This Small Business Innovation Research (SBIR) Phase I project aims to develop long fiber thermoplastic (LFT) based on recycled carbon fiber. The approach is to produce LFTs using recycled chopped carbon fibers with two different polymer matrixes. One is with nylon for the cost-effective automotive industry. The other is with polyphenylene sulfide for high-performance aerospace applications.

The broader/commercial impact of this project will be the potential to achieve considerable reductions of waste fiber that is sent to landfill. Conservatively, about 20% of carbon fiber produced will end up as waste during composite manufacturing and become landfill, which is a serious environmental concern. While recycling waste carbon fiber is highly desirable, few composite manufacturing processes are designed to work with chopped fibers, which is the primary form of the recycled carbon fibers. This technology will provide a manufacturing process to produce LFT composites using chopped carbon fibers. It is anticipated to achieve LFT properties comparable with commercial products made by virgin fibers.

Project Report

This project is developing long fiber thermoplastic (LFT) compositions based on recycled carbon fiber. We used two types of waste carbon fiber: (1) IM7 edge scrap from the manufacture of the main landing gear braces for an airliner; and (2) AS4 fiber reclaimed from end-of-life F-16 fighter aircraft, and also reclaimed from thermoplastic prepreg. Both fibers are aerospace grade: IM7 is an intermediate modulus; AS4 is a standard modulus fiber. We have demonstrated that recycled carbon fiber drawn from multiple sources is a viable raw material for making both nylon (PA66) and polyphenylene sulfide (PPS)-based LFT compounds. The recycled fibers - whether IM7 or AS4 in as-received, pyrolyzed, or regrind conditions - compounded and molded well in both the PPS and PA66 resin compositions. The mechanical properties achieved with recycled IM7-PA66 were superior to those for commercial Plasticomp PA66 LFT material. The properties achieved with as-received IM7-PPS (epoxy sizing) were respectable; however, pyrolyzing and resizing the fiber with a high temperature sizing markedly improved the properties of the composite. In addition, the properties of parts made from PPS-CF regrind made form carbon fiber - PPS thermoplastic prepreg were among the best results we achieved. This opens up another large source of material for recycling because thermoplastic prepreg is becoming common in aerospace construction. LFT made from recycled carbon fiber can therefore provide carbon fiber composite molders and users with a high-­value-added alternative to landfilling or incinerating their in-process and end-of-life scrap. MIT-LLC has been aggressively pursuing commercial partners to implement the LFT approach to making thermoplastic matrix composites. We have visited over a dozen different companies. Several of these have given us positive feedback regarding the use of the LFT approach for making parts for them. We are developing a Roadmap for commercializing recycled carbon fiber LFT. The targeted applications include the following: aircraft interiors (brackets, seats, partitions, bulkheads, stow bins) ground transportation - military (fenders, tool box, hood, latches) ground transportation - civilian (seats, access door, access panels, brackets) shipping, storage & instrument cases - military and civilian (electronics, weapons, other) satellite communication systems - military and civilian (antenna dishes, boom arms) The time frames for implementation of these technologies may be as short as 1-2 years (aircraft brackets) or as long as four years (military applications). The resin systems of interest range from nylon and PBT for civilian transportation and shipping containers to PPS, PEI, PEEK and PEKK for military applications. The commercial drivers are reduction of mass, reducing forming costs, and part consolidation. We have received numerous comments from potential partner companies about the cost and environmental advantages of using an approach like LFT. These advantages start with the materials savings provided by the near net-shape parts that LFT makes; typically, only a small amount of trimming or other finishing work is required to produce the final part. This is particularly important for the high performance polymers like PEI, PEEK, and PEKK, which cost between $20/lb and $50/lb of resin. A further cost advantage is the rapid cycle time that can be achieved with thermoplastic processing; cycle times are often in the three to five minute range. Finally, companies are intrigued by the potential for end-of-life recycling and reuse of LFT materials. This provides a true "closed circle" approach to the material's life cycle.

National Science Foundation (NSF)
Division of Industrial Innovation and Partnerships (IIP)
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Grace Jinliu Wang
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Materials Innovation Technologies, LLC.
United States
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