Improved water resistance of particleboards bonded with glutaraldehyde-blended UF resin

One-layer particleboards were bonded with a UF-glutaraldehyde adhesive system. It was shown that 5 wt % of the glutaric aldehyde in the glue mix can reduce swelling and absorptivity of the boards without deterioration of their mechanical parameters below the requirements of the respective standards.     

Quality assessment of pellets and briquettes made from glued wood waste

European Journal of Wood and Wood Products - In accordance with sustainable economic and social development, Europe supports the use of energy from renewable sources to decrease the use of fossil...     

Shear strength of glued laminated timber made from European beech timber

This paper describes an investigation into the shear strength of glued laminated timber (GLT) made from European beech. Special consideration was paid to the possible strength influence of a frequently occurring discolouration of the timber, termed red heartwood, which is inherent to the species. The beech lamellae were visually graded according to German hardwood grading standard DIN?4074-5. Grade LS13, conforming to European hardwood strength class D40, was split into two sub-grades LS13? and LS13+. Additionally, modulus of elasticity (MOE) was determined by ultrasound pulse, longitudinal vibration and static tension tests. Sub-grade LS13+ showed a mean density and MOE of 690 kg/m³ and 14,800 N/mm², respectively. The GLT shear strength was evaluated by means of four-point bending tests on structural sized I-shaped beams with a depth of 0.6?m and a span to depth ratio of 5:1. The slightly inhomogeneous build-up of the cross-section conformed to glulam strength class GL42c. Two beam samples were investigated, each with seven specimens, where one grouping had no red heartwood and the other with a high red heartwood in the web laminations. Additionally block shear tests on bond line strength were performed with standardized small specimens according to EN?392. Neither the beam shear capacity tests nor the bond line block shear tests revealed an influence of the red heartwood discolouration on strength. The fifth-percentile value of shear strength of all beams was 3.5?N/mm². The results of the block shear tests indicate that the present requirements on minimum block shear strength are set too low in the European standard EN 386 with regard to beech GLT.     

Procedural influence on the properties of particleboards made from AKD modified chips

Wood chips were treated with alkyl ketene dimer (AKD) using three different processes to impart water resistance to particleboards. In the first process, AKD was blended with UF resin. Thickness swelling and water uptake after a 24 h immersion period (20 and 69%) were lower than in the control boards (28 and 81%) but were higher than in the paraffin references (10 and 22%). In process 2, AKD and UF resin were sprayed separately on the chips resulting in a greater reduction of thickness swelling (15%) and water uptake (49%) than in process 1. Paraffin references revealed a thickness swelling and water uptake of 7 and 25%, respectively. An extension of the pressing time in processes 1 and 2 did not increase water repellence. In process 3, particleboards were made from AKD-treated chips that were cured at 130 °C (24 h) prior to gluing. They showed a thickness swelling of 7% and a water uptake of 25%, whereas particleboards with paraffin exhibited levels of 8 and 29%. The thickness swelling and water uptake of boards with AKD increased when the curing time was reduced from 24 to 12 to 6 h (130 °C). Changing the curing temperature from 130 to 100 °C (12 h) had no effect on board properties. The IB of boards made from pre-cured chips with AKD (24 h/130 °C) was 44% lower than in controls and 35% lower than in paraffin references. This indicates that AKD impedes the adhesion.     

The influence of scavengers on VOC emissions in particleboards made from pine and poplar

This paper studies the performance of scavengers on Volatile Organic Compound (VOC) emissions from wood-based composites. Particleboards made from maritime pine (Pinus pinaster Ait.) and European poplar (Populus spp.) were produced with a UF resin doped with melamine and two scavengers, sodium metabisulfite and urea. VOC emission was measured according to EN ISO 16000. Particleboards made from pine present much higher total VOC (TVOC) emissions than boards made from poplar. Pine emits a higher amount of terpenes, but also aldehydes, acids and terpenoids, while poplar emits mainly acetic acid. Sodium metabisulfite showed an excellent ability to reduce aldehydes emission, which represents nearly 50 % of total emission of particleboards made from pine. When sodium metabisulfite was applied to particleboards made from poplar, reduction of TVOCs was not significant due to the low contribution of aldehydes to TVOCs. Urea presents a low reduction in TVOCs for both wood species.     

On the warping behaviour of particleboards coated with melamine formaldehyde resin impregnated papers

Impregnated papers are widely used as decorative, protective and balance sheets in decorative laminates for the furniture, flooring and building industries. One important property of such composites is their warping behaviour. Especially for laminate flooring, warping of the lamellae is undesirable. In the present study the influence of important process parameters in the manufacturing of impregnated papers is quantitatively analyzed based on an industrial experiment carried out at an Austrian impregnation plant. Catalyst concentration, moisture content, resin loading and base paper supplier were varied according to an experimental design. The thermal properties of the impregnated papers and the warping behaviour of the corresponding boards were evaluated using response surface methodology. The resulting models allowed quantifying the relative importance of single factors on composite warp and defining the useful working range. Determination of the thermal properties of impregnated papers using DSC and TMA was not sufficient to predict laminate warp.     

On the warping behaviour of particleboards coated with melamine formaldehyde resin impregnated papers

Impregnated papers are widely used as decorative, protective and balance sheets in decorative laminates for the furniture, flooring and building industries. One important property of such composites is their warping behaviour. Especially for laminate flooring, warping of the lamellae is undesirable. In the present study the influence of important process parameters in the manufacturing of impregnated papers is quantitatively analyzed based on an industrial experiment carried out at an Austrian impregnation plant. Catalyst concentration, moisture content, resin loading and base paper supplier were varied according to an experimental design. The thermal properties of the impregnated papers and the warping behaviour of the corresponding boards were evaluated using response surface methodology. The resulting models allowed quantifying the relative importance of single factors on composite warp and defining the useful working range. Determination of the thermal properties of impregnated papers using DSC and TMA was not sufficient to predict laminate warp.     

静电纺聚丙烯腈/线性酚醛树脂碳纳米纤维电极的制备及其性能

为研究炭化温度对碳纳米纤维电极性能的影响,采用静电纺丝法制备了聚丙烯腈/线性酚醛树脂(PAN/PF)纳米纤维,然后经不同温度炭化处理得到不同结构与性能的碳纳米纤维,并制备成电极材料.对碳纳米纤维的表面形貌、比表面积、孔结构、石墨化程度和元素含量,以及碳纳米纤维电极的电化学性能进行测试与表征.结果表明:PAN/PF碳纳米...     

Optimization of the process of pressing particleboards by means of modifying phenol-formaldehyde resin with amide polymers

The paper investigates the effect of PF resin modification on the possibility of shortening the time or reducing the temperature when pressing particleboards glued with phenolic resin modified with amide polymers, and on the physical and mechanical properties of the boards. The applied activators of PF resin were as follows: polycaprolactam and its N-hydroxymethylene derivative, polyacrylamide and acrylamide. The scope of the research included studies regarding the influence of these modifiers upon properties of fluid PF resin, the production of particleboards at various pressing conditions and the determination of their physical and mechanical properties. The obtained results show that the modification of PF resin with amide polymers makes it possible to increase the reactivity of the resin and to produce, in a shorter time or at a lower temperature, particleboards with comparable or better properties than those of the boards produced under industry-like conditions.     

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.     

Preparation of high-purity phosphatidylcholine from rapeseed oil gums by cation ion-exchange resin

High-purity phosphatidylcholine (PC) was widely used in the food and pharmaceutical. The purification of PC from rapeseed gums is the urgent need to be resolved. In this study, crude PC extraction from the pretreatment of rapeseed oil gums with ethanol was used as the raw material to prepare high-purity PC using ion-exchange resin. ZGD152 was selected from six cation ion-exchange resins to separate rapeseed PC. The adsorption characteristics of PC and phosphatidylethanolamine (PE) on ZGD152 resins have been compared. The equilibrium absorption data of PC and PE on ZGD152 resin were fitted to Langmuir and Freundlich model. The adsorption thermodynamic parameters were also evaluated on pseudo-first-order model. Experimental optimization of dynamic adsorption and desorption was performed in a glass column packed with ZGD152 resin. The PC was successfully separated with gradient elution using 20 % (4 BV), 60 % (13 BV) aqueous ethanol solutions, and 5 wt% hydrochloric acid (8 BV). The content of PC was increased from 50.2 to 87.7 % in the final product with the recovery of 58.2 %.The results indicated that the ZGD152 resin was an effective separation media for the purification of PC from the rapeseed phospholipids, with potential application in the future.     

Characterization of particleboards of African mahogany sawdust made with tannic powders of Bridelia and African locust bean pods

European Journal of Wood and Wood Products - The purpose of this study was to valorize African mahogany wood, especially its residues (sawdust) from carpentry, in the manufacturing of...     

Migration of melamine and formaldehyde from tableware made of melamine resin

Migration of melamine and formaldehyde into food-simulating solvents from cups made of melamine resin was studied under various conditions. Little migration of melamine was observed in any unused cups kept at 60 degrees C for 30 min, room temperature (26 degrees C) for 1 h or cooled at -20 degrees C for several days. Migration of both compounds was strongly affected by heating and acidity. The highest migration of melamine into 4% acetic acid used as a food-simulating solvent was 42.9 +/- 7.2 ppm when the migration test was repeated seven times at 95 degrees C for 30 min. In this time, the migration of formaldehyde was 14.2 +/- 0.6 ppm into the solvent. The molecular ratio of the migration amount of formaldehyde to melamine decreased according to the formula Y = 9.15X-0.813 over seven repetitions of the test, and was maintained at about 1.6 between the 10th and 20th repetitions. The inner surface of the cups became tarnished during the repetition of the test and their roughness increased from 1 micron before the test to 2.5-5 microns after 20 repetitions of the test. Migration of melamine from the cups being used at a cafeteria was 0.4 +/- 0.5 ppm, but that of formaldehyde was undetectable when the cups were kept at 60 degrees C for 30 min with 4% acetic acid.     

Release of formaldehyde and melamine from tableware made of melamine-formaldehyde resin

The relationship between the concentrations of formaldehyde and melamine released into 4% acetic acid from dishes and bowls made of melamine-formaldehyde resin was determined. The average concentrations in the migration solution after the sample had been treated at 60, 80, and 95 degrees C for 30 min with 4% acetic acid were 0.0 +/- 0.1, 0.5 +/- 0.4 and 3.0 +/- 2.2 ppm, respectively for formaldehyde and 0.04 +/- 0.07, 0.21 +/- 0.20 and 1.19 +/- 1.18 ppm, respectively for melamine. The correlation between the concentrations of formaldehyde and melamine released at 95 degrees C was y=0.4858x-0.2728 (r=0.8860), where y is melamine concentration (ppm), x is formaldehyde concentration (ppm) and r is the correlation coefficient. The molar concentration ratios of formaldehyde to melamine (F/M ratio) were 15.4 +/- 11.6 at 80 degrees C and 14.9 +/- 10.1 at 95 degrees C. Hence the release of both migrants was affected by temperature but the F/M ratio was not affected. The release of both compounds was was increased on repetition of the migration test at 95 degrees C but their concentrations remained constant after the tenth and seventeenth repetitions of the treatment. During this period, the F/M ratio decreased according to the equation 1n y=-1.4344 1n x+3.7814 (r=-0.9984) for a sample before the tenth repetition of the treatment and remained between 1.7 and 1.9 after the twelfth repetition, where y is the F/M ratio and x is the number of repetitions of the treatment.     

A study of oriented structural board made from hybrid poplar

Some basic physical and mechanical properties of oriented structural board (OSB) made from fast growing hybrid poplar, such as modulus of rupture, modulus of elasticity, internal bond strength, nail and screw holding power, thickness swelling after water and humidity absorbing, thermal conductivity and sound absorbing coefficient, have been tested and compared with values from random strand board. Effects of board density on these properties were analyzed revealing some general relationships for OSB. The feasibility of hybrid poplar as raw material for OSB production is also discussed.     

A study of oriented structural board made from hybrid poplar

This paper is to study influences of four main factors of the mechanical oriented forming installation with moving saws back and forth, i.e. the distance between two neighbouring saws (D), the moving frequency of the saw (F), the moving length of saws (L) and the height of strands to fall down (H), on orientation effectiveness of strands. The average orientation effectiveness of these strands. The results show that both factorD and factorH have important influence on the orientation of strands, factorL only has fail-sized influence, however, factorF nearly exerts no influence.     

Release of acetic acid and formaldehyde from particleboards bonded with phenolic resins

The gas analysis method (EN 717-2:1994), originally destined for measuring the formaldehyde release from wood-based panels, can also be used to determine the emanation of volatile organic acids such as acetic acid. However, the profile of release of formaldehyde and acetic acid seems to be quite different in the course of the gas analysis test.