Polymers 2020 , 12 , 173
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3. Results and Discussion
3.1. FTIR Analysis of the Polycoat 38 ® Resin The FTIR spectrum of the polymer resin is presented in Figure 3. The characteristic bands of the cationic polyamine [10,19,20] are observed. At 3311 cm − 1 the broad tension vibration band of the O–H bond is observed. The band at 1070 cm − 1 corresponds to the C–O bond in the C–OH group that allows the interaction with the fiber and that is part of the azetidine ring [21]. On the other hand, at 1218 cm − 1 is the tension band of the C–N bond presented in the quaternary nitrogen of the azetidine ring [10], also, the vibration band of the N–H caused by the interaction between the added acid and the groups of free amines appears in 1623 cm − 1 [15] Finally, at 2946 cm − 1 , the C–H tension vibration band of the methylene groups in the main chain of the polymer is observed [22].
Figure 3. Fourier transform infrared spectroscopy (FTIR) spectrum of the polyamine ( Polycoat 38 ® ) resin synthesized. 3.2. 1 H-NMR Analysis of the Polycoat 38 ® Resin In the 1 H-NMR spectrum (Figure 4), the characteristic signals of the protons presented in the coating resin can be observed [23,25]. The signals at chemical shifts of 0.96 and 1.66 ppm correspond to the protons of the CH 2 and CH groups of the azetidine ring, where quaternary nitrogen are generated and relate with OH groups at the end of the ring [25]. These OH groups tend to form hydrogen bonds with the cellulose and hemicellulose (polyoses) allowing the adhesion of the paper to the yankee and a posterior detachment once it comes into contact with the creping blade [24]. On the other hand, the multiplet presented between 2.89 and 3.04 ppm are characteristic of the protons presented in the CH groups of the main polymer backbone [4,25].
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