First automotive refinish coating with bio-based hardener

Sonnenwagen Aachen tests biobased coating-layer from Covestro at the World Solar Challenge

During this year’s World Solar Challenge, currently being driven in Australia, Covestro, in particular will be watching closly. It is testing a biobased coating on the German entry, the Sonnenwagen.

Bildschirmfoto 2017-10-18 um 12.02.16Where better than at what is probably the toughest solar car race in the world to test coatings? Covestro is taking advantage of the harsh climate conditions prevailing along the race´s route to observe how the three-layer polyurethane coating from PPG, and in particular the top clearcoat, which is most exposed to the climate conditions, and which contains the bio-based hardener Desmodur eco N 7300 from Covestro, holds up.

Electric mobility and photovoltaics play a vital role in protecting the climate and conserving fossil resources. Combining them leads to even more innovative and sustainable mobility concepts. To show that these kinds of solutions are already feasible using state-of-the-art materials and technologies, a team of around 45 young researchers has developed a solar-powered electric car. Calling themselves “Team Sonnenwagen,” the students from RWTH Aachen University and Aachen University of Applied Sciences intend to enter their vehicle in the Bridgestone World Solar Challenge 2017 in Australia, probably the toughest race in the world for solar cars.

Covestro has supported the Sonnenwagen project with materials and technical service and as a gold sponsor. The company is also using the project to test coatings under the harsh climate conditions prevailing along the race’s route. Temperatures in the Australian desert can soar to as much as 45 degrees Celsius in October, with intense UV radiation. This time of year also typically sees a high particle concentration in the air.

Road test: automotive coating with sustainable raw material

The most important product application is a three-layer polyurethane coating from PPG, world leaders in paints, coatings and specialty materials, and experts in automotive coatings. The coating system is particularly suited to coating body parts made of carbon fiber composites. Climate conditions have a significant impact on the top clearcoat. The Sonnenwagen uses an innovative automotive refinish coating that contains Covestro’s bio-based hardener Desmodur® eco N 7300. “Some 70 percent of its carbon content comes from biomass,” explains Ulf Wentzien, global head of Industrial Marketing in the Coatings, Adhesives, Specialties Business Unit at Covestro. “This reduces the environmental footprint by around 30 percent.”

“The bio-based hardener achieved the highest sustainability standards and meets both our customers’ and our own requirements,” says Ignasi Roig, EMEA Product Platform Manager at PPG Refinish. “The coating is to the same outstanding quality as a polyurethane clearcoat with a conventionally produced hardener.”

Easy processing

The two-component coating is also impressive on the practical side. In PPG’s training center in Hilden, it was applied to the Sonnenwagen’s bodywork parts under similar conditions to an automotive paint shop. The coating is particularly suitable for the temperature-sensitive surface of the solar-powered car as it hardens at low temperatures.

Covestro and PPG have been working together in the field of coatings development for many years now. Both partners are using the Sonnenwagen project to demonstrate the role coatings can play in sustainable mobility.

The race is on!

The World Solar Challenge, which is taking place from October 8 to 15, 2017, is considered to be the toughest race on Earth for solar cars and this year celebrates its 30th anniversary. Approximaely 40 teams from all over the world are competing in their “homemade” vehicles to win the 3,000 kilometer race from Darwin to Adelaide – without using one drop of fuel. The Sonnenwagen from Aachen is the only German car competing in the Challenger Class this year.


Bioplastics MAGAZINE, 2017-10-10.


Covestro AG
FH Aachen
Rheinisch-Westfälische Technische Hochschule Aachen (RWTH)
Team Sonnenwagen Aachen