Microfibril Angle: Measurement, Variation and Relationships – A Review

IAWA Journal ◽  
2008 ◽  
Vol 29 (4) ◽  
pp. 345-386 ◽  
Author(s):  
Lloyd Donaldson
Keyword(s):  
Cell Wall ◽  
Large Scale ◽  
Juvenile Wood ◽  
Microfibril Angle ◽  
Basic Density ◽  
Angle Measurement ◽  
Axial Stiffness ◽  
Timber Species ◽  
Increment Core ◽  
X Ray

Microfibril angle (MFA) is perhaps the easiest ultrastructural variable to measure for wood cell walls, and certainly the only such variable that has been measured on a large scale. Because cellulose is crystalline, the MFA of the S2 layer can be measured by X-ray diffraction. Automated X-ray scanning devices such as SilviScan have produced large datasets for a range of timber species using increment core samples. In conifers, microfibril angles are large in the juvenile wood and small in the mature wood. MFA is larger at the base of the tree for a given ring number from the pith, and decreases with height, increasing slightly at the top tree. In hardwoods, similar patterns occur, but with much less variation and much smaller microfibril angles in juvenile wood. MFA has significant heritability, but is also influenced by environmental factors as shown by its increased values in compression wood, decreased values in tension wood and, often, increased values following nutrient or water supplementation. Adjacent individual tracheids can show moderate differences in MFA that may be related to tracheid length, but not to lumen diameter or cell wall thickness. While there has been strong interest in the MFA of the S2 layer, which dominates the axial stiffness properties of tracheids and fibres, there has been little attention given to the microfibril angles of S1 and S3 layers, which may influence collapse resistance and other lateral properties. Such investigations have been limited by the much greater difficulty of measuring angles for these wall layers. MFA, in combination with basic density, shows a strong relationship to longitudinal modulus of elasticity, and to longitudinal shrinkage, which are the main reasons for interest in this cell wall property in conifers. In hardwoods, MFA is of more interest in relation to growth stress and shrinkage behaviour.

Changes in Nanostructure of Wood Cell Wall during Deformation

2008 ◽  
Vol 599 ◽  
pp. 126-136 ◽  
Author(s):  
Marko Peura ◽  
Seppo Andersson ◽  
Ari Salmi ◽  
Timo Karppinen ◽  
Mika Torkkeli ◽  
...  
Keyword(s):  
Cell Wall ◽  
Poisson Ratio ◽  
Axial Strain ◽  
Microfibril Angle ◽  
Silver Birch ◽  
Wall Structure ◽  
Crystalline Cellulose ◽  
Tensile Behaviour ◽  
Angle Distribution ◽  
X Ray

The excellent mechanical properties of wood arise from its cellular and cell wall structure. X-ray scattering, ultrasound, and mechanical testing is combined to study the effects of strain on crystalline cellulose in wood. Results for dry and re-moistened softwood samples are reviewed and new results are presented for native, never-dried samples of Silver birch. When softwood is stretched parallel to the cell axis, the mean microfibril angle diminishes significantly in compression wood, but only slightly in clear wood. The cellulose chains in the crystallites elongate and their distance diminishes. In the never-dried Silver birch samples, axial strain caused the mode of the microfibril angle distribution to slightly decrease from the initial value of 14 degrees to 12 degrees. Unlike in softwood, in never-dried birch crystalline cellulose showed auxetic tensile behaviour. The distance of the chains increased and the X-ray Poisson ratio νca was negative, -0.3 ± 0.2. Dehydration of never-dried Silver birch caused no difference to the microfibril angle distribution.

scholarly journals The derivation of the cellulose microfibril angle by small-angle X-ray scattering from structurally characterized softwood cell-wall populations

2005 ◽  
Vol 38 (3) ◽  
pp. 505-511 ◽  
Author(s):  
Kenneth M. Entwistle ◽  
Stephen J. Eichhorn ◽  
Namasivayam Navaranjan
Keyword(s):  
Cell Wall ◽  
Standard Deviation ◽  
Intensity Distribution ◽  
Cell Walls ◽  
Radial Direction ◽  
Microfibril Angle ◽  
Scattered Intensity ◽  
X Ray ◽  
The Real ◽  
X Ray Scattering

A method is presented for the measurement, using small-angle X-ray scattering (SAXS), of the microfibril angle and the associated standard deviation for the cellulose microfibrils in the S2 layer of the cell walls of softwood specimens. The length and orientation of over 1000 cell walls in the irradiated volume of the specimen are measured using quantitative image analysis. From these data are calculated the azimuthal variation of the scattered intensity. The calculated values are compared with the measured values. The undetermined parameters in the analysis are the microfibril angle (M) and the standard deviation (σΦ) of the intensity distribution arising from the wandering of the fibril orientation about the mean value. The two parameters are varied to give the best fit between the calculated and the measured values. Six separate pairs of values are determined for six different values of the angle of incidence of the X-ray beam relative to the normal to the radial direction in the specimen. The results show good agreement. The azimuthal distribution of scattered intensity for the real cell-wall structure is compared with that calculated for an assembly of rectangular cells with the same ratio of transverse to radial cell-wall lengths. Despite the existence of marked differences in the intensity distributions around the zero azimuth angle, the position of the extreme flanks of the distribution is very close for the real and the rectangular cells. This means that useful values of the microfibril angle can be obtained from the curve for the real cells using the Meylan parameter T derived by drawing tangents to the flanks of the intensity distribution and using M = kT. The value of k is M/(M + 2σΦ). Since both of these parameters are determined in the work now described, k is also determined. It is also demonstrated that for β = 45° (where β is the angle between the plane face of the wood specimens and the radial direction) the peaks in the azimuthal intensity distribution for the real and the rectangular cells coincide. If this peak position is Φ45, then the microfibril angle can be determined from the relation M = tan−1(tanΦ45/cos45°), which is precise for rectangular cells.

Preferred crystallographic orientation in mature and juvenile wood

2007 ◽  
Vol 222 (3-4) ◽  
Author(s):  
Jan T. Bonarski ◽  
Wieslaw Olek
Keyword(s):  
Distribution Function ◽  
Juvenile Wood ◽  
Microfibril Angle ◽  
Orientation Distribution ◽  
Experimental Methods ◽  
X Ray Diffraction ◽  
Traditional Concept ◽  
X Ray ◽  
Pole Figures ◽  
The Mean

Investigations of the crystallograpically organized regions of mature and juvenile Scots pine wood were performed. Experimental methods of X-ray diffraction were applied. Incomplete pole figures were measured, in order to calculate the orientation distribution function. The differences in the texture of the mature and juvenile wood were determined. The traditional concept of the mean microfibril angle was enhanced by developing the misorientation parameters. Evident differences in the space arrangement of cellulose of the both zones of wood were identified and described.

Ultrastructural aspects of fibre development during the stone groundwood process: New insights into derived pulp properties

Holzforschung ◽  
2007 ◽  
Vol 61 (5) ◽  
pp. 532-538 ◽  
Author(s):  
Dinesh Fernando ◽  
Peter Rosenberg ◽  
Erik Persson ◽  
Geoffrey Daniel
Keyword(s):  
Cell Wall ◽  
Juvenile Wood ◽  
Raw Materials ◽  
Microfibril Angle ◽  
Ultrastructural Level ◽  
Pilot Scale ◽  
Mature Wood ◽  
Thermomechanical Pulp ◽  
Fibre Development ◽  
Fibre Fraction

Abstract A study was performed on stone groundwood (SGW) pulps produced on a pilot scale. The behaviour of selected juvenile and mature Norway spruce wood samples was investigated. As revealed by standard tests, sheets formed from juvenile wood showed improved light scattering properties, improved tear and tensile strength, and higher sheet density compared to those formed from mature wood. Scanning electron microscopy indicated that the differences are likely related to the manner of fibre processing and development at the ultrastructural level. Mature wood fibres showed greater fibre end breakage, a smaller long-fibre fraction, enhanced S1 fibrillation and frequently open fibres. In contrast, juvenile fibres had a 14% higher long-fibre fraction and showed typical S2 fibrillation. Fibre development of juvenile wood showed fibrillation features similar to those previously reported for thermomechanical pulp fibres. In both cases, the structural hierarchy of the wood fibre cell wall and the microfibril angle of S2 and S1 layers govern cell-wall splitting and fibrillation progression. The superior quality of the fibre furnish prepared from juvenile fibres compared to mature fibres with SGW pulping may offer an alternative process for more effective utilisation of raw materials such as top logs rich in juvenile wood.

scholarly journals VARIATION OF MICROFIBRIL ANGLE OF Pinus radiata D. Don IN RELATION TO TREE SPACING IN CHILEAN PLANTATIONS

2015 ◽  
Vol 39 (4) ◽  
pp. 751-758 ◽  
Author(s):  
Jerome Alteyrac
Keyword(s):  
Pinus Radiata ◽  
Juvenile Wood ◽  
Microfibril Angle ◽  
Radiata Pine ◽  
Mature Wood ◽  
X Ray Diffraction ◽  
X Ray

ABSTRACTFour stands of 28-year-old radiata pine (Pinus radiata D. Don) grown in the eighth region (Biobio) of Chile were sampled to determine the effect of tree spacing on the microfibril angle. The samples were taken at two different stem levels of the tree, 2.5 m and 7.5 m, with increment strip taken in the Nothern direction. The four experimental stands were characterized by the following spacing 2x2, 2x3, 3x4 and 4x4. The microfibril angle was measured by X-ray diffraction with the SilviScan technology at the FP-Innovation-Paprican Division in Vancouver, Canada. The results showed a significant effect of tree spacing on the microfibril angle in both juvenile wood and mature wood as well as at the two stem levels considered. The minimum (9.42º) was reached in 2x2 stand at 7.5 m in mature wood, while maximum microfibril angle (24.54º) was obtained in 2x3 stand at 2.5 m in juvenile wood. Regarding the effect of tree spacing, 4x4 stand had the lowest microfibril angle,except in mature wood at 7.5 m where 4x4 had the highest microfibril angle (11°) of the four stands.

Application of Small-Angle X-Ray Scattering to Predict Microfibril Angle in Acacia mangium Wood

2010 ◽  
Vol 173 ◽  
pp. 72-77
Author(s):  
Tabet A. Tamer ◽  
Aziz Abdul Haji Fauziah ◽  
Radiman Shahidan
Keyword(s):  
Cell Wall ◽  
Standard Deviation ◽  
Intensity Distribution ◽  
Small Angle ◽  
Cell Walls ◽  
Microfibril Angle ◽  
Acacia Mangium ◽  
Cellulose Microfibrils ◽  
X Ray ◽  
X Ray Scattering

Partially crystalline cellulose microfibrils are wound helically around the longitudinal axis of the wood cell. A method is presented for the measurement, using small-angle X-ray scattering (SAXS), of the microfibril angle, (MFA) and the associated standard deviation for the cellulose microfibrils in the S2 layer of the cell walls of Acacia mangium wood. The length and orientation of the microfibrils of the cell walls in the irradiated volume of the thin samples are measured using SAXS and scanning electron microscope, (SEM). The undetermined parameters in the analysis are the MFA, (M) and the standard deviation (σФ) of the intensity distribution arising from the wandering of the fibril orientation about the mean value. Nine separate pairs of values are determined for nine different values of the angle of the incidence of the X-ray beam relative to the normal to the radial direction in the sample. The results show good agreement. The curve distribution of scattered intensity for the real cell wall structure is compared with that calculated with that assembly of rectangular cells with the same ratio of transverse to radial cell wall length. It is demonstrated that for β = 45°, the peaks in the curve intensity distribution for the real and the rectangular cells coincide. If this peak position is Ф45, Then the MFA can be determined from the relation M = tan-1 (tan Ф45 / cos 45°), which is precise for rectangular cells.

scholarly journals Significant influence of lignin on axial elastic modulus of poplar wood at low microfibril angles under wet conditions

2019 ◽  
Vol 70 (15) ◽  
pp. 4039-4047 ◽  
Author(s):  
Merve Özparpucu ◽  
Notburga Gierlinger ◽  
Igor Cesarino ◽  
Ingo Burgert ◽  
Wout Boerjan ◽  
...  
Keyword(s):  
Cell Wall ◽  
Lignin Content ◽  
Construction Material ◽  
Linear Regression Analysis ◽  
Microfibril Angle ◽  
Tensile Tests ◽  
Multiple Linear Regression Analysis ◽  
Axial Stiffness ◽  
The Matrix ◽  
The Individual

Abstract Wood is extensively used as a construction material. Despite increasing knowledge of its mechanical properties, the contribution of the cell-wall matrix polymers to wood mechanics is still not well understood. Previous studies have shown that axial stiffness correlates with lignin content only for cellulose microfibril angles larger than around 20°, while no influence is found for smaller angles. Here, by analysing the wood of poplar with reduced lignin content due to down-regulation of CAFFEOYL SHIKIMATE ESTERASE, we show that lignin content also influences axial stiffness at smaller angles. Micro-tensile tests of the xylem revealed that axial stiffness was strongly reduced in the low-lignin transgenic lines. Strikingly, microfibril angles were around 15° for both wild-type and transgenic poplars, suggesting that cellulose orientation is not responsible for the observed changes in mechanical behavior. Multiple linear regression analysis showed that the decrease in stiffness was almost completely related to the variation in both density and lignin content. We suggest that the influence of lignin content on axial stiffness may gradually increase as a function of the microfibril angle. Our results may help in building up comprehensive models of the cell wall that can unravel the individual roles of the matrix polymers.

Influence of Microfibril angle on within-tree variations in the Mechanical properties of chinese fir (Cunninghamia Lanceolata)

IAWA Journal ◽  
2011 ◽  
Vol 32 (4) ◽  
pp. 431-442 ◽  
Author(s):  
Yafang Yin ◽  
Mingming Bian ◽  
Kunlin Song ◽  
Fuming Xiao ◽  
Jiang Xiaomei
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
Juvenile Wood ◽  
Microfibril Angle ◽  
Basic Density ◽  
Chinese Fir ◽  
Cunninghamia Lanceolata ◽  
Effective Utilization ◽  
Longitudinal Modulus

Radial variations in microfibril angle (MFA) and their effect on the mechanical properties of plantation-grown Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) were investigated with the aim of achieving an effective utilization of the wood. Correlations between MFA and mechanical properties, including longitudinal modulus of elasticity (MOEL), static bending strength (MOR) and compression strength parallel-to-the-grain (CS), were analyzed for predicting the quality of timber. The results indicated that MFA had a greater variation in juvenile wood than in mature wood. The biggest change occurred close to the pith in Chinese fir. The outer-rings (rings 9–30 from the pith) have a relatively low MFA, together with high mechanical properties and high density, when compared with the inner-rings (rings 1–8 from the pith). The MFA had significant negative curvilinear correlations with all the mechanical properties (MOEL, MOR and CS) of Chinese fir, with the value of r2 being 0.88, 0.69 and 0.74 respectively. The correlation between the MFA and basic density (BD) was strong in certain consecutive rings (rings 5–30 from the pith), but this did not apply across the whole billet, i.e. from the pith to the bark.

Wood mechanical properties and their correlation with microstructure in Chinese fir clones

IAWA Journal ◽  
2021 ◽  
pp. 1-10
Author(s):  
Yurong Wang ◽  
Ru Jia ◽  
Haiyan Sun ◽  
Yamei Liu ◽  
Jianxiong Lyu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cell Wall ◽  
Linear Regression Analysis ◽  
Microfibril Angle ◽  
Chinese Fir ◽  
Modulus Of Rupture ◽  
X Ray Diffraction ◽  
Average Cell ◽  
X Ray ◽  
Two Factors

Abstract Mechanical testing, microscopic image analysis, and X-ray diffraction were used to study the mechanical properties and their correlation with microstructure in three 20-year-old Chinese fir clones (Kailin 24, Kaihua 13, and Kaihua 3). The Chinese fir clones featured a modulus of rupture (MOR) of 52–59 MPa, a modulus of elasticity (MOE) of 10–11 GPa, and a compressive strength parallel to the grain of 31–34 MPa. Kaihua 13 and Kailin 24 had similar mechanical properties and were superior to Kaihua 3 among the tree clones. Radial variation indicated that their outerwood (rings 9–18) had better mechanical properties than their corewood (rings 3–7). Kaihua 13 with better mechanical properties had a larger ratio of cell wall to lumen than Kaihua 3 and Kailin 24. Outerwood with better mechanical properties also had a larger ratio of cell wall to lumen and a smaller microfibril angle compared to corewood with poor mechanical properties. Linear regression analysis also shows that for various clones and different radial positions in the same clone, anatomical structure parameters such as average cell wall thickness and the ratio of cell wall to lumen were positively correlated to their mechanical properties, while the microfibril angle was negatively correlated to mechanical properties. The two factors synergistically influence the mechanical properties of wood.

Effect of Physiological Age and Site on Microfibril Angle in Pinus Radiata

IAWA Journal ◽  
1996 ◽  
Vol 17 (4) ◽  
pp. 421-429 ◽  
Author(s):  
L. A. Donaldson
Keyword(s):  
Pinus Radiata ◽  
Juvenile Wood ◽  
Microfibril Angle ◽  
Basic Density ◽  
Seed Orchard ◽  
Physiological Age ◽  
Growth Rings ◽  
Physiological Aging ◽  
Breast Height ◽  
Old Trees

The effect of physiological age (shoot age at propagation) and site on microfibril angle was examined for seedlings (physiological age = 0 years) and cuttings (physiological age = 5-16 years) of Pinus radiata D. Don. Two trials were examined by measuring microfibril angle in alternate growth rings on breast height discs. In the first trial, two sites were compared for ll-year-old trees propagated from seedlings, and cuttings of comparable genotype, at 0 and 5 years physiological age, respectively. In the second trial, a single site was examined comparing 25-year-old trees propagated from open pollinated seedlings, and cuttings physiologically aged by 12-16 years, originating from 10 seed-orchard clones. In each trial there was a significant effect of physiological age for microfibril angle in the first 9 growth rings with a greater effect in the trees of greater physiological age. Physiological aging produced a significant decrease in microfibril angles in the juvenile wood, on average reducing microfibril angle to values below 35° in trees aged by 12-16 years. Juvenile wood size, as indicated by the point at which microfibril angle gradient changes, was reduced by an average of two rings in both sets of aged cuttings examined. There was no effect of site in the material examined. Differences were consistent among seedling/ramet pairs of similar genotype. The use of aged cuttings rather than seedlings should result in increased stiffness of the juvenile wood and reduced longitudinal shrinkage. However, other changes associated with physiological aging, such as reduced basic density and growth rate, may affect the practicality of using highly.

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