Impact of the intumescent formulation of styrene acrylic-based coatings on the fire performance of thin painted red lauan (Parashorea spp.) plywood

Intumescent material with commercial resin, such as styrene acrylic copolymer resin, has been demonstrated to be extremely effective in improving the fire performance of wooden materials used for indoor furnishing. The formulation of the coating is a key to its ability to improve flame retardance. This study investigates the enhancement for painted thin red lauan (Parashorea spp.) plywood. The ability of the material to retard flame arises due to the interactions between the four major components of intumescent formulation: (1) a binder resin (BR), styrene acrylic emulsion resin, (2) a carbonizing substance (CS), pentaerythritol (3) a foam producing substance (FPS), melamine and (4) a dehydrating agent (DA), ammonium polyphosphate. This paper compares the fire performance of the plywood when coated with resin of differing BR/CS ratios (designated as the FRS series) and FPS/DA ratios (designated as the FRD series), by means of a cone calorimeter. These intumescent formulations significantly enhanced the fire retardancy of painted plywood, exhibiting lower peak heat release rates, higher expansion of the intumescent layer and longer time to peak heat release rates (PHRR), when compared to plywood panels coated with sole binder resin. However, worse performance was presented when compared with the data for uncoated plywood panels if the intumescent was produced by equal ratio of the four components. Therefore, the formulation of the intumescent is important. Additionally, lower BR contents in the FRS series and lower FPS contents in the FRD series further enhanced flame retardancy. Advanced investigation by IR and ³¹P NMR demonstrated that lower BR and FPS content extends the survival duration of the phosphor-carbonaceous structure of chars. The findings in this study enhance the state-of-the-art understanding of the effect of the intumescent.     

Physical and mechanical properties of plywood produced with 1.3-dimethylol-4.5-dihydroxyethyleneurea (DMDHEU)-modified veneers of Betula sp. and Fagus sylvatica

The dimensional stability and some mechanical properties were tested in plywood produced with veneers modified with 1.3-dimethylol-4.5-dihydroxyethyleneurea (DMDHEU). The experimental design included Betula sp. and Fagus sylvatica impregnated with 0.8 M, 1.3 M, and 2.3 M DMDHEU. The plywood consisted of five veneers glued with a phenolic resin. Dimensional stability tests were conducted after 10 cycles of soaking/oven-drying to determine volume changes and anti swelling efficiency (ASE). The mechanical properties tested were hardness (Brinell), modulus of elasticity in bending (MOE), bending strength (BS) and work to maximum load in bending (WMLB). The modified samples for both species were considerably more dimensionally stable than the untreated samples. The samples of Betula sp. and F. sylvatica modified with DMDHEU presented a MOE and a BS unaffected by the treatment. The WMLB was consistently lower in the modified samples than in the unmodified samples. As determined by the Brinell method, the DMDHEU-modified plywood of the Betula sp. and F. sylvatica was harder than the unmodified plywood.     

Thermal conductivity and water vapour transmission properties of wood-based materials

For several wood-based materials (plywood, OSB, melamine faced board (MFB), particle board and fibre board), the thermal conductivity was determined as a function of the temperature (ranging between 10 and 30 °C) and also the moisture content (from an oven-dry sample up to a moisture content at 80% RH). Furthermore, the water vapour resistance factor of these materials as well as of the coating (at MFB) and the diffusion coefficient were determined under dry cup (performance at low humidity dominated by vapour diffusion) and wet cup (performance at high humidity with liquid water and vapour transport) conditions. Thermal conductivity increases with rising temperature, moisture content and density. Moreover, a clear decrease of thermal conductivity was found with decreasing particle size at the same density level, from solid wood over plywood and particle board to fibre board. The water vapour resistance factor of the wood-based materials increases with rising density and decreases with increasing moisture content. An influence of the particle and fibre board thickness was also revealed. In contrast to the remaining materials, an increase of the water vapour resistance factor with increasing moisture content was measured for the coating. The diffusion coefficient decreases with rising density and moisture content.     

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.     

Effect of radiata pine juvenile wood on the physical and mechanical properties of oriented strandboard

This work analyzes the impact of radiata pine (Pinus radiata D. Don) juvenile wood on the physical and mechanical properties of oriented strandboards (OSB). Radiata pine logs were obtained from 10 trees of a 26-year old managed stand located in the 8th Region of Chile. The experimental design considered the proportion of juvenile wood and strand orientation as independent variables. OSB panels of 0.4 m×0.4 m×12 mm were produced and tested. The results show that the juvenile wood proportion has a significant impact on the physical and mechanical properties of OSB. Strands orientation had a significant impact on all the properties studied with the exception of the modulus of elasticity in bending. However, this impact was small in all cases and would not change panel grade with the exception of linear expansion. In this case, panels made from tangential strands showed a higher linear expansion. According to these results, radiata pine juvenile wood can be used for the manufacturing of OSB up to a proportion of 70% of the oven-dry wood weight without significant losses of the physical and mechanical properties if the juvenile wood strands are located in the surface layers.     

Effect of quality, porosity and density on the compression properties of cork

The compression properties of cork were studied on samples obtained from cork planks of two commercial quality classes (good and poor quality), with densities ranging from 0.12–0.20g?cm^-3 and porosities from 0.5 to 22.0%. The stress-strain curves were characterized by an elastic region up to approximately 5% strain, followed by a large plateau up to 60% strain caused by the progressive buckling of cell walls, and a steep stress increase for higher strains corresponding to cell collapse. The direction of compression was a highly significant factor of variation, with cork showing higher strength for the radial compression. Density influenced compression and cork samples with higher density showed overall larger resistance to compression in the three directions. In the elastic region, an exponential model of Young’s modulus in function of cork density could be adjusted. The effect of porosity on compression was small and the stress-strain curves were similar regardless of the porosity of the samples, although there was a trend toward an overall increase of stress with porosity for higher strains. Porosity was characterised by a high variability in the anatomical features of the lenticular filling material and the presence of collapsed and thick walled lignified cells. The inclusion of a porosity parameter for the modelling of the elastic modulus did not improve the prediction obtained with density-based models. There was no significant difference in the compression properties of cork samples obtained from cork planks of good and poor quality classes.     

Cold tack of urea formaldehyde resins as an important factor in plywood production

The ability of urea formaldehyde (UF) resins to develop cold tack is needed in plywood production during pre-pressing in a cold press to ensure that the veneers stick together, can be transported, and fit into a multi-daylight hot press. The influence of defined factors on the cold tack was analyzed by determining the tensile shear strength of uncured birch veneers bonded with UF resin, and the statistically significant impact factors were determined. The factors tested were lay-up time, resin amount, resin age, moisture content, veneer temperature and pre-press time. Moisture content and veneer temperature had the highest impact on the cold tack of UF resins. A negative impact of high moisture content on the tensile shear strength and therefore on the cold tack of UF resins was proven as well as a positive impact of a comparably high (30 °C) veneer temperature. Lay-up time and pre-press time showed a minor impact on the tensile shear strength. Models were created using Design-Expert software to calculate the optimum operation conditions for cold tack.     

Mechanical properties of wood treated with PF-pyrolytic oil resins

Jack pine and sugar maple wood samples were treated in a two-step process that involved first a copper chloride or a copper chloride-sodium borate mixture and then a phenol-formaldehyde resin containing a certain percentage of softwood bark pyrolytic oil. Various controls were also prepared for comparison. The modulus of rupture (MOR) of jack pine samples was generally negatively affected by the treatment, the observed values being lower than those of the controls. These values were statistically lower or equal to those of untreated samples. On the other hand, the modulus of elasticity (MOE) of treated jack pine samples was not found to be statistically different from that of the untreated wood. Mechanical properties behaved in a similar way for sugar maple wood. Unlike the other treatments, copper chloride–sodium borate and the resin containing 85% of pyrolytic oil as phenol substitute appeared to slightly improve the mechanical properties of both wood species even if not significantly so. Treatment with PF-pyrolytic oil resin resulted in similar or slightly better mechanical properties when compared to CCA-treated wood. The amount of treating water soluble salts retained in samples after the first treatment had a significant impact on MOR of both wood species and on MOE of sugar maple.     

Characterization of a formaldehyde-free cornstarch-tannin wood adhesive for interior plywood

This study investigated the physical properties (rheological and thermogravimetric analysis) of cornstarch-tannin adhesives and the mechanical properties (dry tensile strength and 3-point bending strength) of plywood made using cornstarch-tannin adhesives. This adhesive was evaluated for its utility in interior plywood manufacture. The optimum cure temperature and cure time of cornstarch-tannin adhesives were 170°C and 4?min, respectively. Plywood bonded with formaldehyde-free cornstarch-tannin adhesive exhibited excellent mechanical properties comparable to commercially available phenol-formaldehyde plywood adhesives. It was found that cornstarch-tannin panels which do not contain formaldehyde and with an emission equal to that of heated but unbound wood can be obtained by the use of hexamethylenetetramine (hexamine) as hardener. The work has indicated that an environmentally friendly wood adhesive can be prepared from a natural renewable resource (cornstarch and wattle tannin) for bonding interior-type plywood.     

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.     

Operations research applications in the plywood industry

There are several areas in the plywood industry where Operations Research techniques have greatly assisted in better decision-making. These have resulted in improved profits, reduction of wood losses and better utilization of resources. Realizing these, some of the plywood manufacturing firms in the developed countries have established separate Operations Research departments or divisions. In the face of limited raw-material resources, raising costs and a competitive environment, the benefits attributable to the use of these techniques are becoming more and more significant.     

Untersuchungen zum Kegelstirnplanfräsen und Stirnplanfräsen am Institut für Werkzeugmaschinen der Universität Stuttgart

Slab milling with a conical shaped milling tool and slab milling with a face milling tool are wood machining techniques which meet the current requirements of wood machining and processing (e.g. changing batch sizes, flexible machines and equipment). That is why the Institute for Machine Tools at University of Stuttgart has already conducted comprehensive basic research in this field (Heisel 1997). Research on slab milling with a face milling tool was especially promoted as an alternative to slab milling with a peripheral milling tool (also known as planing) due to its low noise emission and low energy consumption. Amongst others, slab milling with a face milling tool as pre-milling procedure when calibrating wood-based panel products was examined under technical and economic aspects. The results showed higher service life and continuously better surfaces when choosing the right geometry of the cutting tools as compared to conventional slab milling with a peripheral milling tool. Notwithstanding the high costs, diamond cutting edges are more cost-effective than carbide insert tips due to their longer service life (Heisel 2004).     

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.     

Beobachtungen über das Abstumpfungsverhalten beim Fräsen von Schichtstoff-Verbundplatten

Zusammenfassung Der starke Wettbewerb auf dem Weltmarkt für Sperrholz, der vor allem durch die Entstehung von neuen Sperrholzwerken in den Entwicklungsl?ndern versch?rft wurde, zwingt die Sperrholzindustrie zur ?u?erstm?glichen Rationalisierung. Die dadurch angestrebten Einsparungen sollen vor allem Arbeitskr?fte, Lohnkosten und Aufwendungen für das Rohmaterial betreffen. Die neueste Entwicklung auf dem Gebiete der Sperrholz- und Furniererzeugungsmaschinen geht von diesen Gesichtspunkten aus und versucht, durch fortschreitende Mechanisierung und Automatisierung die neuen Anforderungen zu erfüllen. Es werden Maschinen und maschinelle Anlagen hinsichtlich ihrer Wirkungsweise sowie nach ihrem technischen und wirtschaftlichen Nutzen beschrieben. Es zeigt sich, da? beim Zusammenwirken aller neuen Einrichtungen Leistungssteigerungen bis zu 100% erzielt werden k?nnen. Wichtig ist hierbei, da? sich die Rationalisierungsma?nahmen, z. B. in einem Sch?lfurnierwerk, auf alle Fertigungsabschnitte vor und hinter der Sch?lmaschine erstrecken. Alle Einzelmaschinen müssen dabei in ihrer Leistung auf die jeweiligen Fertigungsbedingungen (Rohmaterial und Fertigungserzeugnisse) abgestimmt werden. Entsprechende Beispiele sind geschildert und in Bildern dargestellt.

---

Observations on the blunting behaviour in the milling of overlayed sandwich boards

Summary The strong competition on the world market for plywood, which was intensified mainly through the establishment of new plywood plants in the development countries, forces the plywood industry to seize utmost rationalization measures. The savings thus aimed at, shall above all regard manpower, wages and cost for raw material. The latest development in the field of plywood and veneer production machines is based on these points of view and through progressive mechanization and automation tries to meet with the new demands. Machines and mechanical installations are described with respect to their mode of operation as well as to their technical and economic use. It appears that in combining all new installations, the output can be increased by up to 100%. It is, however, of importance that rationalization measures, e. g. in a peeler veneer plant, cover all manufacturing processes before and behind the peeler. All single machines have to be, in regard to their efficiency, adapted to the individual production conditions (raw material and finished goods). Corresponding examples are given and demonstrated in pictures.

---

---

Mitteilung aus dem Institut für Werkzeugmaschinen und Fertigungstechnik der Technischen Hochschule Braunschweig, Versuchsfeld für Holzbearbeitung     

Green manufacturing practices among wooden furniture manufacturers in Malaysia

The adoption of green manufacturing practices by the Malaysian wooden furniture industry is limited as is shown by a questionnaire-based survey of wooden furniture manufacturers. The lack of price premium for green furniture products and the high cost involved in adopting such practices have been identified as the major restraints. Currently most green manufacturing practices are related to the use of environmental-friendly materials.     

PF-bonded particleboards from AKD-modified chips

Alkyl ketene dimer (AKD) was used as a hydrophobic agent for PF-bonded particleboards. In contrast to conventionally used paraffin, AKD can be covalently bonded to the chip surface by esterification with wood hydroxyl groups. FTIR analyses before and after toluene extractions indicated that only a small amount of the applied AKD is chemically bonded. Wettability studies on veneer strips suggested that particularly the bonded AKD accounts for the surface hydrophobicity. A subsequent spraying of AKD and PF resin on the chips that were pressed for 15, 30, and 60 s?mm^-1 (Process 1) did not result in decreased thickness swelling and water uptake as compared to the control boards. In Process 2, chips were cured (130 °C/6, 12, 24 h) prior to pressing (15 s?mm^-1) which did not impart significant hydrophobicity either. The low efficacy of AKD as hydrophobic agent in Process 1 is attributed to the hydrolysis of AKD by water vapor during pressing. The low hydrophobic effect of AKD in Process 2 is ascribed to a saponification of esters between AKD and wood hydroxyl groups by the alkaline PF resin.     

Estimation of sawn face width of Sugi (Cryptomeria japonica D. Don) logs by cross-sectional shape with approximation profile

In sawing systems producing high quality lumber from medium diameter sugi (Cryptomeria japonica D. Don) logs, operators must carefully decide the amount of setworks taking into consideration the sawn face width and appearance of knots so that the work efficiency often suffers considerable reduction. A simple mathematical method to estimate the sawn face width on the basis of cross-sectional shape with an approximation profile was proposed. Ninety cross-sectional shapes were measured using a newly developed measuring device and estimated as a circle or an ellipse, where 89% of the cross-sectional shapes fit the ellipses. The error margin in 72–75% of the sawn face width estimates was 2.0 cm or less, which was equal to the conventional value achieved by skilled operators.     

Eigenschaften von extrudierten Holz-Kunststoff-Werkstoffen auf Basis von Refiner-(TMP-)Fasern und Hanffasern

At present, wood particles (wood flour) with a low aspect ratio are mostly used as fillers in wood-plastic composites (WPC). Reinforcement of WPC and improved strength properties may be achieved by using real wood fibres with a high aspect ratio. WPC based on 70% (wt.) refiner (TMP) wood fibres and mechanically processed hemp fibres were extruded in a two-step process. Eleven compounds based on the two natural fibre types were prepared using a thermokinetic mixer and extruded in a conical, counter-rotating twin-screw extruder. Additional formulation components were polypropylene fibres, maleic anhydride-modified polypropylene (MAPP) and lubricant. It was determined that compounding in a thermokinetic mixer is a useful step for processing of WPC with refiner and hemp fibres as little fibre damage occurred. However, during extrusion, both natural fibre types were severely shortened due to strong shear forces, and homogeneous dispersion of fibres in the matrix was not achieved. WPC based on hemp fibres displayed the best strength properties of the formulations tested. Current extruder screw and die configurations need to be modified to achieve improved fibre reinforcement and to create new, structurally demanding applications for WPC. Using dynamic mechanical analysis, fibre-matrix adhesion of WPC was investigated, and activation energies for glass transition of selected formulations were calculated. Activation energy for formulations containing MAPP was higher than for WPC without MAPP. This indicates that better fibre-matrix adhesion was achieved in formulations with MAPP.     

In-treatment cooling during thermal modification of wood in soy oil medium: soy oil uptake, wettability, water uptake and swelling properties

Thermal modification of wood is a process which has gained wider acceptability as an alternative to chemical treatment in wood preservation. In order to maximize the benefits of this technique several options have been adopted including the use of soy oil in transferring the heat to the wood. Available information on thermal treatment in general and the oil method in particular show that there is need for further investigations on the possibilities of improving the available options in order to evolve new techniques. Thermal treatment of ponderosa pine (Pinus ponderosa P Laws ex C Laws) and black spruce (Picea mariana (Mill) BSP) in soy bean oil was carried out at 220 °C for 2 hours followed by cooling inside the hot oil 180 °C and 135 °C. The surface wettability, (contact angle), amount of oil uptake, water absorption and thickness swelling were determined thereafter. The oil uptake ranged from 88 to 93.3% in the permeable ponderosa pine sapwood and from 6.1 to 11.3% in the refractory black spruce with the uptake increasing with cooling time but decreasing with increasing depth of wood in both species. Thermal modification in soybean oil increased the wettability of the surface to water (reduced contact angle). However, there were no significant changes to the surface energies due to in-treatment cooling, as determined by contact angles of water, glycerol, ethylene glycol, and formamide. There were reductions in the hydrophilic behaviour and swelling of wood as a result of the thermal treatment; in-oil cooling resulted in greater hydrophobicity and dimensional stability in the wood. In both species, there were greater reductions in water uptake and swelling with increasing cooling time.     

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.