新型竹材阻燃剂的合成

参照木材阻燃剂的研究成果和目前阻燃剂的发展趋势,针对竹材特性,研究新型竹材阻燃剂合成工艺。在常温常压下,低浓度的阻燃剂处理竹材,可达到国标难燃B1级。     

磷氮系阻燃剂处理刨花板的应用研究

分析磷氮复合阻燃剂处理刨花板的机理，研究其在刨花板生产上的应用技术。结果表明，聚磷酸胺为主剂的有机磷氮复合阻燃剂对刨花板阻燃效果较好，产品的阻燃性能的物理力学性能指标达到了国家相关标准。     

薄竹单板浸渍工艺对阻燃胶合板性能的影响

在常压下研究了温度、时间、复配阻燃剂质量分数等不同浸渍工艺参数对薄竹单板载药量的影响,测定了不同载药量薄竹胶合板的燃烧和力学性能。结果表明,在温度为60℃,时间为8h,复配阻燃剂质量分数为30%时,单板载药量趋于稳定;单板厚度增加,单板载药量会相应减少。力学性能表明,经过阻燃处理的薄竹胶合板随着载药量的增加,胶合强度有所下降,与未处理试样的胶合强度相比,经载药量为6%,8%,10%和12%阻燃处理的胶合板胶合强度分别下降了16.1%,22.0%,28.0%和35.6%,含水率范围为12.3%~13.2%,胶合强度和含水率均能满足Ⅱ类胶合板的要求。燃烧性能表明,随着载药量的增加,胶合板的点燃时间和残余质量逐渐增加,而总热释放量和总烟释放量逐渐减小,阻燃效果明显。因此,利用常压浸渍工艺生产阻燃薄竹胶合板是可行的。     

Influence of temperature and time upon pyrolysis of untreated and fire retardant treated wood

Summary Untreated and fire-retardant treated specimens of Douglas-fir were pyrolyzed up to 30 minutes at temperatures of 250°, 350° and 550° C. Various cell wall components viewed under the scanning electron microscope appeared to decompose at rates related to their chemical composition. No structural differences were noted between pyrolyzed specimens of untreated wood and wood treated with a mixture of zinc chloride and sodium dichromate. Cell walls of specimens treated with a mixture of urea, monammonium phosphate, and glucose exhibited thermoplastic behavior as a result of exposure to high temperatures.     

Changes in the physical and chemical properties of six Japanese softwoods caused by lengthy smoke-heating treatment

The effects of prolonged smoke-heating treatments on wood quality were investigated. Six Japanese softwoods were smoke-heated for 100 and 200h at a temperature of 75° ± 5°C, which was recorded inside the log. After smoke heating, wood quality, including moisture content, amounts of chemical components, relative degree of crystallinity (RDC) of cellulose, and sapwood color were examined. Moisture content decreased as a result of smoke heating, especially in sapwood, leading to a uniform distribution of moisture content within a log. Almost no difference was found in the amounts of chemical components between the control woods and the woods that were smoke-heated for 100h. However, in the wood that was smoke-heated for 200h, the amounts of holocellulose decreased, suggesting that thermal deterioration and/or degradation of hemicelluloses had occurred. We assume that the increase in RDC was caused by smoke heating with the crystallization of cellulose and/or thermal degradation of hemicelluloses. Almost no differences were found in sapwood color between the control woods and the woods that were smoke-heated for 100h. In the wood that was smoke-heated for 200h, however, L*decreased, whereas a* and b* increased. As a result, E*ab, showing the total color change, increased, resulting in a deeper color. These results suggest that thermal degradation of hemicelluloses was caused by smoke heating for over 100h. Therefore, smoke heating of softwood logs using a commercial-scale kiln should not exceed 100h.     

Nitrogen leaching from a forest soil exposed to fire retardant with and without fire: A laboratory study

The application of Long Term fire Retardants (LTRs) for forest fire prevention and/or suppression purposes can result in chemicals leaching, from soil to the drainage water, during the annual rain fall period. In leachates, large concentrations of nitrogen (N), one of the major components of LTRs, could affect the groundwater quality. N leaching due to the application of a nitrogen phosphate based LTR was studied in laboratory microcosms. The concentrations of nitrate (NO ₃ ^? -N) and ammonium nitrogen (NH ₄ ⁺ -N) were measured in the resulting leachates from pots with forest soil and pine seedlings (Pinus halepensis) alone and in combination with fire. Up to 30% of the total N in the retardant was lost to leaching, primarily as NO ₃ ^? -N. The vegetation seems to decrease to some extent the N leaching. The N leaching from treated pots with a burnt tree is lower compared with that from treated pots with a living tree, due to the partial N volatilization during the fire. Although this is a laboratory study, these results may be considered as rough indications of LTR environmental implications, due to the leaching of a significant part of the retardant’s N into groundwater.     

Technological properties and fire performance of medium density fibreboard (MDF) treated with selected polyphosphate-based fire retardants

ABSTRACT

The objective of the work was to evaluate the efficacy of two new polyphosphate-based fire retardants (FRs) and one commercial product named Siriono^® on the fire performance and physical–mechanical properties of medium density fibreboard (MDF) fabricated in the laboratory from Scots pine (Pinus sylvestris L.) wood. The fibres were treated with aqueous solutions of fire retardants, at 12% loading (dry salt on dry wood), and bonded with a melamine urea formaldehyde (MUF) adhesive. The physical and mechanical properties of panels were assessed using the European standards, whereas their fire performance was evaluated using an in-house method and the Cone calorimeter. In overall, the chemicals added enhanced the fire and smoke properties of the panels to varying degrees. Critical FR parameters such as peak heat release rate (peak HRR), total heat release (THR) and total smoke production (TSP) were significantly improved in the FR-treated panels, as exhibited in cone calorimeter tests. However, the internal bond strength of treated panels largely decreased by the addition of fire retardants, while thickness swell and water absorption negatively affected to a significant extent. In contrast, the formaldehyde release of the panels was considerably decreased at the E1 class level, with the incorporation of the polyphosphate-based additives.     

Impacts of low-intensity prescribed fire on microbial and chemical soil properties in a Quercus frainetto forest

Prescribed fire is a common economical and effective forestry practice, and therefore it is important to understand the effects of fire on soil properties for better soil management. We investigated the impacts of low-intensity prescribed fire on the microbial and chemical properties of the top soil in a Hungarian oak(Quercus frainetto Ten.) forest. The research focused on microbial soil parameters(microbial soil respiration(RSM), soil microbial biomass carbon(Cmic) and metabolic quotient(qCO_2) and chemical topsoil properties(soil acidity(pH),electrical conductivity(EC), carbon(C), nitrogen(N), C/N ratio and exchangeable cations). Mean annual comparisons show significant differences in four parameters(C/N ratio,soil pH, Cmic and qCO_2) while monthly comparisons do not reveal any significant differences. Soil pH increased slightly in the burned plots and had a significantly positive correlation with exchangeable cations Mg, Ca, Mn and K.The mean annual C/N ratio was significantly higher in the burned plots(28.5:1) than in the control plots(27.0:1). The mean annual Cmic(0.6 mg g~(-1)) was significantly lower although qCO_2(2.5 lg CO_2–C mg Cmic h~(-1)) was significantly higher, likely resulting from the microbial response to fire-induced environmental stress. Low-intensity prescribed fire caused very short-lived changes. The annual mean values of C/N ratio, pH, Cmic and qCO_2 showed significant differences.     

水泥-过磷酸钙复合材料固化铅污染土的浸出和力学特性

水泥是铅污染土固稳修复常用的固化剂,在修复重度铅污染土时效果较差。而过磷酸钙在稳定铅污染土方面具有溶出风险低、长期稳定性好和环境安全性高的优点。为了研究水泥-过磷酸钙复合材料固化后铅污染土的浸出和力学特性,采用水泥-过磷酸钙复合材料对铅污染土进行固化/稳定化处理,通过浸出试验、无侧限抗压强度试验和渗透试验对固化前后的铅污染土固化体进行浸出和力学特性变化特征对比分析,分别探讨了水泥和过磷酸钙添加量对固化土浸出和力学特性的影响规律。结果表明:水泥可显著改善铅污染土的强度和渗透特性,当水泥的添加量从5%增加到30%时,固化土的抗压强度从0.56 MPa增加到4.78 MPa;渗透系数从8.2×10-7cm/s减小到2.2×10-8cm/s。但水泥在固稳高浓度铅污染土效果较差,当水泥的添加量从5%增加到30%时,固化土的浸出浓度从56.3 mg/L减少到19.8 mg/L,固化土的浸出浓度远高于我国危险废弃物鉴别标准(GB/T 5085.3—2007)。过磷酸钙可显著降低污染土中铅的浸出特性,固化土的浸出浓度从43.5 mg/L减少到0.17mg/L;但过磷酸钙会降低固化土的力学性能。随着过磷酸钙添加量从1%增加到5%,固化土的抗压强度从1.17MPa降低到0.42 MPa;渗透系数从3.0×10-7cm/s增加到1.3×10-6cm/s。因此,在铅污染土实际工程中应根据实际的场地工况和修复目标,合理选择水泥和过磷酸钙的配比,保证修复后的铅污染土强度特性和浸出特性均满足修复标准。     

采伐迹地的火烧清理对土壤理化性质的影响

本文讨论了火烧清理采伐迹地剩余物对土壤理化性质产业的影响，并提出了相应的建议。     

阻燃处理木材的热分析

为研究阻燃处理对木材热解过程的影响,将未处理的和经过阻燃处理的木材进行热分析(包括TG、DTG、DSC),其结果表明:阻燃处理可改变木材发生剧烈热分解时的温度和重量损失速率,并使400℃时的残留物重量明显增加,在20～450℃范围内,未处理木材的DSC图谱有三个峰,相应于三个不同的热解阶段;不同阻燃剂的加入可明显地改变DSC图谱的峰形和峰位,即改变了木材的燃烧性能。此外本文还结合实验结果,对阻燃剂的作用机理提出了初步解释。     

The mechanical and physical properties of strand boards treated with preservatives at different stages of manufacture

The physical and mechanical properties of boards treated with a preservative at different points during the manufacture process were evaluated to determine the best stage for the application of preservative. A copper boron tebuconazole amine water-based preservative was used in 3% PF-bonded strand boards to achieve five different retentions. Preservative addition was examined at different stages of the manufacture cycle, namely, green strand diffusion, dry strand vacuum treatment, glue-line spray addition, heat and cold quench of manufactured board, and by post-manufacture vacuum treatment. The treatment methods had marked effects on the mechanical properties of some of the boards when the boards with the highest preservative retention were compared with their respective untreated controls. The best results were achieved where the preservative was applied by vacuum treatment of dry strands or by diffusion of green strands before board manufacture. Increasing preservative retention had minimal effects on board properties with these two methods but significant deterioration was noted when the preservative was applied by spraying dry strands or by post-board-manufacture heat and cold quench. An increase of pressing temperature resulted in significant improvements to the mechanical properties of the spray-treated boards. Post-manufacture vacuum treatment of boards caused excessively high losses in internal bond strength.     

三种竹碎料板的物理力学性能比较分析

对三种竹碎料板的物理力学性能进行了比较分析。板材弹性模量：竹席增强竹碎料板〉竹碎料/木纤维复合板〉普通竹碎料板;静曲强度：竹席增强竹碎料板〉竹碎料/木纤维复合板〉普通竹碎料板;吸水率：普通竹碎料板〉竹碎料/木纤维复合板〉竹席增强竹碎料板;吸水厚度膨胀率：普通竹碎料板〉竹碎料/木纤维复合板〉竹席增强竹碎料板;内结合强度：竹碎料/木纤维复合板〉竹席增强竹碎料板〉普通竹碎料板。     

Dimensional stabilization of wood with water soluble fire retardant bulking chemicals compared with polyethylene glycol-1000

Summary Mono and diammonium acid phosphate, ammonium sulfamate, and sodium silicate were compared with polyethylene glycol-1000 as bulking dimension stabilizing agents using Engelmann spruce cross sectional wafers. Limiting antiswell efficiencies are equal to the volume fraction of chemical in a saturated solution. The experimental antiswell efficiencies due to bulking are the percent increase in the dry cross sectional area of the wafers caused by deposition of dry chemical within the cell walls divided by the percent swelling in water. These values for the phosphates, the sulfamate, and the polyethylene glycol approach the limiting values from solubility indicating that chemical continues to diffuse into the cell walls as the wood is dried to virtually attain a saturated solution within that structure. The sodium silicate gave an apparent negative antiswell efficiency as collapse of the fibers on drying exceeded the actual bulking. Antiswell efficiencies between 0 and 30% relative humidity, 0 and 90% relative humidity and 30 and 90% relative humidity were in general still lower. This is largely due to the treated systems taking up more water than the controls, especially at the higher relative humidity. Antiswell efficiencies for the mono ammonium acid phosphate ranged from 20 to 27%, for the diammonium acid phosphate from 28 to 37%, the ammonium sulfamate from 51 to 66% and the polyethylene glycol from 63 to 77%.Paper No. 4245 of the Journal Series of North Carolina State University Agricultural Experiment Station, Raleigh, North Carolina     

Strength properties of thermally modified softwoods and its relation to polymeric structural wood constituents

Thermal modification at relatively high temperatures (ranging from 150 to 260 °C) is an effective method to improve the dimensional stability and resistance against fungal attack. This study was performed to investigate the impact of heat treatment on the mechanical properties of wood. An industrially-used two-stage heat treatment method under relative mild conditions (< 200 °C) was used to treat the boards. Heat treatment revealed a clear effect on the mechanical properties of softwood species. The tensile strength parallel to the grain showed a rather large decrease, whereas the compressive strength parallel to the fibre increased after heat treatment. The bending strength, which is a combination of the tensile stress, compressive stress and shear stress, was lower after heat treatment. This decrease was less than the decrease of only the tensile strength. The impact strength showed a rather large decrease after heat treatment. An increase of the modulus of elasticity during the bending test has been noticed after heat treatment. Changes and/or modifications of the main wood components appear to be involved in the effects of heat treatment on the mechanical properties. The possible effect of degradation and modification of hemicelluloses, degradation and/or crystallization of amorphous cellulose, and polycondensation reactions of lignin on the mechanical properties of heat treated wood have been discussed. The effect of natural defects, such as knots, resin pockets, abnormal slope of grain and reaction wood, on the strength properties of wood appeared to be affected by heat treatment. Nevertheless, heat treated timber shows potential for use in constructions, but it is important to carefully consider the stresses that occur in a construction and some practical consequences when heat treated timber is used.     

Durability,reaction to fire properties,and environmental impact of treated and untreated wooden claddings

Abstract

This work summarizes the output of durability, reaction to fire properties, and environmental impact of wooden claddings subjected to treatments modified with TiO₂ and clay nanoparticles. The objective was to investigate the effects of 1 wt% of TiO₂ and clay nanoparticles in existing water-based and stain coatings and preservatives regarding the properties mentioned above. Water vapor resistance properties were used to assess the moisture transfer properties of the specimens by using the cup test. The reactions to fire properties of the specimens were analyzed using small-scale cone calorimeter test. Accelerated aging was used to study the weathering properties of specimens, where the performance of the specimens with aging was characterized using Fourier transform infrared (FTIR) analysis. The effect of increasing the percentage of nanoparticles from 1 wt% to 3 wt% on the weathering properties of the specimens was further analyzed. Moreover, comparison between the overall environmental impact between unmodified water-based paint and water-based paint modified with 1 wt% of TiO₂ nanoparticles was performed using available environmental data and weathering test results as analyzed by FTIR.     

杨村新无性系木材物理力学性质的研究

研究了7个杨树新无性系和I－69杨的木材物理力学性质。结果表明，杨木新无性系的物理力学性质等主要指标均属于小至甚小级，无性系间物理力学性质差异显著，据此可用木材物理力学性质因子选育优良无性系。尽管新无性系的生长速度超过I－69杨，但由于其某些强度指标低于I－69杨，8年生的速生材尚不能完全替代11年生的I－69杨使用，因此不能作为建筑结构材使用。     

低分子酚醛树脂处理杨木物理力学性能测试

采用低分子酚醛树脂对杨木进行浸渍处理,然后采用加热压缩处理使树脂在木材中固化,制得表面压密材,并对其物理力学性能指标进行检测。结果表明：杨木（Populus ussuriensis）素材的平均密度为394kg/m3,随着压缩率的增加,木材密度明显增大,当压缩率为20%时,木材的平均密度为463kg/m3,同时木材顺纹抗压强度、抗弯强度、抗弯弹性模量和表面硬度增大,浸渍处理后的木材颜色变化不大。     

Surface free energy and dynamic wettability of wood simultaneously treated with acidic dye and flame retardant

The use of multifunctional wood for decorative purpose has grown increasingly popular in recent years. In this study, fast-growing poplar wood was treated with dye (0.5%) and flame retardant (0, 10, 20, and 30%) simultaneously to enhance its visual characteristic and safety. The dynamic wettability and surface free energy of wood samples were studied using S-D wetting model and van Oss–Chaudhury–Good (vOCG) method, respectively. Dye uptake, drug load, color difference, and combustion performance were determined. The treated wood was also characterized by infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results indicated that the proposed treatment yields favorable adhesive spreading and penetration ability at the wood surface. The surface free energy of treated wood was higher than that of untreated wood, and the dye uptake, drug load, color difference, and limited oxygen index all increased after the proposed combination treatment compared to dye-only treated wood. The results also indicated that the flame retardant reacted chemically with the wood as the dye and flame retardant molecules diffused into the cell cavity, wood vessel, and aperture.     

Use of near infrared spectroscopy to measure the chemical and mechanical properties of solid wood

Near infrared (NIR) spectroscopy (500 nm–2400 nm), coupled with multivariate analytic (MVA) statistical techniques, have been used to predict the chemical and mechanical properties of solid loblolly pine wood. The samples were selected from different radial locations and heights of three loblolly pine trees grown in Arkansas. The chemical composition and mechanical properties were measured with traditional wet chemical techniques and three point bending tests, respectively. The microfibril angle was measured with x-ray scattering. These chemical and mechanical properties were correlated with the NIR spectra using projection to latent structures (PLS) models. The correlations were very strong, with the correlation coefficients generally above 0.80. The mechanical properties could also be predicted using a reduced spectral range (650 nm–1150 nm) that should allow for field measurements of these properties using handheld NIR spectrometers.