Effects of nanosilver-impregnation and alfalfa-intercropping on fluid transfer in downy black poplar wood

Effects of alfalfa-intercropping and nanosilver-impregnation were studied here on the specific gas permeability of 10-year old Populus nigra var. betulifolia. Specimens were impregnated with a 200 ppm aqueous dispersion of silver nanoparticles under 250 kPa pressure; the results were then compared with the un-impregnated specimens. The size range of silver nanoparticles was 10 to 80 nm. After the initial measurement, specimens were kept in vaporized chamber for six months (43±2°C, and 80±3% relative humidity); permeability was measured every month. Results showed that maximum specific longitudinal gas permeability was observed in the nanosilver-impregnated inner-wood specimens of the treatment with alfalfa (1614,4 × 10-13 m3 m-1), and minimum permeability was found in the un-impregnated outer-wood specimens of the treatment without alfalfa (491,7 × 10-13 m3 m-1) before the vaporization. Vaporized chamber made permeability decrease permeability at the first phases because of the absorption of water vapors and the consequent swelling; however, due to the proliferation of pits and perforation plates by fungi and molds, permeability was eventually increased. Antibacterial property of silver did not significantly decrease the growth of molds and fungi in the nanosilver-impregnated specimens.

Effects of the improvement in thermal conductivity coefficient by nano-wollastonite on physical and mechanical properties in medium-density fiberboard (MDF)

The improving effect of an increase in the thermal conductivity caused by nano-wollastonite (NW) on the physical and mechanical properties of medium-density fiberboard (MDF) was studied. Nanowollastonite was applied at 2, 4, 6, and 8 g/kg, based on the dry weight of wood-chips, and compared with control specimens. The size range of wollastonite nanofibers was 30 to 110 nm. The results show that NW significantly (p < 0.05) increased thermal conductivity. The increased thermal conductivity resulted in a better curing of the resin; consequently, mechanical properties were improved significantly. Furthermore, the formation of bonds between wood fibers and wollastonite contributed to fortifying the MDF. It was concluded that a NW content of 2 g/kg did not significantly improve the overall properties and therefore cannot be recommended to industry. Because the properties of NW-6 and NW-8 were significantly similar, a NW-content of 6 g/kg can be recommended to industry to significantly (p < 0.05) improve the properties of MDF panels

Effects of nano-wollastonite on physical and Mechanical properties of medium-density fiberboard

Effects of nano-wollastonite (NW) on physical and mechanical properties of medium density fiberboard (MDF) were studied. NW was applied at 5, 10, 15, and 20 g/kg dry weight basis of wood fibers; the results were then compared with control specimens. Two application methods of NW were used: surface and internal applications. Density was kept constant at 0,67 g/cm3 for all treatments and tests were carried out in accordance with ASTM D-1037. Addition of NW contributed in improving the physical and mechanical properties of the panels, both when applied internally or as surface treatment.It was concluded that NW contents of 10% and 15% were the optimal levels for industrial purposes for internal and surface applications, respectively

Učinci impregnacije nanočesticama srebra i toplinske obrade na čvrstoću prianjanja premaza na drvo

Effects of impregnation with a silver nano-suspension, as well as of heat-treatment, on pull-off adhesion strengths of the coating system on three commercial solid wood species were studied. The wood species included beech, poplar, and fi r. The size range of silver nanoparticles was 30 – 80 nm. The specimens were coated with an un-pigmented sealer and a clear fi nish on the basis of an organic solvent. The results showed that the highest and the lowest pull-off strengths were found in beech specimens heat-treated at 145 °C (5.7 MPa) and in nanosilver-impregnated poplar specimens heat-treated at 185 °C (2.5 MPa), respectively. Impregnation with nanosilver decreased pull-off strength in the case of all species as a result of formation of micro checks in the cell walls caused by the impregnation under high pressure in vessel. Heat-treatment at the temperature lower than 145 °C increased pull-off strength as to the irreversible hydrogen bonding in the course of water movements within the pore system of the cell walls, resulting in extra bonds among cell wall components and higher mechanical properties. However, heat treatment at the temperature higher than 185 °C significantly decreased the strength as the degradation of hemicellulose and cell wall wood components caused signifi cant decrease in mechanical strength and cell wall thinning. High thermal conductivity coefficient of silver intensified the impact of heat-treatment by rapid absorption of heat on the surface of the specimens.U radu su istraživani učinci impregnacije drva srebrnom nanosuspenzijom, kao i učinci toplinske obrade na čvrstoću prianjanja (adhezije) sustava premaza na tri komercijalne vrste masivnog drva. U istraživanjima je analiziran sustav premaza na drvu bukve, topole i jele. Raspon veličine srebrnih nanočestica bio je 30 – 80 nm. Uzorci su obrađeni nepigmentiranim punilom i završnim premazom na osnovi organskog otapala. Rezultati su pokazali da je najveća čvrstoća prianjanja izmjerena na uzorcima od toplinski obrađene bukovine pri 145 °C (5,7 MPa), a najmanja na uzorcima od drva topole impregniranima srebrnim nanočesticama i toplinski obrađenima pri 185 °C (2,5 MPa). Impregnacija srebrnim nanočesticama smanjila je čvrstoću adhezije na svim vrstama drva, što je posljedica stvaranja mikropukotina na staničnim stijenkama uzrokovanima impregnacijom pod visokim tlakom u posudi. Toplinska obrada na temperaturi nižoj od 145 °C povećala je čvrstoću adhezije s obzirom na ireverzibilne vodikove veze u toku kretanja vode u sustavu pora staničnih stijenki, što rezultira dodatnim vezama između komponenti stanične stijenke i boljim mehaničkim svojstvima. Međutim, toplinska obrada na temperaturi višoj od 185 °C bitno smanjuje čvrstoću adhezije jer propadanje hemiceluloze i komponenti stanične stijenke drva uzrokuje znatno smanjenje mehaničke čvrstoće i stanjivanje stanične stijenke. Visoki koeficijent toplinske vodljivosti srebra pojačava učinak toplinske obrade brzom apsorpcijom topline na površini uzorka

Investigation on lateral resistance of joints made with drywall and sheet metal screws in bagasse particleboard and comparison with that of commercial MDF

In this research, effects of screw diameter, screw type, panel type, and end distance on lateral resistance of the joints made with drywall and sheet metal screws were studied in bagasse particleboard and the results were compared to those obtained from commercial medium density fiberboard (MDF). The accuracy of EYM in prediction of lateral resistance was then investigated. The drywall screws comprised of size 8 with coarse thread and size 10 with fine thread; the sheet metal screws comprised of size 8 and 10 with normal thread. Results indicated that lateral resistance increased with the increase in the diameter of both screw types, although not statistically significant. The lateral resistance obtained from MDF specimens was 20% more than that of bagasse specimens. Increase in the end distance also resulted in an increase in the lateral resistance. In all cases, sheet metal screws showed higher lateral resistance in comparison to those obtained from drywall screws. It can be concluded that Mode IIIs is more accurate than Mode Is in the prediction of lateral resistance in two-member screwed joints (single shear plane) for both MDF and bagasse boards

Utjecaj nanogline na fizička i mehanička svojstva ploča vlaknatica srednje gustoće izrađenih od drva, vlakana pilećeg perja i dviju vrsta smola

Medium-density fi berboards (MDF) were produced, using two different resins of urea-formaldehyde (UF) and phenol-formaldehyde (PF) at 10 % and 8 % contents, respectively. In order to find new source of raw material to satisfy the increasing need of composite manufacturing industry, 10 % of chicken feather was added to the furnish. Moreover, nano-clay was added to investigate its potential improving effects on MDF panel properties. Results showed that panels with PF resin demonstrated significantly lower water absorption and thickness swelling values in comparison to the panels with UF resin. However, mechanical properties of panels containing UF resin were generally higher; this was partially attributed to the higher resin content. It was concluded that panels with PF resin are recommended for applications where panels may be more exposed to water and vapor. In cases where the mechanical properties are of prime importance, panels with UF resin are more preferable. NC can be recommended in panels containing UF-resin to improve the properties, while it is not recommended in panels with PF-resin. Moreover, chicken feather can be included in MDF furnish to provide part of raw materials, though its addition can have diminishing effect on the properties to some extent.Ploče vlaknatice srednje gustoće (MDF) izrađene su uz dodatak dviju različitih smola, ureaformaldehidne (UF) i fenolformaldehidne (PF), i to u udjelu od 10 odnosno 8 %. Kako bi se pronašao novi izvor sirovine i pritom zadovoljile povećane potrebe industrije kompozitnih materijala, smjesi sirovine za izradu ploča vlaknatica dodano je 10 % pilećeg perja. Nadalje, dodana joj je i nanoglina da bi se istražilo moguće poboljšanje MDF ploča. Rezultati su pokazali da su ploče s PF smolom znatno slabije upijale vodu i da im je debljinsko bubrenje u odnosu prema pločama s UF smolom bilo manje. Međutim, mehanička svojstva ploča koje su sadržavale UF smolu u osnovi su bila bolja, što je djelomično povezano s većim udjelom smole. Zaključeno je da se ploče s PF smolom preporučuju za primjenu u uvjetima veće izloženosti vodi i pari. Kada su, pak, važnija mehanička svojstva ploča, pogodnije su one s UF smolom. Nanoglina se preporučuje za poboljšanje svojstava ploča koje sadržavaju UF smolu, a ne preporučuje se za ploče s PF smolom. Nadalje, pileće se perje može dodati sirovini za izradu MDF ploča iako ono može donekle pridonijeti pogoršanju svojstava ploče

A correlation between the gas and liquid permeabilities of beech wood heat-treated in hot water and steam mediums

Heat-treatment, a major method of wood modification for improving dimensional stability and natural durability, has been studied considerably in the scientific literature. This study will focus on the effect of heat-treatment on permeability, an important physical property of wood by subjecting beech samples to two different mediums of hot water and steam, as well as in two buffered hot water of pH 7 and 8. Hydrothermal treatment caused gas permeability to decrease to its lowest value among the treatments (91.6% decrease comparing the control treatment). Hydrothermal treatment in buffered hot water of pH 8 made the lowest impact on gas permeability (12.3% decrease). The decrease in gas permeability was due to settlement of extractives on vessel perforation plates. Gas permeability showed a highly significant correlation with the amount of swelling in radial direction. Low correlation was found between liquid permeability with water absorption and the amount of swelling. Gas permeability is considered a suitable criterion for predicting the amount of swelling in beech wood

Effects of heat-treatment on permeability of untreated and nanosilver-impregnated native hardwoods

The effects of heat-treatment on permeability are the main topic of the present study. Longitudinal dowel shape pairs of specimens were prepared from three native species and their specific gas permeability values were measured. From each pair, one specimen was kept for heat-treatment and the other was impregnated with 200 ppm nano-silver suspension; the size range of nanoparticles was 20-80 nm. In six consecutive steps, each pair was heated at 50, 75, 100, 125, 150, and 185°C. Results showed that gas permeability increased when specimens were heated at 50°C as a result of the loss of bond-water and consequent shrinkage. Permeability sharply decreased when the specimens were heated at 75°C and gradually increased at each step up-to 150°C. At 185°C, permeability again decreased in. The sharp decrease in permeability at 75°C was possibly due to irreversible hydrogen bonding in the course of water movements within the vessel perforations and pore system of cell walls. The gradual increase in permeability at higher temperatures, though, might be due to higher internal stresses that are released as micro-cracks develop, thus leading to a greater capability of fluid-transfer. Nano-silver impregnation intensified this process

Effects of nanosilver-impregnation and alfalfa-intercropping on fluid transfer in downy black poplar wood

Effects of alfalfa-intercropping and nanosilver-impregnation were studied here on the specific gas permeability of 10-year old Populus nigra var. betulifolia. Specimens were impregnated with a 200 ppm aqueous dispersion of silver nanoparticles under 250 kPa pressure; the results were then compared with the un-impregnated specimens. The size range of silver nanoparticles was 10 to 80 nm. After the initial measurement, specimens were kept in vaporized chamber for six months (43±2°C, and 80±3% relative humidity); permeability was measured every month. Results showed that maximum specific longitudinal gas permeability was observed in the nanosilver-impregnated inner-wood specimens of the treatment with alfalfa (1614,4 × 10-13 m³ m-1), and minimum permeability was found in the un-impregnated outer-wood specimens of the treatment without alfalfa (491,7 × 10-13 m³ m-1) before the vaporization. Vaporized chamber made permeability decrease permeability at the first phases because of the absorption of water vapors and the consequent swelling; however, due to the proliferation of pits and perforation plates by fungi and molds, permeability was eventually increased. Antibacterial property of silver did not significantly decrease the growth of molds and fungi in the nanosilver-impregnated specimens