ELASTOMERS AND PLASTICS Does nonlinear Viscoelasticity inherently exist in Rubber?

This study investigates the transition from linear to non-linear viscoelastic behavior in polymers and rubber compounds under cyclic sinusoidal shear deformation. The stress response is analyzed through Fourier series decomposition, enabling the definition of the generalized elastic modulus, G0 ' (γ0) and viscous modulus. These parameters are critical for characterizing the complex viscoelastic properties.

The measurement of the viscoelastic properties of uncured compounds (commonly referred as green rubber compounds) using traditional dynamic-mechanical instruments is not yet widely adopted in the rubber industry. This practice is uncommon both among compounders during the compound development phase and among molders during the production of finished articles. The RPA (Rubber Process Analyzer) instrument was designed to overcome these limitations and provide reliable viscoelastic data for both uncured and cured compound samples. It works under a wide range of strain, frequency, and temperature conditions in a simple, repeatable, and reproducible manner.