The invention relates to a thermoplastic moulding composition comprising an aromatic high-molecular weight polycarbonate based on a diphenol, with a weight-average molecular weight (M.sub.w) of at least 10,000 and from 0.5 to 5% by weight, relative to the high molecular weight polycarbonate, of a polycarbonate which has an M.sub.w of from 1,200 to 9,000 and which corresponds to the formula (I): ##STR1## wherein "E" represents a radical of the formula (II): ##STR2## in which THE GROUPS R' are identical and denote H or halogen x is an integer of from 7 to 24 "Z" is a divalent aromatic radical, and "n", the degree of polymerization, results from the M.sub.w between 1,200 and 9,000.