Disclosed are electret materials with outstanding thermal and charge stability. The electret materials comprise a melt blend of a thermoplastic polymer and one or more compounds selected from the aromatic trisamides. The aromatic trisamides are for example of the formula The melt blends are subjected to an electret treatment, for example a corona treatment. The electret materials are for example nonwoven polyolefin webs and are employed as filter materials, wipes, absorbent materials, filter masks, acoustic materials, printing substrates, measuring devices or contactless switches. The present electret materials may also comprise a further additive selected from the hindered amine light stabilizers and the hydroxyphenylalkylphosphonic esters or monoesters.