| Author | Message | ||
     Gavriel Levin (levin) New member Username: levin Post Number: 2 Registered: 1-2006 |
Hi Lois and all, I have pleanty of experience in differentiating 6 and 66 by NIR from 1200 to 2100 - its all you need. These two are very close - but separable. About the colored - my experience is that colors do not give any trouble - as long as the color is a low level concentration of dye - however, if you work in full range 500 - 2400 you may run into problems - in that case - use from 1200 up, you shall be fine. The black stuff is a differnet story - soemtimes the black is not a dye, but carbon black filler - which is known to absorb strongly across the whole spectrum. In that case the ability to distinguish features in the spectrum is so strongly reduced, that you can't trust it to give you correct identification. The reflected signal becomes very small and the signal to noise drops strongly. I hope this helped a little If anyone wnats info on the separation of 6, 66 and other polymers please write to me [email protected] | ||
| Lois Weyer (lois_weyer) Member Username: lois_weyer Post Number: 20 Registered: 7-2002 |
What I meant by end-tailing is this: color absorption peaks are generally broad peaks in the visible region. They may be so strong that some of the peak will tail into the NIR, like a large mountain or a gaussian distribution peak. There wouldn't actually be a maximum in the NIR, but the tail or curve from the visible peak will lift up the baseline at the shorter wavelengths (longer wavenumbers). Taking a derivative would remove this end-absorption, as it is usually a smooth curve without sharp spectral features. I don't know how your instrument manufacturer would handle this. There should be some means of pretreating your spectra in your software. It can be done in GRAMS, for example. It would have to be done before you use your calibration samples for developing your calibration and then it would again have to be applied before using your prediction samples for prediction. | ||
| Rajeev Bhatia (rajeev) New member Username: rajeev Post Number: 2 Registered: 6-2006 |
Thank you Lois for your input. IF you could please explain to me what end-tailing means it will make more sense to me. Also, the first derivative issue, will this have to be tackled by modifying the algorithm in the software by the manufacturer? If this can be solved then it will be excellent because we have two NIRs and would facilitate our process. Thanks again. | ||
| Lois Weyer (lois_weyer) New member Username: lois_weyer Post Number: 18 Registered: 7-2002 |
You mentioned that NIR has trouble with the black and colored samples. This is probably because of the end-tailing of the color absorption into the NIR region. This could probably be removed by a first derivative treatment, which will flatten the curved baseline and accentuate the real spectral features. | ||
| Rajeev Bhatia (rajeev) New member Username: rajeev Post Number: 1 Registered: 6-2006 |
Thank you all for a very enlightening discussion about the differences between NIR, IR, grated and with interferometer. I work in a plant that deals with nylon 6, nylon 66, polyester and such polymers. We have NIR as our IDing tool for identifying these polymers (fibers). However, NIR does what FTIR does not. FTIR identifies the polyamides but cannot differntiate between the 6 and 66. On the other hand the NIR does not recognize dark/black colored samples but the FTIR does. This has caused some confusion about which instrument should be purchased. | ||
| Annick De Coster (Adc) |
Has anyone ever tryed to distinguish PA6 and PA6.6 by using NIR. Which wavelengths are interesting to see any difference between both? | ||
| Holger Freitag |
Annick- a few years ago we developed filter- and AOTF-based identification systems to solve this problem. Some information is available here: 1)http://www.carpet-recycling-europe.de/English/IdenSor.htm 2)http://www.infralytic.de/g_einsatzfelder_en.htm The patent is: Method of identifying post consumer or post industrial waste carpet utilizing a hand-held infrared spectrometer Patent Number: US5952660 There you can find the necessary wavelengths. Holger | ||
| Gabi Levin |
Annick, Differentiation between the PA6 and PA6,6 was done by me very fast and reliably. For more information, call me at 410 931 7200, Gabi. You can also get more information from Jimmy Rodgers, he is from Solutia and has very wide experience including this particular issue. His phone number is (850)968-7195 and his e-mail is [email protected] I am sure he would love to help you. Gabi Levin |