ASTM D8059 covers the use of a sealed cavity rotorless oscillating shear rheometer to measure strain softening under increasing sinusoidal strain in unvulcanized rubber compounds that contain significant colloidal fillers such as silica, carbon black or both. This strain softening is known as the Payne effect.
ASTM relates the results to mixing conditions, compound composition, the Payne effect of the filler and, for some compounds, the degree of silane reaction with precipitated silica. In the uncured state, time conditioning and strain sweeps can relate to how well filler particles were broken down during mixing, and the G′ strain softening profile depends on filler loading and particle size. With silica and an organosilane, the test can show whether silanization was achieved in the mixer.
The strain sweep is run on a sealed cavity rotorless shear rheometer. Our RPA Ultra rubber process analyzer supports Payne effect testing to ASTM D8059. If you need help matching ASTM D8059 requirements to your parts or setup, contact our team.
