Feasibility of particle board production using bone glue

This feasibility study describes a new procedure for bonding particle boards using animal protein glue produced from bone. Making use of the thermoplastic properties of bone glue, particle boards with mechanical properties partly comparable to a MUF-bonded reference board were obtained at laboratory scale.     

Mechanical characterisation of adhesives in particle boards by means of nanoindentation

Cured urea formaldehyde (UF) and melamine urea formaldehyde (MUF) adhesives present in core and surface layers of particle boards were mechanically characterised in-situ by means of nanoindentation. Comparing results between investigated adhesives showed differences in micro-mechanical properties particularly in the core layers, while mechanical properties in surface layers did not differ significantly from each other. The method presented in this study demonstrates that in-situ characterisation of adhesives within a particle board cross section is feasible.     

Influence of hydrothermal modification of fibers on some physical and mechanical properties of medium density fiberboard (MDF)

Any treatment of fibers can influence properties of medium density fibreboard (MDF). In this research, the effects of hydrothermal treatment on physical and mechanical properties of MDF were studied. Industrial fibers were hydrothermally treated in a stainless steel reactor at 120, 150 and 180 °C for 0, 30 and 90 min as holding time. Test boards were made based on 0.7 g/cm³ target density, with 10 mm thickness under a pressure of 30 bar and at a temperature of 170 °C and a press time of 10 min. The boards were tested for internal bonding (IB), moduli of elasticity (MOE) and rupture (MOR), thickness swelling and water absorption. Results showed that the water absorption was not affected by the hydrothermal treatment; while the thickness swelling was improved and the boards became dimensionally stable. The MOE was slightly reduced due to the hydrothermal treatment. The MOR and the IB were significantly decreased by the hydrothermal treatment.     

Explanation of the embedding strength of particle board

By the earlier derived theory of the embedding strength, based on the equilibrium method of plasticity, it is possible to fully explain the empirical relations and test results of an investigation of the embedding strength of particle boards leading to a new insight for the right design rules.     

Effect of relative humidity on some physical and mechanical properties of different types of fibreboard

Equilibrium moisture content and strength properties as a function of relative humidity (RH) were measured in three types of commercial fibreboards with different densities. The measurements were made after specimens had been conditioned to equilibrium at 35, 50, 65, 80 and 95% RH and 20 °C. It was shown that the modulus of elasticity decreased slightly between 35 and 65% RH and markedly – at above 65% RH for all types of boards. A very strong decrease of modulus of elasticity was observed at about 80% RH (capillary condensation). A similar decreasing trend was observed in bending strength. Overall, high RH had a noticeably detrimental effect both on the MOE and the bending strength for all tested boards. Adequate correlation exists between bending MOE and bending strength with moisture content. The lower the density of boards the higher their equilibrium moisture content.     

Influence of different climatic conditions on the roughness of uncoated medium density fiberboards (MDF)

The surface roughness is primarily a function of the raw material properties, but other factors like type and amount of resin, press cycle, sanding and moisture content of the boards may also affect the roughness and other surface properties. In this study the effect of the equilibrium moisture content on medium density fiberboards (MDF) surfaces was evaluated using different raw materials in the surface layers as well as different binders. The statistical analysis confirmed that the relationship between equilibrium moisture content and average roughness is a complex function of interactions between many variables.     

Use of UF-bonded recycling particle- and fibreboards in MDF-production

The work is related to the use of thermomechanical pulps (TMP) prepared from recycling UF-bonded particle- and fibreboards as a partial substitute for TMP made directly from wood in MDF. The results reveal that TMP from recycling boards show striking differences in their morphological characteristics and chemical properties compared to TMP prepared directly from wood. TMP from recycling boards are of shorter fibre length and higher content of fine fraction. Moreover, their cold water extractives are of higher pH-value and contain appreciably higher amounts of acetate and formate ions. TMP from recycling boards releases also more formaldehyde compared to TMP made directly from wood. Moreover, the results clearly show that TMP from recycling boards can be used up to 30% as a partial substitute for TMP from wood in making UF-bonded MDF without any noteworthy deterioration of the physical-mechanical board properties. Also, the formaldehyde release of the boards made using TMP from recycling boards experiences no negative change. Only small differences were found in the content of formate and acetate ions as well as in the release of volatile acids from MDF made from recycling fibre- and particleboards on the one side and boards directly made from wood on the other side. All the results indicate that chemical interaction seems to take place between the chemically degraded resin in UF-bonded recycling boards and the new binder used in making MDF.     

Comparison of mechanical properties of oriented strand board made from trembling aspen and paper birch

This study compared the performance of oriented strand boards (OSB) made from trembling aspen, a low-density hardwood species, and OSB made from paper birch, a medium-density hardwood species. The birch strands were thinner than the aspen strands to ensure a comparable specific surface. Three levels of adhesive content were used: 3.5%, 5.0%, and 7.0%. Internal bond (IB) and modulus of elasticity (MOE) and modulus of rupture (MOR) for flatwise and edgewise bending were determined. Both species performed equally well in IB (3.5% adhesive content: 0.46 MPa, 5.0%: 0.60 MPa, and 7.0%: 0.65 MPa). The values of MOE in flatwise bending were slightly lower for birch than for aspen panels (11.8 GPa for aspen and 10.6 GPa for birch), and the MOR values were not significantly different (combined 68.3 MPa). Edgewise bending properties were not significantly different for the two species with a MOE of 10.5 GPa and a MOR of 43.2 MPa.     

Modeling the effect of length on yield of sawn timber grades in Norway spruce (Picea abies (L.) Karst.)

The aim of the study was to model and analyse the effect of length on grade yield of timber from different stem parts in Picea abies, and to use the models to simulate the cost of reduced grade yield due to increased length. The boards were simulated having lengths ranging from 20 to 60 dm starting at stump level, 4 m above stump level and 8 m above stump level, respectively. Logistic regression models showed that length had a significant effect on grade yield, and this length effect was stronger in strength grading according to INSTA 142 (IN) compared to appearance grading according to Nordic Timber (NT). The length effect was most pronounced in butt logs, and somewhat greater in middle logs compared to top logs. Also a smaller length effect in inner boards compared to boards farther from the pith was found for IN-grading. The cost of the decrease in grade yield with increasing length will depend on the assumptions about the price gap between the grades. Current market prices in both grading rules gave a decrease in value of the sawn timber in stock by about 6% with an increase in the log length from 45 to 60 dm. In addition, a decrease in yield of timber in longer logs will amplify this effect, while a higher efficiency in the production process will diminish it.     

Modeling the longitudinal variation of sawn timber grades in Norway spruce (Picea abies (L.) Karst.)

Grades derived from visual assessments of sawn timber are determined by the worst part of each piece. Since grade varies longitudinally in timber, grade yield will decrease if the average length of timber increases. The variation in grade is caused by longitudinal variation in knot properties and other features as they appear on the sawn surface taken into account during grading. The objective of this study is to describe and analyze this variation in Picea abies. The study consisting of 768 boards for which all features that could lead to downgrading were recorded noting position, type and size. Based on this information, all boards were graded according to appearance by Nordic Timber, and strength by INSTA 142. Logistic regression models of grade as a function of position in the stem were developed, and the dependence between responses was taken into consideration by using General Estimating Equations (GEE). The models showed a decreasing trend in grade from the butt end toward the top end of the trees, and the effect was more pronounced in strength grading than in appearance grading. Models with binomial response and different correlation structures were tested, and it was shown that both independent and autoregressive correlation structures could be used. This suggests that a multinomial ordinal logistic regression with a GEE-approach with an independent correlation structure is appropriate for modeling grade in this study.     

Gas pressure measurements during continuous hot pressing of particleboard

Knowledge about the development of the internal gas pressure during hot pressing of wood-based composites is important for the optimization of panel properties and production speed. The gas pressure heavily affects the thermodynamic conditions inside the wood furnish mat, and a too high maximum value at press opening might cause an impairment of the panel properties. In this paper, gas pressure and temperature measurements inside a particle mat while passing through a continuous hot press are presented for the first time. The measurements were performed with a transportable system, consisting of a steel tube attached to a miniature pressure transducer and a data logger. The particleboards had a target thickness of mainly 16 mm, but also of 28 mm and 38 mm, respectively. The measurements show a distinct horizontal gas pressure distribution in both directions, in production direction and across the mat’s width. In contrast, cross-sectional gas pressure gradients were only visible inside the panels after leaving the press. By comparing the gas pressure curves measured for particleboard with those for medium density fiberboard (MDF), characteristic differences became evident. Overall, the gas pressure is higher in MDF compared to particleboard. Finally, a comparison between the gas pressure levels measured for three different panel thicknesses showed a clear relation between panel thickness and gas pressure, with a decreasing panel thickness resulting in an increase in gas pressure. The results of this paper will contribute to our understanding about the events inside wood furnish mats during continuous hot pressing.     

Untersuchung von Buchenschnittholz (Fagus sylvatica L.) hinsichtlich der Eignung für Brettschichtholz

Beech glulam for structural purposes has to be manufactured from strength graded beech lumber. At present one can assume that such material is not available on the market: There is not only a lack of practice in strength grading of beech lumber but also a lack of clearly defined raw material to be strength graded for beech glulam. This article aims to show that beech lumber graded following the Rules of the Measurement and Inspection of Hardwood and Cypress (published by the National Hardwood Lumber Association) has a potential as raw material for beech glulam. 218 beech boards approximately complying with two different grades, an upper and a common grade, were examined in regard to visual strength grading according to DIN 4074-5 (2003). The results show that 90% of the upper grade and 50% of the common grade boards fulfil the requirements for grade LS10 in DIN 4074-5 (2003). This finally enables the manufacture of beech glulam in accordance with strength class GL28. In addition, mechanical strength grading taking into account the modulus of elasticity even enables grading of 80% of the upper and 40% of the common grade boards for GL40.     

Effect of sanding and coating with UV-cured finishes on the surface roughness, dimensional stability and fire resistance of oriented strandboard

Oriented strandboard was sanded and roller-coated with UV-cured finishes. The effects of these treatments on the surface roughness, dimensional stability and fire resistance of OSB were assessed. Sanding reduced the average roughness of OSB, but it had a smaller effect on maximum roughness because sanded boards still contained surface voids between some strands. Sanded boards absorbed less than half of the coating material of unsanded boards, and when they were finished with a UV-cured coating system consisting of filler, sealer and two top coats they absorbed less water and were almost as dimensionally stable as unsanded and coated boards. The swelling of coated boards after 72 h immersion in water was less than one third of that of uncoated OSB. This reduction in swelling compares favourably with that which can be achieved using chemical or thermal modification of OSB. Coated boards were more fire resistant than uncoated ones, but sanding reduced the fire resistance of OSB (coated and uncoated), possibly because it removed part of the densified surface layer from panels. Hence, we conclude that light surface sanding makes it easier and more economical to apply moisture resistant finishes to OSB using roller coating, but it should not be used prior to application of fire-retardant finishes.     

Survival of Listeria monocytogenes after cleaning and sanitation of wooden shelves used for cheese ripening

The effect of cleaning and heat disinfection processes of wooden shelves used for cheese ripening on the survival of Listeria monocytogenes was examined. The cut boards were inoculated with a suspension containing 5.5?×?10⁷ colony forming units (CFU)/ml of L.??monocytogenes. Survival of L.??monocytogenes was investigated in the wood shavings. During the 24-hour incubation period in a humidity chamber, Listeria counts increased by 0.8 log units on average (n?=?9), compared to results 1?h after incubation, indicating the absence of antimicrobial properties of the wood in use. Additionally, after incubation for 24?h at room temperature, the boards were cleaned by soaking them for 15?min in a solution of hot alkaline detergent followed by brushing and rinsing with warm water. Some of the cleaned boards were subsequently heat treated at 80°C for 5?min and at 65°C for 15?min, respectively. The cleaning procedure alone was not sufficient to render L.??monocytogenes from the upper 2?mm wood layer inactive. In the case of both temperature-time combinations for heat disinfection, however, L.??monocytogenes was not detectable. The present study shows that the use of wooden shelves does not affect the hygienic safety of cheeses if such shelves are in good repair and are thoroughly cleaned and sanitized by heat treatment. Therefore, there is no reason to replace wood employed in cheese ripening processes with other materials.     

Laboratory-made cement-bonded OSB with negligible swelling: fact or fantasy?

The purpose of this paper was to evaluate the dimensional stability of cement-bonded oriented strand boards produced from fir strands, which have previously been chemically modified at a weight gain of 10.4%, after 30 min reaction with acetic anhydride. The strands were used to form laboratory boards, which were tested in accordance with EN standards. Boards made from these acetylated strands exhibited negligible thickness swelling even after one month of immersion in water.     

Volume yield and profit in the production of clear finger-jointed Scots pine (Pinus sylvestris L.) boards

The aim of this study was to compare the volume yields and contribution margins in the production of clear finger-jointed boards using lower quality raw materials from four suppliers. The study is based on production statistics from 2005 to 2007 and has been carried out in cooperation with a company which manufactures clear finger-jointed boards for mouldings. The raw material was side-boards of Scots pine (Pinus sylvestris L.) with dimensions of 32 by 175 mm². The four raw material suppliers are geographically distributed in different places in Central Sweden. Parallel with the study, a tool for production follow-up has been developed, to make it possible for the company to continuously follow-up its raw material suppliers. The results of the study show that the cheapest raw material gives the highest clear wood volume yield and the highest contribution margin.     

Full-scale industrial wood floor assembly and structures by welded-through dowels

High-speed dowel rotation welding was used to manufacture a full-scale raised access floor, hence an applicable civil engineering structure, to demonstrate that scaling up of the welding technique is feasible. This was coupled with obtaining a more light weight floor assembly at equal stiffness by maximizing the rigidity of the suspended floor while minimizing the number of timber boards used to build it, and maintaining its vibration frequency high and its level of vibration low. Several assembly and connection combinations of two and three boards linked through welded wood dowels were tried out to determine the resistance of the cross-over joints that had to be used for building the floor. Deformation under 4 points static load of the floor was carried out to determine displacement under load and the floor vibration behaviour was determined using accelerometers. The fundamental first natural frequency measured does satisfy the requirements specified by Eurocode 5 well.     

Use of alkyl ketene dimer (AKD) for surface modification of particleboard chips

The study objective was to impart urea-formaldehyde (UF) bonded particleboards higher and longer-lasting hydrophobicity than that resulting from conventionally used paraffin. Alkyl ketene dimer (AKD) is a paper sizing agent that can theoretically esterify wood compounds and result in a surface modification. Particles were 1) impregnated with an aqueous AKD-solution and cured at 130 °C prior to gluing, or 2) sprayed with a mixture of AKD-solution and UF-resin in a single step. Boards with and without paraffin wax were used as controls. Thickness swelling after 2, 24, and 48 h immersion was decreased by 90, 62, and 59% when the chips were impregnated with AKD in comparison to untreated control boards. Water uptake after 2, 24, and 48 h was reduced by 91, 75, and 60%. AKD-impregnation with subsequent curing decreased the internal bond strength by 53%, indicating that AKD impedes the adhesion. The mixture of AKD and UF-glue did not result in considerable hydrophobicity. Increased methyl/methylene and carbonyl bands in FTIR-spectra after toluene-extraction suggest that AKD partially formed ester bonds at the wood surface.     

Clearance wear and normal force of TiN-coated P30 in cutting hardboards and wood-chip cementboards

This paper presents the clearance wear and normal force characteristics of TiN coated P30 when cutting hardboards and wood-chip cement boards. Hardboards and wood-chip cement boards of low density (about 0.8 g/cm³) and high density (about 1.2 g/cm³) were cut by using TiN coated P30. Cutting tests were performed at a cutting speed of 1000 m/min and a feed rate of 0.1 mm/rev to investigate the effect of the work materials on the clearance wear and normal force characteristics of the TiN coated P30. The experimental results showed that the TiN coated P30, compared to uncoated P30, is more advantageous in reducing the progression of wear on the clearance face, and in retaining lower normal force in cutting both hardboards and wood-chip cement boards. The amount of clearance wear suffered by the TiN coated P30 for the wood-chip cement board was larger compared to that for the hardboard. Though the TiN coated P30 suffers higher wear for the low density wood-chip cement board than the low density hardboard, its normal force, however, is always lower for the low density wood-chip cement board. It was observed that the clearance wear of the TiN coated P30 occurs due to delamination of TiN film and the wear of the substrate occurs after the coating film was disappeared from the substrate.