Content Determination: Moisture, Filler and Resin Content

Purpose

To demonstrate the quantitative determination of content, and the influence of furnace atmosphere (inert and oxidative).

Sample

Uncured KU600 epoxy resin powder

Conditions

Measuring cell: TGA/SDTA

Pan: Alumina 70 μL, without lid

Sample preparation: The crucible was filled with loose powder, i.e. without compacting. 

TGA measurement: Heating from 40 to 90 °C at 10 K/min

Atmosphere: Purge gas, 70 mL/min:

A: only air
B: only nitrogen
C: first nitrogen, then automatically switched to air at 750 °C, and in addition 20 mL/min nitrogen as protective gas

Interpretation

Three samples were heated under different atmosphere (curves A, B and C). The fourth curve (dashed line) is that obtained by heating the sample from B a second time but in air (curve D).

Curve A. The polymer decomposition in air is observed in the first step up to about 480 °C. The decomposition represents more than half of the total mass loss and occurs without combustion because no large exothermic can be seen in the SDTA^® curve. During this process, residues are formed that burn completely up 600 °C. The SDTA^® peak is about fifty times greater than that of the curing reaction at 180 °C (41.5 J/g), i.e. the combustion enthalpy is therefore about 2500 J/g based on the original sample mass (see previous diagram and the DSC measurement in Volume 2).

Conclusions

The moisture content is very low. The polymer content is 60.8% and a residue of 39.1% remains at 900 °C. This can be interpreted as a filler. Heating under nitrogen shows that the polymer matrix does not completely depolymerize, but produces carbon-containing residues. So if only the filler content has to be determined, the sample must be burned in air. The choice of the furnace atmosphere also has an important influence on the content determination. At temperatures above 600 °C, no further mass loss steps are visible, which means that the filler does not decompose, as would be the case with CaCO₃.

_{Content Determination: Moisture, Filler and Resin Content | Thermal Analysis Handbook No.HB16 | Application published in METTLER TOLEDO TA Application Handbook Thermosets, Volume 1}