This invention relates to a pressboard comprising a plurality of plies having thermostable floc and at least 40 weight percent aramid fibrids, the pressboard having a final average thickness of 0.9 mm or greater, the pressboard further having an a void content of 25 volume percent or less and a ply adhesion (Y) in megapascals defined by the equation Y>2.97(X)(−0.25) wherein (X) is the thickness of the pressboard in millimeters; the pressboard can have a compressibility of 1.6 percent or less and compression set of 0.18 percent or less.