Thermogravimetric Analysis (TGA)

Thermogravimetric analysis (TGA) measures the change in the mass of a material as a function of temperature.

A derivative weight loss curve can be used to determine the point at which the mass loss is most significant.  TGA can be used to determine mass loss or degradation temperatures for polymers, as well as the absorbed moisture content of a wide range of materials.  Numerous TGA techniques are offered by Arkema Analytical Solutions. These include:

  • Conventional mode TGA
  • Gas switching TGA
  • High resolution TGA
  • Modulated TGA
  • TGA/Simultaneous differential thermal analysis (TGA/SDTA)

TGA (Conventional Mode)

Arkema Analytical Solutions offers TGA at up to 1200ºC with a wide range of heating rates.  Typical purge gases are nitrogen and zero air.  Curie transition analysis can be performed using an internal calibration routine.  In general TGA provides:

  • Volatiles quantification, including moisture and solvent loss
  • Decomposition information to establish
    • Processing parameters
    • Product use temperature
    • Effects of fillers
    • Effects of flame retardants
    • Comparative thermal or oxidative stability
  • Residue or filler quantification
  • Compositional information such as
    • Water loss from hydrates
    • Component rations for mixtures of resins

Gas Switching TGA

At Arkema Analytical Solutions we offer the ability to switch gases during a TGA experiment.  Typically this involves heating a sample in an inert atmosphere and then switching to an oxidizing gas, although other types and combinations of gases may be used.  Heating to a sufficiently high temperature allows for the decomposition and/or volatilization of an organic matrix, then switching to air allows for a quick burn-off, for the determination of carbon black content.  Use of other gases, for example containing additives, can allow for monitoring of specific reactions with the samples being studied.  Gas switching is commonly used for:

  • Carbon black measurement in resins
  • Adsorption/desorption studies

High Resolution TGA

In high resolution TGA variable heating rates are used to separate closely occurring mass loss events.  This technique is especially effective for the quantification of evaporative losses. The high resolution mode applies very high heating rates until mass loss is noted, at which point the rates are automatically reduced.  The result is improved separation of overlapping mass loss events, as well as sharper derivative peaks.

High resolution TGA is typically applied for:

  • Highly defined hydration losses
  • Fingerprinting of subtle mass losses
  • Resolving impurities in polymers, such as monomer and flame retardants

Modulated TGA (MTGA)

Understanding decomposition kinetics is critical for assessing the physical stability of a material with temperature and processing conditions.  Kinetic thermal decomposition studies would require several experiments at different heating rates using conventional TGA.  Modulated TGA can provide the same kinetic information in a single experiment.  As with other modulated techniques, an oscillatory temperature program is applied, which results in a modulated mass loss.  Evaluation of the mass loss that responds to the temperature modulation through sequential cycles allows determination of kinetic parameters.

Modulated TGA provides:

  • Fast kinetic analysis
  • Determination of activation energy

Thermogravimetric Analysis/Simultaneous Differential Thermal Analysis (TGA/SDTA)

Thermogravimetric analysis/simultaneous differential thermal analysis (TGA/SDTA) combines TGA, which monitors mass change, and DTA, which measures heat flow, to allow concurrent determination of decomposition and transition temperatures. The TGA/SDTA capabilities at Arkema Analytical Solutions include a sealed pan piercing kit, which allows volatile samples analysis, and gas switching.  Materials may be tested at temperatures up to 1100ºC over a wide range of heating rates.

The unique capabilities of TGA/SDTA allow:

  • Analysis of hydrophilic samples
  • Analysis of volatile samples
  • Collection of thermodynamic mass loss information
  • Identification of hidden transitions obscured by mass loss