Magnetic Biofoams Based on Polyurethane Applied in Oil Spill Cleanup Processes - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 259

The characteristic bands of the biofoams are the axial deformation related to
hydrogen bonds of NH group, at 3,300cm -1 . The doublet, around 2,900 cm -1 , corre-
sponds to the axial deformation of C-H bond of the CH 2 and CH 3 groups. The intense
characteristic band that appears at 1,727cm -1 , is correlated to the axial deformation
of the C=O bond conjugated with the amide I band. Characteristic bands at 1,600
and 1,512 cm -1 are due to angular deformations of N-H bonds, named amide II band.
The axial deformation of the C-N bond appears at 1,411cm -1 , while, the angular
deformation of the N-H bond is at 1,300 cm -1 . The characteristic band at 1,215 cm -1
corresponds to axial deformation of the (C=O)-O group. Finally, the characteristic
band, around 700 cm -1 , is related to angular deformation out-of-plane of the N-H
bond.
The diffractograms of the maghemite nanoparticles, bioresins and nanocomposite
samples, presented in Figure 8, show that maghemite nanoparticles were not changed
by the bioresins. The crystallinity values are shown in Table 3 and they were calcu-
lated using the Ruland method. (Souza Jr., F. G. et al., 2010b) It can be noticed that
crystallinity of pure foams is always low, independent of their preparing method. In
addition, these values are, statically, equals. It can be seen that the bioresins presented
crystallinity values around 10%, while, the maghemite nanoparticles presented 70%
of crystallinity. On its turn, the biocomposite showed an intermediate crystallinity
around 20%.
Figure 8. Diffractograms of the maghemite nanoparticles, bioresins (PU1-PU4) and nanocomposite
(PU5) samples.