More Sustainable Film Capacitors

TDK has introduced a bio-circular polypropylene film for its ModCap^® series of DC-link capacitors. This is the first step towards fully sustainable film capacitors as Dr. Marisa Rico, coordinator of the materials laboratory, and Victor Alcaide, Director Product Marketing of PEC HP capacitors, explain.
 

Q: When and how did you learn that polypropylene film can also be made from bio-based sources?

Marisa Rico: At TDK, we are focusing on the production of capacitors with the least possible impact in the environment. Therefore, we are constantly investigating different approaches related to the circular economy to extend the life cycle of our components, reduce material required, and better manage end-of-life waste.

Our basic research and development group is actively collaborating with suppliers to develop new sustainable materials without compromising on the final material properties. Bio-based films are already a well-known solution for packaging, especially for the food sector. The Borealis Group has developed such a polypropylene raw material, and they proposed to test it with our capacitors.
 

Q: Normally, polypropylene is obtained from fossil raw material. What is the source of this bio-based film?

Marisa Rico: Depending on the source it comes from – agricultural renewable raw material or wastes and residues – it can be divided into first- and second-generation polypropylene. First-generation renewable material (bio) is obtained from agricultural crops grown for food and livestock feed. On the other hand, second-generation renewable raw materials (bio-circular) come exclusively from waste and residues: from the production of vegetable oil, from the paper and pulp industry, or from used cooking oil, for example. The market is betting on using second-generation polypropylene. Thus, fundamental ethical issues should be avoided, such as conflicts with food cultivation which could increase food prices.

Q: The bio-based propylene TDK uses is ISSC certified. What does this mean?

Victor Alcaide: ISCC stands for International Sustainability and Carbon Certification and is a sustainability certification system for all agricultural and forestry raw materials and markets. The scheme complies with the Renewable Energy Directive and the Fuel Quality Directive of the European Commission.

This ISCC certification for our plant in Málaga is mandatory for TDK to be allowed to promote that our film capacitors produced here are made from 100 percent bio-circular film. By this, we can demonstrate to our customers the use of second-generation films and monitor it. Audits at our plant are carried out every year to prove that the film used for our components is really bio-circular.

Malaga plant

Q: Has this new polypropylene film really the same electrical and physical properties as the conventional one?

Marisa Rico: Bio-circular raw material can be processed the very same way as conventional. Although they come from different sources, the material is identical, and in terms of performance, it is impossible to determine whether the film was made from biomaterial or fossil raw material, as both have the very same electrical and physical properties. Even the suppliers of raw materials and films do not make any difference. This fact is also related to how ISCC certification works.

ModCap series

Q: The first product family with this bio-based propylene is the ModCap^®. Why did you choose this product and in which applications are ModCaps used?

Victor Alcaide: The ModCap series is our most innovative product at PEC HP (Power Electronic Capacitor High Power). It is a disruptive solution because, on the one hand, it is modular and thus shortens the time to market for the customers and also reduces costs. On the other hand, it provides highest energy densities in the MF (middle frequency) version and highest power densities in the HF (high frequency) version.

Our ModCap series offers the most innovative solution for DC link application in inverters with the new generation of silicon carbide semiconductors. The ModCaps can handle quite high switching frequencies and at the same time they are a sustainable product to meet the new requirements of end customers in terms of environmentally friendly materials. 

Q: Having a bio-based film is great, but what about the polyurethane resin and the case? Are these also bio-based?

Victor Alcaide: A fully bio-circular film is just the first step. Our basic research and development team is actively partnering with suppliers to develop new sustainable materials without sacrificing final material properties. These include polyurethane resin, internal insulation, and housing. However, polyurethane is particularly challenging due to the requirements imposed on capacitors.

Bio-based film

Q: What about the cost? Does the bio-based polypropylene cost as much as the conventional one and what is your strategic approach?

Victor Alcaide: Actually, bio-circular film is currently about 20 to 30 percent more expensive than conventional one. But I believe we are doing the right thing to support the competitiveness of TDK’s ModCap series. Furthermore, the bio-circular film in our ModCaps once again demonstrates that TDK is an innovative company which acts sustainable and proactive.
 

Q: When will these ModCaps with bio-based film be available for customers? And when do you expect the polyurethane resin and the case to be bio-based?

Victor Alcaide: The bio-circular film is scheduled to be launched for mass production in June 2023 for all our ModCap series, MF and HF versions. This will be the new standard solution at no additional cost to our customers. Besides, we can also use the bio-based film in customized capacitors if the customers are interested and willing to pay a small premium for it. Other bio-based materials are expected to be approved by 2024.
 

Q: ModCap is the starting point for bio-based film capacitors at TDK. Is this technology also suitable for other types of film capacitors, for example DC- and EMI filter capacitors?

Victor Alcaide: Bio-circular films are fully suitable for other film capacitor technologies. For custom PEC HP capacitors it will be available on request. For the other technologies it will depend on the market acceptance with ModCap.

Dr. Marisa Rico, coordinator of the materials science laboratory (left), and Victor Alcaide, product marketing manager for PEC HP capacitors at TDK in Málaga, are proud that the ModCap series is now based on film made from bio-circular polypropylene.

The ISCC certification for the plant in Málaga is mandatory for TDK to be allowed to promote that the ModCap capacitors produced there are made from 100 percent bio-circular film.