Product
Review
The Many Faces of Thermal Analysis
Manufacturers broaden product lines t o accommodate more applications Fire and a balance. Put them together and you've got the basis of the simplest form of thermal analysis—thermogravimetry or measuring change in mass as a function of temperature. Today's thermal analysis market, however, is not quite that simple. What began as primitive science centuries ago, has evolved into a mature, highly contested $250 million/yr market, encompassing more than a dozen commonly used techniques. Applications of modern thermal analysis are far-reaching, with concentrations in the polymer, food and beverage pharmaceutical and ceramics industries just to nuiTM? a few
Britt E. Erickson
Not everyone interprets thermal analysis to mean the same thing. "If you don't keep the temperature constant when you make a measurement, the measurement is worth nothing," says Bernhard Wunderlich of the University of Tennessee. Wunderlich suggests that thermal analysis includes all techniques that use temperature control, even those performed at constant temperatures. Others argue that thermal analysis is associated with techniques that measure the physical properties of a sample (e.g. mass; temperature; heat or heat flux; dimensions; and mechanical acoustical electrical and optical properties) as a function of temperature Isothermal period*; as part of a temperature program
however, are generally accepted under the definition. This review provides a look at commercially available instruments for six major thermal analysis techniques—differential thermal analysis (DTA), differential scanning calorimetry (DSC), thermogravimetry or thermogravimetric analysis (TGA) ,thermomechanical analysis (TMA), dynamic mechanical analysis (DMA), and dielectric analysis (DEA). Although not comprehensive, a summary of representative thermal analysis manufacturers, along with a list of techniques offered by each is given in Table 1 For 3. more detailed review of these and other thermal analysis techniques see Ref 1
Analytical Chemistry News & Features, October 1, 1999 6 8 9 A
Product
Review DTA/DSC
Table 1 . Selected t h e r m a l analysis instrument manufacturers.
Contact information
Thermal analysis product line
Specialty areas
Reader service number
Astra Scientific International 7020 Koll Center Pkwy. Ste. 130 Pleasanton, CA 94566 925-426-6900 www.astrascientific.com
DSC, DTA, macro DSC with pressure-measuring capability, adiabatic, isoperibolic, and industrial calorimeters
Thermal hazards analysis
401
Cahn Instruments 5225 Verona Rd., Bldg. 1 Madison, Wl 53711 608-276-6333 www.cahn.com
DSC, TGA, TGA/DTA, TGA/MS, TGA/FT-IR
Large-volume TGA
402
Calorimetry Sciences Corp. P.O. Box 799 Provo, UT 84603 801-375-8181 www.calscorp.com
DSC, isothermal titration calorimeter, micro-, isoperibolic, and 2-drop calorimeters
High-sensitivity calorimeters for applications in pharmaceuticals, biopolymers, material stability, and thermal hazards
403
Haake/Seiko Instruments 53 W. Century Rd. Paramus, NJ 07652 201-265-7865 www.haake-usa.com
DSC, TGA/DTA, TMA, DMS (rheology), TMA/ stress and strain (TMA/ SS), dielectric spectrometer (DES), Photo DSC, UVDSC
Robotic DSC and TGA/DTA for quality control
404
Harrop Industries 3470 E. Fifth Ave. Columbus, OH 43219-1797 614-231-3621
[email protected] DTA, TGA, TGA/DTA, TDA (dilatometer)
High-temperature ther405 mal analysis for ceramics and metals industries, glass-testing equipment, gradient furnace
Instrument Specialists 2402 Spring Ridge Dr., Ste. B Spring Grove, IL 60081 815-675-1550 www.instrument-specialists.com
DSC, TGA, TGA/DSC, and upgrade systems for existing thermal analyzers
Low-temperature thermal 406 analysis for polymers industry
LECO Corporation 3000 Lakeview Ave. St. Joseph, Ml 49085 800-292-6141 www.leco.com
TGA
Moisture, volatiles, ash, and fixed carbon analyses
Linseis 20 Washington Rd. P.O. Box 666 Princeton-Jet., NJ 08550 609-799-6282 www.linseis.com
DSC, DTA, TGA, TGA/ DSC, TGA/DTA, TMA, dilatometer
Mettler-Toledo 1900 Polaris Pkwy. Columbus, OH 43240 800-METTLER (638-8537) www.mt.com
MicroCal 22 Industrial Dr., East Northampton, MA 01060-2327 800-633-3115 www.microcalorimetry.com
407
The differential thermal analysis techniques, DTA and DSC, involve measuring the difference between a sample and a thermally inert reference material, such as an empty sample pan. In DTA, temperature is measured {Anal. Chem. 1194, 66,1035 A-1038 A), whereas in DSC, heat or heat flux is measured (Anal. Chem. 1995, 67, 323 A-327 A)) According to the manufacturers, there has been little change in DTA over the past few decades, with the exception of the introduction of computer control and autosamplers. In contrast to DSC, DTA is not a quantitative technique. DTA is used to measure the temperature at which a transition occurs, but it is unable to measure how much energy is associated with that event. Some of the earliest papers on DTA came out of the geological community, describing the analysis of clays and silicate minerals. Today DTA is widely used by the ceramics and metals industries beof its ability to operate at high temperatures (typically 600-1600 °C some units up to 2400 °Q and handle large sample sizes (hundreds of milligrams) to ensure sample homogeneity Measurements include decompositions pha«p trans;
formations glass transitions melting and solidification points and degrees of oxida ti e and thermal sta'hrlitv Altho icrh IPSS sensitive than DSC, DTA instruments are 11
J
Dilatometers for ceramics market, high-temperature TGA/DTA (up to 2400 °C)
408
DSC, TGA/DTA, TGA/ MS, TGA/FT-IR, TMA/ DTA, TOA (hot stage microscopy), TOA/DSC, instruments for melting, boiling, cloud, softening, and dropping points
FlexCal calibration routines, high-sensitivity DSC, TMA/SDTA for films and fibers, combined microscopy/DSC
409
DSC, isothermal titration calorimeter
High-sensitivity thermal 410 analysis for pharmaceutical and biopolymer areas
690 A Analytical Chemistry News & Features, October 1, 1999
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generally less expensive, with prices typill i tti
