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CH 3 asymmetrical stretching), 2924 cm CH 3 symmetrical vibrations) and 2852 cm 2 symmetrical vibrations). The alkyl groups occurring between 2925 cm -1 and 620 cm -1 of the spectrum are easier to identify from its 2 nd derivative spectrum because these bands are better defined. A medium carbonyl band either from lignin or uronic esters is also evident at 1739 cm -1 followed by moderate protein absorbances at 1642 to 1505 cm -1 (Pretsch HWDO . 2000; Li HWDO . 2016). Alkyl chain deformation bands (-CH 2 - and -CH 3 ) trending toward the low frequency region ending at 620 cm -1 (see previous paragraphs). The 620 cm -1 band is analogous to that in processed 100DDGS. There is a single carbonyl band at 1738 cm - 1 assignable either to a uronic ester in the wood component or a lignin carbonyl moiety (Pretsch HWDO . 2000; Li HWDO . 2016). Next there is a low protein carbonyl absorption at 1656 cm -1 , amide I and very intense peaks at 1597 and 1508 cm -1 presumably represent the amide II mode. The -CH 2 - and -CH 3 deformation bands are shown at 1470 and 1372 cm -1 , respectively. There is a sizable O-C=O band at 1246 cm -1 followed by very intense – CHO-, and -CH 2 O- bands located at 1159, 1128, 1037, and 991 cm -1 . Finally an anomalous P-S and P=S band is observed at 670 cm -1 (Fig. 1c). -1 (-CH 2 - asymmetrical stretching), 2876 cm -1 (- -1 (-CH The 50DDGS-PW composite spectra ( Fig. 1d) is characterized by a strong 3410 cm -1 band representing the overlapping -OHs of DDGS and PW together with the -NH stretching bands of the intrinsic protein content. A broad band at 2913 cm -1 is resolved in the 2 nd derivative of its FTIR spectrum into four discrete bands: 2959 cm -1 (-CH 3 asymmetrical), 2923 cm -1 (-CH 2 asymmetrical stretch), 2875 cm -1 (-CH 3 symmetrical stretching) and 2854 cm -1 (-CH 2 symmetrical stretching) absorption. The next absorption series of the spectrum comprise an ester carbonyl band at 1743 cm -1 resulting from the PW, a single amide I absorbance at 1656 cm -1 (probably the α -helix of the DDGS), and prominent amide II peaks at 1596, 1546 and 1517 cm -1 . These are followed by the deformation bands, 1470 and 1378 cm -1 of the – CH 2 - and -CH 3 alkyl moieties, respectively. The latter bands are followed by the -O-C=O stretching of the ester at 1246 cm -1 and the – COH- and -CH 2 O- at 1167, 1130, 1077, 1039 and 992 cm -1 and finally by the P-S and P=S vibration at 621 cm -1 . DSC and TGA Evaluations Ganesan and Rosentrater (2007) observed glass transition temperatures ( 7 g ) at 20 to 50 °C with unmodified DDGS, defatted DDGS, or de-waxed DDGS using DSC. The defatted DDGS used in this study showed a somewhat higher 7 g (54.0 °C) during the first heating cycle, which was shown as a small shoulder in the large water evaporation curve (Fig. 2a). The difference, presumably, resulted from slightly different compositions produced by different processes to obtain the DDGS. The second heating cycle, conducted after the first heating cycle, showed no water evaporation peak and a higher 7 g (117.8 °C). The reason for this weak signal was that the DDGS is a mixture of many ingredie nts and some of them exhibit a “thermoplastic property”. The presence of water lowers the 7 g and acts as a plasticizer in a material having glass transition, and thus removing the water increases the 7 g (Frascareli HWDO . 2012). The DSC of PW did not show an obvious 7 g during the first or the second heating cycles, indicating that the PW did not have ingredients undergoing glass transition (Fig. 2c). The DSC of 100DDGS showed a slightly lower 7 g than that of DDGS in both the first and the second heating cycles, indicating that the materials showing glass transition underwent little change during the process of making this composite (Fig. 2b). In contrast, 50DDGS-PW showed no 7 g (Fig. 2d). In the presence of wood, DDGS binds more completely to produce a
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Tisserat et al . (2018). “DDGS - PW fiberboards” B io R esources 13(2), 2678-2701.
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