The aim of this study was to compare the effects of 5 to 30 parts by weight of unmodified and modified collagen on the properties of XNBR rubber vulcanized with a cross-linking system. This study is a part of experimental series concerning polymeric materials that are biodegradable due to their filling with a waste protein such as collagen. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 1984-1991, 2009