DMA Analysis of PEI
Sample
Two thin films of polyetherimide, PEI, for comparison by dynamic mechanical analysis, DMA. The samples were named A and B.
Conditions
Measuring cell: DMA/SDTA861e with the tension sample holder
Sample preparation: Thin films, length 10.5 mm, thickness 22 µm, width 5.0 and 3.6 mm (samples A and B, respectively)
DMA measurement: -150 to 500 °C at 4 K/min (sample A) and 6 K/min (sample B) respectively, using a frequency of 1 Hz. Maximum force amplitude 1 N; maximum displacement amplitude 25 µm; offset control zero.
Atmosphere: Nitrogen, 200 cm3/min
Evaluation
Peak temperatures of tan 𝛿 and absolute value of E'
Interpretation
Both samples show three relaxation regions. The glass transition of sample B occurs at 319 °C and that of sample A at 370 °C. Below the glass transition, two further relaxation phenomena are observed. The width of the intermdiate relaxation, i.e. the temperature difference between the γ- and the β- relaxation differs quite significantly from sample A to sample B. This indicates that the two samples differ considerably in their structure.
At -100 °C, the absolute value of the modulus of sample B is twice that of sample A (see table above).
Conclusions
Relaxation phenomena in materials can be investigated by DMA. Experiments of this type allow conclusions to be drawn above the molecular structure of the material. The results of this experiment show clear differences in the behavior of the two PEI films. Both have a very high glass transition temperature.
DMA Analysis of PEI | Thermal Analysis Handbook No.HB246 | Application published in METTLER TOLEDO TA Application Handbook Thermoplastics