Natural cellulose fibers from switchgrass with tensile properties similar to cotton and linen

We report the production and characteristics of natural cellulose fibers obtained from the leaves and stems of switchgrass. In this paper, the composition, structure and properties of fibers obtained from the leaves and stem of switchgrass have been studied in comparison to the common natural cellulose fibers, such as cotton, linen and kenaf. The leaves and stems of switchgrass have tensile properties intriguingly similar to that of linen and cotton, respectively. Fibers were obtained from the leaves and stems of switchgrass using a simple alkaline extraction and the structure and properties of the fibers were studied. Fibers obtained from switchgrass leaves have crystallinity of 51%, breaking tenacity of 5.5 g per denier (715 MPa) and breaking elongation of 2.2% whereas the corresponding values for fibers obtained from switchgrass stems are 46%, 2.7 g per denier and 6.8%, respectively. Switchgrass is a relatively easy to grow and high yield biomass crop that can be source to partially substitute the natural and synthetic fibers currently in use. We hope that this research will stimulate interests in using switchgrass as a novel fiber crop in addition to being promoted as a potential source for biofuels.     

Natural cellulose fibers from soybean straw

This paper reports the development of natural cellulose technical fibers from soybean straw with properties similar to the natural cellulose fibers in current use. About 220 million tons of soybean straw available in the world every year could complement the byproducts of other major food crops as inexpensive, abundant and annually renewable sources for natural cellulose fibers. Using the agricultural byproducts as sources for fibers could help to address the concerns on the future price and availability of both the natural and synthetic fibers in current use and also help to add value to the food crops. A simple alkaline extraction was used to obtain technical fibers from soybean straw and the composition, structure and properties of the fibers was studied. Technical fibers obtained from soybean straw have high cellulose content (85%) but low% crystallinity (47%). The technical fibers have breaking tenacity (2.7 g/den) and breaking elongation (3.9%) higher than those of fibers obtained from wheat straw and sorghum stalk and leaves but lower than that of cotton. Overall, the structure and properties of the technical fibers obtained from soybean straw indicates that the fibers could be suitable for use in textile, composite and other industrial applications.     

Characterizing natural cellulose fibers from velvet leaf (Abutilon theophrasti) stems

Velvet leaf (Abutilon theophrasti) that is currently considered a weed and an agricultural problem could be used as a source for high quality natural cellulose fibers. The fibers obtained from the velvet leaf stems are mainly composed of approximately 69% cellulose and 17% lignin. The single cells in the fiber have lengths of approximately 0.9 mm, shorter than those in common bast fibers, hemp and kenaf. However, the widths of single cells in velvet leaf fibers are similar to the single cells in hemp and kenaf. The fibers exhibited breaking tenacity from 2.4 to 3.9 g/denier (325-500 MPa), breaking elongation of 1.6-2.4% and Young's modulus of 140-294 g/denier (18-38 GPa). Overall, velvet leaf fibers have properties similar to that of common bast fibers such as hemp and kenaf. Velvet leaves fibers could be processed on the current kenaf processing machineries for textile, composite, automotive and other fibrous applications.     

Effect of manganese on preferential degradation of lignin by Pleurotus ostreatus during solid-state fermentation.

Practical utilization of the polysaccharides in the lignocellulosic complex is limited because of the high lignin content of the complex. In this study we focused on the effect of Mn on lignin and cellulose biodegradation during solid-state fermentation by the edible mushroom Pleurotus ostreatus. Preferential degradation of lignin was enhanced by the addition of Mn(II) to cotton stalks at concentrations ranging from 30 to 620 micrograms of Mn per g. This effect was most apparent when we compared mineralization rates of [14C] lignin with mineralization rates of [14C] cellulose. Enhanced selectivity was also observed when we analyzed residual organic matter at the end of the fermentation period by using crude fiber analysis. The cellulose fraction in the original material was 1.8 times larger than the cellulose fraction of lignin. The cellulose/lignin ratio increased during 32 days of solid-state fermentation from 2.5 in the control to 3.3 following the addition of Mn to the medium. The in vitro digestibility value for fermented cotton stalks was 53% of the dry matter. Addition of 600 micrograms of Mn per g to the cotton stalks resulted in a digestibility value of 65.4%. Enhancement of preferential lignin degradation could be result of either increased activity of the ligninolytic enzymes or production of Mn (III), which might preferentially degrade aromatic structures in the lignocellulosic complex.     

Preparation and characterization of cellulose nanocrystals from rice straw

Pure cellulose have been isolated from rice straw at 36% yield and hydrolyzed (64% H₂SO₄, 8.75 mL/g, 45 °C) for 30 and 45 min to cellulose nanocrystals (CNCs), i.e., CNC30 and CNC45, respectively. CNC45 was smaller (11.2 nm wide, 5.06 nm thick and 117 nm long) than CNC30 (30.7 nm wide, 5.95 nm thick and 270 nm long). Freeze-drying of diluted CNC suspensions showed both assembled into long fibrous structures: ultra-fine fibers (∼400 nm wide) from CNC45 and 1-2 μm wide broad ribbons interspersed with CNC clusters from CNC30. The self-assembled fibers from CNC30 and CNC45 were more highly crystalline (86.0% and 91.2%, respectively) and contained larger crystallites (7.36 nm and 8.33 nm, respectively) than rice straw cellulose (61.8%, 4.42 nm). These self-assembled fibers had essentially nonporous or macroporous structures with the CNCs well aligned along the fiber axis. Furthermore, the self-assembled ultra-fine fibers showed extraordinary structural stability, withstanding vigorous shaking and prolong stirring in water.     

Influence of silicone oil modification on properties of ramie fiber reinforced polypropylene composites

This paper focused on the analyses of the composition, microstructure, thermal stability and mechanical behavior of modified ramie fiber and its reinforced polypropylene composites. Ramie fiber (RF) was treated with epoxy-silicone oil (ESO) at 160 °C in argon gas. The FTIR and XRD analyses indicated that some silicone molecular chains were bonded on the surface of modified RF, which decreased the crystallinity of the fiber without changing the crystalline type of cellulose. The SEM results of fracture surface showed that the modified RF/PP composite had better interfacial bonding between RF and PP. The mechanical tests showed that the impact strength and the elongation at break of RF/PP were increased by 17.0% and 196% after modification, respectively. The tensile strength of 30RF/PP was improved from 18.95 MPa to 25.96 MPa compared to pure PP. The results of TGA showed that fiber treatment could improve the degradation temperature of RF/PP composites.     

Cellulose nanocrystals as a reinforcing material for electrospun poly(methyl methacrylate) fibers: Formation, properties and nanomechanical characterization

Uniform fibers composed of poly(methyl methacrylate) (PMMA) reinforced with progressively increasing contents of cellulose nanocrystals (CNCs), up to 41 wt% CNCs, have been successfully produced by electrospinning. The morphological, thermal and nanomechanical properties of the composite sub-micron fibers were investigated. The CNCs derived from wood pulp by sulfuric acid hydrolysis were well dispersed in solutions of PMMA and the processing solvent N,N-dimethylformamide prior to fiber formation. Well-formed fibers with controllable diameters were generated reproducibly at all CNC contents investigated including 41 wt%. The orientation of the CNCs along the fiber axis was facilitated by the electrospinning process and observed directly from microscopy examination. Shifts in thermal transitions of PMMA with increasing CNC content suggest hydrogen bonding interactions between CNC hydroxyl groups and carbonyl groups on the PMMA matrix. Nanoscale dynamic mechanical analysis (nano-DMA) was performed using nanoindentation on single fibers perpendicular to the fiber axis. Many of the current challenges associated with single fiber nanoindentation are addressed, such as fiber diameter range and minimum, depth to diameter ratio, and valid depth range under these experimental conditions. Fibers that contained 17 wt% CNCs showed a modest increase of 17% in the storage modulus of PMMA, a high modulus polymer of interest for transparent composite applications.     

Influence of steaming explosion time on the physic-chemical properties of cellulose from Lespedeza stalks (Lespedeza crytobotrya)

The synergistic effect of steam explosion pretreatment and sodium hydroxide post-treatment of Lespedeza stalks (Lespedeza crytobotrya) has been investigated in this study. In this case, Lespedeza stalks were firstly exploded at a fixed steam pressure (22.5 kg/m²) for 2–10 min. Then the steam-exploded Lespedeza stalks was extracted with 1 M NaOH at 50 °C for 3 h with a shrub to water ratio of 1:20 (g/ml), which yielded 57.3%, 53.1%, 55.4%, 52.8%, 53.2%, and 56.4% (% dry weight) cellulose rich fractions, comparing to 68.0% from non-steam-exploded material. The content of glucose in cellulose rich residues increased with increment of the steaming time and reached to 94.10% at the most severity. The similar increasing trend occurred during the dissolution of hemicelluloses. It is evident that at shorter steam explosion time, autohydrolysis mainly occurred on the hemicelluloses and the amorphous area of cellulose. The crystalline region of cellulose was depolymerized under a prolonged incubation time. The characteristics of the cellulose rich fractions in terms of FT-IR and CP/MAS ¹³C NMR spectroscopy and thermal analysis were discussed, and the surface structure was also investigated by SEM.     

Changes in biochemical composition of the cell wall of the cotton fiber during development

The composition of the cell wall of the cotton fiber (Gossypium hirsutum L. Acala SJ-1) has been studied from the early stages of elongation (5 days postanthesis) through the period of secondary wall formation, using cell walls derived both from fibers developing on the plant and from fibers obtained from excised, cultured ovules. The cell wall of the elongating cotton fiber was shown to be a dynamic structure. Expressed as a weight per cent of the total cell wall, cellulose, neutral sugars (rhamnose, fucose, arabinose, mannose, galactose, and noncellulosic glucose), uronic acids, and total protein undergo marked changes in content during the elongation period. As a way of analyzing absolute changes in the walls with time, data have also been expressed as grams component per millimeter of fiber length. Expressed in this way for plant-grown fibers, the data show that the thickness of the cell wall is relatively constant until about 12 days postanthesis; after this time it markedly increases until secondary wall cellulose deposition is completed. Between 12 and 16 days postanthesis increases in all components contribute to total wall increase per millimeter fiber length. The deposition of secondary wall cellulose begins at about 16 days postanthesis (at least 5 days prior to the cessation of elongation) and continues until about 32 days postanthesis. At the time of the onset of secondary wall cellulose deposition, a sharp decline in protein and uronic acid content occurs. The content of some of the individual neutral sugars changes during development, the most prominent change being a large increase in noncellulosic glucose which occurs just prior to the onset of secondary wall cellulose deposition. Methylation analyses indicate that this glucose, at least in part, is 3-linked. In contrast to the neutral sugars, no significant changes in cell wall amino acid composition are observed during fiber development.     

Hydrothermal treatment and ethanol pulping of sunflower stalks

The influence of temperature in the hydrothermal treatment of sunflower stalks on the composition of the liquid fraction obtained was examined. The remaining solid fraction was subjected to ethanol pulping in order to obtain pulp that was used to produce paper sheets. The pulp was characterized in terms of yield, kappa index, viscosity, and cellulose, hemicellulose and lignin contents; and the paper sheets in terms of breaking length, stretch, burst index and tear index. Hydrothermal treatment of the raw material at 190 degrees C provided a liquid phase with maximal hemicellulose-derived oligomers and monosaccharide (glucose, xylose and arabinose) contents (26.9 and 4.2 g/L, respectively). Pulping the solid fraction obtained by hydrothermal treatment at 180 degrees C, with 70% ethanol at a liquid/solid ratio of 8:1 at 170 degrees C for 120 min provided pulp with properties on a par with those of soda pulp from the sunflower stalks, namely: 36.3% yield, 69.1% cellulose, 12.6% hemicellulose, 18.2% lignin and 551 ml/g viscosity. Also, paper sheets obtained from the ethanol pulp were similar in breaking length (3.8 km), stretch (1.23%), burst index (1.15 kN/g) and tear index (2.04 m Nm(2)/g) to those provided by soda pulp.     

Physico-mechanical properties of chemically treated palm and coir fiber reinforced polypropylene composites

In this work, palm and coir fiber reinforced polypropylene bio-composites were manufactured using a single extruder and injection molding machine. Raw palm and coir were chemically treated with benzene diazonium salt to increase their compatibility with the polypropylene matrix. Both raw and treated palm and coir fiber at five level of fiber loading (15, 20, 25, 30 and 35 wt.%) was utilized during composite manufacturing. Microstructural analysis and mechanical tests were conducted. Comparison has been made between the properties of the palm and coir fiber composites. Treated fiber reinforced specimens yielded better mechanical properties compared to the raw composites, while coir fiber composites had better mechanical properties than palm fiber ones. Based on fiber loading, 30% fiber reinforced composites had the optimum set of mechanical properties.     

Properties of natural cellulose fibers from hop stems

This paper reports the development of natural cellulose fibers from hop stems with properties similar to that of hemp. Hop stems are currently considered as byproducts and have limited applications. Since hop belongs to the genus cannabis that also includes hemp, it should be possible to obtain natural cellulose fibers from the stems of hop plants with properties similar to that of hemp. A simple alkaline extraction was used to obtain fibers from the bark of hop stems. Fibers obtained have high cellulose content, low% crystallinity but show good orientation of the cellulose crystals to the fiber axis. The strength and modulus of the fibers are lower but elongation is higher than that of hemp. Based on the properties of the fibers, we expect that the hop stem fibers will be suitable for use in textiles and composites similar to the common cellulose fibers currently in use.     

Carboxymethylation of cellulose using reactive extrusion

Carboxymethyl cellulose was prepared using a continuous, reduced solvent, reactive extrusion process with a short reaction time. The effects of the amounts of NaOH (30 g, 40 g and 50 g), water:ethanol ratio (100%, 70%, 50%, 30% and 10% H₂O) and their interactions on the physical, chemical and morphological properties of carboxymethyl cellulose were studied. Experiments were conducted using to a 5 × 3 blocked factorial design. X-ray diffraction analyses revealed higher degrees of crystallinity and fractions of cellulose-II crystalline structure when 100% H₂O was used as compared to that for 70%, 50%, 30% and 10% H₂O and a commercially available brand of carboxymethyl cellulose, AQUASORB A500. Statistical analysis revealed a significant interaction between the effects of NaOH and H₂O on the degrees of substitutions. The degrees of substitutions decreased with increasing amounts of NaOH and tended to increase with increasing alcohol concentrations. Liquid uptake measurements revealed that the extent of saline uptake, measured at intervals of 1 min, 5 min and 10 min, by carboxymethyl cellulose prepared with 100% H₂O, especially when 40 g and 50 g NaOH was used, was higher than that for 70%, 50%, 30% and 10% H₂O and AQUASORB A500. This may have been because of the higher crystallinity in carboxymethyl cellulose prepared with 100% H₂O. Carboxymethyl cellulose prepared with 70% H₂O and 30 g and 50 g NaOH had the highest saline absorption, using the soak method, before and after centrifugation, respectively. Scanning electron microscopy for carboxymethyl cellulose prepared with 100% and 10% H₂O, through images at 120X magnification, revealed fibers 100 μ to >800 μ in length and 0.8-3.3 μ in breadth. Some non fibrous particles, 0.8-6.7 μ in dimensions, also were observed for 100% H₂O. Images at 900× magnification revealed partially damaged fiber surfaces.     

Protection of cellulose synthesis in detached cotton fibers by polyethylene glycol

Detachment of the cotton fiber cell from the ovule results in loss of over 90% of the in vivo capacity for synthesis of [¹⁴C]cellulose from [¹⁴C]glucose. However, over 50% of the capacity for cellulose synthesis in the detached fiber population is protected when polyethylene glycol 4000 is present during detachment and incubation. Radioautography shows that approximately full capacity is restored in about half the fibers, whereas the other half of the population are incapable of cellulose synthesis from supplied glucose. The rate of cellulose synthesis in such fibers has a pH optimum of 6 and the optimum polyethylene glycol 4000 concentration is 0.06 molal (−9 bars). Cellulose synthesis in such detached fibers is synergistically stimulated by Ca²⁺ and Mg²⁺ and inhibited by K⁺.     

Protein expression changes during cotton fiber elongation in response to low temperature stress

Low temperature stress is one of the major abiotic stresses limiting the formation of cotton (Gossypium hirsutum L.) fiber qualities, especially fiber length. To investigate the molecular adaptation mechanisms of cotton fiber elongation to low temperature stress, two cotton cultivars, Kemian 1 (low temperature-tolerant) and Sumian 15 (low temperature-sensitive), were planted in the field at two sowing dates (25 April and 10 June). The two sowing dates resulted in different growing conditions and the main environmental difference between them was temperature, particularly the mean daily minimum temperature (MDTmin). When the sowing date was delayed, the MDTmin decreased from 26.9 °C (25 April) to 20.6 °C (10 June). Low temperature stress (MDTmin of 20.6 °C) shortened the fiber length significantly in two cultivars, but the decreased extent was larger in Sumian 15 than that in Kemian 1. Proteomic analysis of three developmental stages (10, 15 and 20 days post-anthesis [DPA]) showed that 37 spots changed significantly (p < 0.05) in abundance under low temperature stress and they were identified using mass spectrometry. These proteins were involved in malate metabolism, soluble sugar metabolism, cell wall loosening, cellulose synthesis, cytoskeleton, cellular response, and redox homeostasis. The results suggest that the enhancement of osmoticum maintenance, cell wall loosening, cell wall components biosynthesis, and cytoskeleton homeostasis plays important roles in the tolerance of cotton fibers to low temperature stress. Moreover, low levels of PEPCase, expansin, and ethylene signaling proteins may potentially lead to the low temperature sensitivity of Sumian 15 at the proteomic level.     

Enzyme hydrolysis and ethanol fermentation of dilute ammonia pretreated energy cane

This study is the first one ever to report on the use of high fiber sugarcane (a.k.a. energy cane) bagasse as feedstock for the production of cellulosic ethanol. Energy cane bagasse was pretreated with ammonium hydroxide (28% v/v solution), and water at a ratio of 1:0.5:8 at 160 °C for 1 h under 0.9-1.1 MPa. Approximately, 55% lignin, 30% hemicellulose, 9% cellulose, and 6% other (e.g., ash, proteins) were removed during the process. The maximum glucan conversion of dilute ammonia treated energy cane bagasse by cellulases was 87% with an ethanol yield (glucose only) of 23 g ethanol/100 g dry biomass. The enzymatic digestibility was related to the removal of lignin and hemicellulose, perhaps due to increased surface area and porosity resulting in the deformation and swelling of exposed fibers as shown in the SEM pictures.     

Effect of fiber treatments on tensile and thermal properties of starch/ethylene vinyl alcohol copolymers/coir biocomposites

Coir fibers received three treatments, namely washing with water, alkali treatment (mercerization) and bleaching. Treated fibers were incorporated in starch/ethylene vinyl alcohol copolymers (EVOH) blends. Mechanical and thermal properties of starch/EVOH/coir biocomposites were evaluated. Fiber morphology and the fiber/matrix interface were further characterized by scanning electron microscopy (SEM). All treatments produced surface modifications and improved the thermal stability of the fibers and consequently of the composites. The best results were obtained for mercerized fibers where the tensile strength was increased by about 53% as compared to the composites with untreated fibers, and about 33.3% as compared to the composites without fibers. The mercerization improved fiber–matrix adhesion, allowing an efficient stress transfer from the matrix to the fibers. The increased adhesion between fiber and matrix was also observed by SEM. Treatment with water also improved values of Young’s modulus which were increased by about 75% as compared to the blends without the fibers. Thus, starch/EVOH blends reinforced with the treated fibers exhibited superior properties than neat starch/EVOH.     

Synthesis of novel water-soluble sulfonated cellulose

Water-soluble sulfonated cellulose (SC) samples were synthesized by oxidizing hardwood kraft pulp with sodium periodate followed by the sulfonation reaction with sodium bisulfite. Six levels of oxidation/sulfonation were obtained by using different mmols (0.93-4.67) of periodate per gram of pulp. The aldehyde and sulfonic acid contents, surface morphology, and water solubility property of these treated fibers were characterized. It was found that carbonyl group content increased with the periodate charge and so did the sulfonic acid content in subsequent sulfonation step. Scanning electron microscopy images showed a significant change in surface morphology of the sulfonated samples. Solubility of sulfonated cellulose in water was determined from ¹H NMR spectra and a solubility of 28.57 g/L was found when cellulose was oxidized with 4.67 mmol periodate per gram cellulose followed by the sulfonation reaction.     

Ultrastructural effects of cellulose biosynthesis inhibitor herbicide on developing cotton fibers

Summary Cotton fibers are often utilized as a model system to investigate cellulose biosynthesis and cell wall elongation. In this study, we grew cotton fibers in vitro, with ovules dissected at day zero post anthesis as the expiant source, in the presence of three herbicides that inhibit cellulose biosynthesis. Cultures were sampled for electron microscopy and immunocytochemistry 1–2 days after beginning the treatments. After dichlobenil treatment, the fibers were much shorter than the controls and assumed a variety of abnormal shapes, from shortened versions of the control fiber to nearly spherical. The inner layers of the fiber wall often contained juxtaposed electron-translucent and -transparent areas; this layer reacted strongly with antibodies to callose. Cellulase-gold labeling in these newly developed fibers grown in the presence of dichlobenil was present at only about 3% of the control labeling. After treatment with either isoxaben or flupoxam, the fibers assumed spherical shapes and frequently (more than 60% of fibers) exhibited a new cell plate within the fiber, indicating that cell division had occurred, a process that rarely occurred in the controls. Unlike the dichlobenil-treated fibers, fibers grown in the presence of isoxaben or flupoxam contained an extensive accumulation of chiefly deesterified pectins, replacing the entire wall with an elaborated version of the pectin sheath found in control cotton fibers. These data indicate that all three herbicides are effective disrupters of cellulose biosynthesis and cause radical changes in cell wall structure and composition. Moreover, these data indicate that the composition of the walls may influence indirectly cell cycle kinetics, keeping these fiber cells in a more meristematic mode.     

Dissolution of cellulose from AFEX-pretreated Zoysia japonica in AMIMCl with ultrasonic vibration

In this study, 1-allyl-3-methylimidazolium chloride (AMIMCl), an ionic liquid, was synthesized and characterized by a series of test methods. Pretreatment of Zoysia japonica by ammonia fiber expansion (AFEX) was shown to reduce significantly the mass of hemicellulose and lignin in biomass, thereby breaking the lignocellulosic structure. Z. japonica samples pretreated with AFEX showed reasonable solubility in AMIMCl upon ultrasonic treatment. The rate of cellulose regeneration from Z. japonica samples pretreated with AFEX increased with increase in applied power of ultrasonication within a certain power range from 0 to 110 W. The regeneration rate of cellulose from AFEX-pretreated Z. japonica reached a maximum of 97% when the ultrasonic power was 110 W. Fourier transform infrared spectroscopy and nuclear magnetic resonance analyses indicated that the regenerated cellulose was similar to microcrystalline cellulose.