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Performance of Second 50 Completed ATP Projects — Status Report Number 3 NIST Special Publication 950-3 (January 2006)
Conservation Concerns Drive New Materials Development During the late 1980s and early 1990s, there was increasing interest in using new materials to achieve weight reductions in automobile manufacturing. This interest grew out of the need to conserve energy and recycle automotive materials. Polymer matrix composites, it was thought, could help the automotive industry address these issues.There was increasing interest in using new materials to achieve weight reductions in automobile manufacturing. During this period, the Ford Motor Company Scientific Research Laboratory had been working to develop and evaluate processes to produce large composite structures using polymer-based thermosetting resins systems. Meanwhile, General Electric Central Research (GE) was in the process of identifying properties in molecular compositions of matter that would be utilized in resin development of thermoplastics. Given the research under way by both Ford and GE, tremendous potential existed for developing materials and processes to manufacture composite automobile structural parts through the use of cyclic thermoplastic technology. In 1991, the world market for advanced polymer matrix composites was $4.7 billion, with the U.S. share reaching $2.6 billion or 54 percent of the world market. At the time, polymer matrix composites were predominantly used in the manufacture of military aircraft and missiles, although research indicated that these materials could be used in the automotive industry. Preliminary studies at Ford suggested that the use of carbon fiber/polymer composites could achieve weight reductions in steel body structures of between 34 percent and 65 percent, which could increase the annual market for composite materials by an estimated $20 billion. Other potential applications included commercial aircraft, airframes and engine structures, non-defense space structures, sports and recreation equipment, mass transit systems, offshore oil exploration and production, and industrial facility applications. Joint Venture Identifies Material that Meets World- Market Need In May 2000, a committee of diplomats from the 15 European Union member countries and members of the European Parliament adopted the European Union End-of-Life Vehicle Law. This law requires that manufacturers pay all, or a significant part, of the costs of taking back and recycling the new cars that they sell. As early as 1994, however, Ford and GE had already identified thermoplastic liquid composites as a class of materials that could be easily and affordably recycled. Existing Methods Lack Required Flexibility In 1992, when the joint venture submitted its proposal to ATP, thermoset polymer-matrix composites were prevalent in automotive component manufacturing. These components were fabricated using a process called liquid composite molding, which uses a preformed shell made from glass fibers combined with a molded foam core to create a pre-form in the shape of the final part. The pre-form is then placed in a heated steel mold and clamped in a low-pressure press. Liquid resin is delivered from a pressurized pump into the mold and, once the resin is cured, the part is removed. Traditional thermoplastics have been excluded from the liquid composite molding process Thermosel polymers, when subjected to heat, undergo an irreversible chemical reaction, causing the molecules in the polymer to cross-link, or connect the polymer chains. As a result, the entire finished part becomes a single, large molecule. thermosets are used in liquid composite molding, in large part because of processing issues. The low viscosity of unreacted thermoset resins facilities rapid impregnation and wet-out (elimination of voids or imperfection of bonding) of the pre-form. Large, thermoset-based parts are difficult to manufacture, however, because of the heat (exothermic) generated in the process. This heat can reduce the finished products ability to withstand damage (i.e., its crashworthiness). In addition, thermoset-based parts are difficult to recycle. Thermoplastics, in contrast to thermosets, can be recycled simply by reheating the material. Traditional thermoplastics have been excluded from the liquid composite molding process, however, because they are relatively viscous when melted. This viscosity creates difficulties in establishing a smooth flow of the material through the mold, even if high pressure is used. Cyclic Technology Offers Improvements Like thermosets, cyclic thermoplastics exhibit low viscosity when molten so that they flow like water and low-injection pressure can be used. Moreover, unlike thermosets, cyclic thermoplastics do not have production problems associated with heat generation, which enhances their suitability for use in manufacturing large component parts. Cyclic thermoplastics also are recyclable. Seven-Member Project Team Obtains ATP Funding In 1992, a seven-member joint venture submitted its proposal to ATP and received a $5.3 million, four-year award. It proposed to focus its efforts on the use of cyclic thermoplastics in liquid composite molding, also known as resin transfer molding. The joint venture included the following members:
Pilot Production Proceeds The project team concentrated on laboratory studies of resin chemistry and research and acquisition of a sophisticated melting device. Additionally, it undertook the initial fabrication of a laboratory molding system. Extensive discussions then ensued among team members regarding initiator systems for use in the process, ultimately resulting in the decision to use a low- viscosity liquid as the initiator. Not only were these initiators readily available, but the use of a liquid initiator was preferable because it enabled mixing to occur as the initiator and resin entered the mold. The next step was research selection and acquisition of an extruder that had the ability to melt and convey the polymer according to the team's specifications. At the conclusion of this step, and with the identification of a process and a primary material, the team began pilot production, which included the following:
Reevaluation Leads to Changes in Production Approach The information and data generated throughout pilot production led to the installation of a large-scale system at Ford within the original timeline, as well as the actual production of a prototype. Once production was under way, the team reviewed the prototype results. Actual molded plaque data and cost projections revealed the need to reevaluate the cost approach to resin synthesis and the originally projected physical properties, including recycling potential, in molded composites. Subsequently, the team carefully studied and then selected a potentially lower cost approach to resin synthesis. With the modifications and adjustments to the process in place, and the project now back on track, the team produced acceptable test plaques in sufficient quantity and quality. Preliminary testing, however, determined that the properties of the cyclic plaques did not meet the established baseline requirements of thermosets. At this juncture, researchers experimented with and evaluated a range of initiators, stabilizers, and antioxidants that could improve the properties of the cyclic thermoplastics. During this evaluation period, the team selected a core technology and a supplier, and it continued molded component production. Evaluation of the product indicated that the team had achieved the best properties thus far through adjustments in resin metering and mixing. As the project drew to a close, the team manufactured six composite cross-members, three of which were testable. ATP Support Accelerates Technology Development Ford and GE determined that the ATP funding accelerated the development of the resin system and processing technology by two to four years. Since private capital was not available because of the risks associated with the project, the joint venture would not have been able to set up and operate a project of this magnitude without ATP funding. With ATP's encouragement, Ford and GE were able to recognized the importance of their research for the entire automotive community and shared performance data through the auspices of the Automobile Composites Consortium (composed of Ford, General Motors, and DaimlerChrysler), thus enhancing the entire industry's understanding of the liquid composite molding process. Conclusion At project completion in 1996, the research team had met its manufacturing cost target of approximately $1 per pound. The team did not, however, achieve its goal of translating key properties from laboratory beaker reactions to materials made under simulated production conditions. Additionally, the joint venture had not fully demonstrated key resin attributes, such as toughness and energy-absorbing capability. As a result of ATP funding, however, the project achieved success in the following areas:
In 1999, privately owned Cyclics Corporation, headquartered in Rensselaer , New York , received funding and purchased GE's portfolio of patents related to cyclic thermoplastics. The company has continued to enhance the technology and has developed alliances to manufacture and market resins for applications in the automotive, construction, and powder-coating industries. Cyclics orporation is also undertaking a number of development projects for direct customers in structural composites and related technology areas.
Research and data for Status Report 91-01-0178 were collected during October - December 2001. Return to Table of Contents or go to next section of Status Report No. 3. Date created: April 4, 2006 |
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ATP website comments: webmaster-atp@nist.gov / Technical ATP inquiries: InfoCoord.ATP@nist.gov. NIST is an agency of the U.S. Commerce Department |
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