Excellent ablative properties of ethylene-propylene-diene elastomer (EPDM) composites were obtained by adding pretreated polysulfonamide pulp (PSA-pulp). The effects Of Pulp pretreatment and pulp content on the mechanical and ablative properties of PSA-pulp/EPDM composites were Studied. Experimental results showed that the tensile strength decreased slightly and the ablative properties increased by 3 folds on addition of 10 phr pretreated PSA-pulp. This significant improvement in the ablative properties was attributed to the enhanced dispersion degree and improved interfacial adhesion of pretreated PSA-pulp to EPDM matrix, which were observed from scanning electron microscopy. The ablation behavior of pretreated PSA-pulp/EPDM composites was proposed in accordance with the characterizations of thermogravimetric analysis (TGA), energy disperse X-ray spectroscopy (EDS) and pyrolysis-gas chromatograph-mass spectrometry (Py-GC-MS). The carbonized PSA-pulp acted as a skeleton in retaining the chat layer and reduced the material loss during the high temperature ablation. (C) 2008 Elsevier B.V. All rights reserved.