Thermogravimetry (TG or thermogravimetric analysis, TGA) is the most common method for determining the filler content, e.g., carbon black, within a polymer, e.g., rubber material. The type and quantity of filler in a polymer influences the performance of the polymer.
The polymer sample is placed in a crucible, put on a balance inside of the TGA furnace, and heated. The test parameters such as temperature program and atmosphere depend on the filler material: Organic fillers can be oxidized; inorganic fillers can be inert, non-oxidizable or reactive. In case of an inorganic filler, e.g., glass fiber, in a polymer matrix, a typical temperature program for a TGA measurement would be as follows: at first, heating under nitrogen atmosphere up to 850°C for decomposition of the polymer matrix and then further heating under oxidizing atmosphere for burning the pyrolytic soot and eventually other remaining oxidizable components. The residual mass will be the inorganic filler – in this case the glass fiber.
In case of organic fillers, a separation of filler and polymer matrix can be achievable if the two (organic) components have a different decomposition temperature. In addition, the two decomposition processes should be independent of each other.
TGA delivers the quantity of the residual mass or ash content (in e.g., percentage/% or mass/mg) or in other words what remains from the initial amount of material tested. In general, TGA is suitable to analyze the composition of a material. There are many possible ways to carry out TGA measurements.