Enhanced Toughness of Poly(Ether Ether Ketone) Composites via Low‐Content, Small‐Sized Graphene Oxide and Rapid Cooling

Poly(ether ether ketone) (PEEK) possesses many excellent properties, but its poor toughness restricts wide application. Due to the high processing temperature of PEEK, traditional tougheners are not applicable. In this work, graphene oxide (GO) is applied as a novel toughener for PEEK. GOs with different lateral sizes, namely GO‐1 (7.8 μm), GO‐2 (2.2 μm), GO‐3 (3.3 μm), and GO‐4 (1.4 μm) are prepared by ultrasonic peeling and crushing graphite oxide at controlled ultrasound power and time. Afterwards, GOs are coated on PEEK powder via wet mixing and drying, and then the GO/PEEK composites are prepared by melt processing. It is noteworthy that the addition of GO is highly effective in improving the elongation at break of PEEK. The enhancement effect is highly dependent on the GO size and the cooling rate, with the combination of smaller GO and a faster cooling rate leading to a more pronounced effect. By adding 0.3% GO‐4, the GO/PEEK composite achieves elongation at break, fracture energy, and impact strength of 290.7%, 226.6 MJ m −3 , and 9.5 kJ m −2 . Compared with neat PEEK, the values increase by 184.4%, 212%, and 37.7%, respectively. Notably, the elongation at break is much higher than that ever reported for PEEK composites.