Image analysis of modified cellulose fibers from sugarcane bagasse by zirconium oxychloride

Surface modification of natural fibers has been made using different methods. In this paper, cellulose fibers from sugarcane bagasse were bleached and modified by zirconium oxychloride in situ. The chemically modified cellulose fibers were compared to those of bleached ones. Cellulose fibers were modified with ZrO₂·nH₂O nanoparticles through the use of zirconium oxychloride in acidic medium in the presence of cellulose fibers using urea as the precipitating agent. The spatial distribution characterization of hydrous zirconium oxide on cellulose fibers was carried out by combining both processing and image analyses obtained by SEM and statistical methodologies. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TG) were also used to characterize the nanocomposite. Results indicated that ZrO₂·nH₂O nanoparticles of about 30-80 nm diameter deposited on cellulose fibers were heterogeneously dispersed.     

Adverse effect of nano-silicon dioxide on lung function of rats with or without ovalbumin immunization

Background

The great advances of nanomaterials have brought out broad important applications, but their possible nanotoxicity and risks have not been fully understood. It is confirmed that exposure of environmental particulate matter (PM), especially ultrafine PM, are responsible for many lung function impairment and exacerbation of pre-existing lung diseases. However, the adverse effect of nanoparticles on allergic asthma is seldom investigated and the mechanism remains undefined. For the first time, this work investigates the relationship between allergic asthma and nanosized silicon dioxide (nano-SiO₂).

Methodology/Principal Findings

Ovalbumin (OVA)-treated and saline-treated control rats were daily intratracheally administered 0.1 ml of 0, 40 and 80 µg/ml nano-SiO₂ solutions, respectively for 30 days. Increased nano-SiO₂ exposure results in adverse changes on inspiratory and expiratory resistance (Ri and Re), but shows insignificant effect on rat lung dynamic compliance (Cldyn). Lung histological observation reveals obvious airway remodeling in 80 µg/ml nano-SiO₂-introduced saline and OVA groups, but the latter is worse. Additionally, increased nano-SiO₂ exposure also leads to more severe inflammation. With increasing nano-SiO₂ exposure, IL-4 in lung homogenate increases and IFN-γ shows a reverse but insignificant change. Moreover, at a same nano-SiO₂ exposure concentration, OVA-treated rats exhibit higher (significant) IL-4 and lower (not significant) IFN-γ compared with the saline-treated rats. The percentages of eosinophil display an unexpected result, in which higher exposure results lower eosinophil percentages.

Conclusions/Significance

This was a preliminary study which for the first time involved the effect of nano-SiO₂ to OVA induced rat asthma model. The results suggested that intratracheal administration of nano-SiO₂ could lead to the airway hyperresponsiveness (AHR) and the airway remolding with or without OVA immunization. This occurrence may be due to the Th1/Th2 cytokine imbalance accelerated by the nano-SiO₂ through increasing the tissue IL-4 production.     

Cross-linking chitosan into UV-irradiated cellulose fibers for the preparation of antimicrobial-finished textiles

Chitosan cross-linked cellulose fibers were prepared using non-toxic procedures in order to confer antimicrobial properties to cellulose fibers. Citric acid was used as the cross-linker and NaH₂PO₄ as catalyst in previously UV-irradiated cellulose fibers. Further heat dried-cure process and washing with detergent, water and acetic acid (0.1 M) gave a maximum incorporation of chitosan of 27 mg per gram of functionalized textile. The thermogravimetric analysis of the material with the highest chitosan content showed an increased thermal stability compared to cellulose and chitosan. The UV-irradiation induced morphological changes, such as less entangled cellulose fibers, as observed by scanning electron microscopy, which was prompted to enhance the chitosan incorporation. The biomass and spore germination percentage of Penicillium chrysogenum and colony forming units per millilitre for Escherichia coli decreased significantly on the composed materials as compared to raw cellulose fiber and it was similar to that obtained with a commercial antimicrobial cellulose fiber.     

High performance edible nanocomposite films containing bacterial cellulose nanocrystals

Bacterial cellulose obtained from Gluconacetobacter xylinus in the form of long fibers were acid hydrolyzed under controlled conditions to obtain cellulose nanocrystals. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) confirmed the formation of rod like cellulose nanocrystals having an average diameter and length of 20 ± 5 nm and 290 ± 130 nm respectively. These nanocrystals were used to prepare gelatin nanocomposite films and characterized for elucidating its performance. The formation of percolated networks of cellulose nanocrystals within gelatin matrix resulted in improving the mechanical properties of nanocomposites. The moisture sorption and water vapor permeability (WVP) studies revealed that the addition of cellulose nanocrystals reduced the moisture affinity of gelatin, which is very favorable for edible packaging applications. Results of this study demonstrated the use of bacterial cellulose nanocrystals (BCNCs) in the fabrication of edible, biodegradable and high-performance nanocomposite films for food packaging applications at relatively low cost.     

Deposition of glucuronoxylans on the secondary cell wall of Japanese beech as observed by immuno-scanning electron microscopy

Summary Glucuronoxylans (GXs), the main hemicellulosic component of hardwoods, are localized exclusively in the secondary wall of Japanese beech and gradually increase during the course of fiber differentiation. To reveal where GXs deposit within secondary wall and how they affect cell wall ultrastructure, immuno-scanning electron microscopy using anti-GXs antiserum was applied in this study. In fibers forming the outer layer of the secondary wall (S₁), cellulose fibrils were small in diameter and deposited sparsely on the inner surface of the cell wall. Fine fibrils with approximately 5 nm width aggregated and formed thick fibrils with 12 nm width. Some of these thick fibrils further aggregated to form bundles which labelled positively for GXs. In fibers forming the middle layer of the secondary wall (S₂), fibrils were thicker than those found in S₁ forming fibers and were densely deposited. The S₂ layer labelled intensely for GXs with no preferential distribution recognized. Compared with newly formed secondary walls, previously formed secondary walls were composed of thick and highly packed microfibrils. Labels against GXs were much more prevalent on mature secondary walls than on newly deposited secondary walls. This result implies that the deposition of GXs into the cell wall may occur continuously after cellulose microfibril deposition and may be responsible for the increase in diameter of the microfibrils.Abbreviations GXs glucuronoxylans - PBS phosphate-buffered saline - RFDE rapid-freeze and deep-etching technique - FE-SEM field emission scanning electron microscope - TEM transmission electron microscope     

Development of silica-coated rare-earth doped strontium aluminate toward superhydrophobic,anti-corrosive and long-persistent photoluminescent epoxy coating

Long-persistent phosphorescent smart paints have the ability to continue glowing in the dark for a prolonged time period to function as energy-saving products. Herein, new epoxy/silica nanocomposite paints were prepared with different concentrations of lanthanide-doped aluminate nanoparticles (LAN; SrAl₂O₄:Eu²⁺,Dy³⁺). The LAN pigment was firstly coated with silicon dioxide (SiO₂) utilizing the heterogeneous precipitation technique to provide LAN-encapsulated between SiO₂ nanoparticles (LAN@SiO₂). The epoxy/silica/lanthanide-doped aluminate nanoparticles (ESLAN) nanocomposite paints were coated on steel. The prepared ESLAN paints were studied by transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray fluorescence (XRF) analysis, and energy-dispersive X-ray spectroscopy (EDS). The transparency and coloration properties of the nanocomposite coated films were explored by CIE Lab parameters and photoluminescence spectra. The ultraviolet-induced luminescence properties of the transparent coated films demonstrated greenish phosphorescence at 518 nm upon excitation at 368 nm. Both hardness and hydrophobic activities were investigated. The anticorrosion activity of the nanocomposite films coated onto mild steel substrates immersed in aqueous sodium chloride (NaCl_(aq)) (3.5%) was studied by electrochemical impedance spectroscopy (EIS). The silica-containing coatings were monitored to exhibit anticorrosion properties. Additionally, the nanocomposite films with LAN@SiO₂ (25%) exhibited the optimized long-lasting luminescence properties in the dark for 90 min. The nanocomposite films showed highly reversible and durable long-lived phosphorescence.     

Concentration and shear rate dependence of viscosity in random coil polysaccharide solutions

The concentration (c) and shear rate (γ) dependence of viscosity (η) has been studied for a wide range of random coil polysaccharide solutions, and the following striking generalities are observed:

1. 1. The transition from dilute to concentrated solution behaviour occurs at a critical concentration , when ‘zero shear’ specific viscosity (η_sp) ≈ 10. η_sp varies as c^1.4 for dilute solutions, and as c^3.3 for concentrated solutions.

2. 2. The shear rate dependence of viscosity, and frequency dependence of dynamic (oscillatory) viscosity are closely superimposable.

3. 3. Double logarithmic plots of against (where η₀ is ‘zero shear’ viscosity, and is the shear rate at which ) are essentially identical for all concentrated solutions studied, and thus the two parameters η₀ and completely define the viscosity at all shear rates of practical importance.

Departures from points 1 and 2, but not 3, are observed for concentrated solutions of locust bean gum, guar gum, and hyaluronate at low pH and high ionic strength and are attributed to specific intermolecular associations (‘hyperentanglements’) of longer timescale than non-specific physical entanglements.     

A Comparative Analysis of in vitro cellulose synthesis from cell-free extracts of mung bean (Vigna radiata,Fabaceae) And Cotton (Gossypium hirsutum,Malvaceae)

A comparison of cellulose synthesized in vitro from primary walls of etiolated mung bean (Vigna radiata) seedlings and secondary walls of cotton fibers (Gossypium hirsutum) was made by applying conditions found to be essential for in vitro cellulose I assembly from cotton (Kudlicka et al., 1995, Plant Physiology, vol. 107, pp. 111–123). Mung bean fractions including the plasma membrane (PM), the first solubilized fraction (SE₁), and the second solubilized fraction (SE₂), incorporated more radioactive UDP-Glc into the total product than the same fractions from secondary walls. A significant difference was found with the mild digitonin solubilized fraction (SE₁), which produced eight times more total product than the SE₁ fraction of cotton. However, the SE₁ fraction from cotton produced a larger quantity of cellulose (32.1%) than from mung bean (6.9%). Treatment of the in vitro product by acetic/nitric acid reagent (AN) for varying periods of time demonstrated that cellulose synthesized in vitro from mung bean was more easily degraded than cellulose from cotton fibers. This would suggest that cellulose I produced in vitro from the cotton SE₁ fraction may have a higher crystallinity and DP than cellulose I produced in vitro from mung bean. The fibrils of cellulose produced by the SE, fraction of mung bean were loosely associated and not arranged into a compact bundle as in case of cellulose I synthesized by the cotton SE₁ fraction. The electron diffraction patterns (ED) of both products show reflections characteristic for cellulose I. Products from the SE₂ fraction of mung bean and cotton reveal similarities with the cellulose II allomorph synthesized, as well as abundant β-1,3-glucan.     

PHBV‐TiO2 mats prepared by electrospinning technique: Physico‐chemical properties and cytocompatibility

One of the most important challenges in tissue engineering research is the development of biomimetic materials. In this present study, we have investigated the effect of the titanium dioxide (TiO₂) nanoparticles on the properties of electrospun mats of poly (hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), to be used as scaffold. The morphology of electrospun fibers was observed by scanning electron microscopy (SEM). Both pure PHBV and nanocomposites fibers were smooth and uniform. However, there was an increase in fiber diameter with the increase of TiO₂ concentration. Thermal properties of PHBV and nanocomposite mats were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC analysis showed that the crystallization temperature for PHBV shifts to higher temperature in the presence of the nanoparticles, indicating that TiO₂ nanoparticles change the process of crystallization of PHBV due to heterogeneous nucleation effect. TGA showed that in the presence of the nanoparticles, the curves are shifted to lower temperatures indicating a decreasing in thermal stability of nanocomposites compared to pure PHBV. To produce scaffolds for tissue engineering, it is important to evaluate the biocompatibility of the material. Cytotoxicity assay showed that TiO₂ nanoparticles were not cytotoxic for cells at the concentration used to synthesize the mats. The proliferation of cells on the mats was evaluated by the MTT assay. Results showed that the nanocomposite samples increased cell proliferation compared to the pure PHBV. These results indicate that continuous electrospun fibrous scaffolds may be a good substrate for tissue regeneration.     

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.     

Characterization of cellulose whiskers and their nanocomposites by atomic force and electron microscopy

The aim of this work was to compare and explore electron microscopy and atomic force microscopy (AFM) for structure determination of cellulose whiskers and their nanocomposite with poly(lactic acid). From conventional bright-field transmission electron microscopy (TEM) it was possible to identify individual whiskers, which enabled determination of their sizes and shape. AFM overestimated the width of the whiskers due to the tip-broadening effect. Field emission scanning electron microscopy (FESEM) allowed for a quick examination giving an overview of the sample; however, the resolution was considered insufficient for detailed information. Ultramicrotomy of nanocomposite films at cryogenic temperatures enabled detailed inspection of the cellulose whiskers in the poly(lactic acid) matrix by AFM. FESEM applied on fractured surfaces allowed insight into the morphology of the nanocomposite, although rather restricted due to the metal coating and limited resolution. Detailed information was obtained from TEM; however, this technique required staining and suffered in general from limited contrast and beam sensitivity of the material.     

Regenerated cellulose-silk fibroin blends fibers

Fibers made of cellulose and silk fibroin at different composition were wet spun from solutions by using N-methylmorpholine N-oxide hydrates (NMMO/H(2)O) as solvent and ethanol as coagulant. Different spinning conditions were used. The fibers were characterized by different techniques: FTIR-Raman, scanning electron microscopy, wide-angle x-ray diffraction, DSC analysis. The results evidence a phase separation in the whole blends compositions. The tensile characterization, however, illustrates that the properties of the blends fibers are higher respect to a linear behaviour between the pure polymers, confirming a good compatibility between cellulose and silk fibroin. The fibers containing 75% of cellulose show better mechanical properties than pure cellulose fibers: modulus of about 23 GPa and strength to break of 307 MPa.     

温热中频治疗仪联合热敏灸对腰椎间盘突出症患者腰椎功能、血液流变学及血清PGE2和5-HT水平的影响

摘要 目的：探讨温热中频治疗仪联合热敏灸对腰椎间盘突出症（LDH）患者腰椎功能、血液流变学及血清前列腺素E₂（PGE₂）和5-羟色胺（5-HT）水平的影响。方法：采用随机数字表法,将湖南中医药大学第一附属医院2020年4月~2022年6月期间收治的128例LDH患者分为研究组（n=64,热敏灸联合温热中频治疗仪治疗）和对照组（n=64,热敏灸治疗）。对比两组疗效、腰椎功能、血液流变学及血清PGE₂、5-HT水平,同时观察两组不良反应发生情况。结果：研究组的临床总有效率（93.75%）明显高于对照组（79.69%）（P<0.05）。治疗4周后,与对照组相比,研究组全血高切黏度、血浆粘度、全血低切黏度、红细胞压积、视觉模拟疼痛（VAS）评分和血清PGE₂、5-HT水平更低,日本骨科协会（JOA）评分更高（P<0.05）。治疗过程中两组患者均未出现不良反应。结论：温热中频治疗仪联合热敏灸治疗LDH患者,可有效改善患者的腰椎功能、血液流变学及血清PGE₂和5-HT水平。     

Biosoftening of coir fiber using selected microorganisms

Coir fiber belongs to the group of hard structural fibers obtained from coconut husk. As lignin is the main constituent of coir responsible for its stiffness, microbes that selectively remove lignin without loss of appreciable amounts of cellulose are extremely attractive in biosoftening. Five isolated strains were compared with known strains of bacteria and fungi. The raw fiber treated with Pseudomonas putida and Phanerocheate chrysosporium produced better softened fiber at 30±2 °C and neutral pH. FeSO₄ and humic acid were found to be the best inducers for P. chrysosporium and P. putida, respectively, while sucrose and dextrose were the best C-sources for both. Biosoftening of unretted coir fibers was more advantageous than the retted fibers. Unlike the weak chemically softened fiber, microbial treatment produced soft, whiter fibers having better tensile strength and elongation (44.6–44.8%) properties. Scanning electron microscopy photos showed the mycelia penetrating the pores of the fiber, removing the tylose plug and degrading lignin.     

Biosynthesis of NiFe2O4@Ag Nanocomposite and Assessment of Its Effect on Expression of norA Gene in Staphylococcus aureus

Activity of norA efflux pump has been known as a resistance mechanism to antibiotics like ciprofloxacin in Staphylococcus aureus. This study was carried out to assess the effect of biosynthesized NiFe₂O₄@Ag nanocomposite on expression of norA gene in Staphylococcus aureus. In this experimental study, 30 clinical samples were collected from patients hospitalized at different hospitals in Guilan Province, Iran. Then, clinical isolates of S. aureus were identified by standard microbiological tests. Antimicrobial susceptibility tests of clinical and standard strains of S. aureus were done by disk diffusion method according to CLSI guideline. Fourier transform infrared spectroscopy (FT‐IR) was used to analyze the various functional groups present in the biosynthesized NiFe₂O₄@Ag nanocomposite. This analysis confirmed the formation of alga proteins coated on magnetite nanocomposite. X‐ray diffraction (XRD) verified the crystalline structure of NiFe₂O₄@Ag and the deposition of silver on the surface of NiFe₂O₄. Energy dispersive X‐ray mapping (EDX‐map) analysis confirmed the existence of Ag, Ni, Fe and O in the final product. Scanning electron microscopy (SEM) confirmed that the nanocomposites were spherical in shape and Transmission electron microscopy (TEM) results revealed that the NiFe₂O₄@Ag had the particle size about 100 nm. Antibacterial activity of NiFe₂O₄@Ag alone and combined with ciprofloxacin was evaluated using the disk assay method, and minimum inhibitory concentration (MIC) by broth dilution method. Afterwards, the expression of norA efflux pump gene with and without of NiFe₂O₄@Ag nanocomposite and ciprofloxacin was evaluated by Real‐Time PCR. Real‐Time PCR results demonstrated that the expression of norA gene in the strains exposed to both NiFe₂O₄@Ag nanocomposite (1/4 MIC) and ciprofloxacin (1/8 MIC) significantly reduced in comparison to untreated strains. This study reveals that, when NiFe₂O₄@Ag nanocomposite is combined with ciprofloxacin, the inhibitory effect of ciprofloxacin increases against growth of S. aureus. Therefore, NiFe₂O₄@Ag nanocomposite can be considered as an effective factor to decrease the growth of S. aureus along with ciprofloxacin.     

SiO2 nanoparticles induce global genomic hypomethylation in HaCaT cells

The increasing amount of nanotechnological products, found in our environment and those applicable in engineering, material sciences and medicine has stimulated a growing interest in examining their long-term impact on genetic and epigenetic processes. We examined here the epigenomic response to nm-SiO₂ particles in human HaCaT cells and methyltransferases (DNMTs) and DNA-binding domain proteins (MBDs) induced by nano-SiO₂ particles. Nm-SiO₂ treatment induced global hypoacetylation implying a global epigenomic response. The levels of DNMT1, DNMT3a and methyl-CpG binding protein 2 (MBD2) were also decreased in a dose dependent manner at mRNA and protein level. Epigenetic changes may have long-term effects on gene expression programming long after the initial signal has been removed, and if these changes remain undetected, it could lead to long-term untoward effects in biological systems. These studies suggest that nanoparticles could cause more subtle epigenetic changes which merit thorough examination of environmental nanoparticles and novel candidate nanomaterials for medical applications.     

The dissolution and characterization of Bombyx mori silk fibroin in calcium nitrate-methanol solution and the regeneration of films

Bombyx mori silk fibroin from the silkworm was found to be soluble in a calcium nitrate-methanol system. Fibroin dissolves in 75% w/v Ca(NO₃)₂/MeOH solution at a temperature of 67°C. The viscometric behavior of the fibroin-salt solution was analyzed and the fibroin's secondary structures were determined via ¹³C solution nmr. Fourier transform ir, solid state ¹³C-nmr, x-ray diffraction, differential scanning calorimetry, scanning electron microscopy (SEM), and polarizing microscopy were used to characterize regenerated films and fibers. A compositional phase diagram of fibroin in the salt solution was constructed. Viscosity data indicate that there is aggregation of fibroin chains within the salt solution. The extremely high value of intrinsic viscosity of 8.7 dL/g at 298 K may be due to aggregation. Aggregation may be caused by the complexing of calcium ions with the fibroin chains at their amide linkages. The energy required for viscous flow for the fibroin solution (ΔH_vis = 9.03 kcal/mol) is greater than that of the solvent (ΔH_vis = 7.01 kcal/mol). Chain entanglements may be hindering the free motion of chains thus increasing the energy required for the viscous flow. ¹³C-nmr shows that fibroin chains exist in two independent conformational environments. While most of the molecule is in a random coil conformation, there is evidence of some order within the chains of fibroin. In as-cast regenerated films, the fibroin chains are in a random coil/α-helix conformation with some β-sheet content. Crystallinity induced by immersion of thin films in methanol is evidenced via x-ray diffraction, which shows lattice spacings at 4.042 Å. Thin films have a fibrillar morphology that is clearly shown under the SEM and the polarizing microscope. Fibers were hand pulled from the concentrated fibroin-salt solutions and coagulated with acetone and methanol. A microscopic analysis was done using the polarizer. © 1997 John Wiley & Sons, Inc. Biopoly 42: 61–74, 1997     

The molecular parameters of monomeric and acid-soluble collagens. Low shear gradient viscosity and electric birefringence

The molecular parameters of pronase-treated acid-soluble bovine skin collagen (P-ASC) were determined from low-shear gradient viscosity, electric birefringence, and electron microscopic data in order to determine the shear gradient range in which viscosity studies yield data which can be correctly interpreted by use of the various hydrodynamic equations for prolate ellipsoids of revolution. The P-ASC solutions could be characterized by a single relaxation process in electric briefringence with rotary diffusion coefficient θ of 810 sec^?1 and a corresponding molecular length of 2850 Å. Viscosity data were found to be shear gradient dependent and only the extrapolated zero-shear value [η]D = 0 could be used with the viscosity hydrodynamic equations to provide a correct value of molecular length. Intrinsic viscosities obtained at shear gradients >250 sec^?1 are nearly 30% lower than the zero-shear value. Untreated acid-soluble collagen (ASC) solutions contain aggregates and these appear, from electric birefringence data, to be of endlinked character. ASC solutions show a much more marked shear gradient dependence than P-ASC. For example, at D～500sec^?1,[η] = 22 dl/g, whereas the extrapolated zero-shear value of[η] was found to be 44 dl/g. Thus, the shear gradient dependence of native collagen solutions is much more marked than previously assumed and, in contrast to the usual practice, only viscosities measured near zero shear can be interpreted in terms of molecular parameters for collagen solutions containing aggregates.     

Shear and extensional rheology of cellulose/ionic liquid solutions

In this study, we characterize the shear and extensional rheology of dilute to semidilute solutions of cellulose in the ionic liquid 1-ethyl-3-methylimidazolium acetate (EMIAc). In steady shear flow, the semidilute solutions exhibit shear thinning, and the high-frequency complex modulus measured in small amplitude oscillatory shear flow exhibits the characteristic scaling expected for solutions of semiflexible chains. Flow curves of the steady shear viscosity plotted against shear rate closely follow the frequency dependence of the complex viscosity acquired using oscillatory shear, thus satisfying the empirical Cox-Merz rule. We use capillary thinning rheometry (CaBER) to characterize the relaxation times and apparent extensional viscosities of the semidilute cellulose solutions in a uniaxial extensional flow that mimics the dynamics encountered in the spin-line during fiber spinning processes. The apparent extensional viscosity and characteristic relaxation times of the semidilute cellulose/EMIAc solutions increase dramatically as the solutions enter the entangled concentration regime at which fiber spinning becomes viable.     

Structure and properties of regenerated cellulose fibers from different technology processes

The crystalline and microstructure of the regenerated cellulose fibers prepared from different solvents and technology processes were investigated by synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). WAXD results indicated that the crystal orientation, crystallinity of Lyocell and IL-cell fibers were higher than those of Viscose and Newdal fibers. The size of micro-voids located in the cross-section of regenerated cellulose fibers was analyzed based on the results of SAXS. And the technology process had little effect on the radius of the micro-voids. The micro-voids in Viscose and Newdal fibers have longer length (L) and greater misorientation (B_Φ) than that in Lyocell and IL-cell fibers. This reveals that the average void volumes of Viscose and Newdal fibers were larger. Furthermore, the regenerated cellulose fibers from dry-jet-wet-spinning process exhibited completely a higher E-modulus, tenacity than the fibers spun by wet-spinning method did.