This PFI: AIR Technology Translation project focuses on translating the multilayer dielectric film technology discovered at Case Western Reserve University (CWRU) to fulfill the need of high performance and low cost polymer film capacitors for electric drive vehicles (EDVs). The advantage of EDVs lies in the overall reduction of greenhouse gas emissions and pollution in heavily populated cities. Electric drive vehicles require a power electronics system to operate the motor that ultimately moves the car. The power electronics system requires DC-link capacitors to properly control the motor in response to speed commands from the driver. Current DC-link capacitors in the power electronics of EDVs use biaxially oriented polypropylene (BOPP) films. However, BOPP film capacitors have relatively low energy density and a low temperature rating of 85°C. Thus, a large volume of BOPP film capacitors and a water-cooling system are necessary in present EDVs, contributing to a high overall cost of the power electronics unit. To overcome this economic disadvantage, it is highly desired to develop new high performance capacitor films, which have a higher energy density and can operate efficiently up to 150 °C, thus potentially eliminately the cooling system entirely and resulting in a smaller size and mass system.
Supported by the NSF Science and Technology Center, Center for Layered Polymeric Materials (CLiPS), a unique multilayer dielectric film technology was invented at CWRU. In this technology, a high temperature, high breakdown strength, and low loss dielectric polymer (e.g., polycarbonates, PC) is multilayered with a high energy density polymer (e.g., poly(vinylidene fluoride), PVDF) into a layered configuration using the multilayer coextrusion technique. It is found that high energy density, high temperature tolerance, and low loss dielectric properties can be achieved simultaneously in one system. Therefore, the innovation of this multilayer film technology lies in the fact that without synthesizing and developing new polymers, new dielectric materials can be achieved simply by employing commercially available polymers. Consequently, a shorter commercialization pathway can be anticipated. On the basis of existing results on PC/PVDF multilayer films, this project aims to replace PVDF with a class of cheaper, but still high energy density, even-numbered nylons in multilayer films with high temperature PC. Preliminary results indicate that high energy density, high temperature tolerance, and low loss can also be achieved in the PC/nylon multilayer films.
In this project, a PFI AIR team, comprised of CWRU and two small businesses: PolymerPlus, LLC and SB Electronics, Inc. (SBE), proposes to translate the PC/nylon multilayer dielectric film technology into high temperature and high performance DC-link capacitors for EDVs. Specifically, CWRU will carry out film-level fundamental research to determine the optimal formulation of the PC/nylon multilayer films. PolymerPlus will use this formulation and scale up the film production into wrinkle-free film rolls. After appropriate metallization, PolymerPlus will supply the metallized film rolls to SBE to package into prototype film capacitors. The performance of these capacitor prototypes in comparison with BOPP capacitors will be tested by the team. This research project will offer ideal training opportunities for both graduate and undergraduate students because they can work with experts in the two small business companies and learn the technology translation and commercialization pathways. If successful, the team will be able to use the outcomes from this project and connect to EDV manufacturers for further commercialization of the multilayer dielectric film technology.
