Effects of inorganic acid catalysts on liquefaction of wood in phenol

In order to obtain the effects of acid catalysts on wood liquefaction in phenol, we investigated the liquefaction of wood powder from Chinese fir (Cunninghamia lanceolata) and poplar (Triploid Populus tomentosa Carr) in the presence of phenol with the following weak inorganic acids as catalysts: phosphoric acid (85%), sulfuric acid (36%), hydrochloric acid (37%) and oxalic acid (99.5%). Results show that phosphoric acid (85%) and sulfuric acid (36%) are better than the other catalysts. It was found that lower residue ratios can be obtained under defined reaction conditions: phenol/wood ratio is 4, a 10% catalyst based on the weight of phenol, a temperature of 150°C for 2 h and phosphoric or sulfuric acid. The residue ratios are 3.2% and 4.0%, respectively. __________ Translated from Journal of Beijing Forestry University, 2004, 26(5) [译自: 北京林业大学学报, 2004, 26(5)]     

Fire-retardant and smoke-suppressant performance of an intumescent waterborne amino-resin fire-retardant coating for wood

An intumescent waterborne amino-resin fire-retardant coating for wood (C) was synthesized and its fire-retardant and smoke-suppressant properties were investigated. The main film-builder of C was urea-formaldehyde resin blended with polyvinyl acetate resin. The intumescent fire-retardant system of C consisted of guanylurea phosphate (GUP), ammonium polyphosphate (APP), pentaerythritol (PER) and melamine (MEL). Specimens of plywood painted, respectively, with a commercial intumescent fire-retardant coating (A), a synthesized coating (C), and the main film-builder of coating C (B), as well as an unpainted plywood (S-JHB), were analyzed by cone calorimetry (CONE). The results show a marked decrease in the heat release rate (HRR) and the total heat release (THR), an increased mass of residual char (Mass), a marked postponement in time to ignition (TTI) and a reduced carbon monoxide production rate (P _CO). The smoke production rate (SPR) and total smoke production (TSP) of the plywood painted with coating C were observed with the CONE test. The overall fire-retardant and smoke-suppressant performance of the synthesized coating C was much better than that of the commercial coating A. The thermo-gravimetric analysis (TGA) results of coating C and its film-builder B indicated that the thermal degradation process of B was slowed down by the addition of the intumescent fire-retardant system; the increase in the amount of charring of coating C was considerable. __________ Translated from Scientia Silvae Sinicae, 2007, 43(12): 117–121 [译自: 林业科学]     

Chemical mechanism of fire retardance of boric acid on wood

It is commonly accepted that the fire retardant mechanism of boric acid is a physical mechanism achieved by the formation of a coating or protective layer on the wood surface at high temperature. Although a char-forming catalytic mechanism has been proposed by some researchers, little direct experimental support has been provided for such a chemical mechanism. In this paper, new experimental results using thermal analysis, cone calorimetry (CONE), and gas chromatography–Fourier transform infrared spectroscopy (GC–FTIR) analysis are presented and the fire retardant mechanism of boric acid on wood is discussed. Basswood was treated with boric acid, guanylurea phosphate (GUP), and GUP–boric acid. Treated wood was then analyzed by thermogravimetry (TG/DTG), differential thermal analysis (DTA), CONE, and GC–FTIR analysis. Thermogravimetry showed that the weight loss of basswood treated with boric acid was about three times that of untreated or GUP-treated wood at 165°C, a temperature at which GUP is stable. The DTA curve showed that boric acid treated basswood has an exothermal peak at 420°C, indicating the exothermal polymerization reaction of charring. CONE results showed that boric acid and GUP had a considerable synergistic fire retardant effect on wood. The GC–FTIR spectra indicated that compounds generated by boric acid treated wood are different than those generated by untreated wood. We conclude that boric acid catalyzes the dehydration and other oxygen-eliminating reactions of wood at a relatively low temperature (approximately 100–300°C) and may catalyze the isomerization of the newly formed polymeric materials by forming aromatic structures. This contributes partly to the effects of boric acid on promoting the charring and fire retardation of wood. The mechanism of the strong fire retardant synergism between boric acid and GUP is due to the different fire retardant mechanisms of boric acid and GUP and the different activation temperatures of these two chemicals.The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin. This article was written and prepared by U.S. Government employees on official time, and it is therefore in the public domain and not subject to copyright. The use of trade or firm names in this publication is for reader information and does not imply endorsement by the U.S. Department of Agriculture of any product or service.     

人工林珍贵树种柚木和楸木的热解特性及动力学

木材阻燃体系的选择应考虑其热解特性,选取人工林珍贵树种柚木、楸木和速生材杉木、辐射松为研究对象,通过化学成分和热重（TG）分析试验,研究热解特性、热解动力学模型和参数,为阻燃体系选择提供理论依据。结果表明：四种木材的热解过程均可分为失水、过渡、剧烈降解和成炭等四个阶段;柚木、楸木的最大热解速率温度、活化能和活化因子均低于杉木和辐射松,适用于热解温度相对较低的阻燃体系。     

Fire-retardant mechanism of fire-retardant FRW by FTIR

The structures of the solid state products formed by the partial combustion of Korean pine wood treated with fire-retardant FRW were analyzed by microscopic FTIR. The volatile pyrolytic products of basswood (Tilia amurensis) specimens treated with FRW and its components guanylurea phosphate and boric acid were analyzed by GC-FTIR. The pyrolytic and charring process, the effects of fire-retardant, and the structural characteristics of the pyrolytic products were discussed. It was concluded that upon heating and by the catalysis of FRW and its decomposition products reactions of wood took place successively, namely the dehydration of polysaccharide, the elimination of acetic acid from hemicellulose, the degradation of polysaccharide, the degradation of lignin, the polymerization of the pyrolytic products of wood, reactions of oxygen-element-elimination of aliphatic polymers and the structural change of the latter to form aromatic structures, and charring. The pyrolysis process of wood was altered and the yield of volatile pyrolytic products was decreased by FRW treatment. __________ Translated from Scientia Silvae Sinicae, 2005, 41(4): 149–154 [译自: 林业科学, 2005, 41(4): 149–154]     

Interaction between glycerin and wood at various temperatures from stress relaxation approach

In order to understand the reason why glycerin pre-treatment can accelerate the deformation fixation of compressed wood, the interaction between glycerin and wood at various temperatures was investigated in this study from stress relaxation approach. The compression stress relaxation curves of poplar (Populus cathayana Rehd.) samples impregnated with glycerin were measured at temperatures ranging from 25 to 180°C, together with the curves of oven-dry wood at temperatures between 100 and 180°C for comparison. The activation energy was calculated according to the Eyring’s absolute rate reaction theory. The results showed that temperature had very obvious effect on stress relaxation for both glycerin-treated wood (GTW) and oven-dry wood. The stress released very fast at higher temperatures. Glycerin showed an accelerating effect on stress relaxation. At temperatures exceeding 120°C, a complete relaxation of the stress could be expected. While for untreated wood, it cannot be reached until 160°C. By calculating the apparent activation energy (ΔE) of GTW at different temperatures, it is clear that two mechanisms are responsible for different temperature ranges. From 40 to 100°C, ΔE is only 8.24 kJ/mol, which corresponds to the hydrogen bonds formed between wood and glycerin molecules; from 120 to 180°C, ΔE reached 81.38 kJ/mol, which corresponds to the degradation of hemicelluloses or lignin, and during this process, new cross-linking would happen.     

Effects of high temperature kiln drying on the practical performances of Japanese cedar wood (Cryptomeria japonica) I: changes in hygroscopicity due to heating

The effect of heating on the hygroscopicity of Japanese cedar wood was investigated as a simple evaluation of thermal degradation in large-dimension timber being kiln-dried at high temperatures (>100°C). Small wood pieces were heated at 120°C in the absence of moisture (dry heating) and steamed at 60°, 90°, and 120°C with saturated water vapor over 2 weeks, and their equilibrium moisture contents (M) at 20°C and 60% relative humidity (RH) were compared with those of unheated samples. No significant change was induced by steaming at 60°C, while heating above 90°C caused loss in weight (WL) and reduction in M of wood. The effects of steaming were greater than those of dry heating at the same heating temperature. After extraction in water, the steamed wood showed additional WL and slight increase in M because of the loss of water-soluble decomposition residue. The M of heated wood decreased with increasing WL, and such a correlation became clearer after the extraction in water. On the basis of experimental correlation, the WL of local parts in large-dimension kiln-dried timber was evaluated from their M values. The results indicated that the thermal degradation of inner parts was greater than that of outer parts.     

TGA modeling of the thermal decomposition of CCA treated lumber waste

 To guide the development of thermal decomposition methods for disposal of CCA treated wood, reactions during the thermal decomposition of CCA treated wood were modeled using thermogravimetric analysis (TGA), with special focus placed on arsenic volatilization. Simple inorganic compounds, such as As₂O₅, CuO, and Cr₂O₃, were used to model the thermal behavior of the inorganics in CCA treated wood. In air and nitrogen, arsenic (V) oxide began to volatilize at 600 °C during temperature ramps at 5 °C/min. During a 5 °C/min ramp in a hydrogen mix, arsenic (V) oxide began decomposition at 425 °C. Arsenic volatile loss from CCA treated wood can depend strongly on the gases produced by wood thermal decomposition. In the presence of As₂O₅, chromium (III) oxide and copper (II) oxide formed arsenates in air and nitrogen. Chromium arsenates began decomposition as low as 790 °C. This suggested that chromium arsenates in CCA treated wood formed during original preservative fixation may decompose as low as 790 °C. Copper arsenates were stable up to 900 °C in air, but showed only a limited range of stability in nitrogen. Depending on process conditions, the formation of copper arsenates may limit arsenic loss during thermal decomposition of CCA treated wood up to 900 °C. The thermal decomposition of inorganic oxides was influenced by interactions with wood and wood decomposition products. In a dry YP sawdust/As₂O₅ mix, arsenic (V) oxide volatilized at 370 °C during inert pyrolysis at 5 °C/min and at 320 °C during smoldering combustion at 5 °C/min. Thermal dwells of a dry YP/As₂O₅ mix showed no arsenic loss at 250 °C, but significant loss occurred during higher temperature dwells. During inert pyrolysis at 5 °C/min, the formation of complexes and hydrates were shown to prevent arsenic loss up to 400 °C. Received 14 July 1999     

Effect of thermal modification temperature on the mechanical properties,dimensional stability,and biological durability of black spruce (Picea mariana)

This study was aimed at evaluating the effect of thermal modification temperature on the mechanical properties, dimensional stability, and biological durability of Picea mariana. The boards were thermally modified at different temperatures 190, 200 and 210 °C. The results indicated that the thermal modification of wood caused a significant decrease in the modulus of rupture (MOR) after 190 °C, while the modulus of elasticity (MOE) seemed less affected with a slight increase up to 200 °C and slight decrease with further increase in temperature. The hardness of the thermally modified wood increased in the axial direction. This increase was also observed in tangential and axial directions but at a lesser extent. The final value was slightly higher in axial direction and lower in radial and tangential directions compared to those of the untreated wood. Dimensional stability improved with thermal modification in the three directions compared to the dimensional stability of unmodified wood. The fungal degradation results showed that the decay resistance of thermally modified wood against the wood-rotting fungi Trametes versicolor and Gloephyllum trabeum improved compared to that of the untreated wood. By contrast, the thermal modification of P. mariana had a limited effect on the degradation caused by the fungus Poria placenta.     

Dynamic viscoelastic behavior of wood under drying conditions

In this study heartwood from a Chinese fir [Cunninghamia lanceolata (Lamb.) Hook] plantation was treated using a high-temperature drying (HTD) method at 115°C, a low-temperature drying (LTD) method at 65°C, and freeze vacuum drying (FVD), respectively. The dynamic viscoelastic properties of dried wood specimens were investigated. The measurements were carried out at a temperature range of −120 to 250°C at four different frequencies (1, 2, 5, and 10 Hz) using dynamic mechanical analysis (DMA). We have drawn the following conclusions: 1) the storage modulus E′ and loss modulus E″ are the highest for HTD wood and the lowest for FVD wood; 2) three relaxation processes were detected in HTD and LTD wood, attributed to the micro-Brownian motion of cell wall polymers in the non-crystalline region, the oscillations of the torso of cell wall polymers, and the motions of the methyl groups of cell wall polymers in the non-crystalline region in a decreasing order of temperatures at which they occurred; and 3) in FVD wood, four relaxation processes were observed. A newly added relaxation is attributed to the micro-Brownian motions of lignin molecules. This study suggests that both the HTD and the LTD methods restrict the micro-Brownian motion of lignin molecules somewhat by the cross-linking of chains due to their heating history. __________ Translated from Journal of Beijing Forestry University, 2008, 30(3): 96–100 [译自: 北京林业大学学报]     

High-temperature mechanical properties and thermal recovery of balsa wood

This article presents an experimental study into thermal softening and thermal recovery of the compression strength properties of structural balsa wood (Ochroma pyramidale). Balsa is a core material used in sandwich composite structures for applications where fire is an ever-present risk, such as ships and buildings. This article investigates the thermal softening response of balsa with increasing temperature, and the thermal recovery behavior when softened balsa is cooled following heating. Exposure to elevated temperatures was limited to a short time (15 min), representative of a fire or postfire scenario. The compression strength of balsa decreased progressively with increasing temperature from 20° to 250°C. The degradation rates in the strength properties over this temperature range were similar in the axial and radial directions of the balsa grains. Thermogravimetric analysis revealed only small mass losses (<2%) in this temperature range. Environmental scanning electron microscopy showed minor physical changes to the wood grain structure from 190° to 250°C, with holes beginning to form in the cell wall at 250°C. The reduction in compression properties is attributed mostly to thermal viscous softening of the hemicellulose and lignin in the cell walls. Post-heating tests revealed that thermal softening up to 250°C is fully reversible when balsa is cooled to room temperature. When balsa is heated to 250°C or higher, the post-heating strength properties are reduced significantly by decomposition processes of all wood constituents, which irreversibly degrade the wood microstructure. This study revealed that the balsa core in sandwich composite structures must remain below 200°–250°C when exposed to fire to avoid permanent heat damage.     

Evaluation of fire-retardant properties of edge-jointed lumber from tropical fast-growing woods using cone calorimetry and a standard fire test

 Some tropical fast-growing woods were converted to edge-jointed lumber, and their fire-retardant properties due to chemical coating were evaluated using cone calorimetry and a standard fire test. The woods used were Indonesian and Malaysian albizia and gmelina plantation trees, with Japanese hinoki as a reference. The lumber was coated with 100 g/m² of trimethylol melamine phosphoric acid in a 25% aqueous solution. The treated and untreated lumber was tested in a laboratory-scale exposure furnace in accordance with JIS A 1304 and the cone calorimeter test with heat flux of 40 kW/m² following the ISO 5660. Results showed that fire endurance of all lumber was enhanced by the treatment. The fire-retardant properties were improved with increasing surface density. Though a similar trend was seen, the fire-retardant properties of the lumber revealed by the cone calorimeter test were inferior to those seen with standard fire test. Addition of thermocouples to the cone calorimeter allowed us to obtain information on the critical temperature (260°C) and charring temperature (300°C) of the lumber. Received: January 23, 2002 / Accepted: July 15, 2002 Acknowledgment The authors thank Dr. Shigehisa Ishihara, Professor Emeritus of the Wood Research Institute, Kyoto University for his suggestions about this experiment.     

Hygrothermal effect of bamboo by dynamic mechanical analysis

Dynamic properties of bamboo, Phyllostachys pubescens, with moisture content (MC) ranging from −130 to 130°C, were studied by dynamic mechanical analysis (DMA). The results showed that the hygrothermal effect on dynamic mechanical properties was negative. The storage modulus decreases with increasing temperature and MC, and glass transition temperature decreases with increasing MC. The glass transition temperature and tan delta of bamboo were 30.5°C, 0.02 and 10.61°C, 0.04, when MC was 10% and 34%, respectively. __________ Translated from Journal of Nanjing Forestry University (Natural Sciences Edition), 2006, 30(1): 65–68 [译自: 南京林业大学学报(自然科学版), 2006, 30(1): 65–68]     

BL-环保型阻燃剂对杨木单板吸湿性和尺寸稳定性的影响

该研究采用BL-阻燃剂溶液浸渍处理杨木单板,比较分析BL-阻燃杨木与未阻燃杨木的吸湿性和尺寸稳定性的影响。结果表明:①在不同的湿度条件下,阻燃处理后试件的吸潮率递增值明显高于未处理材。②BL-阻燃剂浓度越高的试件吸潮率也越高,相同浓度的试件在不同湿度中,湿度越高,其吸潮率也越高。③阻燃后杨木单板的尺寸变化率明显高于未处理材的,BL-阻燃剂具有较高的吸湿性,其对杨木单板尺寸稳定性的影响规律为:厚度弦向径向。     

木材功能化阻燃剂研究进展

一剂多效是木材阻燃剂的主要发展方向。文中分别对常用的木材功能化阻燃剂和阻燃处理工艺的国内外研究进展进行了综述,包括磷氮硼阻燃剂、金属化合物阻燃剂、树脂阻燃剂、纳米阻燃剂和微胶囊阻燃剂及新型浸渍法、表面改性法和溶胶-凝胶法等阻燃处理工艺,讨论了木材阻燃研究的发展趋势。     

Determination of formic-acid and acetic acid concentrations formed during hydrothermal treatment of birch wood and its relation to colour, strength and hardness

Formation of benzyl esters from acetic and formic acids during heat treatment of birch at 160–200°C has been studied by gas chromatography. High concentrations of formic and acetic acids formed by the wood itself during hydrothermal treatment were found. The concentrations of acids increased with both treatment time and temperature. The maximum formic- and acetic acid concentrations found at 180°C and after 4 h of treatment performed in this work were 1.1 and 7.2%, based on dry-weight wood, respectively. The treated wood material was characterised by mechanical testing [bending tests perpendicular to the grain, modulus of rupture, modulus of elasticity, Brinell hardness, impact bending and colour measurements (CIE colour space)]. The experiments, where high concentration of acids was formed, showed severe losses in mass and mechanical strength. Indications of possible enhanced mechanical properties for the treated, compared with untreated birch wood were found around 180–200°C at short treatment times. This paper discusses possible degradation reactions coupled with the colour and mechanical properties in relation to acid formation, and suggestions for process optimisations.     

Dynamic viscoelastic properties of wood acetylated with acetic anhydride solution of glucose pentaacetate

 Spruce wood specimens were acetylated with acetic anhydride (AA) solutions of glucose pentaacetate (GPA), and their viscoelastic properties along the radial direction were compared to those of the untreated and the normally acetylated specimens at various relative humidities and temperatures. Higher concentrations of the GPA/AA solution resulted in more swelling of wood when GPA was introducted into the wood cell wall. At room temperature the dynamic Young's modulus (E′) of the acetylated wood was enhanced by 10% with the introduction of GPA, whereas its mechanical loss tangent (tan δ) remained almost unchanged. These changes were interpreted to be an antiplasticizing effect of the bulky GPA molecules in the wood cell wall. On heating in the absence of moisture, the GPA-acetylated wood exhibited a marked drop in E′ and a clear tan δ peak above 150°C, whereas the E′ and tan δ of the untreated wood were relatively stable up to 200°C. The tan δ peak of the GPA-acetylated wood shifted to lower temperatures with increasing GPA content, and there was no tan δ peak due to the melting of GPA itself. Thus the marked thermal softening of the GPA-acetylated wood was attributed to the softening of wood components plasticized with GPA. Received: March 29, 2002 / Accepted: May 21, 2002 Correspondence to:E. Obataya     

含磷型聚合甘油脂肪酸酯阻燃增塑剂的制备与应用

为了提高油脂增塑剂的阻燃性,开发以生物柴油副产粗甘油为直接原料的高附加值产品,以粗甘油、油酸和9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)为主原料,经聚合、酯化、环氧化和开环反应,合成含磷型大分子阻燃增塑剂DOPO-环氧乙酰化聚合甘油脂肪酸酯(DOPO-EAPFAE),并通过红外谱图(FT-IR)和核磁共振(~1H NMR)确认了其结构。研究了DOPO-EAPFAE用量对聚氯乙烯(PVC)体系力学性能的影响;通过对PVC样条的热重分析(TG)、极限氧指数(LOI)测定和垂直燃烧测试等,分析了PVC制品的热稳定性和阻燃性能。结果表明:当DOPOEAPFAE代替邻苯二甲酸二辛酯(DOP)用量为60%时,PVC样条仍具有良好的力学性能;而LOI从21.3上升到了28.7,阻燃级别达到V0级;说明该阻燃增塑剂可有效地改善PVC增塑体系的阻燃性。与小分子阻燃剂磷酸三(2-氯丙基)酯(TCPP)相比,DOPO-EAPFAE阻燃性不仅优于TCPP,而且具有更好的热稳定性能。     

美国阻燃处理木材的现状

总结美国阻燃处理木材的规范与标准,介绍美国主要阻燃处理木材生产商的阻燃木材产品,分析主要阻燃剂的配方及合成工艺、处理木材的工艺与技术特点,为国内阻燃处理木材行业的技术发展提出建议.     

FRW阻燃胶合板的DMA分析

目前世界范围内木材资源短缺的情况日益加剧,发展人造板工业已成为世界各国解决木材资源严重不足的重要途径.其中,胶合板作为室内装饰的主要材料,其产量和需求量都在急剧增长.我国胶合板产量从1980年的33.00万m3增长到2004年的2 098.62万m3,呈现大幅度增长的趋势(张文标等,2000).但由于普通胶合板具有易燃性,在许多领域的应用上受到限制.因为一旦发生火灾,不仅造成重大的经济损失,而且往往会发生人员伤亡.1950-2003年全国共发生火灾4 177 730起,直接经济损失2 434.525 1亿元,因火灾死亡174 855人,受伤329 352人.