PROPERTIES OF ELECTROPOLYMERIZED POLYCARBOXYPHENYLMETHACRYLAMIDE MATRICES GRAPHITE FIBER COMPOSITES - CROSS-LINKING EFFECT

Imide formation from -CONH and -COOH functional groups of 2-carboxyphe nylmethacrylamide (2-CPM), 4-carboxyphenylmethacrylamide (4-CPM), 4-ca rboxyphenyl methacrylamide/methylmethacrylate (4-CPM/MMA) and 4-carbox yphenylmethacrylamide/N-phenylmaleimide (4-CPM/NPMI) electropolymerize d 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 fractio n. T(g) and dynamic storage modulus, owing to crosslinked network form ation. T(g)s of 4-CPM/MMA and 4-CPM/NPMI composites measured by thermo mechanical analysis after thermal heating were increased and were corr elated very well with the preheating time. The 4-CPM/MMA composites wi th a particle crosslinking (T(g) increased to 245-degrees-C) maintaine d a higher Izod impact strength than a typical epoxy composite (200 kJ /m2 VS. 100 kJ/m2). Upon heating to promote crosslinking, a lower shea r strength (65 MPa) of a 4-CPM/MMA composite increased to a strength o f 78 MPa, close to the 80 MPa of an epoxy composite at 67% fiber volum e fraction. A lower water absorption of around 1% was associated with the increased crosslinking. The mechanical properties of the 4-CPM/NPM I composites showed a similar trend upon preheating.