Dilek YAYLALI, Canan URAZ, Esat GÜMÜŞKAYA
was useful for examining the changes in functional groups. Figure 4 shows that the raw, cooked and beaten hemp bast fibres had peaks at about 3338 cm − 1 , indicating the presence of cellulose polymeric OH stretches [Menon et al. 2018].
Fig. 4. FTIR spectral plot of raw, cooked and beaten hemp bast fibres The peaks at 2900 cm − 1 were due to stretching vibrations of the C-H functional group. Also, the absorbance peaks between 1500 and 900 cm − 1 indicate the C-O-C functional group (1050 cm − 1 , 1028 cm − 1 and 984 cm − 1 ). These functional groups do not conflict with the base structure of the cellulose molecule [Munajad et al. 2018]. When cooked, the intensity of the peak at wavenumber 3338 cm −1 increases due to an increase in OH concentration as the alkaline weakened the hydrogen bonding in cellulosic hydroxyl groups [Chieng et al. 2017]. After beating, the peak intensity of the fibre was lower than that of the cooked fibres because of the increase in hydrogen bonding. The peak, which only appears in the raw material spectrum at 1732 cm − 1 , corresponded to the C=O stretching of carbonyl functional groups from hemicellulose and lignin fractions. Cooking causes the removal of carboxylic groups, which may be traces of fatty acids on the fibre surface, and causes the C=O stretching to vanish [Chieng et al. 2017; Munajad et al. 2018]. The raw material spectrum at 1232 cm −1 , which corresponds to the syringyl ring and C – O stretching of lignin and xylan, declined in intensity before decreasing, demonstrating that lignin and a small amount of hemicellulose were removed from the raw material after treatment [Chieng et al. 2017; Zhbankov 1966]. At 900 cm − 1 in the spectrum, the peak of beaten fibre was sharper because the cellulose was ground up. Therefore, the band around 900 cm − 1 is only refer red to as ‘ amorphous ’ because its intensity increased [Zhbankov 1966]. Wastepaper and handsheet preparation In this study, wastepaper pulp and hemp bast fibre pulp (20°SR) were used to prepare handsheets. The wastepaper grade number 1.04.00 was chosen because it
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