A series of composites based on polydimethylsiloxane-alpha,omega-diol (PDMS) as polymeric matrix, silica aerogel as reinforcing filler, and the lignin powder-a biomass derivative, as bulking filler, have been prepared. Different weight ratios between components were used. The composites were investigated by scanning electron microscopy, dynamic mechanical analysis, tensile strength tests, X-ray diffraction analysis, thermogravimetric analysis, and differential scanning calorimetry. The results were compared with those obtained on a reference sample prepared by using a classical material-diatomite and a pure crosslinked PDMS. (C) 2009 Wiley Periodicals, Inc. J Appl polym Sci 113: 2313-2321, 2009