Traveling Green

Automotive lightweight construction and the circular economy are becoming important guiding principles: lightweight plastic components are increasingly replacing heavier materials. More sustainable materials are gaining importance.

Consistent lightweight construction helps to at least partially offset the weight increase caused by the several hundred kilograms of traction batteries in electric vehicles. This increases their range. Moreover, if electric cars are designed to be lighter from the outset, for example, engines can be smaller and batteries can be designed to be more compact, which in turn conserves resources. A particularly significant contribution to future weight savings could come from so-called sandwich constructions. These are modern carbon fiber composite materials with a core made of particularly lightweight rigid foam.

A particular strength of the composite foam ROHACRYL™ lies in its recyclability. The polymer design allows for the recovery of components, thus closing the material loop—a clean solution at the end of the product's life cycle.

This example shows the potential of sandwich constructions, especially when it comes to large vehicles like electric buses. The sheer size of the market ensures that even the optimization of seemingly small components leads to significant improvements.

However, the consistent application of lightweight construction principles requires more than just optimizing materials. Construction processes must also be adapted, particularly in joining technology. Where lightweight construction and aesthetics are required, modern adhesive solutions offer decisive advantages. The extent to which adhesive technology has already established itself is evidenced by two figures from the Adhesives Industry Association: approximately 15 to 18 kilograms of adhesive are processed per car. Overall, the automotive industry uses about nine percent of the total annual adhesive production. 

The requirements for an adhesive change depending on the specific application: sometimes high strength is required, other times high resistance to aggressive liquids or permanent UV exposure from sunlight. Increasingly, the recyclability of bonded materials is coming into focus, for example, by making the bonding reversible. Chemical companies like Evonik offer a wide portfolio of specially tailored additives, binders, and other components. This is the only way adhesives can be specifically optimized for later applications.

Innovative lightweight construction methods can significantly improve the climate footprint of a vehicle during its usage phase. However, the expectations that many vehicle manufacturers set for themselves are already higher: the German automotive industry has set itself the goal of enabling fully climate-neutral mobility by 2050 at the latest—in line with the Paris Climate Agreement.

Without a circular economy, this vision is unlikely to become a reality. While CO₂ emissions during operation are now minimal thanks to alternative drives, emissions generated during raw material extraction, processing, vehicle production, and at the end of the usage cycle will become more significant in the future.

Therefore, it is essential that strategies for CO₂ reduction extend beyond the usage phase of vehicles and consider all stages of value creation. This is precisely reflected in the concept of a circular economy. 

Car seats must meet complex requirements. The frame should be stable and robust, while the backrest needs to provide support, among other things. Therefore, numerous different plastics are usually combined with other materials like steel. Separating this mix for recycling is labor-intensive. Together with engineers from VESTARO, Evonik's plastics experts have developed a demonstrator where all components of a car seat, such as hard shells, foams, nonwovens, or fibers, were made from Polyamide 12.

Specialty chemical companies like Evonik can advance the establishment of a circular economy on various levels. For example, by changing their raw material base: the Essen-based company has long offered circular polyamides. Here, alternative raw materials such as pyrolysis oil from used tires or used frying fat are used in a mass balance approach. Compared to the regular production of a standard material, the footprint improves by about 70 percent. 

Due to the complex value chains, it is generally not sensible in the chemical industry to create a separate infrastructure solely for sustainable raw materials. This is where the mass balance principle comes into play, which compares the input materials with the output products of production processes. This ensures that sustainable end products correspond to the purchased amount of sustainable, i.e., recycled or bio-based raw materials. The entire process is verified and certified by an independent body according to internationally recognized standards, such as ISCC or REDCert. Through strict accounting and external audits, the mass balance approach enables sustainable products on a large scale. Cost-effective solutions are created, with every renewable molecule used being traceable. 

One thing is already certain: lightweight construction and the circular economy will continue to play an important role. And it is chemical companies like Evonik that contribute to greater efficiency, safety, and sustainability with innovative products and solutions.