# Mechanical Properties and Formaldehyde Release of Particleboard Made with Lignin-Based Adhesives
## 3 Results and Discussions  
### Ftir  
The spectroscopic analysis for magnesium lignocellulosic (LIGNEX MG F) is presented in Figure 1. This analysis was done for three variants of the lignocellulosic, as follows: non-modified--as a powder in the initial state, mixed with water in the ratio 10:1 and air-dried, and as a crosslinked adhesive at 160\({}^{\circ}\) for 15 min resulting from the mixture of magnesium lignocellulosic with water in the ratio 10:1. Figure 1: FTIR analysis for (LIGNEX MG F) powder and mixed LIGNEX MG F—water (air-dried and crosslinked). The recorded FTIR spectra in Figure 1 present the characteristic absorption bands of the OH vibration at 3334 cm\({}^{-1}\) and the C-H vibration in the methyl and methylene groups at 2945 cm\({}^{-1}\) (small or shoulder). The most numerous absorption bands were observed in the fingerprint region between 1600 cm\({}^{-1}\) and 600 cm\({}^{-1}\). A pronounced band at 1595 cm\({}^{-1}\) may be assigned to aromatic skeletal vibration (originating from the aromatic C=C stretching). The band at 1512 cm\({}^{-1}\) was assigned to skeletal vibration of lignin, while the band at 1453 cm\({}^{-1}\) may be assigned to C-H deformation in aliphatic CH\({}_{3}\) and CH\({}_{2}\) groups, as observed by other researchers at 1465 cm\({}^{-1}\)[62]. A weak band at 1421 cm\({}^{-1}\) can be assigned to the C-H deformation in lignin and a band at 1332 cm\({}^{-1}\), which appears small as a shoulder, was found to belong to syringeyl ring breathing [63], aliphatic O-H bending [64] or C-H in plane deformation of cellulose rings [65]. The band at 1160 cm\({}^{-1}\) can be assigned to asymmetric -SO\({}_{2}\)- vibration, with reference to 1169 cm\({}^{-1}\) corresponding to asymmetric (at 1169 cm\({}^{-1}\)) and symmetric (at 1142 cm\({}^{-1}\)) -SO\({}_{2}\)- vibrations [66], whereas a double band at 1143 cm\({}^{-1}\) and 1169 cm\({}^{-1}\) was assigned to binding vibrations in the aliphatic C-OH [63]. The 1114 cm\({}^{-1}\) band is assigned to C-O-C vibration and 1034 cm\({}^{-1}\) is assigned to C-O vibration of the phenolic OH [67] and/or -SO\({}_{3}\)H group [62], or Ar-O-C [35]. The peak at 646 cm\({}^{-1}\) is assigned to S-O vibration in lignocellulosic. The comparative spectra of magnesium lignocellulosic powder, the air-dried adhesive prepared from magnesium lignocellulosic powder and water (10 to 1) and the crosslinked adhesive at 160 \({}^{\circ}\)C for 15 min (Figure 1), are similar in terms of absorption bands, indicating a similar chemical structure. There are some differences in the relative intensities of the absorption bands in the range 1600-1000 cm\({}^{-1}\) compared to the -OH absorption at 3400 cm\({}^{-1}\) (with quasi-constant intensity due to the min-max normalization of the spectra). As any water present in the analyzed samples contributes to the absorption at 3400 cm\({}^{-1}\), these differences might be related to different water content in the three types of samples. For the adhesive prepared and crosslinked, the absorption at 1332 cm\({}^{-1}\) is better highlighted. The similar spectra indicate a physical mechanism of bonding, based mainly on the thermoplastic character of lignin. Structural changes (Figure 2) brought by oxidation (LO 20 compared to L20) are, as follows: the appearance of a shoulder at 1728 cm\({}^{-1}\) assignable to unconjugated carbonyl groups; the shift of the aromatic skeletal vibration from 1590 cm\({}^{-1}\) to 1601 cm\({}^{-1}\); a shoulder at 1368 cm\({}^{-1}\) specific to C-H deformation; a small shoulder at 1212 cm\({}^{-1}\), indicating C-O vibration in guiaacyl ring; a shift of absorption from 1160 cm\({}^{-1}\) (assigned to -SO2- and C-OH) to 1150 cm\({}^{-1}\), and its significant decrease; a shift of C-O-C vibration from 1114 cm\({}^{-1}\) to 1106 cm\({}^{-1}\), and its significant decrease. These may indicate depolymerization through the splitting of C-O-C bonds and oxidation leading to carbonyl groups, which is in accordance with the expected effects of mild oxidation [37].