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| 2. |
- Borko, Domen, et al.
(author)
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The potential of citric acid and glucose enhancing the reaction of wood with bicine and tricine
- 2024
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In: Wood Material Science & Engineering. - : Taylor & Francis. - 1748-0272 .- 1748-0280.
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Journal article (peer-reviewed)abstract
- To improve the resistance of wood to biological decay the Maillard reaction between introduced amines and wood cell-wall polymers can be utilised. However, initial studies in wood modification showed almost complete leaching of bicine and tricine from treated wood and the loss of beneficial effects. The objective of this study was to assess whether possible reactions of bicine or tricine with wood could be further enhanced and reaction products stabilised through the addition of glucose and/or citric acid. Thus, Scots pine sapwood specimens were impregnated with tricine or bicine, with or without glucose and citric acid, and then heated to a temperature of 160°C. The dimensional stability, degree of chemical leaching and mechanical properties were assessed. Overall, it was concluded that neither the presence of glucose nor citric acid did appear to enhance the reactivity of tricine or bicine. Anti-swelling efficiency (ASE) of 50% was observed for combined treatments of bicine/tricine and citric acid but the leaching resistance originated mainly from citric acid and glucose, with no indication for the retention of bicine or tricine. The presence of citric acid led to a strongly reduced modulus of rupture.
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| 3. |
- Cristescu, Carmen, et al.
(author)
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Could colour predict hardness of hot-ptressed self-laminated beech boards
- 2015
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In: Pro Ligno. - 1841-4737 .- 2069-7430. ; 11:4, s. 150-156
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Journal article (peer-reviewed)abstract
- Laminated self-bonded densified boards were obtained by pressing five veneers of beech(Fagus sylvatica L.) parallel-grain-oriented, without adhesive and without surface activation. Theboards were pressed according to an experimental design based on fifteen different combinations ofpressing parameters: temperature (200, 225, and 250°C), pressure (4, 5, and 6MPa), and time (240,300, and 360s). The image of the 40 board edges (radial sections) was analysed with ImageJ softwarein the red-green-blue (RGB) colour space. Brinell hardness tests were also performed. The resultsshow an almost linear relation between the brightness values (defined as the arithmetic mean of theRGB channels) and the Brinell hardness. It is suggested that brightness is a predictor of strength forself-bonded laminated boards.
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| 4. |
- Cristescu, Carmen, et al.
(author)
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Influence of pressing parameters on mechanical and physical properties of self-bonded laminated beech boards
- 2015
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In: Wood Material Science & Engineering. - : Informa UK Limited. - 1748-0272 .- 1748-0280. ; 10:2, s. 205-214
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Journal article (peer-reviewed)abstract
- Five-ply self-bonded boards were obtained by pressing beech veneers parallel to the grain without additional adhesives, steam or pre-treatment. Fifteen different combinations of pressing parameters were tested, including temperature (200°C, 225°C and 250°C), pressure (4, 5 and 6 MPa) and pressing time (240, 300 and 360 seconds). Due to severe pressing conditions, the new product showed a higher density and different properties compared to a conventionally glued laminated wooden board. The self-bonding quality was assessed through dry shear strength tests, through a three-point bending test and a water-soaking test at 20°C. The dimensions in the cross section of the boards were measured after soaking in water. Results show that the choice of pressing parameters affects all the mechanical and physical properties tested. A statistical analysis revealed that the pressing temperature is the most influential parameter. Boards pressed at 200°C delaminated rapidly in water, whereas boards pressed at 225°C delaminated only at core-positioned layers after 48 hours and boards pressed at 250°C did not delaminate at all in water. Compared to panels pressed at lower temperatures, boards pressed at 250°C had the highest density, a higher shear and bending strength and a lower water absorption.
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| 5. |
- Cristescu, Carmen, et al.
(author)
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Markers of quality in self-bonded beech boards
- 2017
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Conference paper (peer-reviewed)abstract
- A self-bonding phenomenon takes place when five layers of beech (Fagus SylvaticaL.) veneers are pressed at temperatures higher than 200ºC. If the pressing temperature between veneer surfaces reaches at least 225ºC during pressing and if the pressure applied is optimal, water-resistant bonds are formed between veneers. This study investigates the relation of thickness reduction (marker of compression) and mass loss (marker of heat treatment intensity) to boards quality. The effect of water and water vapour on the bondings between veneer in boards pressed at 200, 225 and 250ºC is studied. The conclusion is that pressing 5 layers of 2 mm rotary-cut beech veneer parallel-fibered at 225ºC, 5 MPa and 300 s leads to a thickness reduction of 33.4 % and mass loss of 1.23 %; in such boards bondings are not resistant to liquid water but are resistant to vapour after one adsorption-desorption cycle. When pressing at 250ºC, 5 MPa and 300 seconds, the thickness reduction is 50% and the mass loss 4%; in such boards no delamination was observed when soaked in water. Boards pressed athigher temperature show lower hygroscopicity. Their equilibrium moisture content (EMC) rangedbetween 3.6 and 7%. Based on the results of this study it ishypothesised that the decay resistance of self-bonded boards will increase when increasing the severity of the hot-pressing.
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| 6. |
- Edlund, Agneta, et al.
(author)
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Symptom profile of delirium in older people with and without dementia.
- 2007
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In: Journal of Geriatric Psychiatry and Neurology. - : SAGE Publications. - 0891-9887 .- 1552-5708. ; 20:3, s. 166-171
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Journal article (peer-reviewed)abstract
- Clinical profiles of delirium in 717 older people with and without dementia age 75 years and older in 4 different types of care were studied. Delirium and dementia were diagnosed according to DSM-IV criteria. Delirious demented participants (n = 135) had more often had previous delirium episodes and were more often being treated with analgesics compared to delirious participants without dementia (n = 180). The clinical profile of delirium in the participants with dementia was more frequently characterized by aggressivity, latency in reaction to verbal stimuli, restlessness and agitation, delusions, anxiousness, hallucinations, and a poorer orientation and recognition. Delirium among demented participants more often had a fluctuating course during the day and was more common in the evening and at night. In conclusion, clinical profiles of delirium in participants with and without dementia are different, which might indicate a different etiology or pathophysiology, or both, and a need for different treatment strategies. ( J Geriatr Psychiatry Neurol 2007;20:166—171)
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| 7. |
- Elustondo, Diego, et al.
(author)
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Development of method for surface modification of wood
- 2015
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In: Proceedings of the Eighth European Conference on Wood Modification. - Helsinki : Aalto University, School of Chemical Engineering. ; , s. 137-140
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Conference paper (peer-reviewed)abstract
- This study concerns the development of a method for surface modification based on the hot-and-cold bath process. In the experiments the wooden boards were first heated in an oven and after that they were immediately soaked in a cold chemical solution. This procedure allowed the chemicals to penetrate partially into the wood without using pressure equipment. In this study copper, furfuryl alcohol and phenol formaldehyde based solutions were used. The impregnation resulted in modified layers below the wood surfaces representing a trade- off between the full-bulk modification and surface coating of wood. It is concluded that the method can be developed further for potential industrial use to produce e.g. flooring, cladding or decking.
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| 8. |
- Garskaite, Edita, et al.
(author)
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Surface hardness and flammability of Na2SiO3 and nano-TiO2 reinforced wood composites
- 2019
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In: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 9:48, s. 27973-27986
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Journal article (peer-reviewed)abstract
- The objective of this study was to explore an effect of the combined inorganic materials on the wood hardness and flame-retardancy properties in a concept of sustainable material management. Herein, the reinforcement of Scots pine (Pinus sylvestris L.) sapwood with sodium silicate and TiO2 nanoparticles via vacuum-pressure technique is reported. Pyrolysis of modified wood was studied by TG-FTIR analysis; the results showed that maximum weight loss for the modified wood was obtained at 40–50 °C lower temperatures compared to the reference untreated wood. The Gram–Schmidt profiles and spectra extracted at maxima absorption from Gram–Schmidt plots indicated chemical changes in wood–inorganic composites. SEM/EDS analysis revealed the presence of Na–O–Si solid gel within the wood-cell lumen and showed that TiO2 was homogeneously distributed within the amorphous Na–O–Si glass-forming phase to form a thin surface coating. EDS mapping further revealed the higher diffusivity of sodium into the cell wall compared to the silicon compound. The presence of amorphous sodium silicate and nano-TiO2 was additionally confirmed by XRD analysis. FTIR spectra confirmed the chemical changes in Scots pine sapwood induced by alkalization. Brinell hardness test showed that the hardness of the modified wood increased with the highest value (44% increase in hardness) obtained for 10% Na2SiO3–nTiO2 modified wood. The results showed good correlation between TG and flammability test; limiting oxygen index (LOI) values for the wood–inorganic composites increased by 9–14% compared to the untreated wood.
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