P.L. Teh- Thermal Analysis

Most materials are
classified as viscoelastic
i.e δ is between 0º and
90º. Most polymers
exhibit this behavior and
have an elastic and
viscous component.

Storage modulus (E'): ability of polymer to store energy (elastic behavior)

Loss modulus (E"): tendency of the material to dissipate energy (viscous
behavior)

Damping factor (tan δ): Fraction of mechanical energy dissipated as heat
during loading/ unloading cycle

Dashpot- Newton’s Law - Viscosity
Spring- Hooke’s law - Elasticity

Damping



DMA Viscoelastic Parameters

DMA analysis mode:

Three Point Bending



The loss modulus E’’ represents the viscous component of the
material.
A higher E’’ value reflects a greater capacity to dissipate
mechanical energy in the form of heat during deformation.

For polymer blend:

Dynamic Mechanical Analysis

Measure change in dimension under constant load during heating
or cooling.

Measure dimension changes under constant load, as
function of temperature





CTE

Below glass transition Above glass transition

Below glass transition CTE

For most materials: Above glass transition
• 7 ppm to 50 ppm
For most materials,
(reinforced) • 50 ppm to 100ppm
• 30 ppm to 150 pmm
(reinforced)
(unreinforced) • 150 ppm to 500 ppm

(unreinforced)

Glass Transition Temperature: – Tg
• Construct a tangent line to the curve above and below the

transition in the curve. The temperature where these
tangents intersect is the TMA determined Tg for the
material.

• Figure shows the typical expansion
behavior of a PI resin casting.

• Cured thermoset typically
exhibited two linear regions:

• The first is associated with the
glassy state and the second linear
region of higher slope associated
with the rubbery state because of
the Tg.

Applications of TMA:
• Determination of linear expansion
coefficient
• Determination of Tg

CTE of Composites