As the automotive industry strives to implement circularity in vehicle production, adhesives and sealants are emerging as key players. These materials enable the bonding of components for easy disassembly, supporting the reuse, repair and recycling of automotive parts. With the European Union's ambitious Green Deal goals, adhesives are becoming essential enablers of a sustainable automotive ecosystem. From making vehicles lighter and more sustainable to facilitating recycling processes, adhesives and sealants contribute significantly to a more circular and safer industry.

The Crucial Contribution of Adhesives in Modern Vehicle Construction

A typical mid-sized car contains less than 10 kg of adhesives, distributed across various specialized applications and formulations. Although their mass is minimal, the positive impact of adhesives on vehicle sustainability and performance is substantial. Adhesives play a critical role in the production and assembly of most vehicle components, including the body, windows, drivetrain (for both electric and internal combustion engine vehicles), suspension, trim and interior, and electrical systems, including the high voltage batteries in electric vehicles. Adhesives enable optimal bonding of parts, with a focus on performance, durability, longevity, and crash safety. In electric vehicles, adhesives provide crucial bonding solutions for the battery systems. The benefits of using adhesives in vehicle construction include enabling of lightweight vehicles with lower energy consumption and emissions, increased safety and crash resistance, and improved longevity, durability, and reusability of car parts.

The Role of Adhesives in Automotive Sustainability

Reducing Vehicle Weight and Emissions

Adhesives are uniquely suited to join different types of materials together, allowing manufacturers to use a variety of materials while meeting design and sustainability goals without compromising on strength or safety. One of the most significant contributions adhesives make to automotive sustainability is enabling the use of materials that facilitate lighter vehicle structures. A lighter vehicle requires less fuel, leading to improved fuel efficiency and reduced CO₂ emissions over the vehicle's lifespan. This weight-saving benefit is particularly crucial for electric vehicles, where efficiency is directly tied to battery range.

Recycling and Recovery of Materials at End-of-Life

Adhesives play a vital role in supporting recycling efforts. Sometimes bonded parts are recycled together or simply cut apart for recycling. Modern adhesive technology has advanced to further support the dismantling and recycling of materials at the end of a vehicle's life. For example, adhesive innovations allow for the disassembly of bonded parts through heat or chemical activation, enabling efficient recovery of valuable components and materials. The flexibility that adhesives offer can play an important role in recycling processes, helping manufacturers bond different materials while reducing potential challenges for recyclers.

When the impact of adhesives on recycling operations is considered, two principal distinctions need to be made that relate to the materials being bonded: whether the adhesive was used to bond similar or dissimilar materials together, and whether the target material for recycling is a certain metal, plastic material, or glass. Where an adhesive bonds similar or identical material together, the bond may not need to be released for recycling. For example, adhesives are known not to impede metal recycling processes, such as steel and aluminium recycling, both of which exhibit very high recycling rates from automotive applications. Adhesive applications are destroyed before melting in the melt processes applied to steel, and in the de-coating processes applied to aluminium waste. This includes not only structural adhesives used on metal body and drivetrain components but also residues left by thread lockers, retaining compounds, and similar products on metal components. Adhesives can also be designed to be compatible with recycling processes for plastic materials. This is an already widely followed approach in the design-for-recycling of plastic packaging materials that are produced using adhesives. In the vehicle sector, an example is the recycling of self-adhesive decorative vehicle wrapping films.

Facilitating Repairs and Extending Vehicle Life

In addition to supporting recycling, adhesives contribute to vehicle repairs, making it easier to extend the vehicle's life and ensuring confidence in the repair process. Adhesives have a long history in vehicle production and assembly and have, in many cases, been allowing the successful dismantling of vehicles, including for repairs. This is evidenced by the large market in Europe for used vehicle components, which have been secured by thread lockers, adhesive tapes, and other adhesive bonds during the vehicles’ service life.

The mechanical separation of adhesive bonds is common in repair jobs. For example, windscreen replacement involves cutting the adhesive bond with a wire. Protective and decorative films on vehicles can be removed by hand after gentle heating, enhancing the lifespan and value of vehicles. Many adhesive bonds, like those on aerodynamic elements and trim components, can be separated by mechanical force, similar to releasing fasteners like rivets. This method may be quicker than removing fasteners like screws. Adhesives used with mechanical fasteners, such as thread lockers, release with the fastener, not adding extra steps in vehicle dismantling. Not all adhesive bonds need dismantling for reuse or recycling. Structural adhesives between metal components, like those in vehicle bodies, do not need to be released and can be sent for metal recycling. Adhesive bonds within vehicle components, like textile and trim lamination, stickers, and adhesives in electrical components, are not typically targeted for dismantling. Recovery and recycling processes may separate these adhesive bonds when required.

A Need for Thoughtful End-of-Life Vehicle Regulation (ELVR)

In July 2023, the European Commission published a proposal for a regulation on circularity requirements for vehicle design and end-of-life vehicles. The proposal outlines various measures to increase the circularity of vehicles, such as through vehicle design or an extended producer responsibility (EPR) system. FEICA fully supports the EU's Circular Economy strategy and the goals of the ELVR. Many adhesive applications have been enabling the successful dismantling of vehicles, including for repairs, for many years. The adhesive industry invests heavily in innovation to further improve the recycling of bonded parts, such as through "debonding by design" and the use of adhesives that do not impact the quality of recycled materials. Adhesives are rightly positioned as facilitators, not obstacles, in circular automotive design. For adhesives to continue contributing to vehicle circularity, regulation needs to be technology-neutral and ambitious. Technology-neutral regulation allows the automotive, adhesive, and sealant industries to continue investing in innovations that meet Europe's sustainability goals. FEICA has published a paper, which was submitted to the European Commission, as input to the development of the ELVR. The paper can be found on the FEICA website here.

For FEICA’s Good Practice story on how adhesives in car production help to reduce the vehicle's weight, and thus also the CO₂ emission of the finished car, visit FEICA's website here.