Wood and Fiber Science (E-Journal)
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TECHNICAL NOTE: WATER VAPOR TRANSMISSION RATE AND PERMEANCE OF CELLULOSE NANOCRYSTALS/POLYDIMETHYLSILOXANE HYBRID MEMBRANES MEASURED BY DYNAMIC VAPOR SORPTION
No full textThis article describes a fast and reliable method of screening membrane materials designed by measuring moisture vapor transmission rate (WVTR) and permeance of membrane materials using a Payne-style diffusion cell (dry cup) placed in a Dynamic Vapor Sorption DVS) instrument. The materials were cellulose nanocrystals (CNC)/polydimethylsiloxane (PDMS) hybrid membranes. A casting method was used to fabricate three types of membrane samples. The WVTR and permeance of the samples were measured at two relative humidity (RH) levels if 60% and 80% at 25OC. The results revealed that the WVTR and permeance of PDMS membrane samples were increased by 34.33% to 39.69% after adding 1 wt% of CNC in the PDMS matrix. WVTR of all samples increased as RH increased from 60% to 80%, but the permeance decreased with increasing RH. The results of all three types of samples showed good consistency in terms of data discrepancy and the trends of WVTR and permeance with RH. Due to the small sample size, the tests could be completed in a few hours at elevates RHs in comparison with the commonly used Mason jar method according to American Society for Testing and Materials (ASTM) E96/E96M-16. Therefore, the Payne cell method in DVS can provide a fast screening of membrane materials
EMPIRICAL MODELS FOR PREDICTION COMPRESSION STRENGTH OF PAPERBOARD CARTON
Full text linkWhen designing packaging in the shape of a rectangular parallelepiped from various paperboard materials, it is important to determine their resistance to vertical compression force, which should be less than the critical compression force. This is especially relevant when the products packed in these boxes are stacked during transport or storage. The developed empirical models make it possible to more optimally / more accurately determine the critical vertical compressive strength of these packages.
The purpose of this work is to create an empirical model of the critical compressive force of a paperboard box (carton) based on the corrected formulas of the critical compressive force of the McKee corrugated cardboard box (taking into account the height) of the box and allowing to optimize of its parameters. The accuracy of the developed empirical models is presented by comparing the results of theoretical and experimental studies.
It should be noted that the determination of the critical compression force of the box is a contact problem of the non-linear theory of elasticity and plasticity for structures whose elements are made of an anisotropic material. On this basis, empirical models of three and one parameters were developed, which also estimated the values of experimental studies previously performed by other authors. One mathematical model also estimates the height of the box, which is not determined by the Mckee formula. For the experiments, we used cartons of different geometric parameters and made from different types of paperboard. During the experiment, the boxes were compressed with vertical force until the packages collapsed.
The results of the compared theoretical and experimental studies show the suitability of the proposed mathematical models for calculating the critical compressive strength of packages since the obtained MAPE error is within acceptable limits.
Taking into account the small discrepancy between the obtained experimental and theoretical research results, the proposed method for calculating the vertical critical compressive force of the rectangular parallelepiped package is suitable for use. The methodology for calculating the critical compressive strength of such packages presented in this document will be extended in the future for additional testing to verify the model with carton size and design variations
EVALUATING LOG STIFFNESS USING ACOUSTIC VELOCITY FOR MANUFACTURING STRUCTURAL ORIENTED STRAND BOARD
Full text linkOriented strand board (OSB) is an engineered panel product formed by layering strands of resinated wood in specific orientations into a mat, then pressing the mat at a high temperature to form a panel of desired strength and stiffness. OSB manufacturing facilities utilize small diameter logs from thinning operations and waste from harvesting. Considerable variation exists in the wood properties of the raw material and ideally the OSB industry would take advantage of such variation, however, it lacks the technology required to rapidly assess log quality on-site. Non-destructive evaluation (NDE) techniques based-on acoustics have the potential to rapidly segregate logs in the field, however the influence of acoustic-based log segregation on OSB panel properties is unknown. The aims of this project were to determine if log quality affects panel properties and if acoustic NDE technology is a satisfactory tool for determining log stiffness prior to entering the manufacturing process. It was found that low velocity (stiffness) logs produced panels with low stiffness while high and medium velocity (stiffness) logs produced panels with similar properties. The Director HM 200 was a satisfactory tool for determining log stiffness. Further studies are required to determine how to incorporate NDE tools into the manufacturing process
A MULTISCALE STUDY ON THE ELASTIC PROPERTIES OF BAMBOO
No full textThe elastic constants play a crucial role in the rigidity designing and numerical model building of bamboo, thus it will enhance the accuracy of numerical model to obtaining the elastic constants fully and accurately. In this paper, the elastic properties of bamboo, bamboo fiber and bamboo parenchyma were studied systematically, and the elastic constant map of bamboo was plotted. The results would provide significant theoretical foundation for the numerical simulation of bamboo and the design and manufacture of new biomimetic materials, meanwhile the experimental design would also provide important reference for the test of other bamboo species and biologic materials
VARIATION OF CHEMICAL PROPERTIES, CRYSTALLINE STRUCTURE AND CALORIFIC VALUES OF NATIVE MALAYSIAN BAMBOO SPECIES
Full text linkThe chemical properties of four common Malaysian bamboo species locally known as Beting (Gigantochloa levis), Semantan (Gigantochloa scortechinii), Lemang (Schizostachyum brachyladum) and Akar (Bambusa vulgaris) were studied. Chemical analysis shows that the alkaline extractive content for Malaysian bamboo species studied was within 24.4% to 25.6%, ethanol-toluene extractive content for Malaysian bamboo species was within 4.0% to 7.2% and water extractive content was within 10.4% to 12.8%. The average value of holocellulose content for Malaysian bamboo was between 64.5% to 70.67%, Klason lignin within 25.3% to 28.4%, cellulose content was between 28.5% to 33.8% and α-cellulose content for all bamboo species was within the range of 40.7% to 47.9%. The crystallinity of bamboo samples was between 42.0 to 44.4%, indicating their semi-crystalline structure. Heating value of bamboo ranged between 17.0 MJ/kg to 18.1 MJ/kg with G. scortechinii having the highest heating value.. The Inductive Couple Plasma Atomic Emission Spectroscopy (ICP-ES) analysis showed that Potassium (K) and Calcium (C) were the major elements in the ash of all bamboo samples. This study demonstrates the potential of native bamboo species as an alternative sustainable raw material to wood for a wide range of applications
WOOD-BASED PREPREG FOR COMPOSITE LAMINATES: Wood-Based Prepreg
No full textA wood-based prepreg was formed using vacuum assisted resin transfer molding (VARTM) and a low viscosity thermoplastic resin. Wood strands were assembled to make a porous mat for resin injection. The resin filled most of the cavities inside the wood cells resulting in a void volume fraction of 7%. The Young’s modulus and strength of the saturated wood strands were 38% and 124% higher, respectively, than those of wood strands prior to resin infusion. Flat laminates were produced by thermoforming prepreg plies at 180 ºC and 830 kPa, for 25 minutes. The Young’s modulus and strength of flat 12-ply laminates were 73% and 20% higher, respectively, than a wood-strand panel produced using compression resin transfer molding (CRTM) and epoxy resin. Wood prepreg shows promise as an alternative to traditional wood composite forming processes, with the potential to simplify the manufacture of complex shapes, while improving the properties of the natural material
THE INFLUENCE OF FOAM DISCONTINUITY IN THE SHEAR ZONE OF STRUCTURAL INSULATED PANEL BEAMS
Full text linkThe effect of foam discontinuity in the shear zone of structural insulated panel (SIP) beams was investigated in the current research. Two depths of 15.24 cm and 31.11 cm (6.5 in and 12.25 in) (SIPs) were evaluated in 1/3-point bending. Panels were sawn into beams, each approximately 29.84 cm (11.75 in.) wide, for mechanical testing. Half of the panels had joints or discontinuities in the foam layer in a location that was subject to shear stress during the bending tests. Half of the panels had joints or discontinuities in the foam layer in a location that was subject to shear stress during the bending tests. Half of the panels did not have joints or discontinuities in the foam layer in the locations that were subject to shear stress during the bending tests. The specimens with no foam discontinuity, stressed in shear, were approximately twice as strong as the specimens with a foam discontinuity. This finding has implications for routine testing and evaluation as well as for allowable properties. In the case of routine testing, foam discontinuities should purposefully be located in the zone of maximum shear as these appear to be a limiting factor. In cases where a producer manufactures SIPs with zero discontinuities, it may be prudent to seek premium value as those panels would achieve superior properties.
Keywords: Structural insulated panels (SIPs), shear stress, bending test, foam, joints and routine testing.
PREPARATION AND CHARACTERIZATION OF CELLULOSE FILMS FROM FICUS NATALENSIS BARK CLOTH FIBERS
No full textIn this study, cellulose films were prepared from Ficus natalensis bark cloth fibers via phase inversion technique using NaOH/urea/water as the solvent. Films were formed at a concentration of 7 wt. % and 8 wt. % of microcrystalline cellulose (MCC) as isolated from Ficus natalensis bark cloth fibers. Their morphology, physiochemical, and mechanical properties were examined with scanning electron microscopy (SEM), Fourier transform IR spectroscopy (FTIR), x-ray diffraction (XRD), thermal gravimetric analysis (TGA) and microcontrolled electronic universal testing machine. The resultant regenerated cellulose (RC) films exhibited rough surfaces morphologically, good tensile strength (19.85 ± 0.13 MPa), exhibited a plastic behavior with considerable strains. However, they are thermally stable at higher temperatures up to 280 °C. Cellulose films from this study could potentially act as biodegradable packaging materials to upgrade the scope of application of Ficus natalensis bar
EFFECT OF LOG HEAT TREATMENT ON RELEASE OF GROWTH STRESSES IN EUCALYPTUS NITENS
No full text The use of Eucalyptus nitens has diversified the Chilean lumber industry in unprecedented ways. However, growth-induced strains cause splitting and warping. The objective of this investigation was to determine the effect of the heat treatment applied to logs of Eucalyptus nitens on the reduction of growth stresses and improvement of quality in sawn wood. Logs were extracted at different heights of the tree for 15-yr and 20-yr-old trees. The sawmill process was allowed to obtain radial, mixed, and tangential plane pieces, at two thicknesses (25 and 50 mm). The evaluation of MC and warping was according to Chilean National Standards. The results obtained in this research suggest that by applying the heat treatment to Eucalyptus nitens logs, a significant reduction in growth strains can be achieved. Heat treatment also increased the quality of the pieces in terms of bow, crooking, and twisting. Therefore, there are substantial benefits of using heat treatments to reduce defects caused by growth strains and thus increase the quality of the wood and reduce its warp.
