木家具表面耐香烟灼烧性能测定

木家具表面耐香烟灼烧性能是木家具是否合格的一项重要的理化性能指标,也是近几年木家具质量问题比较突出的项目。一些耐香烟灼烧差的家具漆膜遇香烟高温灼烧后,漆膜涂层容易出现脱落状黑斑、裂纹、鼓泡现象,导致家具无法使用。为了研究造成家具表面耐香烟灼烧项目合格率偏低的原因,笔者依据GB/T 3324-2008《木家具通用技术条件》和GB/T 17657-1999《人造板及饰面人造板理化性能试验方法》要求对不同厂家、不同工艺制作的家具表面耐香烟灼烧能力进行了测定和分析。结果表明,油漆种类、油漆工艺对家具表面耐香烟灼烧能力有显著影响。另外,木家具经贴装具有耐磨、耐灼烧性能的浸渍膜纸后,具有较高的耐灼烧性,可应用于干燥高温领域。     

Influence of low and moderate temperature kiln drying schedules on specific mechanical properties of Norway spruce wood

The knowledge of the influence of different temperature ranges on mechanical properties of kiln dried timber is very important in structural applications. The current paper deals with an investigation of the influence of low and moderate temperature drying schedules on the selected mechanical properties of Norway spruce wood (Picea abies?L.). The drying experiments were performed at four different temperatures (45, 55, 65, and 80°C) and clear wood specimens were prepared for the mechanical tests, three-point bending test, impact bending test, and tensile test perpendicular to the grain, respectively. The results of this systematic investigation were statistically analysed and as a conclusion, it can be stated that the mechanical properties investigated were not influenced by the drying temperatures applied.     

Effects of high temperature drying in nitrogen atmosphere on mechanical and colour properties of Norway spruce

Heat treatment and drying processes of wood are always accompanied by material changes. These changes are partly caused by oxidative reactions. This study aims to compare high temperature drying in inert gas atmosphere with conventional kiln drying of spruce wood. The mechanical properties as well as colour changes were measured after drying. In general, higher compression strength was observed for samples dried at high temperatures in nitrogen atmosphere. However, tensile and bending strength proved no significant difference. Corresponding to the strength values increased stiffness values were also observed for the compression samples, whereas for tension and bending samples no significant effect was visible. Up to a temperature of approx. 125 °C discolouration is prevented by drying samples in nitrogen atmosphere.     

干燥方式对苜蓿超微粉物化特性及抗氧化活性的影响

为研究不同干燥方式对苜蓿超微粉物化特性及抗氧化活性的影响,以苜蓿超微粉总色差为指标,采用正交实验法,确定苜蓿超微粉的最佳护色方法,优化热风干燥工艺参数;通过测定苜蓿超微粉粒度、溶解度、持水力、持油力、DPPH自由基清除率等理化指标,比较热风干燥和真空冷冻干燥得到的苜蓿超微粉之间的物化特性和抗氧化活性差异。结果表明,采用热风干燥法干燥苜蓿的最佳工艺参数为:干燥温度70℃、干燥时间8 h,护色剂为0.15% L-半胱氨酸时,此条件制备的苜蓿粉具有较好的物化性质。并且苜蓿超微粉粒度的减小能明显提高苜蓿粉的抗氧化活性。真空冷冻干燥苜蓿超微粉具有很好的物理化学特性,经过干燥粉碎后能够很好的保留其中的营养价值和抗氧化活性,但其时间和能源消耗较大;而热风干燥苜蓿粉的物化特性及抗氧化活性相对较差,但其干燥时间短,能源消耗较少。     

Microwave drying kinetics of jack pine wood: determination of phytosanitary efficacy,energy consumption,and mechanical properties

The aims of this study were to determine (1) the effects of microwave irradiation on the drying kinetics of jack pine wood, (2) the phytosanitary efficacy, and (3) the processing energy consumption and mechanical strength of the dried product. Microwave drying experiments were performed at 2.45 GHz frequency and at microwave powers ranging from 300 to 1000 W. Results indicate that higher microwave power and initial wood temperature and lower sample thickness increases the internal sample temperature, improves the drying rate, and reduces both drying time and energy consumption. The microwave irradiation efficacy to sanitize jack pine wood boards was determined in terms of temperature/time combinations based on actual drying kinetics according to standards for phytosanitary measures. The energy required to dry 12 mm thick wood board samples at microwave power ranging from 300 to 1000 W was in the range of 36.4–12.3 MJ/kg of water, respectively, for up to 65% energy consumption savings. The impact of microwave power on the mechanical properties was not statistically significant, although mechanical properties tended to decrease with increasing power.     

Evaluation of low density hybrid panels using expandable granules: effect of granules diameter and content

Low density hybrid panels (16 mm thickness) were produced using wood fiber as face layers and a mixture of coarse wood particles and expandable polystyrene (EPS) as core layer. The EPS was foamed (in-situ foaming) in the core layer during the pressing stage. The effects of granules diameter (0.4, 0.8, 1.15, 1.5, and 2.2 mm) and granules content (5, 10, and 15%) on the physical and mechanical properties were evaluated. The results showed that both variables had significantly influenced the panels’ properties. Mechanical properties mostly depended on the level of mechanical inter-locking of EPS with wood particles, while the physical properties were mostly influenced by the EPS distribution. Stronger mechanical inter-locking of EPS with wood particles was achieved by both larger diameter and higher amount of EPS granules (2.2 mm and 15%). A better EPS distribution between the wood particles was observed with the smaller EPS granules and higher amount of EPS (0.4 mm and 15%).     

Investigation on bonding quality of beech wood (Fagus orientalis L.) veneer during high temperature drying and aging

In the present study, the effects of high drying temperature and UV light induced aging on bonding quality of plywood manufactured from untreated and treated veneer layers were investigated. Rotary cut veneers with dimensions of 500 mm×500 mm×2 mm produced from beech (Fagus orientalis Lipsky) log were selected for topochemical, chemical and mechanical analyses. The veneer sheets were oven-dried at 100°C and 180°C after the peeling process. Afterwards, the surfaces were exposed to artificial UV irradiation in an UV chamber for 24 h, 48 h and 72 h representing natural sun irradiation of 2, 4 and 6 months, respectively. Topochemical distribution of lignin and phenolic extractives of the treated and untreated veneers was investigated on a cellular level using UV microspectrophotometry (UMSP). For the chemical characterization of accessory compounds high performance liquid chromatography (HPLC) was used. Furthermore, the shear and bending strengths of plywood manufactured from the treated samples are determined in order to study the bonding quality. The UV microscopic detection shows that after high drying temperature and aging treatment, lignin condensation occurs. With increasing drying temperature and aging duration, more phenolic extractives are situated in parenchyma cells and vessel lumens which can be proved by increased absorbance at 278 nm. The HPLC analysis of the treated tissue showed distinct signals of polymerized compounds such as catechin and 2,6-dimethoxybenzoquinone which are chromophoric compounds in discolored beech wood. The mechanical properties of plywood showed that with increasing drying temperature up to 180°C does not negatively affect shear and bending strengths of samples. After exposure of the veneers to UV irradiation (especially 6 months), decreasing shear and bending strengths of plywood samples can be observed.     

Lumber drying as a diffusion process

The diffusive character of moisture movement in wood has been investigated by approximating empirical drying schedules as schedules based on diffusion. The diffusivity obtained in this way, checked by drying tests, is discussed on the basis of Eyrings reaction rate theory for diffusion. Schedule parameters have been correlated to wood species properties and physical interpretations on a molecular level with reference to the cell character of wood are discussed tentatively. Criteria were obtained for minimizing of surface checks and for drying defects due to unstable cells.     

基于灰色关联分析法研究不同干燥方式对芜菁脆片的影响

通过比较真空冷冻干燥（freeze drying,FD）、变温压差膨化干燥（explosion puffing drying,EPD）、红外干燥（infrared drying,ID）、热风干燥（hot air drying,AD）4 种不同干燥方式对芜菁脆片物理性质、营养成分、微观结构等的影响,寻找最优的芜菁脆片干燥方式。使用理化分析技术测定芜菁脆片营养成分含量;色差仪、质构仪等测定物理特性;扫描电子显微镜观察微观结构;评分法进行感官评价;灰色关联分析与变异系数分析结合进行综合评价。结果表明：4 种不同干燥方式处理后的芜菁脆片的物理特性和营养成分含量均有显著变化,FD和EPD对营养成分的保留更为完整。扫描电子显微镜观察结果显示FD可使芜菁脆片形成疏松多孔蜂窝状结构,EPD可使芜菁脆片产生轻微蜂窝状效果,同时使结构更为紧密,使口感酥脆。干燥方式综合评价结果为：FD＞EPD＞ID＞AD。但FD设备及加工过程花费较高,生产周期较长。综合考虑脆片的物理特性、营养成分、微观结构、感官评价以及生产周期,可得出EPD为芜菁脆片的最适加工方式。     

不同干燥方式对刺梨多糖多糖含量及抗氧化活性的影响

目的比较3种不同的干燥方式对刺梨多糖的多糖含量及抗氧化活性的影响。方法采用3种不同干燥方包括热风干燥、冷冻干燥和喷雾干燥法干燥刺梨多糖,通过多糖含量、蛋白质含量、红外光谱分析对刺梨多糖的理化性质进行评价,并研究了其清除1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基、羟基自由基和2,2-联氮-二(3-乙基-苯并噻唑-6-磺酸)二铵盐[2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), ABTS]自由基的能力。结果热风干燥多糖,冷冻干燥多糖和喷雾干燥多糖具有不同多糖含量和抗氧化活性。与热风干燥和冷冻干燥相比,喷雾干燥多糖具有更强的抗氧化能力。结论考虑到多糖的理化性质和抗氧化活性,喷雾干燥法是制备刺梨多糖的一种较好的方法,建议在食品工业中应用。     

The mechanical properties of densified VTC wood relevant for structural composites

The mechanical properties of densified wood relevant for structural composites were studied. Low density hybrid poplar (Populus deltoides × Populus trichocarpa) was densified using the viscoelastic thermal compression (VTC) process to three different degrees of densification (63, 98, and 132%). The modulus of rupture (MOR) and the modulus of elasticity (MOE) of the control (undensified) wood and of the VTC wood were determined. The bonding performance of the control and VTC wood, using two phenol-formaldehyde (PF) adhesives, was studied. Four different 3-layer composites were also prepared from undensified and VTC wood, and tested in four-point bending. The results showed that the bending properties of the VTC wood (MOR and MOE) were significantly improved due to the increased density. The bonding performance of VTC wood with PF adhesives was comparable with or better than in the case of the control wood. Increased density of the face layers in the 3-layer VTC composites was advantageous for their mechanical performance.     

Improvement of the heat treatment of Jack pine (Pinus banksiana) using ThermoWood technology

Thermal treatment in inert atmosphere is used to preserve wood without utilisation of toxic chemical agents. In addition, this process increases the dimensional stability of the wood matrix and results in attractive dark colour. On the other hand, it can deteriorate the mechanical strength and the flexibility of wood. For this reason, heat treatment parameters (such as maximum temperature, heating rate, the duration of the first plateau at constant temperature (100–120°C) and the second plateau at the maximum treatment temperature, humidity, final cool down rate) must be optimised in order to benefit from advantages of thermal treatment without deteriorating significantly the mechanical properties of wood. Correlation between wood properties and thermal treatment parameters depends not only on the wood species but also the environment (climate, soil) where the given species grow. This paper presents a study on thermal treatment of Canadian Jack pine (Pinus banksiana) using a medium size prototype furnace. The aim of this study was to optimize the set of parameters used during industrial treatments. The possibility of shortening the process time without causing any deterioration in wood quality was also investigated. The results show that increasing the maximum heat-treatment temperature increased the dimensional stability of Jack pine and darkened its colour. This parameter did not affect the modulus of elasticity but it decreased the modulus of rupture of Jack pine. A slight reduction in gas humidity during the initial warming up period permitted to shorten the drying period and at the same time increased the mechanical strength. This improvement helps save energy and increase productivity.     

Effect of overdrying of yellow-poplar veneer on physical properties and bonding

The intent of this study was to follow the changes of various wood physical properties as the wood was overdried at high temperature and to determine if these changes correlated with the ability of the wood to bond with phenolic resins. Yellow-poplar (Liriodendron tulipifera L.) was dried from a water-soaked state at 170°C, 195°C, and 220°C for various lengths of time. Light reflectance, wettability, equilibrium moisture content (EMC), loss of wood substance, and compression shear bond strength were measured. Wettability was severely affected over time and was very quickly affected at high temperatures. The bulk properties, EMC and loss of wood substance, were slightly affected by drying for 224 min at 170°C but were more affected at the higher temperatures with time. The results for these bulk properties correlated well with light reflectance measurements regardless of temperature level. However, compression shear bond strength remained high and was unresponsive to either drying time or drying temperature. After these laboratory samples were analyzed, yellow-poplar plywood samples produced by an industrial manufacturer were tested for bond quality. One sample was composed of regularly dried veneer, and one sample was overdried.     

有机硅树脂改性对UV固化木器涂料性能的影响

采用有机硅树脂改性紫外光(UV)固化木器涂料,对UV固化木器涂膜力学和光学性能的影响进行了研究,并对其在涂料中的作用机理进行了探讨。结果表明,当有机硅树脂含量为6.25%,干燥时间6 min,UV灯3盏,UV固化木器涂料具有良好的硬度、附着力和冲击强度。光泽度结果表明,UV固化木器涂膜的光泽度值随着有机硅树脂含量的升高而下降,制得的UV固化木器涂膜能在保持较佳力学性能的同时具有亚光光泽度。     

Dracaena mannii Baker—physical, mechanical and related properties

Wood anatomy, physical and mechanical properties and decay resistance of the monocotyledon Dracaena mannii Baker from the Central African Republic were determined and compared with the wood of two dicotyledons of the comparable density. Despite of the completely different anatomical structure the mechanical properties of Dracaena are comparable to the dicotyledonous wood of comparable density. As opposed to mechanical properties the radial and tangential shrinkage in Dracaena is twice as great as in dicots of comparable density and the ratio of tangential to radial shrinkage is almost 3:1.     

<Emphasis Type="Italic">Dracaena mannii</Emphasis> Baker—physical,mechanical and related properties

Wood anatomy, physical and mechanical properties and decay resistance of the monocotyledon Dracaena mannii Baker from the Central African Republic were determined and compared with the wood of two dicotyledons of the comparable density. Despite of the completely different anatomical structure the mechanical properties of Dracaena are comparable to the dicotyledonous wood of comparable density. As opposed to mechanical properties the radial and tangential shrinkage in Dracaena is twice as great as in dicots of comparable density and the ratio of tangential to radial shrinkage is almost 3:1.     

Experimental study of material properties of modified Scots pine

The mechanical and physical properties of modified timber were assessed by experimental work. The timber was modified using three different methods: acetylation with acetic anhydride, modification with methylated melamine formaldehyde resin and heat treatment in an oil bath. The wood material was sapwood of Scots pine (Pinus sylvestris) with dimensions of 45×70×1100 mm. A total of 99 specimens were included in this study. The following properties and their inter-relations were studied: density, modulus of elasticity (MOE), bending creep deflection and relative creep. It was found that all the modifications successfully reduced the relative creep. However, the performance properties of modified timber ought not to be calculated on the basis of density, as is the case for untreated wood. On the other hand, the long-term performance of modified timber can be assessed by its initial MOE and the difference in equilibrium moisture content (EMC) between two climates.     

Correlation between acoustic and physical–mechanical properties of insulating composite boards made from sunflower stalk and wood chips

Physical and mechanical properties of low-density insulating particleboards (0.45 g/cm³) made from wood chips and waste sunflower stalk (SFS) were studied, and correlations with the acoustic properties were determined. Two types of layered boards were manufactured, one with SFS in the central section, and the other with SFS on the surface layers; the layered boards were then compared with two kinds of homogeneous boards made from 100 % SFS and wood chips. Two types of resin were used, urea–formaldehyde (UF) and isocyanate; the press time was 5 and 7 min. Results showed that higher compression ratio in boards containing sunflower stalk resulted in significant improvement of physical–mechanical properties. Interaction between different layers of wood chips and sunflower stalk caused no clear trend in the acoustic properties of the layered boards with none of the resins; however, significant difference was found in the homogeneous boards produced with UF and isocyanate resins. High significant correlations were found between modulus of rupture and elasticity and thickness swelling (24 h) versus six acoustic properties. It can therefore be concluded that acoustic properties, as non-destructive tests, can be used to estimate some of the physical–mechanical properties of new insulating particleboards with different density and compositions.     

不同干燥方式对小麦麸皮膳食纤维理化性质的影响研究

研究了低温真空干燥和真空冷冻干燥对小麦膳食纤维理化性质的影响情况。实验发现经过两种方式所制备的小麦膳食纤维具有较强的持水力、膨胀力、吸附脂肪和亚硝酸盐的能力,但是除两者之间的持水力和吸附亚硝酸盐的能力无明显区别外,经过低温真空干燥制备的不溶性膳食纤维膨胀力强于经过真空冷冻干燥制备的膳食纤维膨胀力,而且小麦膳食纤维吸附饱和脂肪的能力强于吸附不饱和脂肪的能力。     

Evaluation of the physical,chemical and sensory properties of raisins produced from grapes of the cultivar Crimson

The main objective of the present work was to dry grapes of Crimson variety through different methodologies in order to find an alternative for the production of raisins. Different methodologies were used for drying: solar direct exposition in a greenhouse and in convective drying chambers with constant air flow at two temperatures: 50 and 60 °C. Some chemical analyses were made, namely for total sugars, acidity, total phenols, total anthocyanins and total tannins. Also some physical properties were evaluated, specifically color and texture. A sensorial analysis of the dried products was undertaken to evaluate the acceptability by consumers. The raisins produced by the different methodologies didn’t show significant differences at the chemical and physical levels. However, it was observed that the dried samples contained higher amounts of total phenolic compounds, anthocyanins and tannins in comparison to the fresh grapes. Sensory evaluation result showed that dried grapes produced using different methodologies was similar to commercial raisins.