Influence of temperature of thermal treatment on surface densification of spruce

Kariž, Mirko; Kuzman, Manja Kitek; Šernek, Milan; Hughes, Mark; Rautkari, Lauri; Kamke, Frederick A.; Kutnar, Andreja

doi:10.1007/s00107-016-1052-z

Cited by 48 publications

(26 citation statements)

References 23 publications

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“…The process of softening is known as a pretreatment and combined with following mechanical pressing, achieving better compressing result. The thermo-mechanical densification [3][4][5], thermal-hydromechanical [6][7][8], hygro-mechanical steam treatment [9,10], mechanical-microwave treatment [11], and highpressure treatment [12,13] were developed to manufacture densified wood, in which the thermal-hydro is the most common and simplest pretreatment method currently. The cell walls of wood would be swelled by water although it cannot penetrate into crystalline region of cellulose.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of densified wood via synergy of chemical pretreatment, hot-pressing and post mechanical fixation

Shi

Peng

Huang³

et al. 2020

J Wood Sci

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Wood densification can improve the strength of low density wood species and extend wood product applications. To enhance the wood compressive quality, chemical pretreatments for pristine wood have widely been used. Densified Abies wood was fabricated by combining NaOH/Na 2 SO 3 solution treatment, hot-pressing and post mechanical fixation. The appearance, color, chemical composition, and physiology and mechanical properties before and after the densification treatment were examined by the colorimeter, FTIR and mechanical testing machine, respectively. Surface color of Abies wood was changed obviously after the densification. The values of brightness L* and b* decreased but the value of a* showed a slight increase in the densified wood. FTIR results confirmed that the color changes can be explained by the degradation of hemicellulose and lignin in wood cell walls and migration of extractives during the densification process. Sufficient removal of wood polymers resulted in the average compression ratio of about 80% in the radial direction of the natural wood. The density of densified wood increased with the wood thickness up to 1.227 g cm −1 , accounting for a 169% increase compared to that of the pristine wood. Modulus of rupture (MOR) and modulus of elasticity (MOE) in the thickness direction of densified wood also markedly enhanced. Degradation of polymers in wood cell walls also was reconfirmed by the difference of fracture interface. All the results suggested that the densified softwood can be easily fabricated using the proposed method and the new densified softwood can be appropriately used as interior decoration materials.

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Section: Introductionmentioning

confidence: 99%

Fabrication of densified wood via synergy of chemical pretreatment, hot-pressing and post mechanical fixation

Shi

Peng

Huang³

et al. 2020

J Wood Sci

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“…Wood can be densified in its whole volume (Ülker et al 2012; İmirzi et al 2014) or on the surface (Belt et al 2013;Laine et al 2013b;Rautkari et al 2013;Kariz et al 2017). The densification of wood's surface is a less energy-consuming process than the densification of the whole volume of wood.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Process Parameters on the Density Profile and Hardness of Surface-densified Birch Wood (Betula pendula Roth)

Laskowska¹

2017

BioResources

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This study examined the influence of temperature and time of treatment on the density profile and hardness of surface-densified birch wood (Betula pendula Roth). An analysis of the wood density profile was conducted on the basis of the following parameters: thickness, maximum density, and the distance between the maximum density and the wood surface. Depending on the technological parameters' values, the degree of compression of the wood was 13% to 22%, and its maximum density was 808 kg/m 3 to 994 kg/m 3 . As a result of the modification of birch wood at a temperature of 100 °C and 125 °C, the wood was densified on one side. As the temperature of the thermo-mechanical treatment was raised from 150 °C to 200 °C, the wood became densified on both sides. The maximum density of the wood increased gradually with the increase of the temperature of the press plate. The longer the time of thermomechanical treatment, the more distant the maximum density area was from the wood surface. Depending on the temperature and the time of treatment, the hardness of the surface-densified birch wood was 1.4 to 2.2 times greater than the hardness of non-densified wood.

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“…Heat-treatment is an effective method to improve some properties of wood such as biological durability and dimensional stability in changing environments. Heat-treatment changes the chemical composition of wood, which mainly results in the degradation of the hemicelluloses, carbohydrate cleavage, reduction in the degree of polymerization of the carbohydrates (Tjeerdsma et al, 1998;Kariz et al, 2017;Lunguleasa et al, 2018).…”

Section: Introduction 1 Uvodmentioning

confidence: 99%

“…Densifi cation of wood is an effective way for modifying low density tree species to make them comparable with higher density tree species. Furthermore, densifi cation is a way of utilizing low-density wood species instead of high density species in applications of higher value (Kariz et al, 2017). The mechanical properties and dimensional stability of low-density wood can be improved by the heat-treatment in modifi cation chamber followed by densifi cation process (Kwon et al, 2014).…”

Section: Introduction 1 Uvodmentioning

confidence: 99%

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Surface roughness and wettability of surface densified heat-treated Norway spruce (Picea abies L. Karst.)

et al. 2019

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Surface roughness and wettability of the heat-treated and then surface densified spruce (Picea abies L. Karst.) wood were measured to determine the effect of densification and heat-treatment on wood surface properties. The process of heat-treatment with an initial vacuum was performed in a vacuum chamber on oven dried lamellas with dimensions of 630 mm (longitudinal direction) x 45 mm (tangential direction) x 25 mm (radial direction). The lamellas were heat-treated at four different temperatures which were 170 °C, 190 °C, 210 °C and 230 °C. Control specimens were not exposed to heat-treatment. The lamellas were first heated to 100 °C, the creation of a vacuum taking 30 min at this temperature, and then heated to the desired temperature, and treated at this constant temperature for 3 h. The lamellas were then cooled down by using coils with cold water inside the chamber. Surface densification of lamellas with compression from 22 mm to 15 mm thickness was made by press platens heated at 150 °C and held in that position for 60 s. After the 1 min, the heated platen was cooled to 90 °C, whilst the specimen remained under compression to minimize immediate spring back. The total time of compression was 2 min (30 s closing, 60 s pressing and approx. 30 s cooling). In the treatment groups, the optimum treatment temperature on the one-side densified wood specimens was found to be 170 °C based on the surface roughness and wettability values. Surface densification significantly decreased the surface roughness of the wood specimens. The surface quality of wood can be improved when the wood is exposed to the heat-treatment and then surface densification.

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Influence of temperature of thermal treatment on surface densification of spruce

Cited by 48 publications

References 23 publications

Fabrication of densified wood via synergy of chemical pretreatment, hot-pressing and post mechanical fixation

Fabrication of densified wood via synergy of chemical pretreatment, hot-pressing and post mechanical fixation

The Influence of Process Parameters on the Density Profile and Hardness of Surface-densified Birch Wood (Betula pendula Roth)

Surface roughness and wettability of surface densified heat-treated Norway spruce (Picea abies L. Karst.)

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