In January, February and March, we presented the development of our dilatometers, simultaneous thermal analysis instruments and coupling systems. In April, everything is going to be about thermogravimetry, abbreviated TG or TGA.
Thermogravimetric analysis (TGA) is a method of thermal analysis employed for measuring mass changes as a function of temperature or time. This provides information on, for example, absorption, desorption, Thermal StabilityA material is thermally stable if it does not decompose under the influence of temperature. One way to determine the thermal stability of a substance is to use a TGA (thermogravimetric analyzer). thermal stability, corrosion resistance, plasticizer/carbon black/ash content, additives and solvent residues.
Jürgen Zöller, our long-time sales representative, would like to take you back in time and walk you through the history of TGA development.
Jürgen Zöller about himself: “Shortly after finishing my studies as a graduate engineer in physics in 1987, I was hired by NETZSCH Vertriebs-Gesellschaft NVG 6, Hanau (Klein-Auheim), for the sales department of NETZSCH-Gerätebau GmbH, Selb. After a “basic training” in thermal analysis in Selb and some training courses in the laboratory and technical sales, I started sales for NETZSCH-Gerätebau GmbH and was responsible for almost the whole Federal Republic of Germany (Hanover to Lake Constance). Today, after almost 35 years, I have been Sales Senior Manager for South-West Germany and have been working in a sales office in Seligenstadt since 2001. I am 62 years old, almost married, an enthusiastic choir singer, a “Schafkopf” (a German card game) player and have devoted myself extensively to the Seligenstadt Carnival activities for 40 years.”
Thermogravimetry or Simply: Thermobalance
Like the dilatometer, the NETZSCH thermobalance is older than NETZSCH-Gerätebau GmbH itself, the 60th anniversary of which we are celebrating in 2022. Thermogravimetry is the third and last pillar of the “Big Three” in the awakening years of thermal analysis:
Dilatometry (DIL) – Differential Thermal Analysis (DTA) – Thermogravimetry (TG)
Also, the very first thermobalance by NETZSCH saw the light of day in 1959, which means this happened long enough ago to have still taken place in the old ceramic laboratory of the Maschinenfabrik Gebrüder NETZSCH, Selb.
A thermobalance, as the name implies, should be capable of weighing, and if possible, under a variety of temperatures. And – otherwise it wouldn’t be a NETZSCH balance – under very high temperatures. Thus, the first thermobalance was already capable of measuring from room temperature to 1550°C.
A NETZSCH TGA wouldn’t be a NETZSCH TGA – and this is true to this day – if it didn’t feature a top-loading weighing system, as we are familiar with from everyday kitchen or bathroom scales. And that’s as simple as it is ingenious! The so-called TGA sample carrier (see picture) sits on a thermostated and gas-flushable weighing system. The crucible with the sample material rises by means of a carrier rod made of Al2O3 into a furnace positioned over it and is subjected to a defined temperature program.
Highest Precision and Make 2 Out of 1: TGA Becomes STA
At this point, inseparably linked with the NETZSCH thermobalances, comes a second success story that has accompanied the rise of NETZSCH thermobalances from the very first day.
The “heart” of all TGA instruments that have left the NETZSCH factory since 1959 to this day is a customized weighing system by SARTORIUS of Göttingen, Germany. Even though the systems at that time, as with DIL and DTA, were running only with dot and dot-matrix recorders, the best scales in the 1970s and 1980s already had a standard deviation of ± 0.03 mg and a readability of 20 µg/mm (paper). The maximum sample input those days was already 15 g, even though people mostly liked to restrict sample masses to 50 – 100 mg at that time.
The development of the TG 409/419/429 thermobalances evolved rapidly and, after being “married” to the already existing DTA 404 in the late 1960s and early 1970s, those instruments became one of the first STAs on the market and thus probably the biggest success story in the history of NETZSCH-Gerätebau
The top-loading weighing system by NETZSCH features considerably more advantages than disadvantages and has in most cases been enthusiastically adopted by our expert users on the world market, especially as compared to horizontal and, even more so, to hanging systems.
No Rule without Exception
In the mid-1980s, when thermogravimetric needs were still mostly satisfied with measuring instruments having resolutions of 2, 5 or even 10 µg, requests for higher precision, higher resolution and less correction of the TGA signal started to become more frequent. In order to accommodate what was probably the best analytical balance on the market – one by Sartorius which already featured a resolution of 0.1 µg in 1987 – NETZSCH experts like Dr. Wolf-Dieter Emmerich (then Managing Director), Martin Schmidt (then authorized representative) and Gerhard Bräuer (then Head of Development) considered building a symmetrical and virtually “double-hanging” thermobalance.
NETZSCH TG 439 Microbalance with double-platinum furnace system was born!
This thermobalance was exclusively built in small numbers from 1987 until the end of the 90s for customers who needed to measure such extremely small weight changes. These customers were very satisfied that no buoyancy correction was required, thanks to the symmetry of the balance scale and the two furnaces for sample and reference sides.
Here, you can look at the TG 439 brochure from 1987. (German Language)
More exciting information about the TGA, its advantages and an extraordinary drawing will be published in the upcoming week. ?