CONTRIBUTION OF CROSSLINK NETWORK STRUCTURE TO THE VISCOELASTIC CHARACTERISTICS OF EPDM: TUNING DYNAMIC PROPERTIES THROUGH HYBRID CURING

ABSTRACT EPDM is the fourth most widely used general-purpose elastomer, accounting for approximately 10% of total synthetic rubber production. With its broad applications in the automotive and construction industries, the analysis of EPDM’s dynamic viscoelastic properties is critical for optimizing product performance. Although the effects of various fillers and their structures on EPDM’s viscoelastic behavior have been widely studied, the impact of crosslink network architecture on long-term viscoelastic properties is seldom explored. To investigate the influence of different crosslink types and their compositions on the long-term viscoelastic behavior of EPDM, we have used thiol-amine analysis, time–temperature superposition for frequency-dependent properties, and temperature scanning stress relaxation. We establish correlations between crosslink features and the viscoelastic properties of carbon black–filled EPDM. In addition, we explore the effects of unique crosslink networks formed through hybrid cure systems containing accelerated sulfur and peroxide on the viscoelastic performance of EPDM. Our findings indicate that the frequency dependence of viscoelastic properties is governed by crosslink length, whereas temperature dependence is influenced by crosslink type. The results also indicated a strong correlation between plateau modulus and polysulfide crosslinks. These insights offer valuable guidance for optimizing the viscoelastic characteristics of next-generation elastomeric materials.