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1.
Medium density fibreboard (MDF) was produced from fibres treated with maleated polypropylene wax. The objectives of this study were to investigate the effect of fibre treatment with maleated polypropylene wax on the advancing and receding contact angle and wicking of MDF panels by the Wilhelmy plate method; to verify the chemical reactions occurring between fibres and maleated polypropylene wax by infrared spectroscopy, and to verify if there are relationships with the water absorption of panels. Three maleated polypropylene wax contents (0, 3, 5%) and two resin types (urea–formaldehyde, UF and melamine–urea–formaldehyde, MUF) were considered in this study. Our results showed that the treatment increased the advancing contact angle of panels bonded with UF resin. The receding contact angles of MDF panels produced from treated fibres with 5% maleated polypropylene wax content were also increased by the treatment. Also, the wicking was reduced by the treatment independent of the maleated polypropylene wax content. Reductions of the wicking were 59% for panels bonded with UF resin and 73% for panels bonded with MUF. Relationships between the wicking and water absorption were observed. Chemical analysis realized by infrared spectroscopy did not detect the presence of an esterification reaction between wood fibres and anhydride groups of the maleated polypropylene wax. This suggests, therefore, that an esterification reaction did not take place or that chemical modifications were so small that they are not visible by infrared spectroscopy. 相似文献
2.
Xiang-Ming Wang Bernard Riedl Robert L. Geimer Alfred W. Christiansen 《Wood Science and Technology》1996,30(6):423-442
Summary To better understand the curing and bonding behavior of phenol-formaldehyde (PF) resin under dynamic conditions, flakeboards were manufactured either by conventional pressing at 7% or 12% mat moisture content or by steam injection pressing with 10 or 20 seconds steaming duration. Resin-impregnated glass-cloth samples and lap-shear tension specimens were embedded in the core of each flakeboard. After the flakeboards were pressed for various periods of times, the samples and specimens were quickly retrieved. The degree of resin cure was determined on the resin-impregnated glass-cloth samples by dynamic mechanical analysis. The bond strengths were measured from the lap-shear tension specimens on a mechanical testing machine. The results of resin curing and bonding were then correlated to the performance of the resin-bonded boards, which were evaluated by internal bond, modulus of rupture, modulus of elasticity, and thickness swelling. Resin curing and lap-shear bonding did not proceed simultaneously. In conventional pressing, the mat moisture content (MC) at 12% favored resin curing, but slightly retarded lap-shear bonding, as compared to 7%MC. In steam injection pressing, the rates of resin curing and lap-shear bond strength development were much faster for 20 seconds than for 10 seconds of steaming duration. Longer press times were needed to obtain boards with maximum strength in the 12%MC conventional pressing and the 20-s steam duration steam injection pressing than in those conditions where moisture content was lower or steam time was less. The need for longer press times must be attributed to higher internal vapor pressures and/or lower wood and resin component strengths, rather than to incomplete cure or bonding.This material is based on work supported by the Ministry of International Affairs, Quebec Government, the Natural Sciences and Engineering Research Council of Canada, and Laval University (Quebec City). The work was also supported by the U.S. Department of Agriculture under research joint venture agreement FP-92-1835 相似文献
3.
Xiang-Ming Wang Graduate Student Bernard Riedl Alfred W. Christiansen Robert L. Geimer 《Wood Science and Technology》1995,29(4):253-266
Summary The effects of temperature and relative humidity on phenol-formaldehyde resin bonding were evaluated. Two flakes in a lap-shear configuration were bonded under an environment of controlled temperature (110 °C, 120 °C, 130 °C, 140 °C) and relative humidity (41%, 75%, 90%) for a series of time periods (0.25 to 16 min). The lap-shear specimens were then shear-tested on a mechanical testing machine and the results were used to establish a family of bond strength development curves at each temperature and level of relative humidity. At 110°C, the higher relative humidity appeared to retard resin bonding. The effects of relative humidity diminished as temperature increased to 140 °C. Bond strength development was chemical ratecontrolled. The rate of bond strength development at each relative humidity follows a first order reaction mechanism. The activation energy of resin-wood bonding, determined by bonding kinetics, was higher than that of resin alone, determined by differential scanning calorimetry. This comparison indicates that to form a strong resin-wood bond, a higher energy level might be required.This material is based on work supported by the Ministry of International Affairs, Quebec Government, the Natural Sciences and Engineering Research Council of Canada, and Laval University (Quebec City). The work was also supported by the U.S. Department of Agriculture under research joint venture agreement FP-92-1835 相似文献
4.
Cheng Xing Bernard Riedl Alain Cloutier Stephen M. Shaler 《Wood Science and Technology》2005,39(5):374-384
The amount of UF resin penetration into fibers, used for the production of medium density fiberboard (MDF), is unknown. To
evaluate the relationship between resin viscosity and resin penetration depth, an experimental procedure involving confocal
laser scanning microscopy (CLSM) and a Toluidine Blue O staining system was performed. The results indicate that CLSM in combination
with a Toluidine Blue O staining system is a good way to characterize UF resin penetration into wood fibers. The main penetration
direction is toward the fiber lumen. For wet fibers, whose moisture content is about 88%, the effect of resin viscosity with
a range of 80 cps – 340 cps on penetration is very similar, with all adhesives reaching or almost reaching the fiber lumen
after 60 min at room temperature. For MDF industrial samples, the highest depth of penetration of the adhesive was attained
in the second dryer stage. After the second dryer stage, the resin penetration into the fiber did not increase. 相似文献
5.
Hochmalová Miroslava Purwestri Ratna Chrismiari Yongfeng Jian Jarský Vilém Riedl Marcel Yuanyong Dian Hájek Miroslav 《European Journal of Forest Research》2022,141(5):867-886
European Journal of Forest Research - Ecosystem services are investigated from many perspectives, but there are very few studies comparing the perception of forest and demand for forest ecosystem... 相似文献
6.
Tannin-protein complexes as radical scavengers and radical sinks 总被引：8，自引：0，他引：8
The 2,2'-azinobis(3-ethylbenzothiazoline 6-sulfonic acid) radical cation (ABTS(*)(+)) decolorization assay has been used to determine the antioxidant activity of the polyphenol epicatechin(16) (4 --> 8) catechin (procyanidin, PC) alone or in complex with the model proteins bovine serum albumin (BSA) or gelatin. PC had a molar antioxidant capacity of approximately 54, 92, or 108 radicals at pH values of 3.0, 4.9, or 7.4, respectively. Radical scavenging occurred via a rapid step followed by a slow step. Interaction with gelatin reduced the rate of rapid scavenging by 50% (PC-BSA mixtures reduced by 15%). Inhibition paralleled formation of precipitable PC-protein complexes over a range of protein/PC ratios. However, inhibition was virtually overcome in 10 min. Reaction with ABTS(*)(+) converted the PC-protein complexes from a dissociable form to a form resistant to dissociation by strong denaturants such as SDS. This study demonstrates that PC is a potent ABTS(*)(+) scavenger even when bound to protein and that the complexes may act as a radical sink within the gastrointestinal tract. 相似文献
7.
8.
R. Riedl 《Journal of pest science》1969,42(11):174-175
Ohne Zusammenfassung 相似文献
9.
Improved water repellency of black spruce wood surfaces after treatment in carbon tetrafluoride plasmas 总被引：1，自引：0，他引：1
Bouddah Poaty Bernard Riedl Pierre Blanchet Vincent Blanchard Luc Stafford 《Wood Science and Technology》2013,47(2):411-422
Plasma treatments for black spruce wood (Picea mariana (Mill.) B.S.P.), a widespread forest species from Canada, were carried out in order to waterproof the exposed surfaces. Experiments were performed using inductively coupled argon plasma with carbon tetrafluoride as the gaseous precursor for plasma-enhanced chemical vapor deposition of functional fluoropolymer coatings on wood. Analysis of the wettability through water contact angle measurements showed water-repellent characteristics, with static contact angles up to 130° depending on plasma exposure time, CF4 concentration in the Ar/CF4 plasma, and plasma source-to-substrate distance. X-ray photoelectron spectroscopy investigations of plasma-treated wood surfaces confirmed the growth of a thin, fluorocarbon layer with fluorine atomic concentrations close to 50 % on highly hydrophobic wood surfaces. Estimation of the thickness of the coatings by stylus profilometry revealed that a minimum layer thickness of about 80 nm is required to obtain water repellant wood surfaces with minimum water uptake. This complete set of data indicates that fluorocarbon-containing plasmas represent a very promising approach for improving the durability of wood products in wet and humid conditions. 相似文献
10.
Flavones are abundant in parsley and celery and possess unique anti-inflammatory properties in vitro and in animal models. However, their bioavailability and bioactivity depend in part on the conjugation of sugars and other functional groups to the flavone core. The effects of juice extraction, acidification, thermal processing, and endogenous enzymes on flavone glycoside profile and concentration in both parsley and celery were investigated. Parsley yielded 72% juice with 64% of the total flavones extracted, whereas celery yielded 79% juice with 56% of flavones extracted. Fresh parsley juice averaged 281 mg flavones/100 g and fresh celery juice, 28.5 mg/100 g. Flavones in steamed parsley and celery were predominantly malonyl apiosylglucoside conjugates, whereas those in fresh samples were primarily apiosylglucoside conjugates; this was apparently the result of endogenous malonyl esterases. Acidification and thermal processing of celery converted flavone apiosylglucosides to flavone glucosides, which may affect the intestinal absorption and metabolism of these compounds. 相似文献