This Small Business Innovation Research (SBIR) Phase II project seeks to develop and demonstrate flame-resistant, polymer-composite materials based on novel benzoxazine resin chemistries. In the Phase I project, low-viscosity benzoxazine resins were synthesized and composite formulations prepared that exhibit suitable processing characteristics for use in composite manufacture, as well as good mechanical strength and flame resistance. These successes were achieved through the development of polymer synthesis techniques, and validated by the subsequent fabrication and testing of continuous fiber-reinforced composites. For example, the Phase I results showed that these new polymer formulations offer significantly reduced processing temperatures, which simplifies composite manufacturing processes and reduces tooling costs. In addition, the fiber-reinforced composites produced using these materials exhibited 15-20% higher tensile strengths and 50% higher toughness values as compared to composites fabricated using the as-synthesized (i.e., not toughened) material. This finding is important and shows that composites with strengths comparable to those of epoxy-based systems, but with superior flame resistance, can be achieved with these new materials.
The broader impact/commercial potential of this project will initially be in the electronics and aerospace markets. Flame-resistant polymers and composites are becoming increasingly important systems in both of these industries. In each case, the use of fire-resistant materials offers enhanced public safety, while also improving the overall performance of the systems in which they are used. The value of high-strength flame-resistant materials is perhaps most evident in the civil aviation industry. In this instance, the transition to composite materials offers a significant weight savings, with reductions in weight accounting for a large percentage of recent improvements in aircraft fuel efficiency, while also enhancing the flame resistance of aircraft structures. In addition, the use of advanced materials is expected to increase steadily in electronics applications over the next 10 years, and the further development and commercialization of benzoxazine resins will provide the users of this technology with enhancements in both fire safety and system-level performance.
In this Phase II/IIB SBIR program, CTD scaled up the production of low viscosity benzoxazine resin, a product that prior to this work, was not available on the market. CTD-804L was demonstrated at commercial-scale production volumes. In addition, CTD formulated and qualified a fire-resistant benzoxazine resin for commercial aircraft applications, and designed and fabricated a prototype composite tank for use aboard small commercial aircraft. The scale-up and commercialization of CTD-813L is particularly noteworthy because CTD is the first company to introduce a low-viscosity formulation that is comprised primarily of a benzoxazine resin. This product has several features that no other benzoxazine manufacturer has been able to demonstrate, such as compatibility with VARTM processes and a long working time, and establishes a strong market position for CTD in the future. Another significant outcome of this work was the design, fabrication, and qualification of an all-composite conformal tank. This is the first all-composite tank to be qualified for use in aircraft systems and provides a weight savings of approximately 50% as compared to stainless steel vessels. Moreover, a conformal tank allows for the efficient use of the available volume within the aircraft and enables a tank design that is not possible with conventional stainless steel manufacturing methods.
