The invention encompasses the process for the preparation of a cross-linked aramid polymer comprising the step of heating a non-crosslinked polymer comprising the repeating unit of formula (I) at a temperature comprised of from 150 to 400° C. for a period of time comprised of from 1 second to 20 minutes, wherein A and B are independently selected from meta-phenylene and para-phenylene, and R1 and R2 are independently selected from H and N3, with the proviso that at least one of R1 and R2 is N3 and R1 and R2 are attached to any of the positions 1, 2, 3, or 4 in para-phenylene and 1, 2, 3 in meta-phenylene; and the obtained cross-linked aramid polymer.