| 1. |
- Adamopoulos, Stergios, et al.
(författare)
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Fiber composition of packaging grade papers as determined by the Graff “C” staining test
- 2006
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Ingår i: Wood and Fiber Science. - : Society of Wood Science and Technology. - 0735-6161. ; 38:4, s. 567-575
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Tidskriftsartikel (refereegranskat)abstract
- A qualitative and quantitative analysis of the fiber components of 15 representative papers that are used for the production of corrugated board was carried out by the Graff "C" staining test. The method of processing of softwood, hardwood, and nonwood fibers was determined under a light microscope by their color reactions with the stain. All papers, due to the use of recycled pulp raw materials in their manufacturing, were found to incorporate in their furnish fibers that had been produced with a variety of pulping processes: chemical, mechanical, and semi-mechanical. The recycled-based papers (recycled-liner and recycled-medium) were proved to be the most variable comprising 12-15 different fiber components, while in some of the semi-chemicals only up to 7 components were identified. The weight percentages of the fiber components calculated by the application of weight factors showed that in almost all papers the most important fiber component from a quantitative standpoint was hardwood unbleached kraft followed by softwood unbleached kraft. Besides hardwood unbleached semi-chemical pulp and mechanical softwood pulp that were also plentiful in the papers, there was a smaller number of other components which sum, however, accounted for a significant fraction in the total furnish weight. The results taken on the total softwood, hardwood, and nonwood fibers content of the papers demonstrate that Graff "C" staining test is adequate to analyze both the structure and quality of packaging grade papers in practical industrial testing.
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| 2. |
- Adamopoulos, Stergios, et al.
(författare)
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Mathematical approach for defining juvenile-mature wood transition zone in black locust and chestnut
- 2011
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Ingår i: Wood and Fiber Science. - 0735-6161. ; :3, s. 336-342
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Tidskriftsartikel (refereegranskat)abstract
- This article defines age of transition from juvenile to mature wood in two ring-porous species, black locust (Robinia pseudoacacia L.) and chestnut (Castanea sativa Mill.). A logistic function was proposed using fiber length and ring width data of three black locust trees, aged 35-37 yr, and five chestnut coppice trees, aged 25-27 yr, from Sithonia Peninsula, Chalkidiki, Greece. The approach proved to be practical and objective in delineating maturity zones, and it was based on rate of change of yearly fiber length. The juvenile wood zone spread to the sixth growth ring from the pith in both species, whereas the demarcation of juvenile and mature wood was at age 12 and 14 yr in chestnut and black locust, respectively. Transition zone width comprised rings 7-12 in chestnut and rings 7-14 in black locust.
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| 3. |
- Adamopoulos, Stergios, et al.
(författare)
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Strength properties of juvenile and mature wood in black locust (Robinia pseudoacacia L.)
- 2007
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Ingår i: Wood and Fiber Science. - : Society of Wood Science and Technology. - 0735-6161. ; 39:2, s. 241-249
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Tidskriftsartikel (refereegranskat)abstract
- This study was undertaken to investigate the strength properties of juvenile and mature wood in black locust (Robinia pseudoacacia L.). Wood specimens were prepared from various stem heights, up to 9 m, of five naturally-grown black locust trees, 21-37 years old. Mechanical properties tested included moduli of rupture (MOR) and elasticity (MOE), and pure modulus of elasticity (PMOE) in static bending, stress wave modulus of elasticity (SWMOE) in dynamic strength, axial compression, and toughness. Comparisons between juvenile and mature wood specimens of similar densities (0.667-0.894 g/cm3 and 0.682-0.892 g/cm3, respectively) showed that juvenile wood had a statistically significant lower mean MOR (138.78 N/mm2), MOE (13,936 N/mm2), PMOE (18,125 N/mm2), SWMOE (16,813 N/mm2) and toughness strength (155.25 KJ/m2) than the mature wood (148.29 N/mm2, 14,747 N/mm2, 19,498 N/mm2, 17,635 N/mm2 and 181.27 KJ/m2, respectively). On the contrary, no statistically significant differences were found for the mean strength in axial compression among juvenile (63.75 N/mm2) and mature wood (66.65 N/mm2). Fractured surfaces of juvenile and mature wood specimens in static bending and toughness were classified into the "splintering tension" type of failure, while compression failures were of the "shearing type" according to ASTM D 143-83 standards. Lower strength of juvenile wood in most of the properties examined may be attributed to anatomical and chemical properties rather than density of wood specimens. The adverse influence of juvenile wood on strength properties should be considered for effective management (e.g. longer rotation age and other genetic and forest or plantation management measures that reduce juvenile wood content) and utilization of the species.
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| 4. |
- Ahmed, Sheikh Ali, et al.
(författare)
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Moisture properties of heat-treated Scots pine and Norway spruce sapwood impregnated with wood preservatives
- 2012
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Ingår i: Wood and Fiber Science. - : Society of Wood Science and Technology. - 0735-6161. ; 44:1, s. 85-93
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Tidskriftsartikel (refereegranskat)abstract
- An experiment was conducted on commercially heat-treated (HT) Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] Karst.) sapwood collected from Ht Wood AB, Arvidsjaur, Sweden. Secondary treatment on HT wood was performed in laboratory scale by impregnating with water-repellent preservatives (a commercial one and pine tar) to evaluate their retention and different moisture-related properties. Preservative solutions were impregnated using a simple and effective method. Wood samples were heated at 170°C in a dry oven and were immediately immersed in preservative solutions. Considerable retention was observed in HT wood, particularly in pine. Moisture adsorption properties were measured after conditioning in a high-humidity environmental chamber (4°C and 84% RH). Experimental results showed that secondary treatment enhanced moisture excluding efficiencies by decreasing equilibrium moisture content, suggesting better hydrophobicity. Soaking test in water showed that antiswelling and water repellence efficiencies improved, especially in tar-treated wood. In addition, this type of treatment significantly decreased water absorption. It was also possible to decrease volumetric swellings. Thus, secondary treatment of HT wood with preservative, in particular with tar, improved dimensional stability and water repellency.
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| 5. |
- Ananías, Rubén A., et al.
(författare)
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Kiln schedule certification for industrial drying of radiata pine
- 2013
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Ingår i: Wood and Fiber Science. - 0735-6161. ; 45:1, s. 98-104
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Tidskriftsartikel (refereegranskat)abstract
- This is a summary of a study carried out in Chile to certify industrial kiln drying of radiata pine to comply with the international phytosanitary standard ISPM 15. The drying tests were performed in 100-m3 industrial kilns located at four different sawmills of the VIII region in Chile. The objective was to develop a standard protocol to certify industrial drying of radiata pine depending on the drying schedule and wood thickness. In part, the results were used to develop a multiple regression equation that permits sawmills to select their drying schedules in such a way that the lumber can be officially stamped as both kiln-dried and heat-treated for international trade.
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| 6. |
- Briggert, Andreas, 1984-, et al.
(författare)
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Tracheid effect scanning and evaluation of in-plane and out-of-plane fibre direction in Norway spruce using
- 2018
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Ingår i: Wood and Fiber Science. - : Society of Wood Science and Technology. - 0735-6161. ; 50:4, s. 411-429
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Tidskriftsartikel (refereegranskat)abstract
- Local fiber direction is decisive for both strength and stiffness in timber. In-plane fiber direction on surfaces of timber can be determined using the so-called tracheid effect which is frequently used in both research and industry applications. However, a similar established method does not exist for measuring the out-of-plane angle, also known as diving angle. The purposes of this article were to evaluate if the tracheid effect can also be used to determine, with reasonable accuracy, the out-of-plane angle in Norway spruce and to verify an existing mathematical model used to calculate the fiber direction in the vicinity of knots. A newly developed laboratory laser scanner was applied for assessment of fiber directions in a single Norway spruce specimen containing a knot. It was assumed that the specimen had a plane of symmetry through the center of the knot, and by splitting the specimen through this plane into two parts, it was possible to make measurements on orthogonal planes. The results showed that the out-of-plane angle could not be determined with very high accuracy and the difficulties related to this objective were analyzed. Regarding the mathematical model of fiber direction in the vicinity of a knot, fiber directions calculated on the basis of this model agreed well with experimentally obtained fiber directions, but successful application of the model requires that the geometry of the knot is known in detail.
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| 7. |
- Elustondo, Diego, et al.
(författare)
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Simulated comparative analysis of sorting strategies for RFV drying
- 2003
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Ingår i: Wood and Fiber Science. - 0735-6161. ; 35:1, s. 49-55
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a numerical stochastic model is used to compare three possible sorting strategies in radio frequency vacuum (RFV) drying of thick timbers, namely, moisture content based pre-sorting (MCPS), batch dry/sort/redrying (b-DSRD) and continuous or retro-feed dry/sort/redry (c-DSRD). The model parameters were calibrated with experimental data of western hemlock dried in a commercial RFV dryer, and the results of the simulations were compared to a single pass base case (SPBC). The numerical results clearly demonstrated the differences among these strategies. The MCPS showed no significant improvement in final timber quality as defined by average timber moisture content, but there is an evident improvement in both b-DSRD and c-DSRD. The comparison was based on the increment of the percent of the on-grade wood (within moisture content range) and the reduction of overdried and underdried (wets) percentages. Furthermore, it was also shown that the effective drying time is roughly independent of the drying strategy
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| 8. |
- Eriksson, John, et al.
(författare)
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Numerical determination of diffusion coefficients in wood using data from CT-scanning
- 2006
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Ingår i: Wood and Fiber Science. - 0735-6161. ; 38:2, s. 334-344
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Tidskriftsartikel (refereegranskat)abstract
- The radial moisture diffusion coefficient in Fick's law for a sample of Norway spruce (Picea abies) under isothermal drying conditions was determined in a parameterization of Arrhenius' equation type. Using X-ray CT-scanning, the wood density and moisture content distributions were obtained in the radial direction for the wood sample. An optimization scheme, based on finite element computation, was then applied to find the parameter values such that the difference between observed and computed moisture content was minimized. The combined numerical and experimental technique was developed to reduce known disadvantages of similar approaches, and a specific algorithm to determine diffusion coefficients was presented. A comparison of the calibrated diffusion coefficient with those given in the literature showed a good fit. The computed moisture content based on the obtained diffusion coefficient and the observed moisture content agreed well. Finally, the effect of measurement errors on the computed material parameter was found to be small
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| 9. |
- Florisson, Sara, et al.
(författare)
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A numerical study of the effect of green-state moisture content on stress development in timber boards during drying
- 2019
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Ingår i: Wood and Fiber Science. - : Society of Wood Science and Technology. - 0735-6161. ; 51:1, s. 41-57
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Tidskriftsartikel (refereegranskat)abstract
- Timber boards manufactured with a traditional sawing pattern often contain both heartwood andsapwood. In such boards, internal constraints can occur during drying because of a radial variation in greenstate(GS) MC between the heartwood (30-60%) and sapwood region (120-200%). Despite such knowledge,the initial MC is seldom considered when evaluating kiln-drying schedules. The effect of GS MC on thedevelopment of tangential tensile stress during drying is studied for four types of timber boards. A numericalmodel was developed that can simulate transient nonlinear orthotropic moisture flow and moisture–inducedstress and distortion in wood with the use of the finite element method. The stress analysis considers elastic,hygroscopic, and mechano-sorptive strain. The study shows that the GS MC does not significantly influencethe maximum stress state, but that it does influence the time at which the maximum tangential tensile stressoccurs at different exchange surfaces. This results in several periods in the drying schedule where unfavorablehigh stress situations in the tangential direction arise, which could lead to crack propagation.
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| 10. |
- Florisson, Sara, et al.
(författare)
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Analysis of hygro-mechanical behavior of wood in bending
- 2021
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Ingår i: Wood and Fiber Science. - : International society of wood science and technology (SWST). - 0735-6161. ; 53:1, s. 27-47
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Tidskriftsartikel (refereegranskat)abstract
- The empirical test developed as validation for a newbeamelementmodel that can account for bothmechanical and environmental load action in finite element analysis is presented. The testing protocol allowsfor the identification and analysis of contributing deflection components in bending under varying MCconditions, including mechano-sorption. The components of deflection in the shear-free span of a four-pointbending test and their responses to varyingmoisture are evaluatedwith an analytical procedure. The experimentwas conducted on clear, straight-grained sapwood and heartwood specimens of Norway spruce (Picea abies)(30 15 640 mm3). The program consisted of three phases: 1) long-term (LT) experiments under constanttemperature of 60°C and RH cycles between 40% and 80%, 2) a short-term static experiment to determine thevariation in the sample set and the load level of the LT experiment on end-matched specimens, and 3) creeptests at 60°C and constant humidity at either 40%or 80%to determine the effect ofmoisture on the viscoelasticcreep. Mass changes and hygro-expansion measured on matched specimens were used in the analyticalmethod. Constitutive models used for describing the material-level response to loads and moisture changeswere applied to the shear-free segment of the specimens disregarding actual moisture gradients and fiberorientation inside the test specimens. A successful identification of each deflection component and isolation ofmechano-sorption component was accomplished. In the 90 da of testing, the dominant component of the totaldeflection was the elastic component, followed by the mechano-sorptive component. Creep was found to benonnegligible and important in the correct description of mechano-sorption. The effect of moisture on theviscoelastic behavior showedmost important during loading and first stages of decreasing deflection rate phase.
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| 11. |
- Grubîi, Victor, 1990-, et al.
(författare)
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Effect of Chipping Edge Inclination Angle on Size Distribution of Pulp Chips Produced by Chipper-Canter
- 2019
-
Ingår i: Wood and Fiber Science. - : PKP Publishing Services Network. - 0735-6161. ; 51:4, s. 402-415
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Tidskriftsartikel (refereegranskat)abstract
- The effect of oblique cutting on the chipper-canter wood chipping mechanism was studied. A bent knife was modified to obtain inclination angles (IA) of 30° and 50° between the chipping edge and the log feeding direction. The standard knife had an IA of 40°. These three knives were tested on 15 logs each, under frozen (-10°C) and unfrozen conditions. Chip dimensions were assessed by thickness (Domtar distribution) and width/length (Williams distribution). Characteristics and physical properties of the log knots were also measured. Experiments revealed that IA had a significant effect on chip formation mechanism. The IA affected the chipping edge entering the log and the form of the wood slice that was transforming into chips. These changes provoked variations in chip size. An IA of 30° produced wider chips, mostly in the first half of the cut, shaped as an elongated parallelepiped that resulted from a tangential, oblique and radial splitting in a single chip. The shape of chips obtained with IAs of 40° and 50° was more like an upright parallelepiped that was detached mostly by radial and oblique splitting. At the beginning and at the end of the cut, chips were produced by tangential splitting. As a result, for a same chip length of 23 mm, weighted mean chip thickness (WCT) decreased almost 1 mm when IA decreased from 50° to 30°. The knot ratio (total knot area / cant total area) affected both chip size distributions and WCT. Chipping frozen wood at -10°C reduced the chip thickness by 0.55 mm with respect to unfrozen wood. The amount of fines and pin chips also increased nearly two times compared to unfrozen wood. The amount of the Williams accepts chip class increased by 6% when IA decreased from 50° to 30° and by 8% when chipping unfrozen wood compared to frozen wood.
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| 12. |
- Hassan, Enas A., et al.
(författare)
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Improving bagasse pulp paper sheet properties with microfibrillated cellulose isolated from xylanase-treated bagasse
- 2011
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Ingår i: Wood and Fiber Science. - 0735-6161. ; 43:1, s. 76-82
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Tidskriftsartikel (refereegranskat)abstract
- To improve the properties of paper sheets, microfibrillated cellulose (MFC) was isolated from bleached bagasse pulp pretreated with xylanase enzymes and returned to the pulp in varying amounts. The standard hand sheet paper-making method was used. The effect of adding different amounts of MFC on tensile strength (wet and dry), tear resistance, burst strength, opacity, and porosity of paper sheets was studied. Adding MFC to bagasse pulp improved wet and dry tensile strength, but tear resistance and burst strength decreased with increasing amounts of MFC. Also, adding MFC to bagasse pulp did not significantly affect opacity, slightly decreased porosity, and tightened the texture of the paper sheets as observed from scanning electron microscopy images. The strength properties of paper sheets made from bagasse and MFC were compared with those of paper sheets made from bagasse and softwood fibers. Paper sheets containing MFC had higher tensile strength (wet and dry) than those containing softwood fibers, but the later had higher tear resistance and burst strength.
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| 13. |
- Hassan, Mohammad L., et al.
(författare)
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Effect of pretreatment of bagasse pulp on properties of isolated nanofibers and nanopaper sheets
- 2010
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Ingår i: Wood and Fiber Science. - 0735-6161. ; 42:3, s. 362-376
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Tidskriftsartikel (refereegranskat)abstract
- Nanofibers were isolated from bagasse pulp pretreated with dilute hydrochloric acid, dilute sodium hydroxide, cellulase, or xylanase enzymes using high-shear ultrafine grinding and high-pressure homogenization. The effect of the different pretreatments on chemical composition and structure of isolated nanofibers was studied using chemical analyses, X-ray diffraction, and Fourier transform infrared. The dimensions and properties of the isolated nanofibers were followed at the different processing stages using optical microscopy, transmission electron microscopy, atomic force microscopy, and tensile properties (wet and dry). The diameter of the microfibrils was in the range of 7-30 nm for untreated and pretreated bagasse pulps while larger microfibrillar bands (to 150 nm wide) were observed for untreated bagasse pulp than the pretreated pulps (to 90 nm wide). Nanopaper sheets made from nanofibers isolated from alkali- and xylanase-treated pulps showed better wet and dry tensile strength than those made from the other pulps.
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| 14. |
- Hu, Min, 1979-, et al.
(författare)
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Assessment of a Three-Dimensional Fiber Orientation Model for Timber
- 2016
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Ingår i: Wood and Fiber Science. - 0735-6161. ; 48:4, s. 271-290
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Tidskriftsartikel (refereegranskat)abstract
- Wood is an orthotropic material with very different properties along and across fibers, and every board has its own pattern of knots and fiber deviations. Therefore, detailed knowledge of the three-dimensional (3D) fiber orientation of individual boards would enable more accurate assessment of properties such as stiffness, strength, and shape stability. This paper presents a method for modeling 3D fiber orientation of side boards of Norway spruce. The method is based on dot laser scanning and utilization of the tracheid effect, and it is verified by a comparison between strain fields calculated on the basis of the fiber orientation model and corresponding strains determined using digital image correlation (DIC) technique. By means of the method, it is possible to identify knots and to reproduce the fiber orientation in clear wood in the vicinity of knots. Fiber orientation models of side boards including traversing edge knots were established and integrated in finite element models of boards used for simulation of four-point bending tests. The same boards were also tested in laboratory and displacement fields of the wide faces were recorded at different load levels using DIC technique. Comparisons of strain fields from measurements and simulations showed close agreement, regarding both strain patterns and strain levels. Local strain concentrations caused by very small defects were detected using the models and also found from the laboratory test results. The modeling approach may be used both to achieve improved accuracy of existing machine strength grading methods and, after further development, also for more advanced analysis of eg crack propagation and strength of timber.
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| 15. |
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| 16. |
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| 17. |
- Jonsson, Oskar, et al.
(författare)
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CONSUMER PERCEPTIONS AND PREFERENCES ON SOLID WOOD, WOOD-BASED PANELS, AND COMPOSITES : A REPERTORY GRID STUDY
- 2008
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Ingår i: Wood and Fiber Science. - 0735-6161. ; 40:4, s. 663-678
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge about consumer perception and preferences on solid wood, wood-based panels, and wood-based composites is important for product development and marketing. The aim of this study was to identify attributes and associations that people use to describe different types of wood materials and to explore how they relate to preferences. The study involved nine samples that were evaluated with the Kelly's repertory grid technique and content analysis. Based on respondents' answers. 19 core categories reflecting sample attributes were extracted. General preferences for each sample were also recorded. Principal component analysis generated two factors describing 1) naturalness, wood-likeness, softness, unprocessed origin, living, pleasant, and high value; and 2) solid and homogeneous impression. A third, preliminary factor included categories describing irregular pattern,sleekness, and smoothness. The wood samples were most liked, whereas composites and panels were not appreciated. Preferred core categories were naturalness, wood-likeness, smoothness, living impression, and value. The least liked core categories were processed, hard, and high weigh. The implications of the results for product development and marketing are discussed.
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| 18. |
- Kifetew, Girma, 1950-, et al.
(författare)
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Material damage due to electron beam during testing in the environmental scanning electron microscope (ESEM).
- 2000
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Ingår i: Wood and Fiber Science. - 0735-6161. ; 32:1, s. 44-51
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Tidskriftsartikel (refereegranskat)abstract
- This study describes the development of cell-wall damage, i.e., the creation of cracks across or in the vicinity of pits during the testing of twenty microtomed spruce (Picea abies karst.) samples in the Environmental Scanning Electron Microscope (ESEM). Samples were investigated both in an unloaded condition and under a constant tensile load and at different moisture levels. Regions of the moisture-cycled samples that had been exposed to an electron beam during image acquisition showed damage running through pits and their surroundings. Specimens loaded in the green condition and dried in the chamber for 2 h without beam exposure except during imaging showed no noticeable cell-wall damage. The results indicate that the electron beam may be a major source of damage initiation. Therefore, it is essential to note the circumstances of the rest when explaining the observations made in ESEM studies.
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| 19. |
- Källbom, Susanna, et al.
(författare)
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Effects of water soaking-drying cycles on thermally modified spruce wood-plastic composites
- 2020
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Ingår i: Wood and Fiber Science. - : SOC WOOD SCI TECHNOL. - 0735-6161. ; 52:1, s. 2-12
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Tidskriftsartikel (refereegranskat)abstract
- The overall aim of this work was to gain more insight on the potential of modified wood (TMW) components for use in wood-thermoplastic composites (WPCs). Laboratory-scale TMWPCs were produced, and the effects of severe water soaking-drying cycles on the samples were studied. Water sorption behavior and resulting dimensional and micromorphological changes were also studied, and the results were compared with those of unmodified wood-plastic composites (UWPCs) used as control. The TMW was prepared by cutting a spruce board into half and subjecting one-half to an atmosphere of superheated steam at atmospheric pressure with a peak temperature of 210 degrees C, with the other unmodified wood (UW) half as a control. The TMW and UW components were then prepared by a Wiley mill and thereafter sifted into smaller (mesh 0.20-0.40 mm) and larger (mesh 0.40-0.63 mm) size fractions. A portion of the wood components were also subjected to hydrothermal extraction (HE). Composite samples with these different wood components, polypropylene (PP) matrix, and maleated PP (MAPP) as coupling agent (50/48/2 wood/PP/MAPP ratio by weight) were then prepared by using a Brabender mixer followed by hot pressing. The matching micromorphology of the composites before and after the soaking-drying cycles was analyzed using a surface preparation technique based on ultraviolet-laser ablation combined with scanning electron microscopy. The results of the water absorption tests showed, as hypothesized, a significantly reduced water absorption and resulting thickness swelling at the end of a soaking cycle for the TMWPCs compared with the controls (UWPCs). The water absorption was reduced with about 50-70% for TMWPC and 60-75% for HE-TMWPC. The thickness swelling for TMWPCs was reduced with about 40-70% compared with the controls. Similarly, the WPCs with HE-UW components absorbed about 20-45% less moisture and showed a reduced thickness swelling of about 25-40% compared with the controls. These observations also were in agreement with the micromorphology analysis of the composites before and after the moisture cycling which showed a more pronounced wood-plastic interfacial cracking (de-bonding) as well as other microstructure changes in the controls compared with those prepared with TMW and HE-UW components. Based on these observations, it is suggested that these potential bio-based building materials show increased potential durability for applications in harsh outdoor environments, in particular TMWPCs with a well-defined and comparably small size fractions of TMW components.
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| 20. |
- Källbom, Susanna, et al.
(författare)
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Sorption and surface energy properties of thermally modified spruce wood components
- 2018
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Ingår i: Wood and Fiber Science. - : Society of Wood Science and Technology. - 0735-6161. ; 50:3, s. 346-357
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this work is to study the water vapor sorption and surface energy properties of thermally modified wood (TMW) components, ie wood processing residuals in the form of sawdust. The thermal modification was performed on spruce wood components using a steam-pressurized laboratoryscale reactor at two different temperature (T) and relative humidity (RH) conditions, T = 150 degrees C and RH = 100% (TMW150), and T = 180 degrees C and RH = 46% (TMW180). A dynamic vapor sorption (DVS) technique was used to determine water vapor sorption isotherms of the samples for three adsorption-desorption cycles at varying RH between 0% and 95%. Inverse gas chromatography (IGC) was used to study the surface energy properties of the samples, including dispersive and polar characteristics. The DVS results showed that the EMC was reduced by 30-50% for the TMW samples compared with control samples of unmodified wood (UW) components. A lower reduction was, however, observed for the second and third adsorption cycles compared with that of the first cycle. Ratios between EMC of TMW and that of UW samples were lower for the TMW180 compared with the TMW150 samples, and an overall decrease in such EMC ratios was observed at higher RH for both TMW samples. The IGC results showed that the dispersive contribution to the surface energy was higher at lower surface coverages, ie representing the higher energy sites, for the TMW compared with the UW samples. In addition, an analysis of the acid-base properties indicated a higher KB than KA number, ie a higher basic than acidic contribution to the surface energy, for all the samples. A higher KB number was also observed for the TMW compared with the UW samples, suggested to relate to the presence of ether bonds from increased lignin and/or extractives content at the surface. The KB was lower for TMW180 compared with TMW150, as a result of higher modification temperature of the first, leading to cleavage of these ether bonds.
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| 21. |
- Källbom, Susanna, 1988-, et al.
(författare)
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Surface energy characterization of thermally modified spruce using inverse gas chromatography under cyclic humidity conditions
- 2015
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Ingår i: Wood and Fiber Science. - : SOC WOOD SCI TECHNOL. - 0735-6161. ; 47:4, s. 410-420
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Tidskriftsartikel (refereegranskat)abstract
- The surface energy of unmodified and thermally modified spruce wood components was researched at dry and moist conditions using inverse gas chromatography. The results indicate a more pronounced heterogeneous nature of the thermally modified wood surfaces in terms of the dispersive (nonpolar) component of the surface energy, compared with that of the unmodified wood surfaces. The dispersive component of the surface energy of the thermally modified wood ranged between 44 and 38 mJ/m(2) corresponding to an increase in surface coverage from a low level and up to about 10%. Suggested explanations for the more distinct heterogeneity of the thermally modified wood sample are related to chemical changes of the wood substance which seem to result in certain micromorphological features observed by scanning electron microscopy as alternated fracture surfaces created in the grinding process; and also possible changes or redistribution of the wood extractives. An increase of the MC, representing a change from a dry condition of approximately 0% RH to ca 75% RH, of both the unmodified and thermally modified samples seemed to have a marginal influence on the dispersive component of the surface energy. Possible implications of the results in this study can be found in the tailoring of new compatible and durable material combinations, for example, when using thermally modified wood residuals as a component in new types of biocomposites.
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| 22. |
- Li, Rongrong, et al.
(författare)
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Prediction of cutting force during gypsum fiber composite milling process using response surface methodology
- 2017
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Ingår i: Wood and Fiber Science. - : Society of Wood Science and Technology. - 0735-6161. ; 49:4, s. 453-460
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Tidskriftsartikel (refereegranskat)abstract
- Gypsum fiber composite (GFC) is a kind of building material widely used in interior decoration. Milling is the most commonly used machining process for GFC. Cutting force as an important cutting characteristic parameter has significant influence on the quality of machined surface, power consumption, and tools wear. The tangential force (Fx) and normal force (Fy) were measured and analyzed to find out the effects of milling parameters on these cutting forces. Milling parameters considered were spindle speed, feed rate, and depth of cut. The response surface methodology (RSM) was selected to develop mathematical models and optimize milling parameters. The results showed that with the increase of feed rate and depth of cut, the Fx and Fy increased. But the cutting forces decreased with the increase of spindle speed. The optimization results indicated that high spindle speed, low feed rate, and small depth of cut are preferable for milling of GFC to obtain the best result.
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| 23. |
- Liu, X M, et al.
(författare)
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A tool for evaluating the quality of laminated particleboard countertop
- 2016
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Ingår i: Wood and Fiber Science. - 0735-6161. ; 48:4, s. 297-301
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Tidskriftsartikel (refereegranskat)abstract
- To evaluate the quality of laminated particleboard, a typical type of laminate was used in laminating particleboard with operational parameters similar to industry operation. Pull-off tests using Elcometer 510 were conducted. In addition, panel vertical density profiles (VDP) and the pH of particleboard at different layers were tested. The results showed that the laminated panel bonded by polyvinyl acetate (PVA) glue had higher pull-off strength than that of the phenol formaldehyde (PF) glue within corresponding sanding thickness. Sanding off 0.0762 mm resulted in higher pull-off strength than sanding off 0.0254 mm. The laminates had the highest pull-off strength when the PB were sanded off 0.0762 mm and glued by PVA. This has provided a solution to improve lamination pull-of strength for industry. The test results have also shown that the laminated panels produced in the manufactures have the potential to be improved. It also indicates that Elcometer 510 is a good tool to evaluate the particleboard lamination quality.
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| 25. |
- Lundgren, Nils, et al.
(författare)
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Predicting the strength of Norway spruce by microwave scanning: A comparison with other scanning techniques
- 2007
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Ingår i: Wood and Fiber Science. - 0735-6161. ; 39, s. 167-172
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Tidskriftsartikel (refereegranskat)abstract
- In this study, 90 boards of Norway spruce (Picea abies (L.) Karst.) sized 48 x 148 mm in cross-section, have been examined using different scanning and measurement techniques. All of the boards originated from a sawmill located in southern Finland. Planar X-ray scanning, microwave scanning, and grain-angle measurement have been performed. In addition, strength and elastic properties were assessed for eachpiece by four point bending. The purpose of the study was to relate the potential of microwave scanning compared to other, industrially available techniques and to explain the physiological background of the microwave responses. The results show that the microwave signal, after transmission through wood, contains information about the bending strength and the modulus of elasticity. The correlation to densityis a key factor. Annual ring width was also found to be correlated both to microwave measurements and strength properties.
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