IDENTIFICATION OF UNKNOWN MATERIAL β

 

Due to the unique material properties of polymers, there are several characterization techniques especially useful for the analysis of polymeric materials. This project outlines the use of a select number of characterization techniques in order to identify an unknown polymer sample. Thermal properties were studied through TGA and DSC. Chemical structure was analyzed using FTIR. Microscopic structure analysis, as well as quantitative and qualitative elemental analysis, was performed on an SEM equipped with x-ray spectroscopy. Through the use of these techniques, along with referencing literature values, the identity of the unknown polymer was determined to be polyamideimide with 40% glass fiber reinforcement.

PAI
TGA 1

Thermogravimetric Analysis

The unknown polymer was determined to have exceptional thermal stability through TGA. This thermogram displays degradation characteristics of the unknown polymer in inert and oxidative atmospheres. The slope of the inert atmosphere sample is relatively small which indicates slow degradation and a high level of thermal stability. This is the first indication that PAI is a possible identity of the unknown polymer due to its good thermal properties..

Differential Scanning Calorimetry

 

The DSC thermogram exhibited a clear Tg signal at roughly 276 °C. This is very similar to PAI’s reported Tg of 275 °C. Very few polymers have this high of a Tgwhich suggests PAI as the identity of the unknown polymer.

Possible melting and crystallization peaks were found at 326.80 and 313.53 °C, respectively. However, these peaks are extremely small. This suggests a very small melt characteristic of this polymer. This is indicative of a highly amorphous material, because amorphous polymers do not have a true melt temperature, and will not crystallize when cooled. This matches PAI’s amorphous character.

DSC
FTIR
FTIR 2

Fourier Transform Infrared Spectroscopy

 

The FTIR spectrum for the unknown polymer is displayed in the first figure. A broad, short peak was found at 3290 cm-1, which may be due to secondary amine stretching. The second figure displays the region from 1800 - 1600 cm-1, in which peaks at 1710 cm-1 and 1650 cm-1 are visible. These correlate to carbonyl stretching in imide and amide functional groups.

Scanning Electron Microscopy/Energy Dispersive Spectrometry

The SEM and EDAX images were visible findings of filler content in the unknown polymer. The lighter and darker regions were scanned individually to find the elements of which each was composed of. From the table, the EDAX scan determined that the polymer region of the sample was composed mainly of Oxygen and nitrogen. Considering Oxygen and nitrogen are primary elements found in amides and imides, this matches the results found from the FTIR experiment. The results from the EDAX scan shown in the lighter section of the SEM image shows a % composition by weight of 52-56% SiO2, 16-25% CaO, and 12-16% Al2O3.

Conclusion

 

The unknown polymer was identified as a Polyamideimide with 40% glass filler by weight. With analysis of the FTIR spectrum, both an amide and imide functional group were identified. The glass fiber filler was identified by SEM through the visual appearance of lighter regions of the image. The EDAX chart of the lighter region of the SEM image produced a percent composition by weight of 52-56% SiO2, 16-25% CaO, and 12-16% Al2O3. Boron E-glass contains a percent composition by weight of 52-56% SiO2, 21-23% CaO, and 12-15% Al2O4 thus confirming the filler present in the unknown polymer was E-glass. The TGA experiment showed a 40% remaining weight percentage from the oxidative atmosphere run which shows that 40% of the unknown sample was E-glass.  The glass transition temperature of the polymer was found to be 275.68 °C through DSC. Polyamideimides exhibit a glass transition temperature within the range of 207-271 °C.

Questions?

Send me a message and I would be happy to talk about this characterization process and the identification techniques used!