Author |
Message |
David W. Hopkins (dhopkins)
Senior Member Username: dhopkins
Post Number: 162 Registered: 10-2002
| Posted on Tuesday, August 31, 2010 - 8:35 am: | |
Hi Pisal, I am not familiar with those 2 forms of PP, or the distinctions of LLDPE from LDPE and HDPE, but I can say that I have scanned samples of LDPE and HDPE (in transmission) and find that it is easy to distinguish them. I think SIMCA should work well for you, but you will need to pay attention to the wavelength regions you use for each type of polymer. Also, you need to apply good pretreatments. I'd suggest SNV. A first or second derivative used before the SNV may also help significantly to resolve the differences. Did you try any pretreatments? You will also need to evaluate more independent samples of the polymers, in the form you intend to be measuring routinely. Are you using reflection spectra? Be sure to acquire the best signal/noise scans you can, because the differences between the forms are very subtle. Best regards, Dave |
David Russell (russell)
Senior Member Username: russell
Post Number: 48 Registered: 2-2001
| Posted on Tuesday, August 31, 2010 - 8:05 am: | |
Interesting thread. I concur with Gustavo's opinion. |
David Semmes (dsemmes)
New member Username: dsemmes
Post Number: 4 Registered: 6-2010
| Posted on Tuesday, August 31, 2010 - 7:30 am: | |
I don't know, but I wonder if the PE's and PP's could be better distinguished with a sharper resolution, boxcar apodization, and more scans as necessary. Good luck! |
Gustavo Figueira de Paula (gustavo)
Member Username: gustavo
Post Number: 13 Registered: 6-2008
| Posted on Tuesday, August 31, 2010 - 6:48 am: | |
Chemical differentes among LLDPE, LDPE, HDPE are mainly due catalyst residues (very, very small amounts), chain ends and degradation behaviour. Surely you're working with new material (not recycled), of good quality (low residues) and high molecular weight (few chain ends) - all this summed implies that NIR probably will not see chemical differences among them. Even with MID-IR it's not obvious. The same holds for PP. But it's not impossible, only hard to accomplish. Try "backing to the basis": look in the MID-IR range for peaks which allow distinction from one to another - my guess is that tertiary carbons will do the job. After, compute the overtones for such peaks and search in your NIR spectra for peaks that could match the theoretical ones. And let me know if it works! Hugs, Gustavo. |
Francesco Davini (franz)
Member Username: franz
Post Number: 11 Registered: 2-2009
| Posted on Tuesday, August 31, 2010 - 2:58 am: | |
Besides coloring agents, are the granules also free from antioxidants, plastifiers or other additives? |
aniruddha pisal (aniruddhapisal)
New member Username: aniruddhapisal
Post Number: 4 Registered: 7-2010
| Posted on Tuesday, August 31, 2010 - 2:10 am: | |
Thanks Venky, The experimental details are as follows, Scan Range: 10000 - 4000 cm-1 Sampling accessory: NIRA Resolution: 8 cm-1 No. of scans: 32 spectra corrected for baseline offset method development using Assure ID software with SIMCA algorithm The problem is in differentiating LLDPE, LDPE and HDPE. similarly, HOMO-PP, ICP-PP, and RCP-PP. The materials are in form of granules and without any coloring agents. |
venkatarman (venkynir)
Senior Member Username: venkynir
Post Number: 115 Registered: 3-2004
| Posted on Tuesday, August 31, 2010 - 1:55 am: | |
please specify the NIR range used by you . We have worked on classification of consumer polymers like PE,PET,PVC,PP and PS . we are ready to share our work experience. Please provide more information |
aniruddha pisal (aniruddhapisal)
New member Username: aniruddhapisal
Post Number: 3 Registered: 7-2010
| Posted on Tuesday, August 31, 2010 - 1:23 am: | |
Dear All, i am working on developing a simple method for screening of polymers. I have used 7 different polymer samples (granules). They are LLDPE, LDPE, HDPE, ICP-PP, RCP-PP, HOMO-PP, PVC(powder). I tried with SIMCA algorithm. but i could only see the difference between PE, PP and PVC. i can not see the difference between different types of PE granules. I would be grateful if anybody suggest a systematic approach to be followed for this work. |
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