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Thermo-hydro-mechanical (THM) processing can improve the intrinsic properties of wood, produce new materials, and give desired form and function to new applications. THM treatments change the mechanical properties of wood and may change its viscoelastic properties as well. Therefore, the objective of this study was to assess the viscoelastic properties of THM-treated wood at several humidity and load levels. To explore these changes, this study applied a THM treatment to beech (Fagus sylvatica L.) wood with steam (620 kPa) and heat (170 °C), followed by densification and increased temperature (200 °C) in a hot-press, which was then cooled while under pressure. Two initial specimen thicknesses before THM treatment were used to study the difference between density ratios. Specimens were tested in a humidity-controlled dynamic mechanical analyser (DMA) to apply creep stress with different loading levels (20% and 30% of expected modulus of rupture) and relative humidity levels (30%, 50%, and 65% RH). The creep compliance/recovery response was monitored, and dynamic moduli were measured before and after the application of creep stress. The loss modulus measured was highest for specimens tested at 65% RH and lowest in specimens tested at 30% RH, which is a direct result of the viscous response of the material. Increased damping of the specimens was also observed at higher RH, which is typical for wood products due to added moisture in the cell wall acting as a plasticizer to cell wall polymers. Like previous studies, THM treatment lowered the equilibrium moisture content (EMC) of densified wood specimens, which affected their mechanical performance. THM treatment yields higher strength and lower EMC, suggesting that this product could be suitable for structural applications where their service life is in an indoor environment. THM treatment also resulted in decreased creep compliance and recovery compliance as compared to control specimens. [ABSTRACT FROM AUTHOR]

The purpose of this paper was to analyze the effects of various OSB-strand modifications on physical and mechanical properties of strand board. Norway spruce (Picea abies L. Karst) strands were acetylated using acetic anhydride or thermally modified at 180 °C using atmospheric pressure and superheated steam environment. Strand boards made of acetylated strands (Acet), thermally modified strands (TM) and thermally modified strands used only at surface layers (TMSL) were produced. Furthermore, strand boards with 20% (Cork20%) and 40% (Cork40%) cork particles were manufactured. Wood-water relations, i.e., equilibrium moisture content (EMC), water absorption (WA), thickness swelling (TS), as well as mechanical properties, i.e., bending strength and internal bonding, were tested and compared to untreated reference strand board. The EMC for TMSL was no different than the reference boards, however, the other boards had a statistically significant decrease in EMC. Acetylated strand board and boards with cork particles had a significant increase in water resistance. The mechanical properties decreased for TM and Cork40%, but no difference was shown for Cork20%. Acetylation increased internal bond strength. The results provide a comparison between different modifications of strand boards and show a new possibility of reducing the water effects on OSB with cork particles. [ABSTRACT FROM AUTHOR]

The bondability/glueability of aged and sanded thermo-hydro-mechanically (THM) densified beech wood ( Fagus sylvatica L.) was tested and compared with undensified sanded beech wood as a control. THM and control specimens were bonded with five different soy protein isolate (SPI) based adhesives. Commercial SPI powder was thermally modified in the vacuum chamber at 50 or 100 °C and pH adjusted (to pH 10.0) dispersions in water prepared at 24, 50 or 90 °C. Wettability was determined with measuring the sessile drop contact angles of water. Effective penetrations (EPs) and tensile shear strengths of THM and control specimens were determined. THM and control wood had similar wettability. Although THM wood had lower moisture content than control wood, it absorbed the water more slowly than control wood. THM specimens showed lower EPs than control specimens when comparing individual adhesives due to increased density of THM wood. Adhesives prepared with SPI thermally modified at 50 °C showed statistically significantly lower tensile shear strength of bonded THM specimens than that of bonded control specimens. THM densification had no significant effect on the bonding strengths of adhesives prepared with non-modified SPI and SPI thermally modified at 100 °C. [ABSTRACT FROM AUTHOR]

Spruce ( Picea abies L. Karst) wood lamellae, thermally treated at 170, 190, 210 and 230 °C were surface densified by compression at a temperature of 150 °C to three degrees of compression. Immediate springback, set recovery, mechanical properties in 3-point flexure, Brinell hardness and density profiles measurements were used to determine the effect of thermal treatment on the properties of surface densified wood. The highest immediate springback occurred in wood specimens thermally treated at the highest temperature (230 °C) and decreased with decreasing thermal treatment temperature. The untreated samples had the highest set recovery, which decreased with the temperature of thermal treatment. The surface densification increased hardness and bending strength. The highest increase was in the case of untreated wood and decreased with the temperature of thermal treatment. The modulus of elasticity (MOE) and modulus of rupture (MOR) of surface densified wood decreased with increasing thermal treatment temperature. The trend was similar for specimens which were thermally treated but not surface densified. Surface densification increased the density of the specimens in the first few millimetres below the surface. The highest density was achieved in untreated specimens and the lowest in specimens thermally treated at the highest temperature. [ABSTRACT FROM AUTHOR]

Copyright of European Journal of Wood & Wood Products / Holz als Roh- und Werkstoff is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of European Journal of Wood & Wood Products / Holz als Roh- und Werkstoff is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of European Journal of Wood & Wood Products / Holz als Roh- und Werkstoff is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of European Journal of Wood & Wood Products / Holz als Roh- und Werkstoff is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of European Journal of Wood & Wood Products / Holz als Roh- und Werkstoff is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Low-density hybrid poplar ( Populus deltoides × Populus trichocarpa) was densified with the viscoelastic thermal compression (VTC) process to three different degrees of densification (63%, 98%, and 132%). Durability of the VTC treated specimens was assessed by exposure to two white rot fungi ( Pleurotus ostreatus and Trametes versicolor) for four or eight weeks. After incubation, mass loss in grams and percentage mass loss were determined. The results showed that VTC densification did not change decay resistance to Pleurotus ostreatus and Trametes versicolor. The mass losses caused by Trametes versicolor were more extensive than those by Pleurotus ostreatus. As expected, longer exposure time resulted in higher mass loss. Furthermore, the degree of densification did not influence susceptibility to fungal degradation. [ABSTRACT FROM AUTHOR]

The vertical density profile of wood-based composites is often measured using X-ray densitometry. During preliminary studies, in which the density profiles of wood composites with discrete layers of varying density were measured, it was observed that the absolute density values of the layers were incorrect when compared to gravimetric measurements of the individual layers. This is due the recommended calibration process of the X-ray densitometer, which uses the overall density of the composite to determine the X-ray attenuation factor. The severity of the error increases with the difference between minimum and maximum density in the profile. [ABSTRACT FROM AUTHOR]

A correction to the article "The Wettability and Bonding Performance of Densified VTC Beech (Fagus sylvatica L.) and Norway Spruce ( Picea abies (L.) Karst.) Bonded With Phenol-Formaldehyde Adhesive and Liquefied Wood" that was published online on February 21, 2013 is presented.