Improving mechanical properties of high-temperature resistant carbon fiber/phthalonitrile composites via surface modification: a comparative study on modification methods.

The interfacial bonding is of essential importance for the mechanical properties of high-temperature resistant carbon fiber/phthalonitrile composite materials. To promote the interfacial adhesion of carbon fiber/phthalonitrile composites, three surface modification methods, namely HP302 sizing, diazotization modification, and oxidation-diazotization modification, were applied and compared. The results showed that the de-sizing treatment barely affected the mechanical properties of the composites. Both re-sizing with HP302 agent and diazotization modification improved the mechanical properties, while the mechanical properties were drastically decreased via the oxidation-diazotization modification. Among these surface modification methods, the diazotization treatment derived the best mechanical properties of carbon fiber/phthalonitrile composites both at room and high temperature. Specifically, the flexural strengths were 345 MPa (RT), 525 MPa (300°C), and 442 MPa (400°C), which were 47%, 302%, and 281% higher than those of the pristine composites. The interlaminar shear strengths were 33 MPa (RT), 26 MPa (300°C), and 27 MPa (400°C), which were all over twofold than those of the original counterparts. [ABSTRACT FROM AUTHOR]