In this study, the prime factor determining the size, shape, and distribution of liquid-crystalline polymer (LCP) was the viscosity ratio at the processing conditions. The fiber-forming capacity of the LCP depended on the viscosity of the ethylene-propylene-diene monomer rubber (EPDM). With increasing LCP content, the tensile and tear strengths did not increase, perhaps because of incompatibility between the EPDM and LCP. The hardness increased because of the hard mesogenic groups in the LCP. The percentage swelling decreased as the LCP content increased. With increasing LCP content, processability became easier because of a lower melt viscosity. The scorch time increased at higher LCP levels. A higher percentage crystallinity was observed with increasing LCP content. Scanning electron microscopy clearly showed the fiber phase formation, which was two-dimensionally isotropic in nature, confirming fiber formation even in a shear field. The addition of LCP improved the thermal stability. The onset degradation temperatures shifted to higher values with increasing LCP content. Dynamic mechanical thermal analysis revealed that with the addition of LCP, the mechanical damping increased at its lower level. High-temperature processing increased the effective amorphous zone. (C) 2004 Wiley Periodicals, Inc.