Electrification shaking up rubber auto-parts sector

Slowly but surely a picture is emerging of the challenges facing suppliers of rubber-based components for electric vehicles. Patrick Raleigh reports

Electrification is shaking up the automotive parts supply-chain: forcing rubber product companies to add new capabilities to their established areas of expertise in materials science and technology.

Pressure to respond to these trends is high: Claus Moehlenkamp, CEO of Freudenberg Sealing Technologies (FST), for instance estimating that FST could lose 70% of automotive sales if it does not adapt accordingly.

“Any supplier who is heavily focused on the powertrain systems derived from the internal combustion engine (ICE) is at risk and will be challenged in the long run,” Moehlenkamp said in a recent presentation.

That said, the FST boss expects internal combustion engines to remain crucial in the near term, especially as sales of plug-in hybrids with electric powertrain and internal combustion engines grow.

FST has spent years developing components that address some of the automotive industry’s toughest ICE challenges, with developments such as friction-free seals and gaskets.

“These solutions must now be re-oriented to address unique battery-powered and fuel cell systems challenges as well,” emphasised Moehlenkamp.

“Sealing technologies that lower friction, increase power and efficiency and address light-weighting and compact design requirements, for example, will be equally important in an era of new mobility,” he forecast.

FST, added Moehlenkamp, is introducing “unique sealing solutions“ to address thermal management, higher safety standards, electrical transfer, electromagnetic shielding and a longer service life, among other trends.

Tipping point

The emergence of EVs and hybrid vehicles is contributing to high growth in demand for electrical cables and connectors, believes Dr Hans Peter Wolf, manager, R&D silicone rubber at Dow Silicones Deutschland GmbH.

Demand for automotive electronic systems is expected to grow around 16% annually, added the Dow manager, who expects electric/hybrid vehicles to account for a third of car production by 2025.

“And, where in the past you had around 20-40 electrical-connectors on a vehicle, now there is 2,000 to 4,000 such rubber parts, and this is increasing,” Wolf said in an interview at DKT 2018 in Nuremberg, Germany.

As examples, Wolf cited how the number of cable connectors had increased from 45 in the VW Beatle to over 2,100 in a more modern car in 2011 – a trend that has accelerated further in recent years.

While these are small rubber parts, he said they produced in millions leading to an “enormous increase” in volume demand for silicone rubber materials.

Similarly, Dr.-Ing. Thomas Köppl, group product manager, Hexpol TPE GmbH noted increasing demand for thermoplastic elastomers (TPEs) due to the step-change in the amount of cabling required by the electrification of vehicles.

In this application area, he said, TPE’s are mostly used in the mantling or internal insulation of cables, especially those requiring optimum flexural-strength properties.

As well as requirements, such as resistance to heat and aggressive media, all cabling materials need to meet strict standards and specifications around flame retardancy and smoke generation – ideally using halogen-free flame retardants.

Batteries can pose a significant fire hazard, said Koeppl, noting that Hexpol has developed special flame-resistant compounds for injection-moulded parts, such as seals and grommets.

Another materials requirement in EVs concerns conductivity and antistatic properties in applications such as touch panels, display systems and cable management parts. For these applications, the Hexpol manager pointed to the availability of TPEs with resistance of between 10 power3 and 10 power8 ohms.

Noise and vibration

In another presentation at DKT 2018, Florian Luebke of ContiTech noted how: “EVs present new challenges for the engine mount, in part because the motor generates excitations at higher frequencies.”

Work is, therefore, ongoing to optimise the high-frequency characteristics of electric motor-driven vehicles, including the design features and damping materials used, said Luebke.

Designers, he added, must also address vehicle occupants’ perceptions of noise, including high-frequency air sounds and the absence of overlapping noises experienced in ICE vehicles.

As an electric motor runs mostly silently, other noises become more apparent particularly in the passenger compartment.  Car makers, said Luebke, are therefore seeking interior materials and parts with optimised sound dampening properties.

“Car makers,” concluded Luebke, “are seeking for options in order to optimise structure-borne noise. Continental can make a significant contribution with its engine mount systems and corresponding components.”

Challenges around rubber anti-vibration mounting solutions for EVs were also the focus of a presentation by Rob Wardrop of DTR VMS at a recent IoM3 Rubber in Engineering Group (RIEG) conference.

“The need for very rapid application of high torque can lead to ‘tip-in/tip-out’ inputs to the rest of the vehicle if the travel limiting snubbing is not balanced across the mounts,” explained Wardrop.

DTR VMS uses mathematical modelling to define progression requirements of individual mounts to control the containment of the torque application.

Twin-shot moulding, continued Wardrop, can be used to provide different rubber compounds in different parts of a mount.

For example, he said, this means that “the rubber providing travel limitation can have separate properties to the linear travel section providing additional tuning capabilities within a limited package envelope.”

To combat high frequency noise transmission, Wardrop went on to describe how a combination of high frequency testing and FEA studies can be used to develop rubber geometries that incorporate elements that disrupt resonant modes of the main working section of rubber.

This, said the presenter, reduces amplification of vibration transmission that would otherwise occur as the system went through these frequencies.

Additionally, dual isolation systems can be used to provide improved isolation at frequencies greater than the resonant frequency of the inertial mass.

“As the electric motors pass through the low frequency range very quickly, the potential negative effect of the excitation of this mass is minimal,” said Wardrop.

DTR VMS, he noted, is currently working with a number of OEM’s developing mounts for EVs scheduled to be released onto the market from 2021.

Adhesive demand

Frost & Sullivan, meanwhile, predicts increased demand for automotive adhesives and sealants, such as crash-safety adhesives, liquid-applied sound deadeners and high-temperature-resistant silicones.

In a study, F&S foresees a surge in uptake of EVs driving higher adoption of such products for parts-consolidations and the use of lightweight materials to compensate for heavy battery packs.

“Opportunities are emerging due to a growing need to bond dissimilar substrates, increased safety concerns, and OEMs’ focus on enhancing aesthetic appearance,” said Dr Leonidas Dokos, business unit leader, chemicals and materials, EIA at F&S.

The analyst also pointed to a need for manufacturers “to develop advanced adhesives and sealants that offer superior performance over currently used silicone materials in engine and transmission components, and with oily substrates.”