Creep-recovery experiments up to the steady state were performed on neat poly (methyl methacrylate) and on composites filled with 2.1 vol.% silica nanoparticles in order to get information on the long retardation times that occur due to polymer-particle interactions. The temperature dependence of the elasticity was investigated, varying the temperatures between 170 degrees C and 200 degrees C. For the neat polymer it was found that it behaves thermorheologically simple, whereas the composite exhibits a thermorheological complexity. An interpretation of these findings can be given, if the corresponding retardation spectra are regarded. The interactions between the polymer molecules and the particle surface is reflected by a particular maximum at longer retardation times, which exhibits a different temperature dependence compared to the spectra of the unfilled polymer matrix. This thermorheological complex behaviour is not seen in the usual dynamic-mechanical measurements down to angular frequencies of omega = 10(-2) s(-1). If the frequency range of the dynamic moduli is extended, however, by making use of the retardation spectra, a thermorheological complexity can be found, too. These results demonstrate that appropriate experimental time windows have to be applied to obtain a comprehensive picture of the rheological behaviour of nano particle-filled polymer melts. (C) 2011 Elsevier Ltd. All rights reserved.