Preparation of a water-based carboxylated Poly(phthalazione ether nitrile) sizing agent for interfacial reinforcement of CF/PPESK composites

This study focuses on synthesizing a range of hydrolysis-modified poly(phthalazione ether nitrile) polymers with different quantities of carboxyl groups (HPPEN-COOH). These polymers are intended to enhance the bonding strength between carbon fibers (CFs) and poly(phthalazine ether sulfone ketone) (PPESK). The chemical structure of HPPEN-COOH was elucidated using FTIR spectroscopy, and the presence of HPPEN-COOH as a coating on the CFs surface was confirmed by XPS analysis. Compared with the UCF/PPESK composite, the interlaminar shear strength of the CF-5/PPESK composite increased by 39%. In the DMA test, the service temperature and storage modulus of the CF-5/PPESK composite were increased to 268°C and 112 GPa, respectively. Furthermore, the composite showed satisfactory performance in hydrothermal aging studies. This method is simple and easy to implement, has the potential for large-scale industrial production, and is an environmentally friendly method to improve the interface properties of the CF/PPESK composite.