Properties of electropolymerized polycarboxyphenylmethacrylamide matrices/graphite fiber composites: Crosslinking effect

Imide formation from ‐CONH and ‐COOH functional groups of 2‐carboxyphenylmethacrylamide (2‐CPM), 4‐carboxyphenylmethacrylamide (4‐CPM), 4‐carboxyphenyl methacrylamide/methylmethacrylate (4‐CPM/MMA) and 4‐carboxyphenylmethacrylamide/N‐phenylmalemide (4‐CPM/NPMI) electropolymerized matrices was investigated. It was found that 2‐CPM polymers undergo intramolecular imidization and anhydride formation, which result in a small amount of crosslinked network. On the other hand, the thermally cured 4‐CPM polymer demonstrates a significant increase in gel fraction. T g and dynamic storage modulus, owing to crosslinked network formation. T g s of 4‐CPM/MMA and 4‐CPM/NPMI composites measured by thermomechanical analysis after thermal heating were increased and were correlated very well with the preheating time. The 4‐CPM/MMA composites with a particle crosslinking ( T g increased to 245°C) maintained a higher Izod impact strength than a typical epoxy composite (200 kJ/m 2 vs. 100 kJ/m 2 ). Upon heating to promote crosslinking, a lower shear strength (65 MPa) of a 4‐CPM/MMA composite increased to a strength of 78 MPa, close to the 80 MPa of an epoxy composite at 67% fiber volume fraction. A lower water absorption of around 1% was associated with the increased crosslinking. The mechanical properties of the 4‐CPM/NPMI composites showed a similar trend upon preheating.