Isolation and Characterization of Microcrystalline Cellulose from Bamboo Pulp Through Extremely Low Acid Hydrolysis

Microcrystalline cellulose (MCC) has a wide range of applications in food, chemical, pharmaceutical industries, etc. In this study, the one-step preparation of MCC from bleached Kraft bamboo pulp (BKBP) by extremely low acid (ELA; acid concentration ≤0.1?wt %) was demonstrated. The experimental data indicate that the crystallinity, degree of polymerization (DP), and yield of MCC were strongly affected by the time and temperature of hydrolysis, as well as the concentration of hydrochloric acid (HCl). Rod-like MCC was obtained with a yield of 76.4% (based on the mass of original BKBP) and exhibited high crystallinity and narrow particle diameter distribution (78.7%, 30–70?μm) under optimal conditions (acid concentration of 0.08?wt%, 165?°C, 40?min). The Fourier transform-infrared spectroscopy (FTIR) and X-ray diffraction (XRD) measurements showed that the resulted MCC maintained cellulose I structure. Thermal analysis demonstrated that the as-prepared MCC exhibited good thermal stability. The ELA hydrolysis process may provide a green alternative for the manufacture of MCC from bleached Kraft bamboo pulp.     

The Use of Ozone or Oxygen in The First Bleaching Stage

An ODED or a ZEDED sequence bleached kraft hardwood and softwood pulps to 87 — 89‰ ISO brightness. The bleached yields were similar for a given pulp, whether oxygen or ozone was used in the first stage. The strength properties of the fully bleached pulps were essentially the same as those of the unbleached pulps. The COD and colour values of the effluents after ozone delignification and subsequent extraction were 25‰ and 60‰ lower, respectively, than those of the effluents after an oxygen treatment.     

Alkali–methanol–anthraquinone pulping of Miscanthus x giganteus for thermoplastic composite reinforcement

The potential of pulp fiber–reinforced thermoplastics is currently not fully explored in composites. One of the main reasons is that pulp fibers are extracted for the use in papermaking and are thus not optimized for use as reinforcements in thermoplastics. Furthermore, currently used processing methods constitute several severe thermomechanical steps inducing premature degradation of the fibers. A systematic development of these composite materials requires the study of both these aspects. The goal of this work was to optimize fiber extraction against properties relevant to the reinforcement of thermoplastics. To this end, thick‐walled Miscanthus x giganteus pulp fibers were selected. The fibers were pulped by the alkaline–methanol–anthraquinone process. An unreplicated factorial design was applied to determine the effect of key operating variables on fiber thermal stability and mechanical properties. The thermomechanical properties of pulp fibers depend primarily on the morphology and chemical composition of the fiber resource in terms of the respective amounts of lignin, hemicellulose, and cellulose, all strongly influenced by the choice of pulping conditions. Optimal pulping parameters were identified, allowing production of fibers thermally stable up to 255°C with an aspect ratio of 40, a straightness of 95%, and tensile strength as high as 890 MPa. Specific stiffness and strength values with respect to density and material cost of 56 GPa m^?3 $^?1 and 820 MPa m^?3 $^?1 were highly competitive with glass fibers, with corresponding values of 15 GPa m^?3$^?1 and 270–490 MPa m^?3 $^?1, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2132–2143, 2004     

Preparation,Chemical Composition,Characterization, and Properties of Napier Grass Paper Sheets

In this study, perennial fast growth Napier grass fibers were used for pulp and papermaking. Chlorination and alkaline processes were carried out using sodium chlorite and sodium hydroxide respectively, for pulp extraction from Napier grass. Detailed chemical composition analysis of the Napier grass fibers and the extracted pulp was carried out and a comparison with other perennial grasses was made. The extracted fibers and pulp obtained from Napier grass were characterized using scanning electron microscopy and Fourier transform infrared spectroscopy. The physical, optical, and mechanical properties of Napier grass pulp handmade paper sheets produced in the laboratory were investigated by finding the opacity, brightness, tensile index, breaking length, and burst index. Handmade paper sheets made from Napier grass pulp were compared to paper made from other perennial grasses. The superior properties of paper produced from Napier grass pulp indicate the suitability of Napier grass as an alternative non-wood source for papermaking.     

Comparison of the structures and properties of Lyocell fibers from high hemicellulose pulp and high α‐cellulose pulp

Lyocell fibers were produced from a cheap pulp with a high hemicellulose content and from a conventional pulp with a high α‐cellulose content. The mechanical properties, supermolecular structure, fibrillation resistance, and dyeing properties as well as the fibril aggregation size of the high hemicellulose Lyocell fiber and high α‐cellulose Lyocell fiber were compared. The results showed that the high hemicellulose spinning solution could be processed at a higher concentration, which improved the mechanical properties and the efficiency of the fiber process. Compared with the high α‐cellulose Lyocell fiber, the high hemicellulose Lyocell fiber had better fibrillation resistance and dyeing properties. Therefore, it is feasible that this cheap pulp with a high hemicellulose content can be used as a raw material for producing Lyocell fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

QUATAM PROCESS—NEW SULFUR-FREE DELIGNIFICATION

ABSTRACT

An essentially new alkaline chemical pulping process—the Quatam process—has been introduced using an organic base for producing cellulose fibers from wood and annual plants. Solutions of quaternary ammonium compounds, preferably tetramethylammonium hydroxide (TMAH), serve as pulping liquors. The process produces high quality pulp with low kappa number, high brightness and good viscosity—without using sulfur-containing compounds. The process is suitable for both hardwood and softwood. The pulping selectivity of TMAH is demonstrated. Bleachability and mechanical properties of the resulting pulp are compared to those of conventional Kraft pulp.     

高半纤维素浆粕纺制Lyocell纤维的结构与性能

采用成本低、半纤维素含量高的浆粕纺制Lyocell纤维,重点对制得的高半纤维素Lyocell纤维的结晶、取向、力学性能、原纤化和染色性等进行了研究。研究表明:这种用高半纤维素浆粕纺制的Lyocell纤维与用高α-纤维素浆粕纺制的Lyocell纤维相比,它的模量、结晶度、取向度、抗原纤化能力和染色性等都好于后者。     

Reactions of Conventional Kraft and Superbatch Pulp Residual Lignins with Peroxyformic Acid

Abstract

The residual lignins KRL and SRL, isolated from a conventional kraft pulp and a SuperBatch pulp respectively, were reacted with peroxyformic acid (PFA). The reagent consumptions were determined and the products fractionated according to their solubility. Both lignins consumed a roughly equal amount of PFA, which was nearly 50% higher than that consumed by kraft lignin. The undissolved fractions of PFA-treated residual lignins (yield >80%) contained less aromatic units, phenolic hydroxyl and methoxyl groups, and considerably more carboxyl groups (including those of formate esters) than the untreated lignins. The extent of these modifications was approximately equal for KRL and SRL, which together with the similar PFA consumptions and product yields of KRL and SRL indicates that the two residual lignins showed no essential difference in reactivity toward PFA. The effect of fiber wall morphology on delignification efficiency during PFA delignification is suggested to be small because of the cleavage of lignin-carbohydrate linkages occurring under acid conditions. The part of KRL remaining insoluble after PFA-treatment had a 40% higher molar mass than KRL while in the case of SRL there was hardly any such difference in molar mass. The lignins solubilized during the PFA treatments represented the most highly degraded part of the lignins, having very low molar masses and being richer in carboxyl groups and lower in aromatic units, phenolic hydroxyl, and methoxyl groups than the undissolved lignins.     

High Stiffness Natural Fiber‐Reinforced Hybrid Polypropylene Composites

Abstract

Natural fibers are potentially a high‐performance non‐abrasive reinforcing fiber source. In this study, pulp fibers [including bleached Kraft pulp (BKP) and thermomechanical pulp (TMP)], hemp, flax, and wood flour were used for reinforcing in polypropylene (PP) composite. The results show that pulp fibers, in particular, TMP‐reinforced PP has the highest tensile strength, possibly because pulp fibers were subjected to less severe shortening during compounding, compared to hemp and flax fiber bundles. Maleic‐anhydride grafted PP (MAPP) with high maleic anhydride groups and high molecular weight was more effective in improving strength properties of PP composite as a compatiblizer. Coupled with 10% glass fiber, 40% TMP reinforced PP had a tensile strength of 70 MPa and a specific tensile strength comparable to glass fiber reinforced PP. Thermomechanical pulp was more effective in reinforcing than BKP. X‐ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) were used to aid in the analysis. Polypropylene with high impact strength was also used in compounding to improve the low‐impact strength prevalent in natural fiber‐reinforced PP from injection molding.     

Effect of Kraft Cooking Conditions on the Chemical Composition of the Surface and Bulk of Spruce Fibers

By varying cooking temperature, alkali charge, ionic strength, and cooking time in Kraft pulping of spruce chips, pulps ranging between kappa numbers 20–80 were obtained. The unbleached Kraft pulp fibers were subjected to mechanical peeling in order to separate the surface material from the bulk of the fibers and the carbohydrate composition and lignin content of the two fractions were analyzed. As expected, the lignin and xylan contents were higher on the fiber surface than in the fiber wall. The percentage of xylan on the fiber surface was fairly constant, independent of different pulping conditions or degree of delignification. The lignin proportion on the fiber surface gradually decreased with decreasing kappa number. At a given kappa number, pulping at a higher temperature resulted in less lignin on the fiber surface, probably because of the higher solubility of lignin at higher temperature. Cooking at lower alkali charge also resulted in lower lignin content on the fiber surface at a given kappa number. In this case, there was more time available for degradation of the surface lignin since the lower alkali charge resulted in longer cooking time needed to reach a certain kappa number.     

Utilization of Hemicelluloses as Example for Holistic Recovery of Agricultural Residues

The objective of this work was to separate and characterize the hemicellulose from agricultural residues of annual plants and to achieve a suitable application for it. Therefore, different treatments for producing pulp were tested and compared. Wheat straw and oat husks were digested by alkaline pulping and delignification. Pectin from sugar beet pulp was obtained by acid extraction. Beside the production of pulp, the separation and utilization of hemicellulose as resource was a key aspect of this work. The hemicelluloses were tested as paper additives, flame retardants and flotation agents.     

Biodegradable biocomposites from poly(butylene adipate‐co‐terephthalate) and miscanthus: Preparation,compatibilization, and performance evaluation

Miscanthus fibers reinforced biodegradable poly(butylene adipate‐co‐terephthalate) (PBAT) matrix‐based biocomposites were produced by melt processing. The performances of the produced PBAT/miscanthus composites were evaluated by means of mechanical, thermal, and morphological analysis. Compared to neat PBAT, the flexural strength, flexural modulus, storage modulus, and tensile modulus were increased after the addition of miscanthus fibers into the PBAT matrix. These improvements were attributed to the strong reinforcing effect of miscanthus fibers. The polarity difference between the PBAT matrix and the miscanthus fibers leads to weak interaction between the phases in the resulting composites. This weak interaction was evidenced in the impact strength and tensile strength of the uncompatibilized PBAT composites. Therefore, maleic anhydride (MAH)‐grafted PBAT was prepared as compatibilizer by melt free radical grafting reaction. The MAH grafting on the PBAT was confirmed by Fourier transform infrared spectroscopy. The interfacial bonding between the miscanthus fibers and PBAT was improved with the addition of 5 wt % of MAH‐grafted PBAT (MAH‐g‐PBAT) compatibilizer. The improved interaction between the PBAT and the miscanthus fiber was corroborated with mechanical and morphological properties. The compatibilized PBAT composite with 40 wt % miscanthus fibers exhibited an average heat deflection temperature of 81 °C, notched Izod impact strength of 184 J/m, tensile strength of 19.4 MPa, and flexural strength of 22 MPa. From the scanning electron microscopy analysis, better interaction between the components can be observed in the compatibilized composites, which contribute to enhanced mechanical properties. Overall, the addition of miscanthus fibers into a PBAT matrix showed a significant benefit in terms of economic competitiveness and functional performances. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45448.     

高半纤维素浆粕制备Lyocell纤维的研究

采用半纤维素质量分数21%的高半纤维素浆粕在N-甲基吗琳-N-氧化物(NMMO)水溶液中制备Lyocell纤维,并与半纤维素质量分数为10%的高α-纤维素浆粕的可纺性进行了对比。结果表明:高半纤维素浆粕在溶剂NMMO·H_2O中更易溶解,其过滤性能和可纺性能好,可在较高浆粕浓度下纺丝,制备成Lyo- cell纤维的产率高,且能提高Lyocell纤维的力学性能。高半纤维素浆液的稳定性能略低,在溶剂回收中需要消耗较多的双氧水进行氧化回收溶剂NMMO。     

Alkalischer Polyolaufschluss als Basis für eine Lignocellulose‐Bioraffinerie

The utilization of lignocellulose as renewable feedstock for the chemical industry necessitates the development of sustainable pulping processes. A new process is introduced enabling the effective fractionation not only of annual fiber plants or hardwood but also of more resistant softwoods. The resulting ultrapure pulp is free of inhibiting degradation products and can be almost completely enzymatically hydrolyzed.     

TCF BLEACHED PULPS FROM MISCANTHUS SINENSIS BY THE IMPREGNATION RAPID STEAM PULPING (IRSP) PROCESS

ABSTRACT

The production of bleached cellulose pulps from elephant grass (Miscanthus sinensis) via a two-stage soda pulping process and a TCF bleaching sequence is evaluated in this work. The impregnation rapid steam pulping process (IRSP) involves impregnating of the lignocellulosic material with the pulping liquor, withdrawing the excess liquor and rapidly steaming the impregnated material at 180–200°C for a short time. In this paper the process variables and their effect on the kappa number, yield and viscosity of the unbleached pulps are discussed. Bleaching by an ozone-based TCF sequence was tested, and the papermaking properties of the bleached pulp were determined. A kappa number of 19 was obtained by impregnating at an alkali charge of 30 + 0.1% anthraquinone carboxylic acid (AQCA) and pulping at 180°C for only 15 min. Kappa was reduced to 16 by extending pulping time to 26 min. The alkali consumption during impregnation and pulping was 10.2 g NaOH/100 g of dry Miscanthus. Screened pulp yield, viscosity and brightness for this pulp were 54.6%, 913 mL/g and 37.3%, respectively. After bleaching, the pulp had an ISO brightness of 87.4% and a viscosity of 700 mL/g. Refining in a PFI mill provided optimal strength properties of the bleached pulp at 4500 revolutions (71°SR): breaking length 7.2 km, tensile index 72 N m/g, and burst index 4.3 kN/g. Tear index was 7.9 mN m²/g at this degree of refining.     

The Potential of Hydrothermally Pretreated Industrial Barks From E. globulus as a Feedstock for Pulp Production

This study focused on the use of industrial eucalyptus globulus bark as an alternative fiber source for bleached pulp and paper production. Bark has high extractives and ash contents (7.7% and 3.5%, respectively) but a mild hydrothermal pretreatment was tested, decreasing its values to 2.8% and 2.4%, respectively. Untreated and pretreated bark were kraft pulped at 15% and 20% (as Na₂O) active alkali conditions. The pretreatment improved delignification when using low active alkali; kappa number 25.4 vs 17.5, and shives 3.1% vs 0%, respectively, with untreated and pretreated bark. The pretreatment resulted in a lower chemical demand to obtain pulps with similar yield and kappa number. It was possible to produce bleached pulps with good handsheet optical, physical, and mechanical properties with slightly lower values than those of industrial eucalypt wood pulps; e.g., brightness > 85% vs 87%, tear index > 4.2 vs 5.6 mn.m².g^?1, tensile index > 62 vs 69 n.m.g^?1 for bark and wood pulps, respectively.     

Enzymatic hydrolysis of lignocellulosic materials in aqueous media and the subsequent microbiological synthesis of bioethanol

The enzymatic hydrolysis of lignocellulosic materials (LCMs) from miscanthus and oat husks (OH) in an aqueous medium and the subsequent production of ethanol are studied. LCMs are obtained at a pilot plant of the Institute of Problems of Chemical and Energy Technologies by means of one-stage nitric acid treatment. Enzymatic hydrolysis is conducted in an aqueous medium with a high initial concentration of phosphates (90 g/L) using freely available CelloLux-A and BrewZyme BGX industrial enzymatic preparations. The yields of reducing compounds are found to be 65.4 and 73.3% for miscanthus and oat husk LCM, respectively. The composition of monosaccharides (products of enzymatic LCM destruction) is studied for the first time. It is shown that glucose comprises the largest share of monosaccharides. Ethanol is produced from LCM for the first time. Ethanol yields per metric ton of raw material are 19.4 and 16.2 daL/t for miscanthus biomass and OH, respectively. Ethanol samples are characterized by low methanol contents (0.002 to 0.005 vol %).     

Near-Infrared Spectroscopy and Chemometric Analysis for Determining Oxygen Delignification Yield

Abstract

Oxygen delignification studies were carried out using a softwood kraft pulp under varying reaction temperatures (80–140°C) and alkaline charges (1–12%). Near-infrared (NIR) spectroscopy combined with chemometric methods was employed to analyze oxygen delignification pulp yields, which were compared to gravimetric analysis. Principal component analysis (PCA) of the NIR spectra data was performed and a partial least-square (PLS) regression model was developed to predict the pulp yield of oxygen delignified pulps based on the NIR spectra data. PCA analysis indicated that 99.1% of total variances of NIR spectra data in the range of 1100–2266 nm could be expressed by three principle components. A PLS1 model based on the NIR spectra data had good predictive ability and appeared to be an effective tool for pulp yield prediction for the oxygen delignification process.     

Reactive compatibilization and performance evaluation of miscanthus biofiber reinforced poly(hydroxybutyrate‐co‐hydroxyvalerate) biocomposites

Dicumyl peroxide (DCP) initiated reactive compatibilization of poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV)/miscanthus fibers (70/30 wt %) based biocomposite was prepared in a twin screw extruder followed by injection molding. In the presence of DCP, both the flexural and the tensile strength of the PHBV/miscanthus composites were appreciably higher compared with PHBV/miscanthus composite without DCP as well as neat PHBV. The maximum tensile strength (29 MPa) and flexural strength (51 MPa) were observed in the PHBV/miscanthus composite with 0.7 phr DCP. The enhanced flexural and tensile strength of the PHBV/miscanthus/DCP composites are attributed to the improved interfacial adhesion by free radical initiator. Unlike flexural and tensile strength, the modulus of the PHBV/miscanthus/DCP composites was found to slightly lower than the PHBV/miscanthus composite. The modulus difference in the PHBV/miscanthus composite with and without DCP has good agreement with the observed crystallinity. However, the flexural and tensile modulus of all the prepared biocomposites was at least two fold higher than the neat PHBV. The storage modulus value of the PHBV/miscanthus and PHBV/miscanthus/DCP biocomposites follows similar trend like tensile and flexural modulus. The melting temperature and crystallization temperature of PHBV/DCP and PHBV/miscanthus/DCP samples were considerably lower compared with the neat PHBV and PHBV/miscanthus composites. The surface morphology revealed that the PHBV/miscanthus/DCP composites have good interface with less fiber pull‐outs compared with the corresponding counterpart without DCP. This suggests that the compatibility between the matrix and the fibers is enhanced after the addition of peroxide initiator. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44860.     

抗菌蔗渣浆纤维的制备及其性能研究

以漂白蔗渣浆为原料、3-氯-2-羟基丙基三甲基氯化铵为抗菌剂,在碱性条件下发生醚化反应,制备具有广谱抗菌性能的抗菌蔗渣浆纤维。研究了接枝率、接触时间、菌液浓度、洗涤次数对抗菌蔗渣浆纤维抑菌率的影响,试验表明:当接枝率为3%时,抗菌蔗渣浆纤维对大肠埃希菌、金黄葡萄球菌、白念珠菌的抑菌率均为100%;且经过20次洗涤后,抗菌蔗渣浆纤维的抑菌率仍在90%以上,耐洗涤性能好。抗菌蔗渣浆纤维可用于制备具有抗菌性能的食品包装纸,进而实现蔗渣浆纤维的高值化利用。