• The TMA dilatometer uses interchangeable probes at varied loads to make a number of measurements, including the softening temperature or glass transition temperature, tensile modulus, compression modulus, coefficient of thermal expansion (CTE), melting temperature, crystalline phase transition temperature, crystalline to amorphous transition temperatures, and creep under load, by measuring the change of a dimension of a material. Note that the thermal expansion of a material may not be linear.


• DSC can also be used to measure glass transition temperatures, crystalline phase transition temperatures, crystalline phase transformation temperatures, and melting point temperatures.


• Samples in the form of plugs, films, powders, or fibers, are compressed or held in tension by a probe assembly. Movement of the probe is measured electrically by a linear variable differential transformer (LVDT) attached to the probe.


• Capable of testing polymers and plastics, metals, glasses, ceramics, inorganics, composite materials, IC packages, semiconductors, small devices, adhesives, sealants, potting compounds, PCBs, and coatings.


• Temperatures can range from -180°C to 800°C.


• Sample dimensions: a maximum of 25 mm in height and 9.5 mm in diameter; a minimum of 0.1 μm thick and 1.5 mm in diameter, an ideal thickness being 1-4mm. Taller samples should have small lateral dimensions, so the sample interior temperature will not differ substantially from the surface temperature.


• The applied load can range from 0-100 g.


• The change of dimension should be greater than 2x10^-3 μm/°C.

• ASTM E228 - Standard Test Method for Linear Thermal Expansion of Solid Materials with a Vitreous Silica Dilatometer


• ASTM E831 - Standard Test Method for Linear Thermal Expansion of Solid Materials by TMA


• ASTM E1545 - Standard Test Method for Assignment of the Glass Transition Temperature by TMA

TMA dilatometry was used to characterize the properties of various PTFE powder materials. These were examined after pressing them into sheets. The sheet thickness was measured from -100°C to 200°C using a ramp rate of 4°C/min. The first of several TEFLON^® materials (Figure 1) exhibits an extensive crystalline transition at approximately 19°C due to a transformation of the Phase II helix crystal structure first to the Phase IV hexagonal crystal structure and then to the Phase I hexagonal crystal structure. This large peak created at transition indicates a PTFE which has a substantial crystalline phase and exhibits a drastic dimension change as it changes the crystalline phase. Also shown by the TMA is the softening point (Tg or Ts) of the TEFLON^® at approximately 160°C. Data for another of several samples is seen in Figure 2. This TEFLON^® material exhibits a significantly smaller crystalline to amorphous transition dimension increase compared to the material observed in Figure 1. This material initially consisted of a greater concentration of amorphous material. For our customer’s intended use, a rapid thermal expansion of a PTFE material at the crystalline transition temperature could not be tolerated. Their requirement was therefore for an amorphous PTFE material. Note that the first PTFE material has almost no temperature range with a linear thermal expansion characteristic.

Figure 1


Figure 2