We used polymers with the same surface and all of the polymers are transparent. We compared the different techniques on the corresponding grounds, because the range of the FTIR machine is way larger because of different sensors available.
The range of the SCIO device is 700 – 1100 nm.
The range of professional NIR techniques is 700 – 2500 nm
FTIR is used as a reference. We know that FTIR is a well known and approved technique in science. For our investigation we want to see how close the SCIO scan results correspond with the FTIR scan results in the range of the SCIO device.
In order to observe and understand the working of the spectrometer, we went over to the Faculty of Chemical and Physical Engineering to use a professional spectrometry device in the lab. We were assisted by Kaspar Jansen and resident PhD student Vincent Le Sage while using the machine.
Questions we wanted to see be answered by this experiment:
- How far does the result of the SCIO scan differ from the FTIR scan results?
- How far can the result of the SCIO scan results differ from the FTIR scan results s that it is still reliable?
- How does the differentiation in the results of the two techniques compare?
- Does the amount of scans influence the differentiation in the results of the SCIO scan?
- Does the surface the sample lies upon influence the result?
Method 1 of testing :
Before each batch of scans with this FTIR machine we needed to make a background scan. The background scan is a scan without a sample. It makes a scan of the air and then subtracts that from the scans with the samples, so that the air and other possible noise will not interfere with the result of the scan.
The first method to test materials makes use of a crystal that is held (with a little bit of pressure) between the laser and the sample. The laser reflects from the sample back into the crystal and back in to the sample again. This happens many many times. All these reflections eventually give a result.
We chanched from the first method to the second method becasue the samples didn’t reflect enough light from the laser.
Method 2 of testing :
Method 2 was used to scan the polymers as it was proposed that it may produce more accurate results.
The second method is based on the absorbency of laser light. A beam of laser is sent through a transparent material. Some of the light will be absorbed when the laser beam is sent through the sample. The computer will then analyse the sample by comparing the sent signal with the received signal (comparing the spectra).
The part that holds the sample and has the laser beam sent through it needs to be covered to protect it from any external factors that can affect the result, like the air. The equipment needs to be cleaned as well to get an accurate result.
Along with this, the background scan should be conducted every couple of hours as the temperature changes throughout the day and this can cause fluctuations in the result.
We got the results below from scanning the samples using Method 2.
- PP (1)
- PP (2)
- The results have a much wider range, because FTIR has a much bigger scanning range
- The peaks are clear and pointed.
- Each peak represents a bond of molecules.
- There are enough peaks to reliably distinguish between different molecules
- However, some of the graphs show some flat-lining and this is not good. We had this because are samples where not absorbing enough light.
The reference sheet helps us to identify the different chemical bonds/ vibrations by looking at the range within which they can be found.