vehicles by the Chinese manufacturer Geely will be made of a PA6 from Lanxess in the future. © Lanxess

 PA for a Front-End Carrier

Most of the energy in a crash is absorbed by metal parts. A new additional polyamide (PA) crash absorber has for the first time been integrated into the front end of the Mercedes-Benz S-Class. The advantage is that an additional loadpath could be added without significantly increasing the mass of the car.  Close cooperation between the project partners and the use of suitable simulation tools were key to successful realization of this project.

As part of the safety concept in the front end of the latest S-Class, Mercedes-Benz uses a crash absorber made from polyamide.

Crash Absorbers made from PA for the Front End Carrier of the Mercedes-Benz S-Class

Kfz-Sicherheit, passiv

Kfz-Systeme

Kraftfahrzeugtechnik

Accident Protection with Plastics

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.

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

Partner for PEEK

Polyetherketon

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

Electromobility in particular, but also many other electrical applications, are asking for ever higher demands regarding the electrical properties of thermoplastics. This raises the question of whether the polymers commonly used in this area can still meet these demands. The plastics manufacturer, Lanxess, has now investigated how suitable, for example, polyamide and polybutylene terephthalate are for use at higher voltages and temperatures.

How Suitable Are PA and PBT for High-Voltage Applications?

Polybutylenterephthalat

Against the Current

A focal point of the Lanxess booth at the show this year will be materials for electromobility.

The demonstrator of a near-series- production housing for electric vehicle batteries is one of the highlights at  the Lanxess booth.

Messe K-Kunststoffmesse

kunststoffe-international.com

kunststoffe.de

Demonstrator for EV Battery Housings

Electric vehicles can be charged not only at charging stations, but also wirelessly. Here, the energy exchange takes place between an induction coil positioned in the ground and a receiver coil mounted in the e-car.

Wireless charging could increase the range, and therefore the acceptance of electromobility.

Flame Retardant Polyamide for Inductive Charging Systems

No Cable thanks to Suitable Compounds

At the first glance, this year’s K was clearly focused on recycling and the circular economy. However, apart from these topics, many novelties were also exhibited in the classical plastics fields such as automotive. And many materials producers showed exciting new developments for electromobility in particular.

In total, 22 BASF materials were used in Hymer’s VisionVenture concept vehicle. Exciting new developments have been used, particularly for the paintwork and for the bathroom wall paneling seemingly made of solid slate

Automotive Trends at the K 2019

Streifinger, Florian

Verbände, Institutionen, Messen

Dienstleistungen

Polyurethan-Schaumstoffe (PUR)

Halbzeuge und Zwischenprodukte

Kunststoff-Halbzeuge

Polyurethan

Electromobility and a Concept Vehicle

Replacing metal with polyamides (PA) in components can not only reduce weight and costs, but also offers developers greater design freedom. However, this requires materials with improved mechanical properties.

 A 3-point bending test showed that the maximum necessary  work of fracture for Ultramid XP grades which exceeds that of comparable PA6 and PA66 grades

Special Polyamides 6 Match the Properties of Polyamide 66

Metal Substitution with Improved PA

There is still a need to catch up in terms of ion leaching and hydrolysis resistance of the materials used to date for fuel cells. Specially developed PPS represent one possibility for this.

Fuel cells are becoming increasingly important as a drive technology in the vehicle sector

Material Improvements Make Fuel Cells More Reliable

Brennstoffzelle

Stromversorgung

Brennstoffzellen

Fahrzeugbau

Getting Fuel Cell Vehicles Fit for Use

Teknor Apex presents three halogen-free FR glass-reinforced polyamide compounds with UL94 ratings of V0.

Application example: engine cover in the automotive industry

Faserverbundwerkstoffe

Andere Werkstoffe

Glass-Reinforced and Halogen-Free Flame-Retardant

The transition to electric cars is transforming automotive design. And so polymers producer Röhm has developed special polymethyl methacrylate (PMMA) molding compounds with this in mind. These are sold under the company’s well-known Plexiglas brand. At Fakuma, the company will be demonstrating how they can be used to combine design requirements and functional properties.

Plexiglas Resist AG 100 is used, for example, in Volkswagen’s ID.3 electric vehicle

Messe Fakuma

Polymethylmethacrylat

Greater Design Freedom for Electric Cars

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).

BGS Beta-Gamma-Service Co.KG  

https://www.bgs.de

Ausgabenartikel

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

 <b>Dr. Michal Daněk</b> 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>

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