Josarhus: Interesting. So N. Harrit, who knows basically nothing about polymers, is sure now that Jim Millette, as a top forensic expert specialized on the material analyses, misinterpreted somehow his FTIR spectra of red-gray chips
Rather surprisingly for me, they are no easily/freely available FTIR spectra of epoxy resins cured by amines on the net. They are mostly available only in bloody expensive databases. Anyway.... Let me consider what I see in Appendix C in Jim Millette's preliminary report, since here, FTIR spectra are for sure comparable:
In the first graph I see FTIR spectra of four red chips, which are very apparently the same material. Those spectra can serve me as a proof that there is some range of wavenumbers, within which individual characteristic absorption bands wavenumbers can vary for the same material. E.g., band at ca 1710 cm
-1 appears in the range from 1707 to 1725 cm
-1, band at ca 2930 cm
-1 varies from 2928 to 2934 cm
-1 etc. Generally, bands wavenumbers fluctuate in the range of ca 3 to 15 cm
-1 for the same material here.
Naturally, we can expect similar variation in the order of some 3-15 cm
-1 also when comparing chips FTIR spectra with proven epoxy coating, as we see on the second graph.
Here, as for epoxy resin identification, we can consider only the region between ca 3500 and 1100 cm
-1 , since above and below this range, kaolin absorption bands occur.
Now, I will summarize wavenumbers of distinct bands which are observed for red chip and for epoxy coating in some very primitive table (sorry for idiotic "formatting":
Epoxy: 2934-2957 (double peak)
Chip: 2928
Epoxy: 2867
Chip: 2858
Epoxy: 1731
Chip: 1716
Epoxy: 1607
Chip: 1604
Epoxy: 1508
Chip: 1509
Epoxy: 1415
Chip: 1412
Epoxy: 1361
Chip: 1361
Epoxy: 1294
Chip: 1297
Epoxy: 1243
Chip: 1231
Epoxy: 1181
Chip: 1183
For me, the epoxy binder is proven in this way (but I'm not expert on infrared spectra material identifications, I just rely on Jim's long time experience with various materials).
Just for the record, let me also again past this paragraph from this page named
Identification of polymers by IR spectroscopy:
"Bisphenol epoxy resin (our case, I.K.)
Since both bisphenol epoxy and polycarbonate are based on Bisphenol A, there are a number of similarities in their infrared spectra. There is no carbonyl band in the bisphenol epoxy spectrum, but the aromatic ring-breathing mode at 1,510 [cm.sup.-1] is very strong. Here the 1,610 [cm.sup.-1] ring-breathing mode is also relatively strong. The C-O stretch is strong and appears as two bands, a broad band with a maximum near 1,247 [cm.sup.-1] and a narrower and slightly weaker band with a maximum near 1,182 [cm.sup.-1]. Significant intensity is also seen in the out-of-plane aromatic C-H wag at 830 [cm.sup.-1]."
And what I see in the FTIR spectra of both epoxy coating and red chips in Appendix C, Millette's report (among others)? Quite strong bands at ca 1610 and 1510 cm-1 and some bands at ca 1240 and 1180 cm-1 . This is of course not really conclusive finding, just some hint that Jim Millette is right (basically in everything)