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A Green and Novel Technology for Recovering Copper and Wood from Treated Waste - Part I
2015 - IRG/WP 15-50309
Preservative treatment of wood extends its service life. The US consumes about 70 million pounds of copper and produces about 7 billion board feet of treated wood annually. Burning and reusing CCA and copper treated wood wastes are disallowed by US EPA due to health and environmental concerns. Millions of pounds of copper and wood are disposed by landfill annually. The objective of this study was to develop a green technology that can remove copper from the treated wood wastes so that copper and wood can be reused. In this study, seven different aqueous solutions were evaluated for copper removal from treated wood sawdust and chips. Citric acid demonstrated the highest efficiency by recovering 100% copper followed by ammonium citrate and ammonium carbonate/bicarbonate solutions. Formation of copper complexes with the ligands such as citrate and ammonium ions attributed to the key chemical mechanisms for efficient copper removal. The changes of extraction solution color progressively from yellowish orange to dark blue corresponded to the changes in the ratio of citrate ions to ammonia in the solutions. Citric acid has been used extensively as a food and cosmetic additive. The safety, high efficiency and low cost of citric acid compared to the chemicals previously reported for treated wood remediation can overcome the obstacles for commercial consideration. The performance demonstrated in the extraction study by the ammonium salts provides a novel extraction system with further cost reduction options. The finding of excellent copper removal using treated wood chips is very significant since it saves a great amount of energy required to produce sawdust. After removal of copper, the chips offer more opportunities than sawdust for reuse in landscaping, pulping, energy production and many other applications. With the development of such a green and novel technology, we can reuse millions of tons of wood and copper to protect the environment, save natural resources and benefit generations to come.
Selective adsorption of antisapstain actives from two aqueous suspensions, and movement of actives into wood
1996 - IRG/WP 96-30103
Green-off-saw rough sawn Pinus elliottii (slash pine) boards were dipped in aqueous suspensions of two antisapstain formulations, NeXgenâ and Busanâ Sap Stain Preventative (Busan 1009), at three product concentration levels. Concentrations of active ingredients (NeXgen: CTL (chloro-thalonil) and MTC (methylene bisthiocyanate); Busan 1009: TCMTB (2(thiocyanomethylthio)-benzothiazole) and MTC) were monitored with respect to the amount of material dipped. Selective adsorption (removal of actives from the suspension at greater than simple volumetric transfer rates) varied with formulation and active ingredient, and increased with decreasing product concentration. Movement of active ingredients into dipped boards was monitored for 30 days after dipping. Mobility order was MTC >> TCMTB > CTL. Surface depletion characteristics were obtained for each active ingredient.
M J Kennedy, T L Woods
Effects of timber surface properties and dipping conditions on uptake of antisapstain actives from two aqueous suspensions, and ultimate effects on efficacy against mould and staining organisms
1995 - IRG/WP 95-30073
Green-off-saw rough sawn Pinus elliottii (slash pine) boards were dipped in aqueous suspensions of two antisapstain formulations, and the resultant surface retentions of active ingredients MTC (methylene bisthiocyanate), CTL (chlorothalonil) or TCMTB (2(thiocyanomethylthio)benzothiazole) were monitored by chemical analysis. Surface retentions increased with suspension concentration and surface roughness, and decreased with initial timber moisture content. Dipping time beyond 20 seconds, timber basic density and earlywood content had little effect. Relatively low surface retentions, produced by dipping smoother boards with higher initial moisture contents, provided lower protection against mould and stain during seasoning than higher retentions. Equations describing the effect of surface retention on efficacy were developed for both formulations, and retentions providing complete protection under the conditions of the test were determined.
M J Kennedy, T L Woods
Amines – Promising Wood Preservatives
2002 - IRG/WP 02-30287
Environmental concerns require a new approach in the field of wood protection. Band of many traditional wood preservatives has lead to intense researches for new environmental-friendly wood preservatives. Amines seem to be promising substitutes for classical biocides. Fungicidal and leaching resistance as well as some other chemical analysis of beach and Norway spruce samples treated with ethanolamine, triethanolamine or ammonia was examined. Initially, percentage of fixed nitrogen in samples was established. Afterwards fungicidal resistance against Trametes versicolor and Gloeophyllum trabeum were determined according to the standard laboratory test EN 113. Finally, leaching resistance was performed according to the modified standard EN 1250 procedure. We found out that the mayor part of amines remained in wood and did not evaporate from it. The results indicated that amine treated wood increased resistance against wood decay fungi. On the other hand amine treated wood was not found suitable for use in hazard class 4, since amines were leached out of the wood.
M Humar, F Pohleven, Š Kesnar, P Kalan
Ammoniacal wood preservative for use in non-pressure treatment of spruce and aspen poplar. Part 1
1984 - IRG/WP 3273
End-matched lumber of Picea glauca (Moench)Voss (white spruce) and Populus tremuloides Michx. (aspen poplar) timbers was treated by a thermal diffusion process in open tank treating vessels using an ammoniacal copper-arsenate wood preservative. The process proved technically feasible with respect to controlling the vapourization of ammonia from open tanks during treatment at high temperatures. Treatments of 48 hours or more on unseasoned and partially dried lumber produced net oxide retentions above that required by the Canadian Standard Association CSA-080 wood preservation standard for timber in above ground contact situations. Although preservative penetrations did not meet the penetration requirements (10 mm), of the CSA 080.2 standard for ground contact, five of the seven non-pressure charges on spruce lumber had heartwood penetrations greater than 7 mm in depth. A 24-hour treatment on air-dried spruce had penetrations equivalent to a five-hour vacuum-pressure treatment. Retention was adequate for above-ground exposure
C D Ralph, J K Shields
Natural exposure weathering tests: Their role in the assessment of wood preservative efficacy
1993 - IRG/WP 93-20006
Previous work has demonstrated the potential and usefulness of natural ageing procedures in e evaluation of wood preservative efficacy. This results from the combination of physico-chemical influences and microbiological interactions with both substrate and wood preservative. In this paper, results are presented for a range of biocide types. Discussions are centred on the value of natural exposure weathering tests for preservative efficacy assessment and the importance of biological persistence in the design of effective wood preservatives.
G R Williams, J Brown
Improvement of some technological and biological properties of poplar wood by impregnation with aqueous macromolecular compounds
1992 - IRG/WP 92-3721
Poplars (Populus spp) belong to the most important tree species in afforestation programs of the Netherlands. Due to their rapid growth, the wood quality is usually low. Therefore, studies were performed to elucidate whether some technological properties and the resistance against fungal attack could be improved by impregnation with water-soluble resins. The results showed that swelling and shrinkage of poplar wood may considerably be reduced by a treatment with certain resins. The anti-shrink efficiency (ASE) strongly depends upon the resin type. An air-curing alkydresin based on polybutadiene and an air-curing acrylate modified alkydresin emulsion caused the best effects. Additions of wood preservatives to the resins further improved the ASE. Some disadvatages of the tested resins may be seen in their leachability with consequent loss of the dimension-stabilizing effects. The resins by themselves don't reveal fungistatic properties but an impregnation of poplar wood with these materials led in all cases to a better durability against Coniophora puteana and Coriolus versicolor. Leaching procedures influenced the durability in various ways. With resin/fungicide combinations, a good resistance against Coriolus versicolor could be reached even after leaching. SEM and EDXA methods were used to localize the resins in the cell walls and lumina and to detect the growth of mycelium in the specimens.
R D Peek, H Militz, J J Kettenis
Some factors affecting the treatability of spruce roundwood with ammoniacal preservative solutions
1976 - IRG/WP 371
Permeable wood species for use in preservative-treated commodities are becoming depleted in Canada. Spruce can be a convenient replacement for them from local resources provided it can be treated to levels adequate for protection of commodities in ground contact. Basically, two approaches were taken to improve treatability of difficult-to-penetrate softwood species; first, to improve the permeability of wood and second, to improve the penetrating properties of liquids. The first approach involves various means of wood pre-treatment: biological (enzymes, moulds and bacteria including ponding), chemical (removal of extractives), mechanical (precompression) and technological (presteaming of green wood, replacement of water in wood by solvents). There are a great many publications devoted to individual topics mentioned here indicating the significance of the subject. The second approach is the selection of a solvent capable of penetrating into the wood better than conventional solvents for, preservative compounds.
Decay resistance of densified ammonia-plasticized stems of oil palm (Elaeis guineensis)
1991 - IRG/WP 3673
When wafers of oil palm stems (Elaeis guineensis) were plasticized with 28% aqueous ammonia and immediately compressed mechanically, the treated material, gained 73% in basic density (average basic density, 0.695 g/cm³), and was highly resistant to decay by wood rot basidiomycetes. Compared with the control specimens (density, 0.403 g/cm³), resistance to decay of the densified specimens by Coriolus versicolor increased by 55%, and Gloeophyllum trabeum, 74%. Fungal decay was significantly correlated with basic density (densification effect) (r-value, between -0.77 and -0.92), mediated in part by a similar pattern of correlation (-0.86) between densification and decaying tissue moisture content. Mass losses of specimens which were plasticized but not subsequently densified, did not differ significantly (P<0.05) from the controls while basic density of such treated specimens decreased slightly (density, 0.358 g/cm³). Total nitrogen contents for the controls, specimens plasticized without densification, and densified plasticized specimens were respectively; 0.24, 0.65 and 0.63% (g/g), the control differing significantly from the rest. Substrate pH were similar among the three samples. It appeared that artificial densification (rather than total nitrogen levels) assumed an overriding influence on decay resistance of compressed ammonia-plasticized oil palm stems
A H H Wong, M P Koh
Preservative treatment of green timber by diffusion
1984 - IRG/WP 3291
The preservative treatment of green timber by diffusion is reviewed together with criteria which influence the economics of the process. New process options are described which should overcome some of the technical and economic disadvantages of double diffusion. These include the use of coagulating agents which increase the viscosity of the preservative solution and facilitate treatment by momentary immersion. It is anticipated that the main application for the diffusion treatment process will be for the treatment of refractory timbers for both ground contact and above ground exposure. The system is most suitable for low density and higher heartwood moisture content wood species - for example Sitka spruce, and is ideally suited for use in the tropics for treating both plantation grown softwoods and mixed tropical hardwoods.
Preservative treatment of wood by diffusion processes - Simulation of commercial treatment processes
1988 - IRG/WP 3498
Spruce (Picea abies), Scots pine (Pinus sylvestris) and birch (Betula pendula) were preservative treated by diffusion with mixtures of copper sulphate and arsenic pentoxide. The preservative was fixed after a suitable diffusion storage period by soaking in ammonia solution. A high standard of treatment could be achieved in spruce sapwood. This was attributed to its low wood density, and high wood moisture content. The variable treatability of spruce heartwood and poor treatability of Scots pine heartwood was related directly to their moisture-content. Complete preservative penetration could be achieved in spruce heartwood when moisture contents were 60% or above whereas Scots pine heartwood with a fresh moisture content of 30% was untreatable by diffusion. Preservative penetration was directly related to preservative retention and immobilisation by fixation. This was demonstrated clearly for birch which because of its high basic wood density tended to immobilise a greater quantity of preservative salt per unit volume. The effects of preservative retention and diffusion storage time on the subsequent distribution of preservative was determined for Pinus ponderosa. The relationships established can be used for defining suitable diffusion treatment schedules.
Decay and termite resistance of wood treated with boron-containing quaternary ammonia compound, didecyl dimethyl ammonium tetrafluoroborate (DBF) incorporated with acryl-silicon type resin
2004 - IRG/WP 04-30334
This study evaluates the decay and termite resistance of surface-treated wood with didecyl dimethyl ammonium tetrafluoroborate (DBF) incorporated with acryl-silicon type resin emulsion. DBF is a quaternary ammonia compound and contains boric tetrafluoride (BF4-) as a counter ion in its chemical structure. In the study, DBF was incorporated with an acryl-silicon type resin to increase water-resistant of the preservative solution, and, in turn, to increase decay and termite resistance of surface-treated wood after severe weathering processes. Laboratory decay resistance tests were performed using brown-rot fungus Fomitopsis palustris and white-rot fungus, Trametes versicolor. Treated wood specimens were also subjected a 3-week-termite resistance tests using subterranean termites, Coptotermes formosanus. Wood specimens surface-treated with preservative solution including 2% DBF and the resin showed decay resistance against both F. palustris and T.versicolor even after severe weathering. Results suggested that treatment with DBF at 2% or greater concentrations containing acryl-silicon type resin emulsion would protect wood used outdoors against both fungal decay and termite attack.
S N Kartal, W J Hwang, K Shinoda, Y Imamura
Silicic acid-Boric acid complexes as wood preservatives
2001 - IRG/WP 01-30273
A silicic acid monomer aqueous solution (SAMS) or colloidal silicic acid solution (CSAS) was combined with various metal compounds or boric acid. Agents where SAMS or CSAS was combined with boric acid gave good protection against decay caused by the brown-rot fungus Fomitopsis palustris, the treated wood (Cryptomera japonica D. Don) specimens after the leaching test maintained a high resistance to decay. The leaching and decay tests revealed high quantities of chemicals leaching from wood treated with SAMS-metal agents. However, when wood was treated with SAMS-boric acid, there was little leaching of agent in either test. The mechanism of resistance of wood, which was treated with boric acid mixed with CSAS or SAMS, to the brown-rot fungus F. palustris were investigated. When the concentration of boric acid was high, mycelial growth was inhibited completely and no protein production was detected. When the amount of boric acid was low, the xylanase, mannase and cellulase activities were lower than with control wood powder. When wood was treated with silicic acid only, its resistance to termites increased, but not to the marked extent observed after treatment with a mixture of silicic and boric acids. Also, increasing the quantity of boric acid increased the mortality rate of termites, and shortened the time to death. From field tests on stakes over three years, it was shown that even if stakes were placed near the termite exit, those treated with silicic acid and high levels of boric acid maintained their original form. Combustion tests showed that with high levels of boric acid, flaming and glowing combustion times were shortened. When boric acid-methanol solution was added at of rate of not less than 25 ml for 100 ml of CSAS, flaming and glowing combustion were not observed. Though the charring length of the wood- specimen, which was treated with silicic acid¡boric acid agent, decreased to 1/3 of that of control wood, the charring lengths were not influenced by the level of boric acid. However, the volume of smoke decreased relative to the amount of boric acid that had been added. When powdery boric acid was combined with CSAS, it was considered that the treated woods have higher anti-weather properties than when boric acid-methanol solution was mixed with CSAS. The agent- preparation method adopted should be considered carefully after taking the treatment process and the intended use of the preservative-treated wood into account.
A laboratory evaluation of tributyltin ethanesulphonate as an aqueous fungicide in wood preservation
1983 - IRG/WP 3229
Toxic limit data, using both leached and unleached wood test blocks, are reported for aqueous solutions of tributyltin ethanesulphonate against four Basidiomycete fungi, Poria placenta, Gloeophyllum trabeum, Coriolus versicolor and Coniophora puteana. An in situ study of the tributyltin compound in Scots pine and ponderosa pine sapwood has been carried out, using the technique of 119mSn Mössbauer spectroscopy.
R Hill, P J Smith, J N R Ruddick, K W Sweatman
Effect of aqueous polymer treatments on wood properties. Part 2: Mechanical properties
1990 - IRG/WP 3611
Partially air-dried sapwood of sweetgum (Liquidambar styraciflua) and southern pine (Pinus spp.) was treated with either aqueous polyacrylate or aqueous dimethyloldihydroxyethyleneurea (DMDHEU) solutions. Tests for static bending, toughness, and hardness were conducted on matched treated and untreated pieces according to ASTM Standards. Properties of pine were not affected by treatment with the polyacrylate. With sweetgum, the modulus of rupture and modulus of elasticity were reduced, while hardness was improved. For the DMDHEU treatment, reduction in property values for both species was related to curing temperature.
Z Ashaari, H M Barnes, D E Lyon, R C Vasishth, D D Nicholas
The effect of aqueous leaching on moisture uptake by CCA-treated blocks during soil burial
1987 - IRG/WP 2283
Mass loss, moisture content and nitrogen data from two soil burial experiments with untreated and CCA-treated Scots pine (Pinus sylvestris L.), Sitka spruce (Picea sitchensis Carr) and lime (Tilia vulgaris Hayne) are presented. These show that aqueous leaching of CCA-treated wood prior to burial significantly reduces its subsequent moisture uptake from soil. In the case of lime, a reduction in the rate of microbial invasion and decay of leached, treated blocks, when compared with their unleached counterparts, was demonstrated. The implications of these observations with regard to accelerated testing methods are discussed.
C A Green, G M Smith, B King
Decomposition of biocides in aqueous media cases of MTC and TCMTB
1993 - IRG/WP 93-50001-26
Our laboratory is interested in the fate of modern biocide molecules in the environment. Here we present recent work which has been done on the fate of two compounds with fungicidal and bactericidal properties: methylenedithiocyanate (MTC: NCS - CH2 - SCN) and thiocyanomethylthiobenzothiazol (TCMTB). We have studied separately the influence of pH, temperature and ultraviolet irradiation in aqueous media. The results show that the higher the pH (the more basic) and the higher the temperature, the easier these biocides decompose, liberating other compounds, essentially cyanide and thiocyanate ions CN¯ and SCN¯ along with organic decomposition products, namely mercaptobenzothiazole in the case of TCMTB and a thioamide and a diamine in the case of MTC. Moreover, for both of the biocides, we have noticed shown both in the aqueous phase and in the gazeous phase bordering the aqueous phase the formation of CS2 and a sulfur containing heterocyclic compound, i.e. 1,2,4 - trithiolane. The photochemical decomposition of TCMTB (between 350 and 700 nm) in water as such and in presence of traces of H2O2 is significant for long exposition times. In both cases we noticed the formation of mercaptobenzothiazole. On the other hand, MTC is not decomposed in this wavelength interval.
R Perraud, M Papazian
Chemically modified tannin and tannin-copper complexes as preservatives for wood
2001 - IRG/WP 01-30271
The efficacy of Mimosa tannin, chemically modified tannin, and tannin-copper complexes as wood preservatives was studied. When the tannin-ammonia-CuCl2 solutions were impregnated into wood specimens in a one-step procedure, a large quantity of the tannin-copper complex was fixed in the specimens. Little of the complex was leached from specimens by a weathering treatment, and these specimens showed satisfactory decay resistance in a basidiomycete laboratory test according to the Japanese Industrial Standard (JIS) K 1571-1998. Only the tannin-treated wood had a retention of agent after treatment, in increasing order from untreated tannin (MT), resorcinolated tannin (RMT) and catecholated tannin (CMT). When RMT or CMT was mixed with ammonia¡copper, the wood retained twice as much of these solutions as the MT-ammonia-copper solution. The solutions penetrated 2~13mm from the tangential sections of the logs. Presumably, chemical modification increased the degree of retention by altering the structure of the tannin and increasing its hydrophilic properties. The degree of retention of RMT-NH3-Cu and CMT-NH3-Cu in logs with cross-sections ranged from 268 kg/m3 to 326 kg/m3. Wood decay by F. palustris was markedly suppressed by processing wood with agents made by mixing chemically modified tannins with ammonia and cupric chloride. When wood powder was treated with these agents, mycelial growth and generated protein increased to some extent. The preservative effects of the chemically modified tannins (RMT and CMT) or compound agents composed of the tannins and ammonia¡copper were considered to be due to inhibition of the activities of mannase and Cx-cellulase. In the culture medium which treated wood powder was put in with these agents, drop of pH by oxalic acid, which Fomitopsis palustris produces, is not generated. The potency of the effect was thought to be due to chelation of copper, an essential trace element for wood decay by F. palustris, by the tannin, and/or neutralization or suppression of oxalic acid production by ammonia-copper. Also, these active ingredients hindered eating-damage of wood by the termites. However, the mortality of the termites during the eating-damage test (over 21d) did not reach 100% for all active ingredients. The fact that living termites were still present suggests that tannin-ammonia-copper is not perfect for destroying termites.
Preliminary evaluation of new quaternary ammonia compound, didecyl dimethyl ammonium tetrafluoroborate for preventing fungal decay and termite attack
2005 - IRG/WP 05-30375
This study evaluates the decay and termite resistance of wood treated with didecyl dimethyl ammonium tetrafluoroborate (DBF), a recently developed quaternary ammonia compound containing boron. DBF contains boric tetrafluoride as a counter ion in its chemical structure. Laboratory decay resistance tests were performed using brown-rot fungus, Fomitopsis palustris and white-rot fungus, Trametes versicolor. Treated wood specimens were also subjected a 3-week-termite resistance tests using subterranean termites, Coptotermes formosanus. Decay resistance tests showed that wood specimens treated with 0.5 and 1.0% DBF solutions were well protected from both fungi even after a 10-day severe weathering process, suggesting the adequate fixation of DBF in wood. DBF treatment at 0.1% concentration was efficient against subterranean termites, Coptotermes formosanus Shiraki based on weight losses in both weathered and unweathered wood specimens. These results suggested that DBF could be used effectively to protect wood used outdoors against both fungal decay and termite attack and discolorations by fungi.
S N Kartal, W J Hwang, Y Imamura
Effect of aqueous polymer treatments on wood properties. Part 1: Treatability and dimensional stability
1990 - IRG/WP 3610
Partially air-dried sapwood of sweetgum (Liquidambar styraciflua) and southern pine (Pinus spp.) was treated with either aqueous polyacrylate or aqueous dimethyloldihydroxyethyleneurea (DMDHEU) solutions. Tests for dimensional stability were conducted on matched treated and untreated pieces. Measurement of the antishrink efficiency indicated that DMDHEU was a better stabilizer than the polyacrylate system. Stability was related to polymer retention and curing temperature.
Z Ashaari, H M Barnes, R C Vasishth, D D Nicholas, D E Lyon
The fixation of copper in Pinus sylvestris using the sodium salts of two polyhydroxycarboxylic acids
1992 - IRG/WP 92-3706
As part of the research concerned with the development of fixed, copper based preservatives, the salts of polyhydroxycarboxyIic acids, have been used in copper sequestration studies and fixation trials in Pinus sylvestris splinters. Selected compounds have been shown to be effective sequestrants at low concentrations allowing alkaline solutions to be formulated. Leaching trials following a 48 hour wet fixation period at 40°C showed that aximum copper fixation can be achieved from formulations within the pH 7 to pH 9.0 range, providing sequestrant concentrations are optimised.
M Bacon, J A Cornfield
Effect of amphiphilic antioxidant alkyl ammonium ascorbate on inhibition of fungal growth: Application to wood preservatives formulation
2008 - IRG/WP 08-30466
Amphiphilic surfactants were synthesized from ascorbic acid and different fatty amines and evaluated for formulation of wood preservation products. Characterization of physicochemical properties of the new compounds indicated classical behavior of cationic surfactants. Antioxidant properties, estimated using methyl linoleate oxidation inhibition method, were similar to that of ascorbic acid tested in the same conditions. Growth inhibition assays indicated that amphiphilic dodecylammonium ascorbate is able to inhibit Coriolus versicolor mycelium development, while butylammonium ascorbate deprived of surfactant properties has no effect. This compound was then investigated in the formulation of wood preservation mixtures containing propiconazole and compared to formulation obtained with an industrial surfactant. Biological tests based on the ability of these formulations to protect beech wood blocks exposed to a white rot fungus Coriolus versicolor were carried out under laboratory conditions. Results indicated that use of propiconazole formulation in aqueous solution allows to reduce the quantity of biocide compared to solutions of the same concentrations in ethanol. Protection achieved with antioxidant surfactant was slightly superior to that conferred by conventional surfactant.
C Gérardin , T Koumbi Mounanga, P Gérardin
Sorption properties of wood impregnated with aqueous solution of boric acid and montan wax emulsion
2010 - IRG/WP 10-40492
Non-biocidal techniques for wood protection become more and more important, nowadays. One of the possible treatments is use of water repellents. In the present research influence of, one of the possible water repellent, the montan wax emulsion, on the moisturizing and the sorption characteristic of impregnated wood was investigated. To achieve a better protection against wood decay fungi, montan wax emulsion enriched with boric acid, was used for impregnation of wood. The equilibrium moisture content (EMC) during the adsorption and the desorption process at five levels of relative humidity (φ1 = 20%, φ2 = 33%, φ3 = 65%, φ4 = 88% and φ5 = 98%) was monitored. Water repellence efficiency was monitored in the chamber with high relative air humidity (87%) and during dipping in the water. Impregnated samples were also exposed outdoor in cowered position for five months. The results showed that the sorption properties of the impregnated wood are strongly related to retention of preservative solutions after impregnation and its compositions. Montan wax reduced equilibrium moisture content of the impregnated wood up to 25% while specimens impregnated with combination of montan wax and boric acid in some cases resulted in the decreased and in some cases in the increased EMC. The Guggenheim-Andersen-deBoer (GAB) model of sorption isotherms was fitted to experimental data to explain the sorption mechanisms.
B Lesar, M Humar
Dynamic mechanical analysis (DMA) of nano cupric oxide (CuO) modified aqueous phenol formaldehyde (PF) resin
2014 - IRG/WP 14-40654
Phenol formaldehyde (PF) resins, modified by nano CuO incorporating alkane surfactant and polyvinyl alcohol (PVA) 17-99, were analyzed by dynamic mechanical analysis (DMA). The mechanical properties of its bonded plywood including tensile strength, modulus of rupture (MOR), modulus of elasticity (MOE) and shear strength under five test conditions were evaluated. Results indicated that the incorporation of nano CuO and PVA 17-99 separated the gel point and vitrification point delaying of moisture loss in modified PF resin during the curing process. The modification caused adverse effect on tensile strength but only minimal influence on MOR and MOE. Additionally, PVA 17-99 reduced the water resistance of cure PF resins. However, under the special test conditions, PVA consolidated the re-curing effect and compensated for the strength loss by hydrolysis.
Wei Gao, Guanben Du
The use of new, aqueous chemical wood modifications to improve the durability of wood-plastic composites
2017 - IRG/WP 17-40787
The wood flour used in wood-plastic composites (WPCs) can biologically deteriorate and thus the overall mechanical performance of WPCs decrease when exposed to moisture and fungal decay. Protecting the wood flour by chemical modification can improve the durability of the wood in a nontoxic way so it is not harmful to the environment. WPCs were made with modified wood flour and then evaluated for moisture sorption, fungal resistance and mechanical performance. Two different chemical modifications at 2 different levels were used: organosilicate (OS, 1% and 2.5%) and cobalt sulfate (CoS, 2.5% and 5%). All modifications had less weight loss than the unmodified controls with the 2.5% OS blend showing no weight loss from decay by either brown or white rot fungi. Water soaking for 1-week at elevated temperature (70°C) was more aggressive for laboratory decay and mechanical testing as shown by higher weight loss and lower mechanical properties compared to 2-week water soaking at room temperature (23°C). Moisture exposure decreased the mechanical properties, but 2.5% OS, 2.5% CoS and 5% CoS had better performance than the unmodified controls and 1% OS after 70°C conditioning and decay.
R E Ibach, C M Clemons, G C Chen