Thermal analysis instrumentation is united by its focus on the effect of temperature on samples. Techniques differ in the properties each measures during the analysis. In the case of dielectric thermal analysis (DETA), the measurements provide information on the electrical behavior of the material in the sample.

The heart of a DETA instrument is similar to an electrical capacitor: two electrodes separated by a gap in which the sample is placed. Depending on the type of sample being analyzed, the researcher chooses an appropriate geometry of the electrodes. For testing thin films, the electrodes can be parallel plates with the film sandwiched between the electrodes. For liquid or bulk samples, two matching crenellated electrodes can be used inside the volume of a sample holder. The basic measurement is achieved by varying the voltage on one electrode at a particular frequency and measuring the voltage at the other electrode.

The main measurement of interest is the phase shift between the driving voltage and the response, which depends on the conductance and dielectric properties of the sample. Conductance relates to the transfer of charge from one electrode to the other. The dielectric response is more interesting. The electric field between the electrodes exerts a force on polar bonds within the polymeric molecules that twists them to align with the field. The phase difference and the relaxation, or delay, between the external field and the dielectric response of the sample provides key information on the polymerization process, as well as related processes, such as crystallization or the effects, as water or other solvents are driven out of the sample. DETA measures the response of the sample as a function of a few different variables; foremost among them are temperature, humidity and the frequency of the driving voltage.

Applications are largely restricted to polymer science; specifically to particular polymeric materials such as epoxies, where DETA is used to determine the optimal conditions of temperature and humidity for curing the epoxy. More generally, DETA can be used to probe other polymeric processes. Other samples include thin films, powders, adhesives, paints and liquid crystals. DETA is complementary to dynamical mechanical analysis, where a physical force, rather than electric voltage, is used to test the material. DETA allows researchers to probe the material’s response at much higher frequencies.

The market demand for DETA was roughly $10 million in 2012. The vendors that participate in the market tend to specialize in thermal analysis. NETZSCH is the leading vendor. The other significant suppliers, Novocontrol Technologies and Lacerta Technology, are niche players in thermal analysis. Following Mettler-Toledo’s purchase of Triton Technologies (see IBO 11/30/11), Lacerta was launched to continue Triton’s DETA business and other businesses. TA Instruments (Waters) offers DETA as an accessory on its ARES-G2 rheometer.

DETA at a Glance:

Leading Suppliers

• NETZSCH

• Lacerta Technology

• Novocontrol Technologies

Largest Markets

• Polymers

• Thin Films

• Paints

Instrument Cost

• $20,000–$50,000