# Viscoelasticity

Dynamic Mechanical Analysis (DMA) is used for polymers and rubber materials with a fixed geometry. An oscillation is applied during a frequency sweep while the temperature is increased. The complex modulus, the storage and loss modulus combined, is then determined as a function of frequency and temperature.

**Storage Modulus** (E’) is a measure of the elasticity of a polymer material. **Loss Modulus** (E”) is a measure of the capacity for a polymer to convert mechanical energy into heat. **Loss Factor**, referred to as **tan δ**, is the ratio of E” to E’.

When sample size or function requires a small volume, a dynamic nanoindentation test analogous to DMA is used to determine E' and E''. Nanoindentation can be used to characterize a larger frequency range than DMA. Less heat can be applied to due the smaller sample size.

**Tire cross-section with storage and loss modulus 3D maps from nanoindentation data**