Morphology of poly(ether ether ketone)/poly(ether imide) blends and their application as a matrix for carbon fiber-reinforced plastic

Abstract This study aims to develop composite materials that combine high chemical resistance with superior thermal stability by blending poly(ether ether ketone) (PEEK), known for its chemical resistance, and poly(ether imide) (PEI), recognized for its heat resistance. The interfacial adhesion between carbon fibers (CFs) and PEEK/PEI blends was systematically investigated from the perspective of the blend morphology. Compared with that between PEEK and CFs, the interfacial shear strength (IFSS) between PEI and CFs was greater, and the IFSS of the PEEK/CF composites increased with increasing PEI content. At 50 wt% PEI, the IFSS became nearly equivalent to that of the PEI/CF composite. The distribution of PEI and PEEK near the CFs in the PEEK/PEI (50/50) matrix was examined using micro-Raman spectroscopy and scanning electron microscopy (SEM). The results revealed a submicron-sized PEI-rich region near the CF surface. While PEI was completely soluble in chloroform, the solubility of the PEEK/PEI (50/50) blend was limited to 13%, indicating enhanced chemical resistance due to PEEK incorporation. The glass transition temperature (Tg) of PEEK also increased with the addition of PEI. These findings demonstrate that submicron-scale heterogeneous structures in PEEK/PEI blends enhance thermal and chemical resistance and interfacial adhesion between the matrix and the CFs.