Improving the curing reactivity, interfacial strength, thermal and mechanical properties of phthalonitrile resin/basalt fiber composites by reactive organic coating

Phthalonitrile (PN) resin is a thermosetting resin with excellent properties, but its poor processability hinders its wide application. Meanwhile, as a high-performance green fiber, basalt fiber (BF) shows good overall properties, but the chemical inertness and smooth surface limits its application as well. In this work, a highly reactive organic coating polydopamine (PDA) was used to promote the curing of PN resin and enhance the interfacial interaction between the polymer matrix and the fiber cloth. The successful coating of PDA was verified by SEM observation, FTIR and XPS spectra. It was found that PDA could not only increase the polarity of BF, aid the infiltration of PN resin into the fiber cloth, enhance the interfacial strength, but also promote the consumption of cyano groups and increase the chemical crosslinking density. Consequently, the overall performance of the composites was enhanced. Specifically, the laminate 0.4DABF/BAPh showed flexural strength of 447 MPa and flexural modulus of 23.3 GPa, which was 131 MPa and 4.5 GPa higher than those of BF/BAPh. The glass transition temperature of 0.4DABF/BAPh was also 77 °C higher than that of BF/BAPh.