Source Year: 1999

Ethylene-propylene-diene rubber (EPDM) grades are becoming increasingly more sophisticated in terms of polymer microstructure. As a result, more sophisticated quality assurance tests, such as gel permeation chromatography (GPC), Mooney stress relaxation (MSR) and dynamic mechanical testing (DMT) are required to insure consistent polymer rheology. These tests were historically restricted to research settings. The role of these tests in the production setting is presented. Three polymers of equivalent Mooney viscosity that vary in terms of branching were characterised to demonstrate the sensitivity of the tests to structure. Then, a series of 12 consecutive production lots of EPDM were characterized by the same tests. The samples were also compounded in an ASTM type recipe. Both compound processability and cure properties were evaluated. Cured compound samples were tested for carbon black dispersion. Rheology of the raw polymer samples is compared to the ultimate compound rheology. Vanadium based catalysts systems are shown to be capable of producing EPDM with very consistent lot to lot polymer rheology. MSR and DMT can provide valuable information related to polymer microstructure, and along with GPC, can play an important role in quality control and quality assurance of EPDM production.