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(a) Fracture toughness of neat epoxy and epoxy system modified with different content of polyphenylene ether (PPO). Reprinted with permission from ref. [44], Copyright [2018], American Chemical Society, (b) fracture toughness of epoxy blends with PEEK-PR or PEEK-TOH. Reprinted with permission from ref. [38], Copyright [2019], John Wiley and Sons.
