Preparation and property assessment of eco-friendly composite based on polyvinyl alcohol and lignin extracted from biomass
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- 3. Results and discussion 3.1. Characterization of hydrogen bonding interactions between PVA and lignin in the composites
| 2.4. Characterization
The appearance of specific functional groups in the chemical structures of PVA and lignin in composite samples was examined by Infrared spectroscopy (FTIR). The mechanical properties of the composite films, including tensile strength and elongation at break were investigated according to ASTM D882 standard using a tensile testing machine (Tensilon RTC-1210A, A&D Co., Ltd., Japan) with a tensile speed of 5 mm/min. The surface features of the samples were characterized by a scanning electron microscope (SEM, S4800-NHE, Hitachi, Japan). The ultraviolet radiation absorbency of the films was evaluated by a double-beam UV-Vis spectrophotometer (U-2910, Hitachi, Japan). To prepare for testing, all samples were fabricated with the same thickness at about 250 μm. 3. Results and discussion 3.1. Characterization of hydrogen bonding interactions between PVA and lignin in the composites Chemical structures of PVA and lignin were illustrated by FTIR spectra (Figure 1). Lignin had adequate functional groups, revealed by specific peaks in FTIR spectra (Figure 1a). The peak at 1607 cm -1 indicated the presence of hydroxylcinnamic ester in the lignin sample, 1360 cm -1 was associated with the structure of the syringyl lignin molecule breathing with C-O stretching, 1261 cm -1 corresponded to guaiacyl ring breathing with C=O stretching, 1208 cm -1 reflected the vibration of the C-O-C linkages in ethers and esters or phenolic hydroxyl, the band at 1125 cm -1 was associated with the C-H in-plane deformations vibration in syringyl aromatic ring types, and 1033 cm -1 originated from aromatic C-H in-plane deformation and C-O bending vibration in primary alcohols, guaiacyl type [11]. The specific peaks of PVA were shown at 3282, 2919, 1713, 1423, 1374, 1085, and 829 cm −1 , which were assigned to the O–H stretching vibration of the hydroxy group, CH 2 asymmetric stretching vibration, C=O carbonyl stretch, C–H bending vibration of CH 2 , C–H deformation vibration, C–O stretching of acetyl groups and C-C stretching vibration, respectively (Figure 1c) [7]. The hydrogen bonding interactions between PVA and lignin in the composites were demonstrated by FTIR spectra. Pristine PVA indicated hydroxyl (O-H) stretching vibration peak |