Types Of Plywood Research Articles

On the glow of cremated remains: long-lived green photo-luminescence of heat-treated human bones.

The long-lived green luminescence of human bone (that has been heated to 600°C for a short duration) is attributed to a carbon quantum dot material (derived from collagen) encapsulated and protected by an inorganic matrix (derived from bone apatite) and is more intense in dense rigid and crystalline parts of (healthy) human bones. The strong collagen-apatite interaction results (upon decomposition) in a protective inorganic environment of the luminescent centers allowing long-lived triplet-based emission of a carbon (quantum) dot-like material at room temperature, as well as resilience against oxidation between 550 and 650°C. The graphitic black phase (obtained upon heating around 400°C) is a precursor to the luminescent carbon-based material, that is strongly interacting with the crystalline inorganic matrix. Human bone samples that have been heated to 600°C were subjected to steady-state and time-resolved spectroscopy. Excitation-emission matrix (EEM) luminescence spectroscopy revealed a broad range of excitation and emission wavelengths, indicating a heterogeneous system with a broad density of emissive states. The effect of low temperature on the heat-treated bone was studied with Cryogenic Steady State Luminescence Spectroscopy. Cooling the bone to 80K leads to a slight increase in total emission intensity as well as an intensity increase towards to red part of the spectrum, incompatible with a defect state model displaying luminescent charge recombination in the inorganic matrix. Time-resolved spectroscopy with an Optical Multichannel Analyzer (OMA) and Time Correlated Single Photon Counting (TCSPC) of these samples showed that the decay could be fitted with a multi-exponential decay model as well as with second-order decay kinetics. Confocal Microscopy revealed distinct (plywood type) structures in the bone and high intensity-fast decay areas as well as a spatially heterogeneous distribution of green and (fewer) red emissive species. The use of the ATTO 565 dye aided in bone-structure visualization by chemical adsorption. Conceptually our data interpretation corresponds to previous reports from the material science field on luminescent powders.

Comparison of the properties of phenolic resin synthesized from different aldehydes and evaluation of the release and health risks of VOCs

Different amounts of glyoxal and paraformaldehyde were used to synthesize phenol-glyoxal (PG) and phenol-paraformaldehyde (PPF) resins, which were compared with conventional phenol-formaldehyde (PF) resins. Glyoxal oxidation leads to a pH value of 9.83 for PG 2.2. With the addition of polyformaldehyde, PPF 2.2 exhibited the highest viscosity at 17333.33 mPa s. The PPF 2.0 plywood has a maximum bonding strength of 1.94 MPa. The formaldehyde emission of PG 1.8 plywood is found to have a minimum value of 0.025 mg/m3, reaching the ENF limit (≤0.025 mg/m3). Acetaldehyde is found only in volatile organic compound (VOC) emissions from PG plywood and is associated with increased glyoxal. PPF plywood emitted more aromatic and total VOC (TVOC) than the other two plywood types. The measured TVOC for PPF 2.2 is 196.07 μg/m3. The results showed that the total cancer risk (TCR) values of PPF 1.8, PPF 2.0, and PG 1.8 were above the threshold of 1.00E-4, indicating a definite carcinogenic risk. Acetaldehyde in the PG plywood exceeded the safety threshold for noncarcinogenic risk. The use of paraformaldehyde in the wood-based panel production is been considered a possible means of improving the bonding strength of plywood. Glyoxal has also been shown to be a viable method for lowering the formaldehyde emissions from plywood. The VOC emissions from plywood changed significantly depending on the aldehyde used. Limiting VOCs that present high health hazards is crucial for reducing the negative impact of plywood on both indoor environments and human health.

Preparation, characterization, and application of waterborne lignin-based epoxy resin as eco-friendly wood adhesive

A series of novel waterborne lignin-based epoxy resin emulsions (WLEPs) were successfully synthesized, and then the WLEPs were cured with polyamide (PA) to give formaldehyde-free wood adhesives with high-performance. The chemical structures and properties of WLEP emulsions were determined. The effects of the emulsifiers on thermal and mechanical properties of the adhesives were investigated, and the potential application of WLEPs in the formulation of plywood were also evaluated. The results demonstrated that the WLEP dispersions presented excellent storage stability (>180 days) with their viscosities range from 110 mPa·s to 470 mPa·s and particle sizes in the range of 321–696 nm, which were beneficial for the fluidity and permeability of the wood adhesives. Furthermore, the thermal and mechanical properties of adhesives could be tuned effectively by controlling the length of PEG chains. The adhesive bearing PEG 6000 exhibited the highest tensile strength of 24.0 MPa and Young's modulus of 1439 MPa. Notably, the plywood prepared with the resulting adhesives displayed good bonding performance, especially water resistance, which were much higher than the national standard requirement for exterior-grade plywood type I. These results indicated that the WLEPs could be used as sustainable alternatives for traditional formaldehyde-based wood adhesives in practical applications.

Influence of the use of chestnut starch as a binder filler in plywood technology

: Influence of the use of chestnut starch as a binder filler in plywood technology. Fillers play a crucial role in the production of plywood glues, providing enhanced performance and stability to the end product. Plywood, being a composite material, requires fillers to improve its mechanical properties, adhesion, and overall quality. One common filler used in plywood glues is calcium carbonate. It acts as a bulking agent, increasing the volume and density of the adhesive mixture while reducing production costs. Calcium carbonate also enhances the glue's viscosity, ensuring proper bonding and uniform application during the plywood manufacturing process. Another widely used filler is rye or wheat flour, which consists of finely ground grains. The flour not only improves the adhesive's viscosity but also contributes to the overall strength and stability of the plywood. It helps to prevent warping and enhances dimensional stability, making the final product more durable. Additionally, other fillers like talc or clay minerals may be incorporated into the glues to improve their adhesive properties and increase moisture resistance. Chestnut starch is a type of vegetable flour made by grinding edible chestnuts into a powder. It has a different texture and properties than traditional wheat or rye flour. When used as a binder filler in plywood technology, it can be biodegradable and environment-friendly. In the study, there were produced five types of plywood with 0, 1, 5, 10, and 20 parts by weight chestnut flour and one reference. All samples were produced in laboratory conditions and the selected mechanical and physical properties of the produced boards were studied. The mechanical properties of the boards increased with the addition of chestnut flour. In some tests, the results even met the highest requirements of European standards for plywood. According to this finding, a well-chosen addition of chestnut flour could be positively considered in plywood production.

Effect of Freeze–Thaw Cycling on the Screw Direct Withdrawal Resistance of Beech, Ozigo, and Okoume Plywoods

Wood has been used in the construction, furniture, and automotive industries since ancient times. In areas where wood material is used, it is combined with various fasteners. The durability of the products produced using wooden materials depends on the performance of the fasteners. Since wood is a hygroscopic and biodegradable material, various changes occur in its structure when exposed to external weather conditions. Wood materials used especially in the field of construction and urban furniture are exposed to effects such as extreme temperatures, freezing, moisture, or drying depending on the seasons. In this study, the effect of the freeze–thaw cycling (FTC) process on screw direct withdrawal resistance (SDWR) of plywood produced from beech, ozigo, and okoume species was investigated. In this context, the effects of screwing time (before or after), screw orientation (face or edge), the number of cycles (0 to 7) in the FTC process, and plywood type parameters on SDWR were investigated. As a result of the tests, when the mean SDWR values were examined according to the plywood type, the highest values were obtained in beech, ozigo, and okoume plywood, respectively. Considering the screwing time parameter, it was determined that there was no statistically significant difference between the mean SDWR values in other plywood types except beech plywood (p < 0.05). When the screw orientation parameter was examined, screwing in the face direction gave better results than screwing in the edge direction in all plywood types. There was a decrease in the mean SDWR values that was inversely proportional to the increase in the number of cycles in FTC-treated plywood.

Developing carbon dots as green modifiers for improving the bonding performance of low-molar-ratio urea-formaldehyde resin

Reducing formaldehyde-to-urea molar ratio is conducive to improving environmental-friendliness of urea-formaldehyde (UF) resin-bonded wooden products, but at the expense of bonding performance, such contradictoriness is intrinsically due to the decreased cohesion of resin polymer structures. In this study, we proposed a novel strategy to enhance the bonding performance of low-molar-ratio UF resins by use of carbon dots (CDs) as green modifiers. Taking advantages of surface-contained plentiful carboxyl and hydroxyl groups, the synthesized CDs could generate strong physicochemical interactions with polymer segments and further improve cohesion of resin matrix. The optical microrheology demonstrated that the microscopic viscoelasticity of CDs-modified UF resin was increased as increasing of CDs content due primarily to the formation of strong hydrogen bonding interactions between CDs and resin polymers. Based on the analysis for curing behavior, the polycondensation reactivity of resin oligomers was almost free from the interaction or connection between CDs and polymer segments. Furthermore, as confirmed by nanoindentation technology, the physicochemical interactions formed between oxygenous functional groups of CDs and polymer matrices could improve the cohesion of resin after curing reaction, thus resulting in the enhanced micromechanical strength of wood-resin interphase and further bonding strength of resin at macroscopic level. Remarkably, this reinforcing effect imparted by CDs resulted in the tensile shear strength of plywood increased to 0.96 MPa, which was 77.8% increase in comparison to the panels bonded with unmodified resin and largely exceed the requirement given by national standard (0.7 MPa for plywood type Ⅱ). Taken together, this work demonstrated that the synthesized CDs are efficient and provided a potential platform for improving the bonding performance of low-molar-ratio UF resins.

Development of easy-handled, formaldehyde-free, high-bonding performance bio-sourced wood adhesives by co-reaction of furfuryl alcohol and wheat gluten protein

Bio-sourced wood adhesives are an alternative of actuality for petroleum-derived binders used to-day in the timber industry. Inspired by the classical furfuryl alcohol (FA) acid-catalyzed polymerization strategy, a convenient preparation method is proposed for developing wood adhesives derived from sustainable hydrolyzed wheat gluten protein (HWG) and furfuryl alcohol (FA). The obtained HWG-FA wood adhesives show a correct non-volatiles content and initial viscosity. The interaction mechanism of HWG and FA is suggested based on the analyses of FT-IR, 13C NMR, and MALDI-TOF spectra. A competitive reaction relationship was observed between FA-catalyzed self-condensation and the crosslinking of the HWG amino group by the FA hydroxymethyl groups, central to help lengthen the storage life of the adhesives. The adhesive network built-up by FA self-polymerization presents an excellent bonding performance and retardation of water intrusion. The products obtained from the reactions between HWG and FA improve the adhesive network level of crosslinking, which enhances the performance of the adhesives. Moreover, the HWG-FA wood adhesive shows outstanding wet shear strength that exceeds the China National Standard (GB/T 9846-2015, ≥ 0.7 MPa) requirement for exterior-grade plywood type I. This result has seldom been obtained in previous research concerning high biomass content wood adhesives. This research provides a method for preparation of sustainable, eco-friendly, formaldehyde-free, wood adhesive with high-performance.

Staple Holding Strength of Furniture Frame Joints Constructed of Plywood and Solid Wood

The withdrawal and lateral holding properties of three types of plywood with one stapled as well as one-row multi-stapled joints were studied and compared. The results show that variations in plywood density have a significant effect on withdrawal strength and a relatively small effect on lateral holding strength. At four staples, the withdrawal strength of the eucalyptus plywood with a density of 0.59 g/cm3 is 1821 N, which is 21% higher than that of poplar plywood with a density of 0.51 g/cm3 at 1498 N and 32% higher than that of eucalyptus/poplar composite plywood with a density of 0.53 g/cm3 at 1275 N. In terms of lateral holding strength, eucalyptus plywood has a lateral holding strength of 1603 N 12% lower than the 1807 N of eucalyptus/poplar composite plywood and 10% lower than the 1761 N of poplar plywood. As the number of staples increased from 1 to 4 in increments of 1, the withdrawal strength of eucalyptus plywood continued to increase, while the nodal strengths of the poplar plywood as well as eucalyptus/poplar composite plywood did not differ significantly between 3 and 4 staples, and there is a significant increase in the lateral holding strength for all three plywood nodes. Equations for predicting the withdrawal and lateral holding strengths of one-row multi-stapled joints were derived separately.

Comparative Study of Plywood Boards Produced with Castor Oil-Based Polyurethane and Phenol-Formaldehyde Using Pinus taeda L. Veneers Treated with Chromated Copper Arsenate

Plywood is widely used in civil construction. Due to the importance of preservation and gluing in bio-composites, this study compares the influence of a chemical treatment with CCA (chromated-copper-arsenate) on Pinus taeda L. wood veneers to produce two plywood types using phenol-formaldehyde (PF) and castor oil-based polyurethane (PU). Four different treatments were performed to analyze both varieties’ physical and mechanical properties. As a result, an improvement in the properties of the treated panels was observed. Lower moisture contents and better interactions caused by less thickness swelling and water absorption were identified in the PU-based plywoods. The treatment with CCA was efficient, improving these properties when they were compared to the reference panels. Most treatments evidenced increases in the modulus of elasticity and modulus of rupture for both adhesives when the CCA treatment was applied to the veneers. Comparing the resins, the PF showed the best values of modulus of elasticity. All treatments met the requirements defined by the Brazilian standard document for the glue line shear.

Reducing the Energy Consumption of Circular Saws in the Cutting Process of Plywood

Cutting, as the most widely used machining process, is applied in both primary and secondary wood processing. Optimum cutting conditions that result in the high quality of the machined surface and low energy consumption are crucial for wood processing. The effects of the feed speed, cutting speed and average chip thickness on the energy consumption and surface temperature of a circular saw blade during the cutting process of two types of plywood with a thickness of h = 14 mm is described in this paper. In experimental measurements, two circular saw blades with cutting tungsten carbide inserts for wood were used as tools. One circular saw blade was standard, and was not surface treated (CSB1), and second circular saw blade (CSB2) differed by the powder coating surface and the length of the cutting edge. In the experiment, the energy consumption and the surface temperature of the circular saw blade was measured in order to find the optimal cutting conditions for the most energy-efficient cutting process. The results show that the cutting power and the surface temperature of the circular saw blade increased when the feed speed increased. The investigated values of the surface-treated circular saw blade were lower compared to the values of the standard circular saw blade. When comparing the lightweight plywood with the classic plywood, experimentally obtained cutting power values of the circular saw were made 19% lower on average by using the circular saw blade CSB1. When using the CSB2 circular saw blade, these values of the cutting power of the circular saw were 22% lower on average. The surface temperature of the circular saw blade is the highest on the outer edge (tooth root area 31.7 °C) and decreases towards the center of the circular saw blade. There must be a reasonable compromise between machine productivity and energy consumption.

Selected problems concerning volatile organic compounds emission reduction from thick-veneer pine plywood

Selected problems concerning volatile organic compounds emission reduction from thick-veneer pine plywood. The paper presents results of research conducted on volatile organic compounds emissions, considering two different production parameter sets for thick-veneer pine plywood, manufactured in industrial conditions. Both types of plywood were produced from raw wood material, which was hydrothermally treated under two different variants of parameters (I – 47˚C, 19 h; II – 55˚C, 24 h). Based on the results it was stated that severe hydrothermal treatment of raw wood material (longer soaking time, higher temperature) had impact on reduction of plywood VOC emission rates. Main VOCs emitted from pine plywood were monoterpenes and carbonyl compounds. Of the monoterpenes, α-pinene and 3-carene had the highest emission. Of the carbonyl group of compounds, the highest emission had hexanal and caproic acid.

The Effect of Veneer Densification Temperature and Wood Species on the Plywood Properties Made from Alternate Layers of Densified and Non-Densified Veneers

In this study the properties of plywood manufactured from densified and non-densified veneer sheets and alternate layers of such veneers with and without densification using low amount of adhesive as a function of densification temperature and wood species were investigated. The plywood panels were made from rotary-cut birch and black alder veneers using urea-formaldehyde (UF) adhesive. Veneer sheets with thickness of 1.5 mm were subjected to the thermal-compression at three different temperatures while keeping constant the pressure during a same time span. Five-layers plywood panels were produced using a constant hot-pressing schedule using different amounts of glue spread as a function of the plywood type; such as plywood made from non-densified (80 g/m2) and densified (60 g/m2) veneers only; and combination of them (70 g/m2). The bending strength (MOR) and the modulus of elasticity (MOE) along with the shear strength of the plywood samples for bonding class 1 (dry conditions) have been determined. As expected bending strength of the plywood samples increased with the increasing in density. The increase of veneer densification temperature resulted in a gradually decrease of MOR; MOE and shear strength values for the plywood panels made of densified veneers and mixed panels of both species. The temperature of 150 °C for veneer densification seemed to be enough to achieve enhanced bending and bonding properties. All plywood panels in this study were manufactured using reduced glue consumption and they presented satisfactory properties performance for indoor applications.

Ефективність виготовлення фанери, склеєної термопластичною плівкою

Досліджено ефективність виготовлення фанери, склеєної термопластичною плівкою. Ефективністю виготовлення фанери вважали сукупність економічної та екологічної ефективностей за результатами економії грошових ресурсів способом порівняння затрат під час виготовлення фанери, склеєної термопластичною плівкою, замість традиційної фанери. Встановлено, що застосування термопластичної плівки у виробництві фанери збільшує затрати на фанерну сировину на 100,8 грн/м3 та клейовий матеріал на 1874,0 грн/м3. З'ясовано, що основними відмінностями під час виробництва досліджуваних видів фанери є затрати на потреби в електроенергії, у гарячій воді на дільницях приготування клею і нанесення його на поверхню шпону та збори за викиди небезпечних сполук у навколишнє середовище. Встановлено, що найбільше споживання потреби води здійснюється на дільницях приготування клею та нанесення його на поверхню шпону. Відповідно затрати електроенергії на цих дільницях теж є значними. З'ясовано, що одним з вагомих факторів у виробництві фанери є викиди небезпечних сполук у навколишнє середовище, причиною якого є застосування термореактивних клеїв. Застосування термопластичних плівок у виробництві фанери відкидає потребу у становленні очисних споруд та щорічному збору за викиди формальдегіду та аміаку. Порівняння статей затрат на фанерну сировину (кряж) та клейові матеріали у виробництві традиційної фанери та фанери, склеєної термопластичною плівкою ПЕНГ, показує, що затрати коштів збільшуються в 1,4 раза під час виготовлення фанери, склеєної ПЕНГ. Однак, враховуючи затрати на потреби в електроенергії та у споживанні гарячої води, економія коштів становить 492337,56 грн. Незважаючи на затрати виробництва на фанерну сировину та клейовий матеріал, виготовлення фанери, склеєної термопластичною плівкою, є економічно вигіднішим за виробництво традиційної фанери. Окрім цього, екологічність отриманого продукту підвищує його конкурентоспроможність над традиційною фанерою. Запропонований спосіб виготовлення фанери підвищує продуктивність виготовлення завдяки відсутності трудовитратних операцій, гарантує високий ступінь чистоти атмосферного повітря для забезпечення якісних умов роботи працівників та екологічність готової продукції, яка навіть під час експлуатації є нетоксичною, що цим самим розширює можливості подальшого застосування.

Structural organization of bacterial cellulose: The origin of anisotropy and layered structures

In this paper, we perform a systematic analysis of the structural organization of bacterial cellulose (BC). We report four types of organization of the BC mass, produced by Gluconacetobacter hansenii that occur depending on cultivation conditions. Two of those, particularly, plywood type one and layers of micro-sized tubes were observed and described for the first time. In spherical BC particles (pellets), we found the layered structure that had previously been reported for planar geometry only. We suggest a model explaining why layers form in BC films and attempt to reveal the impact of different factors on the BC microscale morphology. We assume that the main factor that has direct impact on the type of structure formed is the rate of BC mass accumulation.

Understanding the interaction between bonding strength and strain distribution of plywood

Plywood is an important engineered wood product manufactured by orthotropically bonding veneers together. Bonding strength plays a crucial role in the performance of plywood. However the interaction between bonding strength and strain distribution has not been fully understood yet. Therefore, in this study, relationships between bonding strength and shear strain distribution in six types of plywood were illustrated using digital image correlation (DIC) approach as performing the lap-shear tests. Both urea formaldehyde (UF) and phenol formaldehyde (PF) resin were used as the bonding adhesive. Fluorescence microscopy was adopted to visualize the resin distribution within the micro-structure of the specimens. Results showed that the failure load (FL) of plywood positively and negatively correlated to the quantity of UF and PF resin, respectively. Increased quantity of UF resin facilitated to form a consecutive bond line, while large quantity of PF resin made the specimens brittle. Large ratio between load and strain, and homogenous strain distribution contribute to the high FL. Strain starts in regions adjacent to the notches and transfers to the remaining areas in the region of interest (ROI) by smoothly crossing the bond line. The properties of wood veneers play an important role in the bonding strength as strain is more likely to be started from the veneers. Findings of this study can contribute to the improvement of design strategies aiming the enhancement of the mechanical properties of plywood with small amount of resin.

A novel application of silicone-based flame-retardant adhesive in plywood

A silicone-based elastomer filled with vinyl-silane treated aluminum hydroxide was used to replace conventional polyurethane-based adhesive to provide a flame-retardant adhesive for plywood. The shear strength and fire performance of such a silicone-based (SI) adhesive glued plywood (SI/plywood) were investigated and compared to those of the polyurethane-based (PU) adhesive glued plywood (PU/plywood). The shear strength of the SI/plywood [(0.92 ± 0.09) MPa] was about 63% lower than that of the PU/plywood at room temperature, but it was less sensitive to water (62% reduction for the PU/plywood and 30% reduction for the SI/plywood after hot-water immersion at 63 °C for 3 h). The fire performance of plywood was assessed by a simulated match-flame ignition test (Mydrin test), lateral ignition and flame spread test, cone calorimetry, and thermocouple measurements. With a higher burn-though resistance and thermal barrier efficiency, and lower flame spread and heat release rate, the SI/plywood exhibited a superior fire-resistance and reaction-to-fire performance and improved fire-resistance as compared to the PU/plywood. The SI adhesive generated an inorganic protective layer on the sample surface that visibly suppressed glowing and smoldering of the plywood during combustion. The SI adhesive was also combined and reinforced with cellulosic fabric (CF) or glass fabric (GF) to prepare composite plywood (SI/CF/plywood and SI/GF/plywood) with improved fire performance. The cone calorimetry and thermocouple measurements indicated that the use of CF or GF in SI/CF/plywood and SI/GF/plywood, respectively, suppressed the delamination and cracking of the composite plywood and promoted the formation of an effective thermal barrier during smoldering and flaming combustion. Particularly, the SI/GF/plywood exhibited the most effective fire barrier with no crack formation, and the lowest heat release rate among the plywood types investigated in this study.

Experimental investigation of impact behavior of wood-based sandwich structures

Low carbon emission and sustainable development are shared goals throughout the transportation industry. One way to meet such expectations is to introduce lightweight materials based on renewable sources. Sandwich panels with plywood core and fiber reinforced composite skins appear to be good candidates. Additional properties of wood such as fire resistance or thermal and acoustic insulation are also essential for many applications and could lead to a new interest for this old material. In this paper, Sandwich panels with two different types of plywood and four different skins (aluminum and glass, CFRP, or flax reinforced polymer) are tested under low-velocity/low energy impacts and their behavior is discussed.

A Novel Application of Silicone-Based Flame-Retardant Adhesive in Plywood

A silicone-based elastomer filled with vinyl-silane treated aluminum hydroxide was used to replace conventional polyurethane-based adhesive to provide a flame-retardant adhesive for plywood. The shear strength and fire performance of such a silicone-based (SI) adhesive glued plywood (SI/plywood) were investigated and compared to those of the polyurethane-based (PU) adhesive glued plywood (PU/plywood). The shear strength of the SI/plywood [(0.92 ± 0.09) MPa] was about 63% lower than that of the PU/plywood at room temperature, but it was less sensitive to water (62% reduction for the PU/plywood and 30% reduction for the SI/plywood after hot-water immersion at 63 °C for 3 h). The fire performance of plywood was assessed by a simulated match-flame ignition test (Mydrin test), lateral ignition and flame spread test, cone calorimetry, and thermocouple measurements. With a higher burn-though resistance and thermal barrier efficiency, and lower flame spread and heat release rate, the SI/plywood exhibited a superior fire-resistance and reaction-to-fire performance and improved fire-resistance as compared to the PU/plywood. The SI adhesive generated an inorganic protective layer on the sample surface that visibly suppressed glowing and smoldering of the plywood during combustion. The SI adhesive was also combined and reinforced with cellulosic fabric (CF) or glass fabric (GF) to prepare composite plywood (SI/CF/plywood and SI/GF/plywood) with improved fire performance. The cone calorimetry and thermocouple measurements indicated that the use of CF or GF in SI/CF/plywood and SI/GF/plywood, respectively, suppressed the delamination and cracking of the composite plywood and promoted the formation of an effective thermal barrier during smoldering and flaming combustion. Particularly, the SI/GF/plywood exhibited the most effective fire barrier with no crack formation, and the lowest heat release rate among the plywood types investigated in this study.

Classification of uncoated plywood based on moisture dynamics

Moisture has a significant influence on the mechanical and physical properties and on the biological durability of wood and wood based materials. As plywood is commonly used as a building material for outdoor applications knowledge regarding its moisture behaviour is of utmost importance. The aim of this research is to model water accumulation in plywood panels in terms of their basic characteristics and in-service moisture conditions. Therefore, moisture dynamics of 29 uncoated plywood types consisting of different wood species, adhesives and layering were evaluated using a simple laboratory water floating test and an outdoor continuous moisture measurement set-up. A significant correlation was found between laboratory and field test results. By means of regression analysis the material characteristics affecting the moisture dynamics of plywood were evaluated. The most influential parameters were wood species, glue type and thickness of the top veneer. Limit values for the water left in the plywood specimen after 72 h absorption and subsequent 72 h desorption, the residual moisture content (rm72), were calculated as to develop a classification tool for plywood. Based on such a classification tool some recommendations for uncoated plywood regarding end use and service life were drafted. Enhanced performance should be obtained by means of wood preservation or by reducing its residual moisture by applying a coating or by an optimal selection of adhesive, wood species and top veneer thickness.

ANALISIS PENGARUH KEHALUSAN ABU TERBANG (FLYASH) TERHADAP STABILITAS DAN KEPADATAN CAMPURAN BETON ASPAL (AC-WC)

In this study, the use of fly ash material as substitution material of fine fraction on asphalt mixture of AC-WC Concrete to study Marshall and Durability. Concrete of bitumen is one of plywood type of pavement construction of pavement. In this study will focus on the extent of the effect of Ash ash Effect on Asphalt Concrete Mixture -WC tehadap Stability and density of the concrete mixture of asphalt. and in the end it is hoped that later fly ash of coal which used to be a waste material can be utilized as substitution material of fine fraction and alternative filler in road construction. The conclusion obtained from the analysis of the influence of fineness to the stability and density of AC-Wc asphalt concrete is as follows : Stability: Value stability of the mixture in the review of fineness variation tends to increase substitution of fly ash content variation occurs at the rate of 6% optimum zone 3 is equal to 1.435kg and at the level of 8% zone 3 decreased to 1.421kg.KepadatanNilai Density (Bulk density Standard) the mixture in review of the fineness variations tends to increase. variation of fly ash content substitution occurred optimum at 8% level of zone 3 that is equal to 2,421kg / cc. Some suggestions that can be submitted to improve the results performance of concrete asphalt mixture (AC-WC) using subtitution smoothness and fly ash content are: a) for subsequent research in order to analyze the optimum asphalt content to the optimum ash content as the greater the use of fly ash content, the Marshall parameter value tends to be less than optimal andb) It is advisable to combine other types of substitution materials with fly ash to obtain more economical results.