Specialty thermoset resins designed for carbon-carbon composites

Kaneka Aerospace (Benecia, Calif., U.S.) manufactures specialty high-performance prepregs, resins and adhesives for the aerospace and industrial markets. Some of the offerings being presented include Kaneka’s novel diamine-based bis-benzoxazine resins with aldehyde end-terminated groups. Matrix options for high-temperature carbon fiber-reinforced plastics (CFRPs), the resins’ thermal and mechanical properties feature:

• Melt flowability at temperatures below 150°C for processing and converting of uncured resins into fully cross-linked structures by hot press molding at 220°C.
• Cured resins exhibit a high T_g temperature formally well over 230°C with little drop in storage modulus.
• Optimal elongation at break (>4%).
• Weight retention of around 70% for the cured resin when heated in an inert atmosphere to temperatures up to 1000°C
• Resins pyrolyzed up to 1800°C also showed improved residual weight.

Kaneka has also successfully fabricated carbon fiber prepregs with these resins, which were subsequently stacked and cured to yield CFRPs. A presentation in the CAMX theater, titled “Aldehyde Groups Terminated Bis-Benzoxazine Resins With High Char Yield for Carbon-Carbon Composite Applications,” presented by Hideki Yamamoto, highlights some of the preliminary studies on the processing of prepregs using the benzoxazine-based prepregs. Further, details of the post-curing pyrolysis and thermal treatment of the CFRPs are being presented, including a preliminary analysis of the pyrolyzed structure. Notably, the high weight retention of the reported cured resin is said to have translated well even at the CFRP level, which demonstrates optimal weight as well as dimensional retention. These results provide glimpses of the potential of these new materials toward their applications in carbon-carbon composites for the purposes of thermal protection.