Thermogravimetry. “…. a technique in which the mass of a substance is measured as a function of temperature, while the substance is subjected to a controlled temperature programme.”. “Controlled temperature programme” can mean: heating and/or cooling at a linear rate (by far commonest)
“…. a technique in which the mass of a substance is measured as a function of temperature, while the substance is subjected to a controlled temperature programme.”
Mass (%) in green, rate of mass loss (%/°C) in blue.
EXCHANGE OF GASES: REACTING GASES IN, PRODUCTS OUT
CONVECTION THROUGH SURROUNDING ATMOSPHERE
RADIATION FROM FURNACE WALL
CONDUCTION THROUGH SAMPLE PAN AND INSTRUMENT
INDICATION OF SAMPLE TEMPERATURE
For a given instrument, careful standardisation of experimental procedures leads to highly reproducible results.
10 mg samples of PTFE, heated at 2.5, 5, 10 and 20 °C/min in nitrogen
CaC2CO4.H2O in air and nitrogen
These are lumped together as the “buoyancy” correction, and if significant, can be allowed for by a blank run
Temperature calibration difficult to carry out accurately.
Many methods exist, but none totally satisfactory.
Best accuracy from simultaneous TG-DTA or TG-DSC instrument.
a = PVC, b= nylon-6, c = LDPE, d= PTFE
PROCESSWEIGHT GAINWEIGHT LOSS
Ad- or absorption
Solid-solid reactions (some)
D. M. Price, D. J. Hourston & F. Dumont, “Thermogravimetry of Polymers”, R. A. Meyers (Ed.), Encyclopedia of Analytical Chemistry, John Wiley & Sons Ltd., Chichester (2000) pp. 8094-8105.
G. R. Heal, “Thermogravimetry& Derivative Thermogravimetry”, in P.J. Haines (ed.) Principles of Thermal Analysis & Calorimetry, ch. 4, Royal Society of Chemistry, Cambridge (2002) pp. 10-54.
C. M. Earnest (Ed.), Compostional Analysis by Thermogravimetry, ASTM STP 97, American Society for Testing and Materials (1988).