A coupling strategy for excellent mechanical properties and enhanced interfacial performance of polyimide/carbon fiber composite with metal-free catalyzed-curing route

The structure and properties of carbon fiber reinforced composites (CFRC) depend on main factors, especially the unpredictable interface. In this work, a kind of thiocarbonyl disulfide compound is introduced to achieve the catalyzed-cure of phenylethynyl terminated polyimide (PI) and plays the role of coupling medium to constitute covalent-bonded structure at the PI/CF interface. The organocatalyzed cure not only follows the free radical mechanism with an initial curing temperature down to 260.4 degrees C, but also endows the composite with reduced internal thermal stress and enhanced interface structure. Due to both CF surface-initiated free radical curing reaction and coupling reaction between thiocarbonyl-containing PI matrix and hydroxyl-rich sizing layer, the composite performs an improved interfacial shear strength (IFSS) of 123.9 MPa, being 2.47 times as the thermally cured ones, plus the anti-bacterial reinforcement of the PI matrix. Besides, the interface enhancement brings the CFRC specimen improved electrical properties, performing a 92.6% increase of transverse electrical conductivity to 367.6 S/m. This study gives perspective for improving the interfacial performance of hightemperature processed CFRC with "as-received" fiber reinforcers, plus a clear outlook to future research directions and open challenges to prepare high-performance CFRC.