Volume 5 Issue 3

Effects of chemical treatment on the potential for recycling of bagasse pulp were evaluated. The pulps were recycled three times with water (without treatment), sodium hydroxide, and ethylamine separately. Changes in crystalline structure of the pulp during recycling were investigated by x-ray diffractometry. Water retention content was measured by centrifugation. Morphological changes were investigated by scanning electron microscopy. The breaking length, burst index, fold number, water retention value, and density decreased continuously after recycling. Chemical treatment didn't have a positive effect on the swelling of the recycled pulp. But the light scattering coefficient increased continuously. The crystallinity index and crystallite size increased to an extent, compared to virgin pulp. Some particles on recycled fibers with chemical treatment and treated handsheets had more curled fibers than untreated handsheets.

Steam explosion pretreatment was used to release hemicelluloses from the stalks of Lespedeza crytobotrya, a potential woody biomass crop. Hemicelluloses from Lespedeza crytobotrya subjected to five different pretreatment severities were extracted with 60% aqueous ethanol solution containing 1% NaOH, characterized by component analysis, gel permeation chromatography (GPC), FT-IR, NMR spectroscopy, and thermal analysis, and compared with hemicelluloses obtained from untreated stalks. It was found that the hemicellulosic fractions mainly consisted of arabinoxylans and β-glucans or xyloglucans. Steam explosion pretreatment yielded noticeable degradation and debranching reactions, illustrated by a linear decrease of molecular weight and Ara/Xyl ratio with increasing severity. For further high-value utilization of the hemicellulosic polymers, steam explosion at 20 or 22.5 kg/m2 for 4 min is promising because of improved extraction efficiency and avoidance of over-drastic degradation of the polymers.

Non-wood fibers such as bamboo and wheat straw have been playing important roles in the pulp and paper industry in China. In this study an ECF-bleached bamboo kraft pulp was compared with a bleached softwood kraft pulp (NBSK) as the reinforcement pulp in fine paper production. Areas that were examined include the refining of pure fibers, influence of bamboo on dewatering, retention, and sizing. The influence of bamboo kraft pulp as a part of a furnish replacing NBSK was compared as well. Results show that fiber shortening was more prominent with bamboo when refined. This resulted in a higher amount of fines, and addition wet-end chemicals may be required to compensate. Handsheets with bamboo as a reinforcement fiber showed similar mechanical and optical properties to handsheets containing NBSK.

d. Extrusion pulping of rice stem was conducted following a central composite design using a two-level factorial plan involving three process variables (pretreatment NaOH concentration: 0.4, 0.8, 1.2%; extrusion temperature: 40, 60, 80 oC; and extruder rotational speed: 55, 70, 85 rpm). Responses of pulp and handsheets properties to the process variables were analyzed using statistical software (MINITAB 15). As the results show, pulping of rice stem fiber can be done at a relatively short pretreatment time about 4 hours and a low NaOH concentration about 0.8% by twin-screw extruder with limit extrusion temperature of about 80 and extruder rotational speed about 85 rpm. The effect of pretreatment solvent, NaOH, is greatly enhanced by increases in the extrusion temperature. Analysis of the results revealed that this process has to be used to obtain a pulp with yields approximately equivalent to neutral sulfite semi-chemical pulping at fixed kappa number, which is applicable for fluting paper and linerboard production.

Ball-milled bamboo (Neosinocalamus affinis) was first treated under ultrasound at 20 oC in 95% ethanol solution for 0 to 50 min, dissolved in sodium hydroxide/urea solution (7% NaOH/12% urea) at –12 oC, and then extracted with ethanol and dioxane to isolate lignin. The structure of the isolated lignin was characterized with a set of wet chemical and spectroscopic methods, including UV, FT-IR, 13C NMR, and HSQC spectroscopies. The results showed that the lignin extracted from bamboo consisted of p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) type lignins with minor cinnamate units. The predominate lignin inter-units were β-O-4´ ether linkages, followed by phenylcoumaran and a lower proportion of resinol and spirodienone. It was also found that the ester groups of lignin were cleaved during the pretreatment process with cold alkaline solution.

As a pulp bleaching agent, dimethyldioxirane (DMD) is effective and selective. In this study, it was employed as a delignifying agent or as an activating agent for hydrogen peroxide treatment in bleaching acetate-grade pulp. Brightness, kappa number, degree of polymerization (DP), and alpha-cellulose content were evaluated to determine the optimal charges of DMD: 2.5% AO, and 4% HSO5-, respectively. Results from the totally chlorine-free (TCF) sequences MEQMPA, MEpQMPA, and OQMPA suggested that DMD is both effective and selective as a delignifying agent but not as a brightening agent as compared to oxygen. And in a long sequence for the bleaching of dissolving pulp, acid treatment can be used in two approaches: to remove the metal ions without washing before the chelation stage, and to reduce hemicellulose and ash in the final stage.

In the present communication, the effect of positional density on the DC electrical conductivity of bamboo fibres was studied. A comparative study was made between the DC conductivity behavior of bamboo fibres taken from upper and lower portions of bamboo. Four samples from each portion going from centre to periphery were taken. Bamboo fibers taken from the upper portion were less dense, hence showing lower values of DC conductivity. In spite of the lower portion of bamboo being more dense, it showed higher values of DC conductivity, which is attributed to moisture content. Bamboo fibres from centre to periphery were taken from the strips cut at 2 mm distance from centre. The DC conductivity increased from centre to periphery. A theoretical model was developed and verified with the experimental results. It was also found that experimentally determined σdc values of bamboo fibres taken from different radial locations from center to periphery were in agreement with those values obtained from the proposed equation.

In order to obtain the adhesion force of fiber in a paper sheet easily, the relationships between internal bonding strength (IBS) and surface lignin content of masson pine CTMP treated with peracetic acid (PAA) have been investigated with XPS technique, and the surface morphology of fibers was also imaged by AFM. The results showed that the extent of lignin covered on the fiber surface was two times as high as that of whole pulp lignin, and the IBS was inversely proportional to surface lignin. The relationship between IBS and lignin coverage was formulated based on the experimental data. The mutual adhesion forces, cellulose-to-cellulose and lignin-to-lignin, were calculated using these equations, and the results were 28.69 mN/m and 2.487mN/m, respectively.

A chemo-mechanical method was used to prepare cellulose nanofibrils dispersed uniformly in an organic solvent. Poly(ethylene glycol) (PEG 1000) was added to the matrix as a compatibilizer to improve the interfacial interaction between the hydrophobic poly(lactic acid) (PLA) and the hydrophilic cellulose nanofibrils. obtained by solvent casting methods from N,N-Dimethylacetamide (DMAc) were characterized by tensile testing machine, atomic force microscope (AFM), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FT-IR). The tensile test results indicated that, by adding PEG to the PLA and the cellulose nanofibrils matrix, the tensile strength and the elongation rate increased by 56.7% and 60%, respectively, compared with the PLA/cellulose nanofibrils composites. The FT-IR analysis successfully showed that PEG improved the intermolecular interaction, which is based on the existence of inter-molecular hydrogen bonding among PLA, PEG, and cellulose nanofibrils.

In this study, the effect of pine cone ratio on wettability and surface roughness of particleboards was examined. Contact angles of water on the produced samples were measured with a goniometer. The surface roughness of the samples was determined with a fine stylus tracing technique. Particleboards made from 100% wood particle had the lowest average contact angle (95.6°), but the highest was for the particleboards containing 50% pine cone (116.3°). Average surface roughness was higher for samples containing a higher amount of pine cone in the mixture. The smoothest surface (9.77 μm Ra) was observed when panels were produced using 100% wood particles. On the other hand, the roughest surface (15.50 μm Ra) was found for the samples containing 50% cone particles in the mixture. Rmax and Rz parameters had similar trends to the Ra values. Increasing the pine cone ratio in the mixture negatively affected the contact angle and surface roughness parameters of the particleboard.