Abstract. In order to characterize the morphology and size distribution of the cellulose fibers, natural cellulose from kenaf bast fibers was extracted using two chemical treatments; (1) alkali-bleaching-ultrasonic treatment and (2) alkalibleaching-hydrolysis. Solutions of NaOH, H 2 O 2 and H 2 SO 4 were used for alkalization, bleaching and hydrolysis, respectively. The hydrolyzed fibers were centrifuged at a rotation speed of 10000 rpm for 10 min to separate the nanofibers from the microfibers. The separation was repeated in 7 steps by controlling pH of the solution in each step until neutrality was reached. Fourier transform infrared (FTIR) spectroscopy was performed on the fibers at the final step of each treatment: i.e. either ultrasonic treated-or hydrolyzed microfibers. Their FTIR spectra were compared with FTIR spectrum of a reference commercial α-cellulose. Changes in morphology and size distribution of the treated fibers were examined by scanning electron microscopy (SEM). FTIR spectra of ultrasonic treated-and hydrolyzed microfibers nearly coincided with the FTIR spectrum of commercial α-cellulose, suggesting successful extraction of cellulose. Ultrasonic treatment for 6 h resulted in a specific morphology in which cellulose nanofibers (≥100 nm) were distributed across the entire surface of cellulose microfibers ( 5 m). Constant magnetic stirring combined with acid hydrolysis resulted in an inhomogeneous size distribution of both cellulose rods (500 nm-3 m length, 100-200 nm diameter) and particles 100-200 nm in size. Changes in morphology of the cellulose fibers depended upon the stirring time; longer stirring time resulted in shorter fiber lengths.
Isolation of cellulose nanocrystals (CNCs) was carried out by unrepeated or repeated alkalization and bleaching followed by sulfuric acid hydrolysis and air cooling (unrepeated) or ice cooling (repeated). The influence of unrepeated and repeated alkalization and bleaching, and cooling rate (cooling medium) after hydrolysis on the morphology and crystallinity of the isolated micro- and nano-celluloses were characterized. Scanning electron microscopy (SEM) showed that repeated alkalization and bleaching led to a higher degree of fibrillated microcellulose (~10 mm) with higher surface roughness than unrepeated alkalization and bleaching. Transmission electron microscopy (TEM) revealed that air and ice cooling after acid hydrolysis producing different CNCs morphologies; heterogeneous CNCs nanowhisker and nano-spherical (~50 nm), and homogenous CNCs nanowhiskers (~50 nm width and ~500 nm length), respectively. The homogeneous nano whisker was related to single phase monoclinic b-cellulose. Residual lignin agglutinating between the nanoparticles was observed in TEM image as well as in Fourier transform infrared (FTIR) spectra. The existence of residual lignin after hydrolysis is comparable in crystalinity (crystallinity index,Ic: ~91%) with that of isolated CNCs, as confirmed by x-ray diffraction (XRD) analysis.
Plastic waste has become an environmental problem for all countries. People dispose goods made of plastic causing a build-up of waste because it is difficult to degrade. For this reason, it is necessary to develop environmentally friendly plastics known as biodegradable plastics. This study used starch extracted from cassava peel as base material and tobacco stem powder as a natural reinforcement. Beside the cassava peel starch and tobacco stem powder, glycerol is needed as plasticizer. The purpose of this study was to determine the effect of tobacco stem powder and glycerol addition variations on the mechanical properties. This study is designed using a completely randomized design with two factors and three replication. The parameters observed were mechanical properties (thickness, tensile strength, elongation, modulus young) and the morphology of thickness. The results show that the addition of tobacco stem powder and glycerol had a significant effect on mechanical properties. The addition of tobacco stem powder and glycerol could increase the thickness value of biodegradable plastic between 0.173-0.283 mm. The elongation value obtained were inverse with the tensile strength value. The modulus young value was between 0.08-0.81 MPa.
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