Research Articles

Corn stalk, an agricultural waste, was valorized by the production of cellulose nanofibers (CNF), which were tested for improving recycled paper properties. CNF from eucalyptus kraft pulp (E-CNF) was used as a reference. Addition of 0.5% wt. CNF produced from corn organosolv pulp (C-CNF) to recycled paper increased the tensile index by 20%, whereas the same improvement with E-CNF was achieved at 1.5% wt. Tensile index was further enhanced by increasing the E-CNF, whereas C-CNF achieved its maximum effect at this dose. Different recycled furnish compositions were studied to evaluate C-CNF as a product additive. C-CNF improved tensile strength in all the different recycled furnishes studied. The tensile index improvement caused by C-CNF did not depend on the proportions of old newspaper and old magazine paper used. Addition of C-CNF to recycled corrugated board fluting increased the tensile strength, but to a slightly lower extent than in the case of recycled newsprint paper.

This study investigated alterations in the lignin of pinewood (Pinus sylvestris L.) during heat sterilization. The Klason lignin content was determined, and the dioxane lignin was isolated. Changes in the dioxane lignin were evaluated by size exclusion chromatography (SEC) as well as Fourier transform infrared (FTIR) spectroscopy. The analyses illustrated an increase in the percentage of extractives and the amount of dioxane lignin yields, while a decrease in the acid-insoluble lignin content was also observed. Changes in the macromolecular characteristics of the dioxane lignin (molecular weight and polydispersity) were not significant (p < 0.05); however, they indicated that simultaneous degradation and condensation reactions had occurred. The FTIR spectra of the dioxane lignins showed an increase at 3420 cm-1 (O-H stretching vibration), indicating the cleavage of ether bonds. The band at 1715 cm-1 (unconjugated C=O stretching) increased after an initial decrease due to the cleavage of the β-alkyl-aryl ether bonds. Also, the band at 1660 cm-1 (conjugated C=O groups) increased, which was caused by the cleavage of the α-alkyl-aryl ether bonds.

Biomorphic charcoal/TiO2 composites (C/TiO2) were produced from poplar templates. The poplar templates were impregnated with butyl titanate sol with a vacuum/positive pressure technology. From the anatomic structure of poplar and fluid thermodynamics, the alternative vacuum/positive pressure technology was an efficient method of infiltrating bio-templates with sol and overcoming the embolization effect of the sol in capillaries. After sol infiltration, the maximum density of the poplar was approximately 0.958 ± 0.005 g/cm3. Using X-ray diffraction (XRD), thermogravimetric data (TG-DTG), and scanning electron microscopy (SEM), it was found that the pore sizes in the cell walls of C/TiO2 were, respectively, 30 to 150, 3 to 15, and 1.5 μm, and a surprising mesoporous-like honeycomb structure formed at approximately 800 °C in a N2 atmosphere. The phase structure of C/TiO2 shifted from anatase to rutile between 700 and 900 °C in N2. Furthermore, the temperature of the maximum combustion rates of C/TiO2 sintered at 800 °C in N2 was approximately 610 °C. The average shrinkage values from the native poplar to C/TiO2 along the radial, tangential, and axial directions were 28.53%, 21.80%, and 17.03%, respectively.

Microcelluloses (MCs) were chemically isolated from two different biomass sources, empty fruit bunches (EFB) and sugarcane bagasse (SCB). The resulting MCs were compared to the commercially available cellulose (MC-Sigma) that was used as a standard. Structural, crystalline, morphological, and thermal properties of all specimens were characterized and compared by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). FTIR analysis verified that the chemical treatments removed non-cellulosic constituents including hemicelluloses and lignin. XRD patterns revealed the crystallinity increment from 43.1% to 52.1% for MC-EFB and 38.9% to 52.4% for MC-SCB. SEM images demonstrated the fibrillar structure of both MC-EFB and MC-SCB, and their surfaces were smoother compared with MC-Sigma. From the TG curves, MC-EFB provided the highest thermal stability, as it had the highest maximum degradation temperature at 345 °C. DSC results showed only one endothermic peak for all specimens. Taken together, these results reasonably confirmed that the MCs from EFB and SCB are comparable to standard MC-Sigma.

To obtain a high transmittance blend within ultraviolet and visible regions, various transparent samples of ascending percentages of polymethylmethacrylate (PMMA)/cellulose acetate propionate (CAP) were prepared by melt blending using a twin screw extruder. These blends were characterised by ultraviolet-visible spectroscopy, and the curves illustrated that the blending ratio of 10% CAP in PMMA meets the required purpose. The morphological, mechanical, and thermal properties for pure PMMA and the PMMA/CAP 10% blend were investigated using X-ray diffraction, scanning electron microscopy, dynamic mechanical analysis, and thermogravimetric analysis. The results showed that the PMMA/CAP 10% blend has an amorphous structure and low stiffness than pure PMMA. The miscible PMMA/CAP 10% blend exhibited mechanical stability below the glass transition temperature (Tg), with a slight increase in Tg value relative to that of pure PMMA. The study also demonstrated that the intermolecular interaction between blend elements has an effective influence on the physical properties of the blend.

This paper presents results on the thixotropic behaviour of hardwood and softwood pulp fibre suspensions. Three rheological tests including hysteresis-loops, creep tests, and step-wise experiments were used to investigate the thixotropic rheology. Both suspensions exhibited a plateau in their flow curves where a slight change of the applied shear stress led to a dramatic change in the corresponding shear rates. During creep experiments under controlled stress, they evolved either towards a rapid shear (liquid regime) or stoppage (solid regime), depending on the relative values of the imposed stress, leading to a viscosity bifurcation around a critical stress. The transient response of pulp to step changes in shear rate was marked by a characteristic time, which can be used to understand the rate of structural change for pulp suspensions. Moreover, the yielding and thixotropic behaviour of the pulp suspensions were highly dependent on shear history and the time of rest prior to the measurement.

Technical lignin, which can be potentially obtained in large amounts as a by-product from kraft pulping, represents a potential resource for manufacturing fuels and chemicals. Upgrading of lignin, by lowering its molecular weight, is a valuable alternative to precipitation from black liquor, which occurs in the Lignoboost process. The solubility properties of Lignoboost lignin and filtered lignin in a number of technically feasible solvents were compared, and it was found that both lignins were dissolved in similar solvents. With the exception of furfural, the best lignin solvents generally were organic solvents miscible with water, such as methanol. It was possible to dissolve more filtered lignin in higher concentrations than Lignoboost lignin; additionally, the viscosities of the filtered lignin solutions were also considerably lower than those of Lignoboost lignin, especially at higher concentrations. Methods for non-organic component removal from filtrated lignin were tested, and it was concluded that several cold acidic treatments after dewatering can lower the ash content to values below 0.5% by weight.

The perennial grass Pennisetum alopecuroides was degraded using a conventional heating method with sulfuric acid. The effects of temperature (150 to 200 °C), reaction time (30 to 210 min), acid concentration (2% to 10%), and solid-liquid ratio (1:10 to 1:4) were optimized for P. alopecuroides hydrolysis. The production of levulinic acid was strongly affected by variations in these parameters. The optimum conditions with respect to reaction temperature, time, acid concentration, and solid-liquid ratio were 190 °C, 60 min, 8%, and 1:6, respectively. The maximum levulinic acid yield using the optimum conditions was 50.49%. The residues obtained from various temperatures were also intensively characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and thermogravimetric (TG) analyses. These results extend the current understanding of the bioconversion and utilization of renewable lignocellulosic biomass.

This study investigated the performance of recycled polypropylene (RPP)/peanut shell powder (PSP) composites with untreated PSP and treated PSP with alkaline peroxide. The RPP/PSP and RPP/PSP-H2O2 composites were prepared by melt mixing and compression molding at different PSP loadings (10 wt.% to 40 wt.%). The samples were characterized by processing properties, tensile properties, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and water absorption behavior. The treated PSP enhanced the stabilization torque, tensile strength, elongation at break, tensile modulus, and water absorption of RPP/PSP-H2O2 composites. FTIR spectra and SEM showed that the elimination of lignin content strongly influenced the fractured surface and chemical characteristics of the RPP/PSP-H2O2 composites.

The density and its spatial distribution of wood-plastic composites (WPCs) were tested by the computer tomography (CT) method. Based on the correlation among the attenuation coefficient, density, and CT number, a mathematical model between CT number and density of WPCs was established. This contributed to the realization of fast and nondestructive detection of WPC density and to the determination of the quality of wood-plastic composite products. Taking pine and poplar wood powder WPCs as subjects, the density was higher near the edge and lower in the middle of the sample, which resembled a “V” shape in the width direction. Compared with the density variations of poplar wood powder WPCs, those of pine wood powder had more of a “V” distribution.