| 1. |
- Ahmed, Sheikh Ali, et al.
(författare)
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Accelerated Mold Test on Dried Pine Sapwood Boards : Impact of Contact Heat Treatment
- 2013
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Ingår i: Journal of wood chemistry and technology. - : Taylor & Francis. - 0277-3813 .- 1532-2319. ; 33:3, s. 174-187
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Tidskriftsartikel (refereegranskat)abstract
- We test the hypothesis that the combination of kiln drying of double-stacked boards and contact heat treatment will reduce the susceptibility of treated boards to colonization by mold fungi. Winter-felled Scots pine (Pinus sylvestris L.) sapwood boards were double-stacked in an industrial kiln in ''sapwood out'' and ''sapwood in'' positions. Dried samples were then contact heat-treated using a hot press at three different temperatures (140°C, 170°C, and 200°C) for three different periods (1, 3, and 10 min). An accelerated mold test was performed in a climate chamber where naturally mold-infected samples were used as a source of mold inocula. Contact heat treatment degraded the saccharides that accumulated at dried surfaces, and reduced the mold growth. The threshold temperature and time for inhibiting mold growth were 170°C for 10 min. However, for industrial application, the most feasible combination of temperature and time would be 200°C for 3 min. We concluded that double stacking/contact heat treatment used is an environmentally friendly alternative to chemicals for reducing mold on Scots pine sapwood boards.
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| 2. |
- Ahmed, Sheikh Ali, et al.
(författare)
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Development of a new rapid method for mould testing in a climate chamber : preliminary tests
- 2013
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Ingår i: European Journal of Wood and Wood Products. - : Springer. - 0018-3768 .- 1436-736X. ; 71:4, s. 451-461
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to develop fast, simple and robust solid wood mould testing methods for the use in small-scale laboratory tests. The objective was to investigate mould susceptibility of different wood materials within the batches. The proposed method is based on natural contamination of non-sterile surfaces in climates conducive to mould growth. For this purpose, a climate chamber with regulated temperature and relative humidity was used. The conditioning chamber was divided into upper and lower chamber by a thin layer of stainless steel placed horizontally above the fan to minimise air circulation to the sample in the upper compartment. Mould-infected samples from outdoor tests were used as a source of mould inocula, and test trials were conducted on Scots pine (Pinus sylvestris L.) sapwood. Samples were suspended from the top of the upper chamber, and the chamber was exposed to different temperature and humidity levels. Severe mould infestation was observed after 12–14 days of incubation. Visual mould rating was then performed. Regardless of some constraints, this test method was very simple, fast, and effective. More importantly, unlike other test methods, it closely models mould infestation as it would occur under natural condition.
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| 3. |
- Ahmed, Sheikh Ali, et al.
(författare)
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Evaluation of preservative distribution in thermally modified European aspen and birch boards using computed tomography and scanning electron microscopy
- 2013
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Ingår i: Journal of Wood Science. - : Springer. - 1435-0211 .- 1611-4663. ; 59:1, s. 57-66
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this experiment was to impregnate thermally modified wood using an easy and cost-effective method. Industrially processed thermally modified European aspen (Populus tremula L.) and birch (Betula pubescens Ehrh.) were collected and secondarily treated at the laboratory scale with the preservatives tung oil, pine tar and Elit Träskydd (Beckers) using a simple and effective method. Preservative uptake and distribution in sample boards were evaluated using computed tomography (CT) and scanning electron microscopy (SEM) techniques. Preservative uptake and treatability in terms of void volume filled were found the highest in Beckers and the lowest in tung oil-treated samples. Thermally modified samples had lower treatability than their counterpart control samples. More structural changes after thermal modification, especially in birch, significantly reduced the preservative uptake and distribution. The differences of preservatives uptake near the end grain were high and then decreased near the mid position of the samples length as compared with similar type of wood sample. Non-destructive evaluation by CT scanning provided a very useful method to locate the preservative gradients throughout the sample length. SEM analysis enabled the visualization of the preservative deposits in wood cells at the microstructural level.
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| 4. |
- Ahmed, Sheikh Ali, et al.
(författare)
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Mould susceptibility of Scots pine (Pinus sylvestris L.) sapwood : Impact of drying, thermal modification, and copper-based preservative
- 2013
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Ingår i: International Biodeterioration & Biodegradation. - : Elsevier. - 0964-8305 .- 1879-0208. ; 85, s. 284-288
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Tidskriftsartikel (refereegranskat)abstract
- The development of mould on wood surfaces depends on several factors. Although mould does not affect the mechanical properties of wood, it greatly reduces the aesthetic value of wood such as the sapwood of Scots pine (Pinus sylvestris L.), which is very prone to mould. In addition, adverse health effects of mould on humans are a great concern. Different types of dried and treated wood were used to observe whether they had enhanced durability against mould following an accelerated laboratory test method in a climate chamber. Samples were green, air-dried, industrially thermally modified, treated with copper-based preservative, and kiln-dried wood, which were tested within a single test run. The test produced the following main results: The thermal modification increased the durability of the wood, and the protective effectiveness of alternative treatments was comparable to that of commercially available copper-based treatment. However, the initial moisture content of the samples during mould exposure had a great influence on the onset of mould growth. The risk of mould susceptibility of industrial kiln-dried lumber can be reduced by drying using the double-layering technique and planing off the nutrient enriched evaporation surfaces.
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| 5. |
- Ahmed, Sheikh Ali, et al.
(författare)
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Uneven distribution of preservative in kiln-dried sapwood lumber of Scots pine : Impact of wood structure and resin allocation
- 2012
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Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 66:2, s. 251-258
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Tidskriftsartikel (refereegranskat)abstract
- Scots pine (Pinus sylvestris L.) sapwood lumber was collected after kiln drying and preservative treatment with Celcure AC 800 (a copper-amine wood preservative). Distribution of the preservative throughout the lumber was visually examined. Not all, but some samples showed specific localized areas without any preservative distribution throughout their entire length. Those samples were assessed further for anatomical properties, specifically in impregnated and unimpregnated areas. Additional study was conducted on the morphological nature and redistribution of lipophilic extractives using three different histochemical staining methods. Intrinsic wood properties – especially the frequency of axial resin canals and the percentage of canals blocked – were found to be responsible for the irregular distribution of the preservative. Furthermore, the inability to create continuous and frequent interstitial spaces due to the collapse of thin-walled ray cells throughout the lumber resulted in un-even distribution of preservatives. Staining techniques were useful to localize places with more or less abundance of extractives (e.g., fats) in impregnated and unimpregnated wood, which varied considerably. Histochemical observations revealed information pertaining to the kiln dry specific distribution and redistribution of extractives between the areas. Moreover, resin reallocation and modification in ray parenchyma and resin canals induced by kiln drying would be another reason for the impregnation anomalies.
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| 6. |
- Johansson, Dennis, et al.
(författare)
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Effect of heat treatment on capillary water absorption of heat-treated pine, spruce and birch
- 2006
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Ingår i: Wood structure and properties '06. - Zvolen, Slovakia : Arbora Publishers. ; , s. 251-255
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Konferensbidrag (refereegranskat)abstract
- Longitudinal absorption of water in matched heat-treated and untreated boards was studied. The boards are from three different species. Scots pine (Pious sylvestris), Norway spruce (Picea abies) and birch (Betula pubescens). The heat treatment was performed according to the Thermowood process at two different temperature levels (170 degrees C and 200 degrees C) for all three species. Computer tomography (CT) scanning was used to intermittently monitor the ascent of the water front. The use of CT scanning enables a study of the liquid water ascent in three dimensions over time. This means that it is possible to determine the influence of different treatment temperatures and species as well as the difference between heartwood and sapwood on capillary action.The results show that longitudinal water absorption in pine sapwood was substantially lamer when heat-treated at 170 degrees C compared to untreated pine sapwood. In pine heartwood, the ascent of water was low in heat-treated as well as in untreated boards. Spruce boards showed low water absorption in sap- and heartwood in heat-treated as well as in untreated boards. Birch showed a decreasing uptake of water with increasing treatment temperature
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| 7. |
- Karlsson, Olov, et al.
(författare)
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Heat treatments of high temperature dried norway spruce boards: Saccharides and furfurals in sapwood surfaces
- 2012
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Ingår i: BioResources. - : BioResources. - 1930-2126 .- 1930-2126. ; 7:2, s. 2284-2299
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Tidskriftsartikel (refereegranskat)abstract
- Carbohydrates that migrate to wood surfaces in sapwood during drying might influence properties such as mould susceptibility and colour. Sugars on the surface of Norway spruce boards during various heat treatments were studied. Samples (350mm×125mm×25mm) were double-stacked, facing sapwood-side outwards, and dried at 110°C to a target moisture content (MC) of 40%. Dried sub-samples (80 mm × 125 mm × 25 mm) were stacked in a similar way and further heated at 110°C and at 130°C for 12, 24, and 36 hours, respectively. Glucose, fructose, and sucrose as well as 5-hydroxymethylfurfural (HMF) and furfural in the sapwood surface layer of treated wood were analysed using HPLC (RI- and UV-detectors). Carbohydrates degraded to a lower extent at 110°C than at 130°C. Furfural and to a larger extent HMF increased with treatment period and temperature. Heat treatment led to a decrease in lightness and hue of the sapwood surface of sub-samples, while chroma increased somewhat. Furthermore, considerably faster degradation (within a few minutes) of the carbohydrates on the surface of the dried spruce boards was observed when single sub-samples were conductively hot pressed at 200°C. Treatment period and initial MC influenced the presence of the carbohydrates in wood surface as well as colour change (ΔE ab) of the hot pressed sub-samples.
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