Carbonized polybenzoxazine for electromagnetic interference shielding

A kind of highly thermally stable polybenzoxazine prepared from the monomer bearing both acetenyl and aldehyde groups was treated at different temperatures till 1000 degrees C. The evolution of the chemical structures of the products during the heat treatment process was studied by FTIR, EA, XRD, XPS and Raman spectroscopy. It is learned that the pyrolysis process dominates below 600 degrees C while the carbonization plays a leading role when the temperature rises above 800 degrees C. Polybenzoxazine can rapidly carbonize and form N-containing heterocyclic structures such as pyridine, pyridinium and O-containing structures like cyclic ketones and ether groups at high temperatures (>800 degrees C). The resultant carbonaceous material treated at 1000 degrees C shows the electrical conductivity as high as 2.36 S/m, which is nine orders of magnitude higher than that of polybenzoxazine. Consequently, a 1 mm thick carbonaceous material shows an electromagnetic interference shielding effectiveness (EMI SE) more than 24 dB over the range of X-band, which means 93.7% of incident electromagnetic energy can be blocked.