This paper presents the use of statistical analysis for studying the responses of two continuous devulcanization processes (of the EPDM roofing sheet and the EPDM profile) in the extruder. The response is represented by the reaction conversion, which is denoted as the relative decrease in crosslink density. Experimental design is considered as a useful tool when the kinetic data for the physical modeling are not available. The models derived show similar tendency of both processes with respect to the temperature and the screw speed. A difference is observed in their responses to the feed rate, which might be the consequence of their different devulcanization rates. (c) 2006 Wiley Periodicals, Inc.