For the value-added utilization of discarded agricultural wastes,corn silk( CS) obtained abundantly in the farming field has been tested as a new source of cellulosic materials. Cellulose microfibril( CMF) and cellulo...For the value-added utilization of discarded agricultural wastes,corn silk( CS) obtained abundantly in the farming field has been tested as a new source of cellulosic materials. Cellulose microfibril( CMF) and cellulose nanocrystal( CNC) were isolated from CS by ethanol and alkali pretreatments,and acid hydrolysis.The characterization was performed by scanning electron microscopy( SEM),Fourier transform infrared spectroscopy( FT-IR),X-ray diffraction( XRD), thermogravimetric analysis( TGA) and transmission electron microscopy( TEM). After chemical pretreatments,the lignin,hemicelluloses and other non-structural components were removed. The degree of crystallinity and thermal stability of CMF and CNC were increased compared to raw CS. The crystallinity indexes of CS,CMF and CNC were 45. 90%,65. 77%,and 73. 75% respectively. The CNC was flat and rod like shape with diameter and aspect ratio range of 13. 96-33. 69 nm and 34. 34-23. 02 nm respectively. The nanocrystals had an alternative potential to be used as reinforcing filler for bio-nanocomposites preparation.展开更多
Kaschin-Beck disease （KBD）, endemic in China, occurs along a low selenium belt where the Se contents of water, soil, crops and patients’ blood and hair are all in a low state. Supplementation of Na<sub>2</...Kaschin-Beck disease （KBD）, endemic in China, occurs along a low selenium belt where the Se contents of water, soil, crops and patients’ blood and hair are all in a low state. Supplementation of Na<sub>2</sub>SeO<sub>3</sub> has been effective in preventing such a disease. The main pathological changes of KBD are the necrosis of cartilage, early展开更多
Atomic force microscope(AFM) was used to investigate the arrangement of cellulose microfibrils (CMF) in Moso bamboo (Phyllostachys pubescens) fibers. Two methods of sample preparation were used here for different purp...Atomic force microscope(AFM) was used to investigate the arrangement of cellulose microfibrils (CMF) in Moso bamboo (Phyllostachys pubescens) fibers. Two methods of sample preparation were used here for different purposes. The first method was chemical maceration with a mixture of hydrogen peroxide and glacial acetic acid, through which the obtained fibers were suitable for observing the orientation of CMF in the primary wal1. The other method was to prepare tangential microtomed sections with a thickness of approximately 30 μm, which was used to investigate the arrangement of CMF in the inner wall of cell cavity of bamboo fibers. The results indicated that the CMF are randomly oriented in the primary wall while in the inner wall of cell cavity they are nearly vertical to the long axis of fibers , which is similar to the arrangement of CMF in the corresponding layer of wood fibers. Meanwhile, the highly oriented arrangement of CMF is also observed in a certain layer of bamboo fibers, though it is incapable of determining which layer it is in this study. The pilot investigation demonstrates that AFM is a powerful tool for the high-resolution observation of CMF in bamboo fibers, meanwhile it has the advantages of simple procedure of sample preparation and easy operation compared to the traditional transmission electron microscopy.展开更多
The microfibril angle of seven poplar clones was determined by using X-ray diffraction technique. Microfibril angle, wood basic density, fiber length, fiber width and cellulose content were assessed for every growth r...The microfibril angle of seven poplar clones was determined by using X-ray diffraction technique. Microfibril angle, wood basic density, fiber length, fiber width and cellulose content were assessed for every growth ring at breast height for all sample trees. Significant variation in microfibril angle was observed among growth rings. Mean microfibril angle (MFA) at breast height varied from 7.8?to 28?between growth rings with cambial age and showed a consistent pith-to-bark trend of decline an-gles. Analysis of variance also indicated that there were significant differences in wood basic density, fiber length, fiber width and cellulose content between the growth rings, which had an increasing tendency from pith to bark. Correlations between MFA and examined wood properties were predominantly large and significant negative (?0.01), and the coefficients were -0.660 for cellulose content, -0.586 for fiber length, -0.516 for fiber width and -0.450 for wood basic density, respectively. Regression analysis with linear and curve estimation indicated that a quadratic function showed the largest R2 and the least standard error for describing the relationships between microfibril angle and measured wood properties, and the correlation coefficients were over -0.45 (n=125). The results from this study suggested that microfibril angle would be a good characteristic for improvement in the future breeding program of poplars.展开更多
The reinforcing impact of Lignocellulosic micro and nanofibrillated cellulose(L-MNFCs)obtained from Eucalyp-tus Globulus bark in Urea-Formaldehyde UF adhesive was tested.L-MNFCs were prepared by an environmentally fri...The reinforcing impact of Lignocellulosic micro and nanofibrillated cellulose(L-MNFCs)obtained from Eucalyp-tus Globulus bark in Urea-Formaldehyde UF adhesive was tested.L-MNFCs were prepared by an environmentally friendly,low-cost process using a combination process involving steam explosion followed by refining and ultra-fine grinding.Obtained L-MNFCs showed a web-like morphology with some aggregates and lignin nanodroplets.They present a mixture of residual fibers and fine elements with a width varying between 5 nm to 20μm,respec-tively.The effects of the addition of low amounts of L-MNFCs(1%wt.)on the properties of three different adhe-sives(Urea-Formaldehyde UF,Phenol-Formaldehyde PF,and Tannin-Hexamine TH)were studied by the evolution of the pH,the viscosity,and the mechanical properties.Results showed that the viscosity of PF and UF adhesives increased with the addition of L-MNFCs,unlike TH.Meanwhile,the addition led to better mechan-ical behavior for the three adhesives.Particleboards were then prepared using modified UF with L-MNFCs and tested.Results showed that an amount of 1%wt.of L-MNFCs was sufficient to increase the internal bonding by≈67%,the modulus of elasticity by≈43%,and the modulus of rupture by≈29%.展开更多
According to current knowledge on collagen fibril-logenesis, collagen fibrils are formed by a cooperative process involving lateral fusion of small protofibrils. Almost all the experimental research, however, was carr...According to current knowledge on collagen fibril-logenesis, collagen fibrils are formed by a cooperative process involving lateral fusion of small protofibrils. Almost all the experimental research, however, was carried out on tendon collagen, whose fibrils are characterized by approximately straight subfibrils. By contrast, in most tissues the collagen fibril sub-units follow a helical course in which geometrical constraints prevent lateral fusions, thereby implying a different mechanism where collagen fibrils grow by addition of individual microfibrils rather than by lateral fusion of pre-assembled subfibrils. The proc-ess at the origin of these fibrils may provide a simple, automatic explanation for the remarkable uniformity in fibrils size observed in most tissues without re-quiring the intervention of unknown mechanisms of diameter control. Other mechanisms of growth con-trol remain indispensable to terminate the fibril-logenesis process in tendons and ligaments.展开更多
The periodontal ligament (PDL) contains oxytalan fibers as well as collagen fibers, which helps it to withstand the mechanical stress to which it is constantly exposed. The oxytalan fibers are produced by PDL fibrobla...The periodontal ligament (PDL) contains oxytalan fibers as well as collagen fibers, which helps it to withstand the mechanical stress to which it is constantly exposed. The oxytalan fibers are produced by PDL fibroblasts. However, the arrangement of PDL fibroblasts and the orientation of oxytalan fibers relative to the fibroblast cell axis have not been investigated under the condition of mechanical stress. We hypothesized that such stress would alter the arrangement and orientation of these cells and their oxytalan fibers. The aim of this study was to evaluate the effects of stretching strain on PDL fibroblasts, focusing on the cellular arrangement and orientation of oxytalan fibers relative to the long cell axis in cell/matrix layers by staining the major component of the fibers, fibrillin-1. The angle between the long cell axis and the oxytalan fibers was approximately 70 degrees under both non-stretching and stretching conditions. Moreover, stretching induced the rearrangement of the cells. This is the first study to demonstrate that stretching induces the rearrangement of the PDL fibroblasts without altering the angle between the long cell axis and the oxytalan fibers. These results may reflect the orientation of oxytalan fibers in the PDL under the condition of mechanical stress.展开更多
Konjac glucomannan nano gel microfibrils were prepared by using electrospinning method. Topology structures were analyzed by Fourier transform infrared spectroscopy （FT-IR） and Field emission scanning electron micro...Konjac glucomannan nano gel microfibrils were prepared by using electrospinning method. Topology structures were analyzed by Fourier transform infrared spectroscopy （FT-IR） and Field emission scanning electron microscopy （FESEM）, while the differential scanning calorimetry （DSC） was carried out to check the thermal stability of the structure. Results reveal that the interaction of KGM intermolecular hydrogen bonds and topological tangle rate are increased by electrospirming, while stable structures of nano gel microfibrils are formed without altering the molecular groups of origin, These structures compose of topological networks of clustered nano fibers with lower porosity and higher density.展开更多
Collapse-type shrinkage is one of highly refractory drying defects inlow-medium density plantation-grown eucalypt wood used as solid wood products. Basic density (BD),microfibril angle (MFA), double fibre cell wall th...Collapse-type shrinkage is one of highly refractory drying defects inlow-medium density plantation-grown eucalypt wood used as solid wood products. Basic density (BD),microfibril angle (MFA), double fibre cell wall thickness (DWT), proportion of ray parenchyma (RP),unit cell wall shrinkage, total shrinkage and residual collapse, which are associated withcollapse-type shrinkage characteristics, were investigated by using simple regression method forthree species of collapse-susceptible Eucalyptus urophyll,, E. grandis and E. urophyllaxE.grandis,planted at Dong-Men Forest Farm in Guangxi autonomous region, China. The results indicated that:unit cell wall shrinkage had a extremely strong positive correlation with BD, moderately strongpositive correlation with DWT, and a weakly or moderately negative correlation with RP and MFA;total shrinkage was positively correlated with BD, DWT and RP and negatively related to MFA, but notable to be predicted ideally by any examined factors alone owing to lower R^2 value (R^2≤0.5712);residual collapse was negatively correlated with BD and DWT, linearly positively correlated withMFA, and had strongly positive linear correlation with RP. It is concluded that BD can be used assingle factor (R^2≥ 0.9412) to predicate unit cell wall shrinkage and RP is the relatively soundindicator for predicting residual collapse展开更多
Microfibrillated cellulose(MFC)is often added to polylactic acid(PLA)matrixes as a reinforcing filler to obtain fully-biodegradable composites with improved mechanical properties.However,the incompatibility between MF...Microfibrillated cellulose(MFC)is often added to polylactic acid(PLA)matrixes as a reinforcing filler to obtain fully-biodegradable composites with improved mechanical properties.However,the incompatibility between MFC and the PLA matrix limits the mechanical performance of MFC-reinforced PLA composites.In this paper,DL-lactic acid-grafted-MFC(MFC-g-DL)was used to improve the compatibility with PLA.Reinforced composites were prepared by melt extrusion and hot-cold pressing.The tensile strength of the PLA/MFC-g-DL composite increased by 22.1%compared with that of PLA after adding 1%MFC-g-DL.Scanning electron microscopy(SEM),differential scanning calorimetry(DSC),and dynamic thermomechanical analysis(DMA)were used to explore the enhancement mechanism.The energy dissipation in the MFC network and the improved compatibility between PLA and MFC-g-DL played important roles in the reinforcement.The SEM results showed that there was a closer combination between PLA and MFC-g-DL.The DSC results showed that the addition of cellulose changed the glass transition temperature,melting temperature,and crystallization temperature of PLA.The TG results showed that the initial and maximum decomposition temperature were lower than those of PLA.The ultraviolet spectra showed that the composite had good transparency at a low concentration of MFC-g-DL.展开更多
In this study,we investigated the barrier properties of different kinds of microfibrillated cellulose(MFC)coating layers.The air,oxygen,and water vapor permeability,as well as the water contact angles(WCA),were measur...In this study,we investigated the barrier properties of different kinds of microfibrillated cellulose(MFC)coating layers.The air,oxygen,and water vapor permeability,as well as the water contact angles(WCA),were measured to quantify the barrier efficacy of the applied coatings.The WCA data showed that the surfaces of MFC-coated cardboards are more hydrophilic than those of uncoated cardboards.However,different MFC coatings realize different oxygen transmission rates(OTRs)and water vapor transmission rates(WVTRs).The MFC coating derived from bleached bamboo pulp subjected to carboxyethylation pretreatment(MFCCBP)gave the best oxygen and water vapor barrier performances.The OTR of the virgin cardboard(>16500 cm^(3)/(m^(2)·24 h))decreased to 4638 cm^(3)/(m^(2)·24 h)after coating with the MFCCBP.The WVTR similarly decreased from 1016.7 g/(m^(2)·24 h)to 603.2 g/(m^(2)·24 h).展开更多
The microfibril angle of fiber walls is an ultra-mieroscopic feature affecting the performance of wood products. It is therefore essential to get more definitive information to improve selection and utilization. X-ray...The microfibril angle of fiber walls is an ultra-mieroscopic feature affecting the performance of wood products. It is therefore essential to get more definitive information to improve selection and utilization. X-ray diffraction is a rapid method for measuring microfibril angles. In this paper, the variability of microfibril angle in plantation-grown Masson pine was investigated by peak-fitting method. This method was compared with the traditional hand-drawn method, 40% peak height method and half peak height method. X-ray diffraction measurements indicated that the microfibril angle changed as a function of the position in the tree. The mean microfibril angle decreased more gradually as the distance increased from the pith and reached the same level in mature wood. The microfibril angle also seemed to decrease clearly from the base upward. Differences of angle-intensity curves between heartwood and sapwood were also examined.展开更多
Microfibrillated cellulose(MFC) was first prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl(TEMPO) oxidation pretreatment and mechanical grinding in the presence of a certain amount of ground calcium carbonate(GCC).The...Microfibrillated cellulose(MFC) was first prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl(TEMPO) oxidation pretreatment and mechanical grinding in the presence of a certain amount of ground calcium carbonate(GCC).The effects of GCC dosage and grinding concentration on the fibrillation were investigated.The obtained MFC was then added to the bulk GCC to form MFC-modified GCC fillers.The properties of MFCmodified GCC fillers were compared to those of the traditional GCC fillers.Results showed that the resulting fibrils became more uniform when the dosage of GCC was 10%~15% and the concentration of the suspension was 6.97%.Compared to traditional GCC,the average particle size of the MFCmodified GCC fillers was larger.Scanning electron microscopy images showed that GCC and MFC formed a bridge structure in the MFC-modified GCC fillers.In the process of papermaking,the MFC-modified GCC fillers decreased the drainage rate but increased the retention of fillers.The prepared papers filled with MFC-modified GCC fillers had higher tensile strength than those filled with traditional GCC fillers.展开更多
Cellulose microfibril (CMF) was the extraction with acid mixture from peel of Musa sapientum Linn type of banana (Kluai Nam Wa). The fibrous-shape of CMF interconnected weblike structure with the average diameter 26 n...Cellulose microfibril (CMF) was the extraction with acid mixture from peel of Musa sapientum Linn type of banana (Kluai Nam Wa). The fibrous-shape of CMF interconnected weblike structure with the average diameter 26 nm were observed by TEM. In order to prepare zein/CMF nanocomposite films, 16% wt zein solution was prepared by dissolved in 80% ethanol aqueous solution which contain glycerol 20% w/w. The suspension of CMF and zein solution was mixed with 0% - 5% weight fractions of solid CMF in zein matrix. The morphology of the zein films is more roughness by increased amount of cellulose microfibrils. It was found that as CMF content increase from 0 to 5% wt results in increasing tensile strength and Young’s modulus of zein nanocomposite films. The highest strength obtains at 4% wt CMF.展开更多
In this study,lignin-containing microfibrillated cellulose(MFC)was prepared from corncob residue after xylose extraction via co-grinding with calcium hydroxide.The product was then compared with the MFC obtained by di...In this study,lignin-containing microfibrillated cellulose(MFC)was prepared from corncob residue after xylose extraction via co-grinding with calcium hydroxide.The product was then compared with the MFC obtained by direct grinding and applied to strengthen paper.The chemical composition and morphological structure analysis results showed that the corncob residue can be used to prepare lignin-containing MFC and does not require further purification.Moreover,the co-grinding with calcium hydroxide is easier to fibrillate corncob residue.The MFC obtained by cogrinding with calcium hydroxide had a higher aspect ratio,and its surface was coated with calcium carbonate nanoparticles.MFCs obtained by both the methods mentioned above had an obvious strengthening effect on paper.Compared with the paper without MFC,the tensile index,elongation,burst index,and folding strength of the paper with MFC obtained by co-grinding with calcium hydroxide significantly increased by 17.5%,22.1%,19.5%,and 157.1%,respectively.This study provides a novel idea for the utilization of corncob residue,which may enhance the value and promote the comprehensive utilization of corn by-products.展开更多
Microfibrillated cellulose(MFC)was obtained by mechanical grinding of different pulps.MFC-modified ground calcium carbonate(GCC)was prepared in two different ways,designated MFC-GCC composite filler and MFC-GCC flocs ...Microfibrillated cellulose(MFC)was obtained by mechanical grinding of different pulps.MFC-modified ground calcium carbonate(GCC)was prepared in two different ways,designated MFC-GCC composite filler and MFC-GCC flocs filler.The opacity of pulp handsheets loaded with MFCmodified GCC was measured.The effects of MFC originated from different pulps,pretreatment method,and filler modification on the opacity of handsheets loaded with MFC-modified GCC were discussed.The results show that MFC originated from alkaline peroxide mechanical pulp(APMP)was optimal for improving the opacity of the handsheets and PFI grinding pretreatment for MFC provided a denser structure in the corresponding MFCAPMP-GCC floc filler while enzyme pretreatment was more effective in increasing the opacity of the filled paper.Under the experimental conditions,the opacity of handsheets increased from 81.0%to 82.7%when the unmodified GCC was replaced by an equivalent amount of MFCAPMP-GCC composite filler,while other properties were unchanged.展开更多
Understanding the assembly and spatial arrangement of bamboo cell wall components is crucial for its optimal utilization.Bamboo cell walls consist of aggregates of cellulose microfibrils and matrix.In the present stud...Understanding the assembly and spatial arrangement of bamboo cell wall components is crucial for its optimal utilization.Bamboo cell walls consist of aggregates of cellulose microfibrils and matrix.In the present study,the size and arrangement of cellulose microfibril aggregates in the cell walls of sclerenchyma fibers and parenchyma cells in moso bamboo were investigated with NMR and FE-SEM.The NMR measurement showed that the characteristic sizes of the microfibril aggregates of fibers and parenchyma cells were approximately 25.8 nm and 18.8 nm,respectively.Furthermore,high-resolution SEM showed the size of microfibril aggregates varied little across the cell wall of sclerenchyma fiber.However,there were significant size differences between the broad and narrow lamellae both in fiber and parenchyma cells,which is thought to be closely related to the orientation of microfibrils in these layers.The microfibril aggregates in the fibers mainly appear in a random arrangement,although occasionally in a radial or tangential arrangement in individual cell.Parenchyma cells have a relatively thinner cell wall layers,in which microfibril aggregates appear in a concentric lamellar arrangement.展开更多
Increasing usage of foams in various industry sectors had causing serious disposal problems once it reaches the end of its life-cycle.Herein,PVA-MFC foam was prepared by freeze-drying using polyvinyl alcohol(PVA)and m...Increasing usage of foams in various industry sectors had causing serious disposal problems once it reaches the end of its life-cycle.Herein,PVA-MFC foam was prepared by freeze-drying using polyvinyl alcohol(PVA)and microfibrillated cellulose(MFC)as a reinforced material from sugarcane bagasse(SCB).In this study,the PVA-MFC foam was chemically silylated with Y-methacryloxypropyltrimethoxysilane(MPS)and tetraethoxysilane(TEOS).The wetting ability and mechanical strength of the silylated_(2,20)PVA-MFC foam was greatly enhanced compared with unmodified_(2,20)PVA-MFC foam.The silane chemicals(MPS and TEOS)had been confirmed grafted on_(2,20)PVA-MFC foam due to the presence of Si-C and Si-O-C stretching vibration as showed in Fourier Transform Infrared(FTIR)spectra and cloud-like coating of porous pore was observed in scanning electron microscopy(SEM)images.The silylated_(2,20)PVA-MFC foam(MPS and TEOS)exhibited a series of desirable properties such as lower swelling ratio and high absorption capacity of solvents and oils but had low thermal stability in thermogravimetric(TGA)analysis.The characterization of_(2,20)PVA-MFC foam using TEOS was further investigated.A significant difference in morphology was clearly observed between the unmodified and silylated_(2,20)PVA-MFC-TEOS foam through field emission scanning electron microscopy(FESEM)images.The X-ray photoelectron(XPS)analysis of silylated_(2,20)PVA-MFC-TEOS foam confirmed the presence of C,O and trace amount of Si elements.These synthesized_(2,20)PVA-MFC foam could be a promising material for broad range of polymer foam applications.展开更多
Microfibrillated cellulose(MFC)aerogels are bio-based materials with high thermal resistance.In this study,MFC aerogels and MFC-kapok composite aerogels were prepared.A series of experiments were carried out in a clim...Microfibrillated cellulose(MFC)aerogels are bio-based materials with high thermal resistance.In this study,MFC aerogels and MFC-kapok composite aerogels were prepared.A series of experiments were carried out in a climate chamber to study the influence of MFC concentration,the temperature gradient,testing methods and introduction of kapok fibers on the thermal insulation properties of aerogels.The results suggested that the density of MFC aerogels was less than 10 mg/cm3 and the porosity was higher than 99%.Besides,the minimum thermal conductivity of MFC aerogels was 0.0357 W·m-1·K-1 observed at 0.8%MFC aerogels.The minimum thermal conductivity of MFC-kapok composite aerogels was 0.0382 W·m-1·K-1 when the ratio of MFC to kapok was 2∶6.展开更多
Scanning Probe Microscopes (SPMs) observe specimen surfaces with probes by detecting the physical amount of a material between the cantilever and the surface. SPMs have a high resolution and can measure mechanical cha...Scanning Probe Microscopes (SPMs) observe specimen surfaces with probes by detecting the physical amount of a material between the cantilever and the surface. SPMs have a high resolution and can measure mechanical characteristics such as stiffness, adsorptive properties, and viscoelasticity. These features make it easy to identify the surface structure of complex materials;therefore, the use of SPMs has increased in recent years. Wood cell walls are primarily composed of cellulose, hemicellulose, and lignin. It is believed that hemicellulose and lignin surround the cellulose framework;however, their detailed formation remains unknown. Therefore, we observed wood cell walls via scanning probe microscopy to try to reveal the formation of the cellulose framework. We determined that the size of the cellulose microfibril bundle and hemicellulose lignin module composite was 18.48 nm based on topography and that the size of the cellulose microfibril bundle was 15.33 nm based on phase images. In the viscoelasticity image, we found that the viscoelasticities of each cell wall of the same cell were not the same. This is because the cellulose microfibrils in each cell wall lean in different directions. The angle between the leaning of the cellulose microfibril and the cantilever affects the viscoelasticity measurement.展开更多
基金Fundamental Research Funds for the Central Universities,China(Nos.16D310102,2232018A3-04)
文摘For the value-added utilization of discarded agricultural wastes,corn silk( CS) obtained abundantly in the farming field has been tested as a new source of cellulosic materials. Cellulose microfibril( CMF) and cellulose nanocrystal( CNC) were isolated from CS by ethanol and alkali pretreatments,and acid hydrolysis.The characterization was performed by scanning electron microscopy( SEM),Fourier transform infrared spectroscopy( FT-IR),X-ray diffraction( XRD), thermogravimetric analysis( TGA) and transmission electron microscopy( TEM). After chemical pretreatments,the lignin,hemicelluloses and other non-structural components were removed. The degree of crystallinity and thermal stability of CMF and CNC were increased compared to raw CS. The crystallinity indexes of CS,CMF and CNC were 45. 90%,65. 77%,and 73. 75% respectively. The CNC was flat and rod like shape with diameter and aspect ratio range of 13. 96-33. 69 nm and 34. 34-23. 02 nm respectively. The nanocrystals had an alternative potential to be used as reinforcing filler for bio-nanocomposites preparation.
文摘Kaschin-Beck disease （KBD）, endemic in China, occurs along a low selenium belt where the Se contents of water, soil, crops and patients’ blood and hair are all in a low state. Supplementation of Na<sub>2</sub>SeO<sub>3</sub> has been effective in preventing such a disease. The main pathological changes of KBD are the necrosis of cartilage, early
基金Supported by the "948" Project of the State Forestry Administration (2002-45)the National Natural Science Foundation Project(30400337)the Key Project of Science & Technology Supporting Programs Funded by China during the 11th Five-year Plan(2006BAD19B0402)
文摘Atomic force microscope(AFM) was used to investigate the arrangement of cellulose microfibrils (CMF) in Moso bamboo (Phyllostachys pubescens) fibers. Two methods of sample preparation were used here for different purposes. The first method was chemical maceration with a mixture of hydrogen peroxide and glacial acetic acid, through which the obtained fibers were suitable for observing the orientation of CMF in the primary wal1. The other method was to prepare tangential microtomed sections with a thickness of approximately 30 μm, which was used to investigate the arrangement of CMF in the inner wall of cell cavity of bamboo fibers. The results indicated that the CMF are randomly oriented in the primary wall while in the inner wall of cell cavity they are nearly vertical to the long axis of fibers , which is similar to the arrangement of CMF in the corresponding layer of wood fibers. Meanwhile, the highly oriented arrangement of CMF is also observed in a certain layer of bamboo fibers, though it is incapable of determining which layer it is in this study. The pilot investigation demonstrates that AFM is a powerful tool for the high-resolution observation of CMF in bamboo fibers, meanwhile it has the advantages of simple procedure of sample preparation and easy operation compared to the traditional transmission electron microscopy.
基金This research was supported by National Natural Science Foundation of China (Grant No. 30070616).
文摘The microfibril angle of seven poplar clones was determined by using X-ray diffraction technique. Microfibril angle, wood basic density, fiber length, fiber width and cellulose content were assessed for every growth ring at breast height for all sample trees. Significant variation in microfibril angle was observed among growth rings. Mean microfibril angle (MFA) at breast height varied from 7.8?to 28?between growth rings with cambial age and showed a consistent pith-to-bark trend of decline an-gles. Analysis of variance also indicated that there were significant differences in wood basic density, fiber length, fiber width and cellulose content between the growth rings, which had an increasing tendency from pith to bark. Correlations between MFA and examined wood properties were predominantly large and significant negative (?0.01), and the coefficients were -0.660 for cellulose content, -0.586 for fiber length, -0.516 for fiber width and -0.450 for wood basic density, respectively. Regression analysis with linear and curve estimation indicated that a quadratic function showed the largest R2 and the least standard error for describing the relationships between microfibril angle and measured wood properties, and the correlation coefficients were over -0.45 (n=125). The results from this study suggested that microfibril angle would be a good characteristic for improvement in the future breeding program of poplars.
基金The authors gratefully acknowledge the financial support of Labex Tec21 and Labex Arbre for the thesis funding.This work was also supported by the Franco-Chilean EcosSud Collaborative Program C18E05,ANID PIA/Apoyo CCTE AFB170007 of Universidad de Concepcion.
文摘The reinforcing impact of Lignocellulosic micro and nanofibrillated cellulose(L-MNFCs)obtained from Eucalyp-tus Globulus bark in Urea-Formaldehyde UF adhesive was tested.L-MNFCs were prepared by an environmentally friendly,low-cost process using a combination process involving steam explosion followed by refining and ultra-fine grinding.Obtained L-MNFCs showed a web-like morphology with some aggregates and lignin nanodroplets.They present a mixture of residual fibers and fine elements with a width varying between 5 nm to 20μm,respec-tively.The effects of the addition of low amounts of L-MNFCs(1%wt.)on the properties of three different adhe-sives(Urea-Formaldehyde UF,Phenol-Formaldehyde PF,and Tannin-Hexamine TH)were studied by the evolution of the pH,the viscosity,and the mechanical properties.Results showed that the viscosity of PF and UF adhesives increased with the addition of L-MNFCs,unlike TH.Meanwhile,the addition led to better mechan-ical behavior for the three adhesives.Particleboards were then prepared using modified UF with L-MNFCs and tested.Results showed that an amount of 1%wt.of L-MNFCs was sufficient to increase the internal bonding by≈67%,the modulus of elasticity by≈43%,and the modulus of rupture by≈29%.
文摘According to current knowledge on collagen fibril-logenesis, collagen fibrils are formed by a cooperative process involving lateral fusion of small protofibrils. Almost all the experimental research, however, was carried out on tendon collagen, whose fibrils are characterized by approximately straight subfibrils. By contrast, in most tissues the collagen fibril sub-units follow a helical course in which geometrical constraints prevent lateral fusions, thereby implying a different mechanism where collagen fibrils grow by addition of individual microfibrils rather than by lateral fusion of pre-assembled subfibrils. The proc-ess at the origin of these fibrils may provide a simple, automatic explanation for the remarkable uniformity in fibrils size observed in most tissues without re-quiring the intervention of unknown mechanisms of diameter control. Other mechanisms of growth con-trol remain indispensable to terminate the fibril-logenesis process in tendons and ligaments.
文摘The periodontal ligament (PDL) contains oxytalan fibers as well as collagen fibers, which helps it to withstand the mechanical stress to which it is constantly exposed. The oxytalan fibers are produced by PDL fibroblasts. However, the arrangement of PDL fibroblasts and the orientation of oxytalan fibers relative to the fibroblast cell axis have not been investigated under the condition of mechanical stress. We hypothesized that such stress would alter the arrangement and orientation of these cells and their oxytalan fibers. The aim of this study was to evaluate the effects of stretching strain on PDL fibroblasts, focusing on the cellular arrangement and orientation of oxytalan fibers relative to the long cell axis in cell/matrix layers by staining the major component of the fibers, fibrillin-1. The angle between the long cell axis and the oxytalan fibers was approximately 70 degrees under both non-stretching and stretching conditions. Moreover, stretching induced the rearrangement of the cells. This is the first study to demonstrate that stretching induces the rearrangement of the PDL fibroblasts without altering the angle between the long cell axis and the oxytalan fibers. These results may reflect the orientation of oxytalan fibers in the PDL under the condition of mechanical stress.
基金supported by the National Natural Science Foundation of China(31471704 and 31271837)major projects of industries,university and research in Fujian Province(2013N5003)
文摘Konjac glucomannan nano gel microfibrils were prepared by using electrospinning method. Topology structures were analyzed by Fourier transform infrared spectroscopy （FT-IR） and Field emission scanning electron microscopy （FESEM）, while the differential scanning calorimetry （DSC） was carried out to check the thermal stability of the structure. Results reveal that the interaction of KGM intermolecular hydrogen bonds and topological tangle rate are increased by electrospirming, while stable structures of nano gel microfibrils are formed without altering the molecular groups of origin, These structures compose of topological networks of clustered nano fibers with lower porosity and higher density.
基金This work was supported by both the project ( No. 30170754)from Chinese National Natural Science Fund and the national significant fundamental research 'Ascending Plan' program (No.95- 07) authorized by Ministry of Science and Technology, China. And was partly presented at the 54th Annual Meeting of the Japan Wood Research Society in Hokkaido, Japan and at the 7th Pacific Rim Bio-based Composites Symposium in Nanjing, P. R. China.
文摘Collapse-type shrinkage is one of highly refractory drying defects inlow-medium density plantation-grown eucalypt wood used as solid wood products. Basic density (BD),microfibril angle (MFA), double fibre cell wall thickness (DWT), proportion of ray parenchyma (RP),unit cell wall shrinkage, total shrinkage and residual collapse, which are associated withcollapse-type shrinkage characteristics, were investigated by using simple regression method forthree species of collapse-susceptible Eucalyptus urophyll,, E. grandis and E. urophyllaxE.grandis,planted at Dong-Men Forest Farm in Guangxi autonomous region, China. The results indicated that:unit cell wall shrinkage had a extremely strong positive correlation with BD, moderately strongpositive correlation with DWT, and a weakly or moderately negative correlation with RP and MFA;total shrinkage was positively correlated with BD, DWT and RP and negatively related to MFA, but notable to be predicted ideally by any examined factors alone owing to lower R^2 value (R^2≤0.5712);residual collapse was negatively correlated with BD and DWT, linearly positively correlated withMFA, and had strongly positive linear correlation with RP. It is concluded that BD can be used assingle factor (R^2≥ 0.9412) to predicate unit cell wall shrinkage and RP is the relatively soundindicator for predicting residual collapse
基金the Natural Science Foundation of China(No.32071704).
文摘Microfibrillated cellulose(MFC)is often added to polylactic acid(PLA)matrixes as a reinforcing filler to obtain fully-biodegradable composites with improved mechanical properties.However,the incompatibility between MFC and the PLA matrix limits the mechanical performance of MFC-reinforced PLA composites.In this paper,DL-lactic acid-grafted-MFC(MFC-g-DL)was used to improve the compatibility with PLA.Reinforced composites were prepared by melt extrusion and hot-cold pressing.The tensile strength of the PLA/MFC-g-DL composite increased by 22.1%compared with that of PLA after adding 1%MFC-g-DL.Scanning electron microscopy(SEM),differential scanning calorimetry(DSC),and dynamic thermomechanical analysis(DMA)were used to explore the enhancement mechanism.The energy dissipation in the MFC network and the improved compatibility between PLA and MFC-g-DL played important roles in the reinforcement.The SEM results showed that there was a closer combination between PLA and MFC-g-DL.The DSC results showed that the addition of cellulose changed the glass transition temperature,melting temperature,and crystallization temperature of PLA.The TG results showed that the initial and maximum decomposition temperature were lower than those of PLA.The ultraviolet spectra showed that the composite had good transparency at a low concentration of MFC-g-DL.
文摘In this study,we investigated the barrier properties of different kinds of microfibrillated cellulose(MFC)coating layers.The air,oxygen,and water vapor permeability,as well as the water contact angles(WCA),were measured to quantify the barrier efficacy of the applied coatings.The WCA data showed that the surfaces of MFC-coated cardboards are more hydrophilic than those of uncoated cardboards.However,different MFC coatings realize different oxygen transmission rates(OTRs)and water vapor transmission rates(WVTRs).The MFC coating derived from bleached bamboo pulp subjected to carboxyethylation pretreatment(MFCCBP)gave the best oxygen and water vapor barrier performances.The OTR of the virgin cardboard(>16500 cm^(3)/(m^(2)·24 h))decreased to 4638 cm^(3)/(m^(2)·24 h)after coating with the MFCCBP.The WVTR similarly decreased from 1016.7 g/(m^(2)·24 h)to 603.2 g/(m^(2)·24 h).
基金This study was financially supported by the National Natural Science Foundation of China （Grant Nos. 30371125 and 30400337）.
文摘The microfibril angle of fiber walls is an ultra-mieroscopic feature affecting the performance of wood products. It is therefore essential to get more definitive information to improve selection and utilization. X-ray diffraction is a rapid method for measuring microfibril angles. In this paper, the variability of microfibril angle in plantation-grown Masson pine was investigated by peak-fitting method. This method was compared with the traditional hand-drawn method, 40% peak height method and half peak height method. X-ray diffraction measurements indicated that the microfibril angle changed as a function of the position in the tree. The mean microfibril angle decreased more gradually as the distance increased from the pith and reached the same level in mature wood. The microfibril angle also seemed to decrease clearly from the base upward. Differences of angle-intensity curves between heartwood and sapwood were also examined.
文摘Microfibrillated cellulose(MFC) was first prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl(TEMPO) oxidation pretreatment and mechanical grinding in the presence of a certain amount of ground calcium carbonate(GCC).The effects of GCC dosage and grinding concentration on the fibrillation were investigated.The obtained MFC was then added to the bulk GCC to form MFC-modified GCC fillers.The properties of MFCmodified GCC fillers were compared to those of the traditional GCC fillers.Results showed that the resulting fibrils became more uniform when the dosage of GCC was 10%~15% and the concentration of the suspension was 6.97%.Compared to traditional GCC,the average particle size of the MFCmodified GCC fillers was larger.Scanning electron microscopy images showed that GCC and MFC formed a bridge structure in the MFC-modified GCC fillers.In the process of papermaking,the MFC-modified GCC fillers decreased the drainage rate but increased the retention of fillers.The prepared papers filled with MFC-modified GCC fillers had higher tensile strength than those filled with traditional GCC fillers.
文摘Cellulose microfibril (CMF) was the extraction with acid mixture from peel of Musa sapientum Linn type of banana (Kluai Nam Wa). The fibrous-shape of CMF interconnected weblike structure with the average diameter 26 nm were observed by TEM. In order to prepare zein/CMF nanocomposite films, 16% wt zein solution was prepared by dissolved in 80% ethanol aqueous solution which contain glycerol 20% w/w. The suspension of CMF and zein solution was mixed with 0% - 5% weight fractions of solid CMF in zein matrix. The morphology of the zein films is more roughness by increased amount of cellulose microfibrils. It was found that as CMF content increase from 0 to 5% wt results in increasing tensile strength and Young’s modulus of zein nanocomposite films. The highest strength obtains at 4% wt CMF.
基金The authors are grateful for financial support from the National Key Research and Development Program of China(2017YFE0102500 and 2017YFB0307901).
文摘In this study,lignin-containing microfibrillated cellulose(MFC)was prepared from corncob residue after xylose extraction via co-grinding with calcium hydroxide.The product was then compared with the MFC obtained by direct grinding and applied to strengthen paper.The chemical composition and morphological structure analysis results showed that the corncob residue can be used to prepare lignin-containing MFC and does not require further purification.Moreover,the co-grinding with calcium hydroxide is easier to fibrillate corncob residue.The MFC obtained by cogrinding with calcium hydroxide had a higher aspect ratio,and its surface was coated with calcium carbonate nanoparticles.MFCs obtained by both the methods mentioned above had an obvious strengthening effect on paper.Compared with the paper without MFC,the tensile index,elongation,burst index,and folding strength of the paper with MFC obtained by co-grinding with calcium hydroxide significantly increased by 17.5%,22.1%,19.5%,and 157.1%,respectively.This study provides a novel idea for the utilization of corncob residue,which may enhance the value and promote the comprehensive utilization of corn by-products.
文摘Microfibrillated cellulose(MFC)was obtained by mechanical grinding of different pulps.MFC-modified ground calcium carbonate(GCC)was prepared in two different ways,designated MFC-GCC composite filler and MFC-GCC flocs filler.The opacity of pulp handsheets loaded with MFCmodified GCC was measured.The effects of MFC originated from different pulps,pretreatment method,and filler modification on the opacity of handsheets loaded with MFC-modified GCC were discussed.The results show that MFC originated from alkaline peroxide mechanical pulp(APMP)was optimal for improving the opacity of the handsheets and PFI grinding pretreatment for MFC provided a denser structure in the corresponding MFCAPMP-GCC floc filler while enzyme pretreatment was more effective in increasing the opacity of the filled paper.Under the experimental conditions,the opacity of handsheets increased from 81.0%to 82.7%when the unmodified GCC was replaced by an equivalent amount of MFCAPMP-GCC composite filler,while other properties were unchanged.
基金The authors gratefully acknowledge the National Natural Science Foundation(31770600)for its financial support.
文摘Understanding the assembly and spatial arrangement of bamboo cell wall components is crucial for its optimal utilization.Bamboo cell walls consist of aggregates of cellulose microfibrils and matrix.In the present study,the size and arrangement of cellulose microfibril aggregates in the cell walls of sclerenchyma fibers and parenchyma cells in moso bamboo were investigated with NMR and FE-SEM.The NMR measurement showed that the characteristic sizes of the microfibril aggregates of fibers and parenchyma cells were approximately 25.8 nm and 18.8 nm,respectively.Furthermore,high-resolution SEM showed the size of microfibril aggregates varied little across the cell wall of sclerenchyma fiber.However,there were significant size differences between the broad and narrow lamellae both in fiber and parenchyma cells,which is thought to be closely related to the orientation of microfibrils in these layers.The microfibril aggregates in the fibers mainly appear in a random arrangement,although occasionally in a radial or tangential arrangement in individual cell.Parenchyma cells have a relatively thinner cell wall layers,in which microfibril aggregates appear in a concentric lamellar arrangement.
基金support provided by the Ministry of Education of Malaysia under grant FRGS 16-044-0543 and FRGS19-091-0700.
文摘Increasing usage of foams in various industry sectors had causing serious disposal problems once it reaches the end of its life-cycle.Herein,PVA-MFC foam was prepared by freeze-drying using polyvinyl alcohol(PVA)and microfibrillated cellulose(MFC)as a reinforced material from sugarcane bagasse(SCB).In this study,the PVA-MFC foam was chemically silylated with Y-methacryloxypropyltrimethoxysilane(MPS)and tetraethoxysilane(TEOS).The wetting ability and mechanical strength of the silylated_(2,20)PVA-MFC foam was greatly enhanced compared with unmodified_(2,20)PVA-MFC foam.The silane chemicals(MPS and TEOS)had been confirmed grafted on_(2,20)PVA-MFC foam due to the presence of Si-C and Si-O-C stretching vibration as showed in Fourier Transform Infrared(FTIR)spectra and cloud-like coating of porous pore was observed in scanning electron microscopy(SEM)images.The silylated_(2,20)PVA-MFC foam(MPS and TEOS)exhibited a series of desirable properties such as lower swelling ratio and high absorption capacity of solvents and oils but had low thermal stability in thermogravimetric(TGA)analysis.The characterization of_(2,20)PVA-MFC foam using TEOS was further investigated.A significant difference in morphology was clearly observed between the unmodified and silylated_(2,20)PVA-MFC-TEOS foam through field emission scanning electron microscopy(FESEM)images.The X-ray photoelectron(XPS)analysis of silylated_(2,20)PVA-MFC-TEOS foam confirmed the presence of C,O and trace amount of Si elements.These synthesized_(2,20)PVA-MFC foam could be a promising material for broad range of polymer foam applications.
基金National Natural Science Foundation of China(No.51903034)Fundamental Research Funds for the Central Universities,China(No.2232019D3-12)。
文摘Microfibrillated cellulose(MFC)aerogels are bio-based materials with high thermal resistance.In this study,MFC aerogels and MFC-kapok composite aerogels were prepared.A series of experiments were carried out in a climate chamber to study the influence of MFC concentration,the temperature gradient,testing methods and introduction of kapok fibers on the thermal insulation properties of aerogels.The results suggested that the density of MFC aerogels was less than 10 mg/cm3 and the porosity was higher than 99%.Besides,the minimum thermal conductivity of MFC aerogels was 0.0357 W·m-1·K-1 observed at 0.8%MFC aerogels.The minimum thermal conductivity of MFC-kapok composite aerogels was 0.0382 W·m-1·K-1 when the ratio of MFC to kapok was 2∶6.
文摘Scanning Probe Microscopes (SPMs) observe specimen surfaces with probes by detecting the physical amount of a material between the cantilever and the surface. SPMs have a high resolution and can measure mechanical characteristics such as stiffness, adsorptive properties, and viscoelasticity. These features make it easy to identify the surface structure of complex materials;therefore, the use of SPMs has increased in recent years. Wood cell walls are primarily composed of cellulose, hemicellulose, and lignin. It is believed that hemicellulose and lignin surround the cellulose framework;however, their detailed formation remains unknown. Therefore, we observed wood cell walls via scanning probe microscopy to try to reveal the formation of the cellulose framework. We determined that the size of the cellulose microfibril bundle and hemicellulose lignin module composite was 18.48 nm based on topography and that the size of the cellulose microfibril bundle was 15.33 nm based on phase images. In the viscoelasticity image, we found that the viscoelasticities of each cell wall of the same cell were not the same. This is because the cellulose microfibrils in each cell wall lean in different directions. The angle between the leaning of the cellulose microfibril and the cantilever affects the viscoelasticity measurement.
