Extraction and Characterization of Cellulose Nanowhiskers from Balsa Wood

Summary: In this study cellulose nanowhiskers were obtained from balsa wood. For this purpose, fibers of balsa wood were exposed to hydrolysis reactions for lignin and hemicellulose digestion and acquisition of nano-scale cellulose. Transmission electron microscopy (TEM) results demonstrated that the obtained cellulose nanocrystals had average length and thickness of 176 (±68 nm) and 7.5 (±2.9 nm), respectively. Infrared spectroscopy (FTIR) and wide angle x-ray diffraction (WAXD) showed that the process for extracting the nanowhiskers digested nearly all the lignin and hemicellulose from the balsa fiber and still preserved the aspect ratio and crystallinity satisfactory enough for future application as nanofillers in polymer nanocomposites. The thermogravimetric analysis (TGA) showed that the onset temperature of thermal degradation of the cellulose nanocrystals (226 °C) was higher than the onset temperature of the balsa fiber (215 °C), allowing its use in molding processes with polymers melts.     

Kinetics of thermal degradation applied to biocomposites with TPS, PCL and sisal fibers by non-isothermal procedures

The thermal degradation behavior of the biocomposite with thermoplastic starch (TPS), poly(ε-caprolactone) (PCL) and bleached sisal fibers were investigated by thermogravimetry analysis (TG/DTG) under synthetic air atmosphere, differential scanning calorimetry, and their crystal structure by X-ray diffraction. Applying the non-isothermal Ozawa method, the TG/DTG curves average activation energy could be obtained for thermal degradation of the biocomposites with 5, 10, and 20 % of bleached sisal fibers. The apparent activation energy values for the biocomposites decreased when compared with the TPS/PCL blend, requiring lower energy to recycle this material. However, continuous addition of sisal fibers increased the activation energy of composites.     

Obtaining nanofibers from curauá and sugarcane bagasse fibers using enzymatic hydrolysis followed by sonication

This paper is an initial study of the implementation of two new enzymes, an endoglucanase and a concoction of hemicellulases and pectinases to obtain cellulosic nanoparticles. In this study, curauá and sugarcane bagasse were dewaxed and bleached prior to enzymatic action for 72 h at 50 °C, and then followed by sonication. The concentration between these two enzymes was varied, and for the concentrations and time of enzymatic treatment used, subsequent sonication was necessary for cellulose nanoparticle release. It was easier to extract cellulose nanofibers from sugarcane bagasse which resulted in nanoparticles without damage of cellulose chains. On the other hand, curauá fibers needed a higher concentration of enzymes and the nanofibers obtained displayed a decrease of crystallinity suggesting that the cellulose structure was compromized. For both fibers, cellulose nanocrystals (single crystals) and larger diameter nanofibers were attained after the sonication.     

Interfacial behavior of composites of recycled poly(ethyelene terephthalate) and sugarcane bagasse fiber

This paper reports on a study of composites of recycled poly(ethylene terephthalate) (PETr) and sugarcane bagasse fiber with and without compatibilizing agents. The interfacial behavior of these composites was investigated by torque rheometry, tensile tests, dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM). A comparison of the torque values resulting from the use of ethylene/n-butyl acrylate/glycidyl methacrylate (EBGMA) and ethylene–methyl acrylate (EMA) copolymer compatibilizing agents indicated that EBGMA increased the interaction between the constituents more effectively than EMA. The addition of bagasse sugarcane fiber did not affect the tensile modulus and reduced the tensile strength and elongation of PETr, as is normally observed in these types of composites. Consistent with the results of torque rheometry and DMA, the SEM analyses indicated that EBGMA improved adhesion between the constituents. All the composites showed promise as good alternatives for the production of environmentally friendly products.     

Sulfonated Kraft lignin addition in urea–formaldehyde resin

Journal of Thermal Analysis and Calorimetry - Urea–formaldehyde (UF) resins are widely used over the world as an adhesive, principally in the civil construction, but its use leads to...     

Obtaining nanocomposites of polyamide 6 and cellulose whiskers via extrusion and injection molding

Nanocomposites of polyamides with cellulose whiskers are difficult to obtain by conventional processing of extrusion and injection molding because of the low thermal stability of the cellulosic nanostructures and the relatively high processing temperature of polyamides, which is higher than the temperature of thermal degradation of cellulose whiskers. Thus, in this study cellulose whiskers were coated with polyamide 6 (PA6) in order to increase their thermal stability and prevent the formation of agglomerates. This coating on cellulose whiskers allows their application to obtain nanocomposites with polyamides, whose processing temperatures are relatively high, around 250 °C. Cellulose whiskers (CWs) were obtained from cotton fibers by acid hydrolysis. The freeze-dried CWs were coated with PA6 by dispersing them in formic acid; PA6 was solubilized in this suspension. The cellulose-coated whiskers (CCWs) were characterized by X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetry (TG), scanning electron microscopy (SEM-FEG) and infrared spectroscopy. SEM-FEG and TG results showed that the PA6 coating on CWs prevented high agglomeration of dried CWs and promoted an increase in their thermal stability from 180 to 280 °C, allowing the use of CCWs to obtain nanocomposites with PA6 using conventional processing routes, such as extrusion and injection molding, at appropriate processing temperatures. In this way, 1 wt% CCWs was used to prepare nanocomposites with PA6. The PA6 + 1CW nanocomposites were compared to neat PA6 without CWs. The samples were characterized by tensile tests and DSC, and the results showed that the PA6 coating on CWs was effective in raising the thermal stability of CWs, improving the dispersion of CWs in the matrix of PA6, resulting in a 45 % increase in the elastic modulus of the nanocomposite with only 1 wt% of coated cellulose whiskers in comparison to neat PA6.