Reduced de-doping and enhanced electrical conductivity of polyaniline filled phenol-divinylbenzene composite for potential lightning strike protection application

Phenolic resin was mixed with a cross-linking agent divinylbenzene (DVB) to prepare a polyaniline-based electrically-conductive thermosetting polymer composite. It has been shown that this Phenol-DVB mixture can undergo cationic polymerization in the presence of the dodecylbenzene sulfonic acid (DBSA)-doped polyaniline (PANI). Composites with different weight ratios of phenolic resin and DVB were mixed with a fixed weight of DBSA-PANI (i.e. 30 wt. %). Increasing the phenol content in the resin system was found to improve the electrical conductivity of the composite to almost 2700%. This improvement has been assigned to the reduced de-doping of polyaniline in phenol-DVB resin. Active sites of phenol effectively attached to the β carbon of DVB and reduced the proton subtracting species of DVB, leading to reduced de-doping of PANI. This behavior was studied through various characterization techniques including differential scanning calorimetry (DSC), FT-IR spectroscopy and Scanning Electron Microscopy (SEM). Electrical conductivity measurement, mechanical properties, and in-situ electrical conductivity measurements were performed to find the optimized properties of the composite. Optimized composites prepared with the composition of 30 wt. % DBSA-PANI and 70 wt. % of phenol-DVB (50 wt. % each), have shown electrical conductivity of 0.20 S/cm and a flexural modulus of 2.1 GPa, which is a significant improvement in the flexural properties of polymer based-thermosetting composites with similar electrical conductivity. This material can be a potential candidate for the lightning strike protection of fiber reinforced plastics.