Potential of pulp and paper secondary sludge as co-adhesive and formaldehyde scavenger for particleboard manufacturing

This study investigated the potential of secondary sludge (SS) as urea–formaldehyde (UF) co-adhesive for particleboard manufacturing. Three proportions of SS from three conventional pulping processes were added in the formulation of particleboard manufacturing. A 3³ factorial design was used. All panels were tested for thickness swell (TS), linear expansion (LE), internal bond strength (IB), flexural modulus of elasticity (MOE), flexural modulus of rupture (MOR) and formaldehyde emission. Results indicated that particleboards made with SS from thermomechanical pulp (TMP) and kraft pulp (Kraft) met the ANSI standards for LE, IB, MOE, and MOR (with 7 and 9 % UF). However, the TS of panels made with SS was higher than that of control panels and adding SS to the formulation affected negatively this property. Most of the properties studied in the particleboards made with SS from chemical–thermomechanical pulping (CTMP) process failed to meet the ANSI standards. The main advantage of using SS as co-adhesive is the reduction of formaldehyde emission, in the best case here, about 50 %, with CTMP sludge added, of the particleboards.     

Some Properties of Composite Panels Manufactured from Eastern Redcedar (Juniperus virginiana L.) Using Modified Starch as a Green Binder

The objective of this study was to evaluate basic properties of particleboard panels manufactured from Eastern redcedar (Juniperus virginiana L.) using modified starch and low percent of urea formaldehyde as binder. Experimental panels in the form of three-layer configuration were made from the raw material at two density levels. Bending characteristics, namely, modulus of elasticity (MOE), modulus of rupture (MOR), and internal bond strength (IB) in addition to dimensional stability and surface roughness of the samples were determined. The highest MOE and MOR values of the samples with 0.80 g/cm³ density level were found as 2344.32 and 12.14 MPa, respectively. Both bending and IB values of the samples were comparable to those of commercially manufactured panels from other species. It appears that dimensional stability of the panels needs to be enhanced. Based on the findings in this work, modified starch could have potential as green binder in particleboard panels manufactured from Eastern redcedar without having substantial adverse influence on their properties.     

The manufacture of particleboards using mixture of reed (surface?layer) and commercial species (middle layer)

This research was conducted to investigate the suitability of reed (Arundo donax) as a substitute for wood in laboratory made 3-layer particleboard in order to supplement the supply of raw material for the Iranian particleboard industries. The ratio of the mixture of reed and wood particles were 20:80, 30:70, and 40:60, respectively, in the surface and middle layers. Press temperatures were chosen at two levels of 165 and 185?°C. Three levels of urea formaldehyde resin were selected for the surface layers, namely: 8, 10, and 12 percent. The experimental panels were tested for their mechanical strength including modulus of elasticity (MOE), modulus of rupture (MOR), internal bonding (IB) and physical properties (thickness swelling and water absorption) according to the procedure in DIN 68763. In general, the results show that reed has a positive effect on the mechanical and physical properties of boards. In this research, the treatment with 40% reed, 12% resin in the surface layers and a 185?°C press temperature has resulted in an optimum reed board product.     

Improving the physical and mechanical properties of particleboards made from urea–glyoxal resin by addition of pMDI

The effect of pMDI on physical and mechanical properties of the particleboards made from urea–glyoxal resin was investigated. The nontoxic and ecofriendly urea–glyoxal (UG) resin was synthesized under weak acid conditions, and its different properties were measured. Then, pMDI at various contents (4, 6 and 8% on resin solids) was added to the UG resin prepared. The thermal and physicochemical properties of the resins prepared as well as their water absorption, flexural properties (flexural modulus and strength) and internal bond (IB) strength of the particleboard panels bonded with them were measured according to standard methods. According to the physicochemical results obtained, the addition of pMDI significantly accelerated the gel time and increased the viscosity and solids content of UG resins. Differential scanning calorimetry indicated that the addition of pMDI decreases the onset and curing temperatures of the UG resin. Physical analysis results of the panels indicated that the particleboards made from UG resins with isocyanate yielded lower water absorption when compared to those bonded with the control UG resins. Based on the findings of this research work, the mechanical properties of particleboard panels bonded with UG resins could be significantly enhanced by the addition of increasing percentages of pMDI. The panels having 8 wt% pMDI exhibited the highest flexural modulus, flexural strength and IB strength value and the lowest water absorption among all the panels prepared.     

Untersuchungen an Holzwerkstoffen für Möbel-Einlegeböden

The bending deflection of six different wood based materials used as shelves in the manufacture of furniture (unlaminated particleboard, melamine laminated particleboard, veneered particleboard, block-board, plywood and solid wood panel) of approximately equal thickness was investigated. Deflection data were obtained by applying loads to the board surfaces for a period of 28 days followed by a period of unloading of equal length. For all types of particleboards the deflections appeared to be greater than for the other wood based panels. The lowest bending deflection was found for the solid wood panel while plywood performed better than blockboard. Surface treatments improved the performance of particleboards but veneering appeared to be more advantagous than laminating with melamine. The bending deflection of the tested panels is strongly related to their bending strength and modulus of elasticity.     

Emissions during combustion of particleboard and glued veneer

The combustion of particleboard and glued veneer was studied in order to evaluate if there are any negative effects on the environment from incineration of waste with adhesive. The particleboard was made with urea formaldehyde (UF) resin and the veneers were glued with different types of adhesives, UF, polyvinyl acetate, emulsion polymer isocyanate (EPI), melamine urea formaldehyde (MUF) and phenol resorcinol formaldehyde. The combustion tests were carried out in a fluidised sand bed reactor with a good oxygen supply at temperatures between 500°C and 1000°C for particleboard and at 750°C and 850°C for glued veneer. The emissions were compared with the emissions from combustion of pure wood and pellets made from wood. The results show that the emissions from both particleboard and glued veneer are similar to the emissions from pure wood. The only main difference is that the nitrogen oxide (NO_x) is increased when particleboard and nitrogen-containing adhesives, like UF, EPI and MUF, are combusted. The nitrogen from the adhesive is only to a minor extent converted to NO_x, e.g. only 4% of the nitrogen in particleboard gives NO_x.     

Paricá (Schizolobium amazonicum) and embaúba (Cecropia sp.) as new raw materials for particleboards

In this work two potential new species for forest plantation projects in Northern Brazil were evaluated for their suitability in particleboard production. The main evaluated parameters of the laboratory boards were pH value and buffer capacity of the particles, compaction ratio, thickness swelling, modulus of elasticity (MOE), modulus of rupture (MOR) and internal bond (IB). The results showed that both species are highly suitable for particleboard production as they presented low densities (400–430 kg/m³), light color, good compressibility and no apparent adverse reactions after UF-resination.     

On the performance of a melamine–urea–formaldehyde resin for decorative paper coatings

The decorative laminates industry is a highly competitive industrial sector. To be profitable, manufacturers of impregnated papers for surface laminated MDF and particleboards need to significantly reduce their production costs. Melamine formaldehyde resin (MF) formulations are commonly used for impregnation and coating of such papers, melamine being an important, but costly raw material used in high quantities. While MF is substituted by cheaper urea formaldehyde resins (UF) in the core impregnation, for paper surface films pure MF is used. Therefore, a further reduction in cost could be achieved if a portion of the melamine in the surface film was replaced by urea. In the present contribution, recent results of technological tests on paper laminates using a novel melamine–urea–formaldehyde resin (MUF) formulation are reported and their performance is compared to traditional surfaces made from MF.     

Utilization of bark flours as additive in plywood manufacturing

Increasing demand for wood based panel products and shortage of wood as raw material have triggered many efforts to utilize residues generated annually by the forest industries including a large portion of bark in panel production. In this study, the effects of using bark flours as additives obtained from different wood species (walnut, chestnut, fir and spruce), having much polyphenol content, on some physical and mechanical properties and formaldehyde emission of plywood panels were examined. Wheat flour, which has been used widely as additive in plywood manufacturing, served as control. Plane tree (Platanus orientalis) logs were obtained for veneer manufacturing. Urea formaldehyde (UF) resin with 55 % solids content was used as adhesive. The bonding shear strength, bending strength, modulus of elasticity (MOE), density, equilibrium moisture content and formaldehyde emission of plywood panels were determined according to related standards. It was found that the use of flours obtained from the barks of chestnut and fir trees in the glue mixture decreased the formaldehyde emission of panels. The bonding strength values of the test panels made using the glue mixture including the flour of walnut and spruce barks as additive were lower than those of the panels with adhesive containing the flour of fir and chestnut barks. The panels manufactured with adhesives including the flour of fir bark gave the highest bending strength and modulus of elasticity values.     

Influence of utilization of?bagasse in surface layer on bending strength of three-layer particleboard

It is well known that wood species and particle size used influence the bending strength of three-layer particleboard. The objective of this study was to investigate the influence of using bagasse particles in surface layer on bending strength of three-layer particleboard panels. The ratio of the mixture of bagasse and wood particles was 3:7 and 4:6 in the surface and middle layers, respectively. Press temperatures were chosen at two levels of?165 and?180?°C. Three levels of urea formaldehyde resin were selected for the surface layers, namely: 8, 10, and 12?percent. Bending strength of the panels was determined according to the procedure of European Union (EN) Standard. The results show that bagasse has a positive effect on the bending strength of boards. In this research, the treatment with 40% bagasse and 12% resin in the surface layers and a?180?°C press temperature has resulted in an optimum bagasse board product.     

Some investigations concerning density profile,internal bond and relating failure position of particleboard

Testing machines for the measurement of density profiles of wood based panels have become a wide-spread tool in production laboratories. New equipment for the in-line measurement of density profiles was presented recently. The high significance of the density profile for the properties of particleboard ticleboard is well known for some years. Maximum densities in the outer zones of the profile are closely related with MOE, bending strength, water uptake and swelling. Minimum density is closely related with shear modulus (G _(xz , (G _(yz ), shear strength and compression strength. However, results about the correlation of the minimum density with internal bond are contradictory, and statements concerning the failure positions relating to the internal bond-test are published rarely. For five different thicknesses of furniture grade particleboard the relation between internal bond, parameters derived from the density profile and the respective failure position were determined. Indeptendent of panel thickness the failure position was found to be in a range of the 25-75%-panel thickness. A correlation between the failure position and parameters derived from the density profile could not be found. There appear to be three predetermined failure lines (35, 50, 65% of panel thickness). The correlation between mean density and internal bond is high for the total sample (r=0.81). The correlation between minimum density and internal bond is lower, especially with regard to results relating to a single panel thickness.     

The effect of fine strands in core layer on physical and mechanical properties of oriented strand boards (OSB) made of beech (Fagus sylvatica) and poplar (Populus tremula)

This paper discusses the influence of three different content levels of fine strands in the core layers on the physical and mechanical properties of European beech and poplar oriented strand boards (OSB). The results show that increasing the fines content in the core layer from 10 to 50 %, based on total board weight has no significant effect on bending strength and modulus of elasticity (MOE). All panels exceeded the minimum requirement for bending strength and MOE set by EN standards. The highest modulus of rupture (MOR) and modulus of elasticity (MOE) was determined for panels solely made of poplar with different level of fines content. Increasing the amount of fines in the core layer raised the internal bond (IB). Panels made with 30 % fines in the core layer showed highest internal bond strength values. As the fines content increased from 10 to 50 %, thickness swelling decreased. Water absorption after 24 h showed the same declining trend as thickness swelling.     

芦苇／木材复合包装材料制造工艺的研究

研究利用芦苇为原料制造单层刨花板的可行性。分别制备了纯杨木、纯芦苇、杨木/芦苇刨花板,按照国家标准的要求,对板材的物理性能（吸水厚度膨胀率）和力学性能（静曲强度、弹性模量、内结合强度）进行了测试。测试了芦苇添加量及热压时间对芦苇/木材复合材料性能的影响。试验结果表明,纯芦苇制造的刨花板的质量最差。杨木/芦苇刨花板的性能随着混合原料中芦苇含量的上升而下降,而适当延长热压时间可提高板材的物理力学性能。芦苇添加量不高于50％时,杨木/芦苇刨花板的力学性能达到国家标准的要求。     

Fatigue life of oil palm wood (OPW) for furniture applications

Oil palm wood (OPW) from different portions of the trunk was tested on edge to evaluate its fatigue life, a criterion necessary for furniture application. It was found that as the stress levels increased, as a percentage of its MOR, a reduction in fatigue life was observed. Further, the phenol–formaldehyde resin impregnated OPW from the middle and center portion of the oil palm trunk showed comparable fatigue life with those untreated samples from the periphery of the trunk, and hence, the allowable design stress for the OPW for furniture applications could be set at 40 % of its MOR. The results show oil palm wood of acceptable density can be successfully used for furniture applications.     

Dimensional stability of heat oil-cured particleboard made with oil palm trunk and rubberwood

Dimensional stability of heat oil-cured particleboard made with admixture of oil palm trunk and rubberwood was evaluated. Particleboard made with oil palm trunk had better dimensional stability due to better compact ratio and lower hygroscopicity than rubberwood. Combination of repellent properties of oil and application of heat had greatly reduced the hygroscopicity of particleboard by decreasing its equilibrium moisture content, thickness swelling and water absorption.     

Hydroxymethyl furfural-modified urea–formaldehyde resin: synthesis and properties

Considering the importance of urea–formaldehyde (UF) resins in the wood industry, this work reports on a new bio-based modification of UF resins. The use of 5-hydroxymethyl furfural (HMF) is motivated by the current concerns about the effects of formaldehyde on human health. UF and urea–HMF–formaldehyde (UHF) resins were synthesized by an alkaline-acid method and characterized by FTIR, thermogravimetric analysis, and differential scanning calorimetry. The UHF, as a newly modified polymeric resin, was thermally characterized, and it was found that its thermo-stability and char yield was improved. In order to investigate the performance of the UHF, the preparation of particleboards with the UHF as adhesive, as well as its film formation ability have been studied. The UHF films formed on wood panels were uniform without any crack. Film formation ability of the UHF resin was improved due to the presence of more hydroxyl groups as well as furan rings of the HMF moieties resulting in more activated groups to be bonded by wood. Furthermore, formaldehyde release of the particleboards bonded by UHF was significantly lower than that of which bonded by the UF resin. Lab particleboards using the UHF resins showed higher modulus of rupture, modulus of elasticity, and internal bond compared to boards with UF resins, as well as lower water absorption and thickness swelling. Based on these results UHF resin can be considered as a possible candidate as adhesive for wood and wood based panels.     

Evaluation on some finishing properties of oil palm plywood

Oil palm is the largest and most important plantation crop in Malaysia. The oil palm generally lasts for 25–30 years before the next replantation is done. Substantial amount of biomass in the form of palm trunk results from plantation cycle. This resource is simply left on the ground to decay and is not used as raw material to manufacture any kind of value-added products. The objective of this study was to investigate the possibility of manufacturing plywood from oil palm trunks and to evaluate some of the finishing properties of such experimental panels in comparison to those from Shorea sp as control samples. Three-ply plywood samples were produced from 5 mm thick veneers of oil palm using urea formaldehyde adhesive. Three types of chemicals, namely nitrocellulose, pre-catalyzed lacquer and polyurethane were used to finish experimental panels. The surface finished with nitrocellulose had the lowest contact angle on raw surface of oil palm plywood and wood. The average cross cut tape index of oil palm plywood was comparable to Shorea sp. All finishing materials of oil palm plywood produced impact rating of 4 except for surface finished with nitrocellulose while finishing on wood indicated an impact rating of 3. Oil palm plywood had higher weight loss compared to Shorea sp. Based on results from contact angle, cross cut tape index, impact rate test, weathering, and soil burial test methods it appears that the samples showed acceptable finishing properties comparable to those of solid wood.     

Hydrothermal treatment of strand particles of pine for the improvement of OSB panels

The aim of this study was to evaluate the effect of hydrothermal treatment in strand particles of pine used for oriented strand boards (OSB) production. Strand particles of pine were hydrothermally treated at 130, 150 and 170 °C for 7 and 21 min, for the determination of chemical composition, pH, equilibrium moisture content, particles mass loss, and contact angle of these particles with phenol–formaldehyde resin. Afterwards, OSB panels were produced using 8% phenol–formaldehyde resin, with a nominal density of 0.7 g/cm³, and pressing cycle at 170 °C and 3.14 MPa for 8 min. Then, the panels were kept in climate chamber until mass stabilization for the determination of their physical and mechanical properties, and for comparison with the European standards. The hydrothermal treatment in the particles decreased carbohydrate, especially mannan, xylan and arabinans, resulting in reduced equilibrium moisture content, pH, and contact angle, and increasing buffer capacity and mass loss. In OSB panels, treated particles caused the drop in the equilibrium moisture content and reduction of the thickness swelling of the panel, without reducing the mechanical strength, making the hydrothermal treatment very attractive. The hydrothermal treatment at 170 °C for 7 min allowed the resulting OSB panel being classified into the categories 1 and 2 of the European standard, expanding its range of use.     

Formaldehyde emission from particleboards manufactured with waste materials from plywood industry

Peeling cores, dried veneer residues and plywood edge pieces containing adhesive are used for particleboard production. So, in this study, the effect of waste materials from plywood industry used for particleboard manufacturing on the formaldehyde emission of panels was investigated.     

Bonding behaviour of chemically modified wood particles for board production

The objective of this paper was to evaluate the bonding behaviour of chemically modified wood particles towards an isocyanate resin system, as determined from internal bond strength of the board, and to determine which resin system, isocyanate or formaldehyde is suitable for use in boards made from modified raw material. It was found that chemical modification of wood chips and strands did not significantly affect the bonding efficiency of isocyanate resin, but the bonding efficiency of formaldehyde resins was strongly influenced. This behaviour can be a consequence of the usage of a less pH dependent resin that is fully cured during hot pressing in combination with the high mobility of the resin which causes penetration to considerable depth into compressed particles repairing weak zones, which are created during the modification process as chips are exposed to elevated temperatures, by sticking them together. It is suggested therefore, that the isocyanate resin system is more suitable for use in boards made from modified raw material than the formaldehyde resin system.