Resins, Group spectra

Several historic wax samples were analysed successfully with GALDI-MS. It was found that a group of eighteen white seals from medieval documents (thirteenth to fourteenth century) from the archive of the Canton of Lucerne (Switzerland) all mainly consisted of beeswax. For example, the mass spectrum of a white seal from 1377 (inventory no. URK636/12663) is shown in Figure 5.14b. The typical pattern of beeswax, as described for the reference sample, can be clearly recognised. An additional peak at m/z 303 may be caused by abietic acid in the form of the molecule cation (C2oH3o02, MW 302), as found for rosin (see Section 5.3.2). This hints at the use of a diterpenoid resin, which was a common hardener for beeswax. A more detailed discussion of the composition of medieval white wax seals has been published elsewhere [57]. 

As shown in the infrared absorbance spectrum of the condensation polymer (See Fig. 1), bands characteristic of absorbance of the urea resin at 3,400 cm-1, 3,000 cm-1, 1,680 cm-1, 1,540 cm-1, 1,380 cm-1, 1,100 cm-1, 1,020 cm-1, 780 cm-1, and characteristic absorbance of acrylami demethyl base at 800 cm-1 are present judging from this data, it is considered that N-methylacrylamide is connected with the end group of urea resin main chains and the imino group. The nuclear magnetic resonance (See Fig. 2) spectrum of the oligomer shows a resonance value of 6.48 ppm based on CH2= and a resonance value of 5.74 ppm based on -CH=. 

To check the completion of the reaction depicted in Scheme 12.9, single bead FTIR seemed quite conclusive because the IR band from the starting material (alcohol) has converted to the product carbonate band (Fig. 12.13). The hydroxyl stretch disappeared completely in the FTIR data. However, the possible presence of a trace amount of hydroxyl groups might not be evident in the IR spectrum. The fluorescent dye 9-anthroylnitrile reacted with resin-bound alcohol and it was very sensitive in detecting trace amount of hydroxyl groups [19]. It was used to detect the residual resin-bound alcohol and to confirm the reaction completion. 

Oxidation studies have been made for cured epoxy resins and the relative stability of the functional groups was established by following the changes in the absorbance ratios of bands associated with the particular functional group 231>. Hence the most unstable groups can be determined easily and their reactions separated from the more stable units. The irreversible 232) and reversible 2331 effects of moisture on epoxy resin systems have also been studied by FT-IR using the difference spectrum method 234). (Fig. 20) shows the interaction spectra obtained after three cycles of water sorption and redrying. The reversible nature of the interactions are clearly demonstrated. 

Fig. 24. Effect of degree of hydration on the Mdssbauer spectrum of an ion exchange resin containing iron. Water concentration (1) 0, (2) 0.22, (3) 1.24, (4) 2.93, (5)4.5, (6) 6 HzO molecules per sulfonic acid group. Zero velocity is with respect to a 57Co in chromium source. Figure according to Gol danskii et al. (187).

On comparing the spectrum of the epoxy resin in Fig. 4a with that obtained after reaction with APS dried at 25°C (Fig. 4b), one can see the disappearance of the epoxide peak at 912 cm and the appearance of a strong band at 3500 cm-1 due to —OH groups, as expected from the above reaction. However, after reaction for the same duration with APS dried at 170°C, the disappearance of the epoxide peak at 912 cm"1 and the appearance of the hydroxyl band at 3500 cm 1 are both less significant. The ratio of peak intensities, 912/3500 cm, remains high, indicating inhibition of the amine-epoxide reaction when APS is dried at 170°C. 

Products of the Reaction. A solution containing 5 X 10"2 mole/liter hydroperoxide and 2 X 10"2 mole/liter dilauryl thiodipropionate was allowed to react at 70 °C. until no hydroperoxide remained. A brown resinous precipitate was formed which was filtered, washed, and dried in vacuo. The infrared spectrum of the solid revealed the presence of —O—SOo— groups and the presence of an ortho-substituted aromatic compound, but no further details of its constitution could be obtained. This precipitate was not formed in the kinetic experiments which had a... 

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