DYNAMIC MECHANICAL ANALYSIS

Abstract

DMA can be simply described as applying an oscillating force to a sample and ana- lyzing the material’s response to that force (Figure1.1). This is a simplification and we will discuss it in Chapter 5 in greater detail. From this, one calculates properties like the tendency to flow (called viscosity) from the phase lag and the stiffness(modulus) from the sample recovery. These properties are often described as the ability to lose energy as heat (damping) and the ability to recover from deformation(elasticity). One way to describe what we are studying is the relaxation of the polymer chains.14 Another description would be to discuss the changes in the free volume of the polymer that occur.15 Both descriptions allow one to visualize and describe the changes in the sample. We will discuss stress, strain, and viscosity in Chapter 2.