Chlorinated polyethylene (CPE) taken as a modifier for NR rubber compound changes the mechanical properties of their vulcanizates. With the help of a novel thermomechanical methodology it was found that it also influences the structures of both the tested master batches and the vulcanizates. Some characteristics of the structure of NR/CPE rubbers obtained by using thermomechanical analysis (TMA) correlate satisfactorily with their mechanical properties measured at static and dynamic conditions. This supports our previous conclusion about the suitability of TMA to study some of the underlying reasons for changes in rubber properties resulting from rubber formulation, compounding, and processing. (C) 2003 Wiley Periodicals, Inc.