ISSUE 011 Autumn 2021 Candela C-7 hydrofoil speedboat dossier l In conversation: Robert Hoevers l Battery recycling focus l Vehicle dynamics insight l ZeroAvia hydrogen-electric aircraft digest l Motor materials

Elastomeric seals with metallic stoppers offer the advantages of tool- bound forming concepts, meaning that sets of features formed in the same part of a mould can be held to tighter tolerances relative to each other than if they were formed in different parts. This allows seals to be precisely matched to mating surfaces, the use of multi- lip designs, and integrating fixing pins and metallic stoppers directly into the gasket. As well as acting as force shunts, the metallic stoppers can also establish electrical contact between the battery housing and its cover, which helps meet the requirement of the electromagnetically compatible housing concept. Such seals allow the housing to be opened and re-sealed multiple times. In a third concept, the solid gasket can be attached to the side of a metal carrier plate, forming a redundant seal. As well as providing end-stop/ force shunt and EMC functionality, the circumferential carrier helps with rapid and reliable installation. According to one supplier who helped with the research for this article, this is the best technical solution for batteries with flat profiles found in skateboard EV platforms, although it has the disadvantage of needing large- format tools. A solution to that is the ‘de-foldable’ gasket concept, in which the rigid metal carrier plates alternate with flexible, unsupported elastomer segments, enabling manufacture and transport of the gasket in the folded condition, only being unfolded immediately before installation by the assembly robots. Health & safety Sealants and adhesives come under scrutiny for their impact on health & safety and the environment, which is particularly important to the perception of EVs because a large part of their appeal to vehicle buyers comes from their environmental credentials. Sealant and adhesive developers are therefore under growing pressure to reduce their use of hazardous chemicals and SHVCs and to switch to alternatives that are also biodegradable and renewable. Some of these requirements will be tricky to achieve while meeting other important requirements. For example, non-flammable materials must also be non-toxic. When planning the next generation of solutions, the expectation is that the EV industry will have to understand the full life cycle, and that materials will have to be sourced responsibly to enhance energy efficiency and enable their re- use or recycling. The industry has also started to look at its CO 2 footprint at the level of product categories and even individual products and, in support of vehicle OEM priorities, it is under pressure to be transparent about that throughout the supply chain. Future directions In the foreseeable future, EVs with more complex designs and greater use of reinforced polymers will challenge the sealing industry with further new requirements and greater stringency of existing ones. For example, some expect stronger demands for features such as temperature resistance, vibration resistance, repair friendliness and recyclability. These last two are expected to bring new requirements such as de- bonding and re-bonding on demand, while more new requirements are expected to emerge from the desire for lightweight designs. Combined with the need to drive EV costs down, the pressure for further weight reductions will push the industry to refine the supply chain for highly specialised sealants and adhesives. Conventional bonding processes are reaching their limits, and those manufacturers that have begun to bond materials without welding, punching, folding or using mechanical fasteners have simplified and sped up their assembly processes and reduced their production costs. Ongoing r&d seeks to improve the bonding and sealing of composites, and to find lighter metal alloys along with blends of plastics and natural fibres. Sealants will be impacted most by new liquids to be sealed, particularly the dielectric oils and esters used in the emerging immersion cooling systems for batteries that, as yet, are still unfamiliar in the automotive industry. The growing importance of new requirements such as resistance to chemical permeation and fire will influence sealant formulas and seal designs, and the sealing materials are likely to become more specific to the materials, structures and mechanisms they must seal as well as the media whose leakage they must prevent. Seals may usually be out of sight and out of mind, but they are always essential. Acknowledgements The author would like to thank Andy Jorissen at bdtronic, Peter Kritzer, Christian Favetto, Frederic Boyer and Marina Nussko at Freudenberg Sealing Technologies, Nathan Whitford and Christoph Muller at HB Fuller, Wolfgang Mayer and Rainer Kohlstrung at Henkel, and Axel Weiman at Trelleborg for their help with the research for this article. Focus | Sealing Smart dispensing technologies such as speedUP intelligently link axis movements and dispensing rate to cut cycle time and improve seal quality (Courtesy of BDTronic) 72 Autumn 2021 | E-Mobility Engineering