Thermomechanical Analysis (TMA) 

For measuring both the thermal and the mechanical properties, a thermomechanical analyzer (TMA) is used. Temperature-dependent dimensional changes in solids, liquids and pastes determine the suitability of an application for a given material or provide information about the composition, structure and conditions of processing.

TMA measures these dimensional changes while allowing the sample to be subjected to an additional mechanical load (DIN 51005, ASTM E 831, ASTM D 696, and ASTM D 3386). This makes it possible to determine the thermal length change (with negligible mechanical load: dilatometry, DIN 51045) as well as the thermomechanical characteristics.

Besides the linear thermal expansion and the coefficient of thermal expansion, TMA can also be used to study Phase TransitionsThe term phase transition (or phase change) is most commonly used to describe transitions between the solid, liquid and gaseous states.phase transition temperatures, SinteringSintering is a production process for forming a mechanically strong body out of a ceramic or metallic powder. sintering temperatures, shrinkage steps, Température de Transition VitreuseThe glass transition is one of the most important properties of amorphous and semi-crystalline materials, e.g., inorganic glasses, amorphous metals, polymers, pharmaceuticals and food ingredients, etc., and describes the temperature region where the mechanical properties of the materials change from hard and brittle to more soft, deformable or transition temperatures, dilatometric softening points, volumetric expansion, density changes, delamination and sintering kinetics.

Instruments for thermomechanical analysis are applied in all areas from research and development to quality control. Typical domains include plastics and elastomers, thermosets, composite materials, adhesives, films and fibers, ceramics, glass and metals.

Measurement on an epoxy resin with a sample length of 6 mm in expansion mode (fused silica sample holder); 1st and 2nd heating runs at a rate of 2 K/min.

Thermal Expansion

The linear thermal expansion is an important variable for assessing the dimensional behavior of a material in response to a change in temperature.

This plot shows the thermal expansion (dL/L0 in %) of an epoxy resin between -70°C and 270°C. In the first heating (blue curve), the onset of the glass transition (Tg) occurs at 123°C. In the second heating (red curve), the onset of Tg is slightly shifted, to 125°C. This shift could be due to RelaxationWhen a constant strain is applied to a rubber compound, the force necessary to maintain that strain is not constant but decreases with time; this behavior is known as stress relaxation. The process responsible for stress relaxation can be physical or chemical, and under normal conditions, both will occur at the same time. relaxation effects or post-curing.