DETERMINE ON INITIAL DIMENSIONAL STABILITY OF CHEMICAL MODIFIED WOOD

Strain development along radial direction was continuously determined by D—200Linear Variable Differential Transformers(L.V.D.T).When a wood specimen was put into waterand begin to swell from absolute dry moisture content to the maximum.Experiment results showthat the differences of swelling with soaking time between untreated and treated wood specimens dueto uptaking water.It would also give an indication to the effectiveness of various chemicals on thedimensional stability of modified wood.ASE of modified wood samples with SA-EP,EP and SA were found to be better than MA-AGE.SA-EP had got the best effetiveness on dimensional stabili-ty in reducing the swelling.     

Properties of PEG/thermally modified wood flour/polypropylene (PP) composites

In order to improve the dimensional stability of wood-polymer composites, wood flour pre-treated by polyethylene glyco1 (PEG) at two different concentrations and then thermally treated at 140°C, was used as raw material to produce wood flour/polypropylene (PP) composites at a wood content of 40%. The structure of modified wood flour was analyzed with a scanning electron microscope (SEM) and its effect on the physical and mechanical properties of wood flour/PP composites was evaluated. The SEM results indicated the "bulking" effect of PEG on wood flour, which resulted in reduced water uptake. The combination of PEG and heat treatment further improved the moisture resistance of the composites. However, PEG modification had a negative effect on the flexural modulus of rupture (MOR) and the modulus of elasticity (MOE); whereas heat treatment partly compensated for this reduction. For dynamic mechanical properties, PEG treatment decreased the storage modulus (E′). However, the heat treatment resulted in an increase of E′ of the wood flour/PP composites, with the temperature of loss factor peaks shifting to a higher temperature.     

Characteristics of fast-growing wood impregnated with nanoparticles

Falcataria moluccana or sengon is one of the fast-growing wood species widely grown in Indonesia.However,its wood is low quality with low density,and poor strength,durability,and dimensional stability.This study determined the effects of impregnation with monoethylene glycol(MEG)and nano-SiO2 on the characteristics of sengon wood,including its dimensional stability and density.Impregnation with MEG and nano-SiO2 had a significant effects on dimensional stability in terms of the weight percent gain,anti-swelling efficiency,water uptake,bulking effect,and density.The impregnated wood was examined by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and X-ray diffraction.The results show that MEG and nano-SiO2 were distributed homogeneously into cell walls of wood treated with 0.5%MEGSiO2.     

Treatment of fir wood with chitosan and polyethylene glycol

Chitosan is a natural biopolymer, derived from chitin, which is used for wood modification. Polyethylene glycol(PEG) was reacted with wood to provide possible fixation of the chitosan to wood. Wood blocks were treated with chitosan and PEG, as well as pre-treatment with the PEG at different temperatures and further reaction with the chitosan. The samples were soaked in water to study leaching of the chemicals, water absorption, swelling, as well as anti-swelling efficiency. Any prior reaction of the wood with PEG provided better reaction to the chitosan.Bulking was increased after the treatment of the wood with PEG. Swelling was reduced in the PEG-treated wood blocks as well as the pre-treated samples. Chitosan was not able to protect wood against water penetration: the treated samples showed more water absorption and swelling.However, pre-treatment of the samples decreased swelling in the wood, and the density was not noticeably affected by the treatments. Heating during the treatment caused more reduction in swelling for PEG–chitosan treated samples.     

Creep of Chinese fir wood treated by different reagents

In order to investigate the effect of different reagents on changes of the crystalline region and amorphous region (Matrix) in wood cell walls, the creep behavior of Chinese fir (Cunninghamia lanceolata) wood treated with dimethyl sulfoxide(DMSO) and diethyl amine, sulfur dioxide and dimethyl sulfoxide mixture (1)EA-SO2-DMSO), and the untreated wood at oven-dried, air-dry and water-saturated states during adsorption and desorption processes were all examined in air or in water. The measurements were carded out at ambient temperature and atmospheric pressure. The load is constant with 62 g or 0.607 6 N. The results obtained were as follows: 1) The instantaneous compliance J0 and the creep compliance J of specimens decrystallized with DEA-SO2-DMSO solution were bigger than those of DMSO swollen wood, and the latter was still much bigger than those of untreated wood. 2) For untreated wood, J0 and J increased with equilibrium moisture content (EMC) of wood, but there was not apparent correlation between wood EMC and the relative compliance. 3) Specimens treated with DMSO and DEA-SO2-DMSO mixture were recrystallized after immersion in water, and the degree ofrecrystallization of the former was larger. 4) For oven-dried specimens, the creep compliances in water were bigger than those in air. But for fiber-saturated and water-saturated specimens they were nearly equivalent to each other.     

Theoretical modeling of the effects of temperature and moisture content on the acoustic velocity of Pinus resinosa wood

To investigate the effects of temperature and moisture content(MC) on acoustic wave velocity(AWV)in wood,the relationships between wood temperature,MC,and AWV were theoretically analyzed.According to the theoretical propagation characteristics of the acoustic waves in the wood mixture and the differences in velocity among various media(including ice,water,pure wood or oven-dried wood),theoretical relationships of temperature,MC,and AWV were established,assuming that the samples in question were composed of a simple mixture of wood and water or of wood and ice.Using the theoretical model,the phase transition of AWV in green wood near the freezing point(as derived from previous experimental results) was plausibly described.By comparative analysis between theoretical and experimental models for American red pine(Pinus resinosa) samples,it was established that the theoretically predicted AWV values matched the experiment results when the temperature of the wood was below the freezing point of water,with an averageprediction error of 1.66%.The theoretically predicted AWV increased quickly in green wood as temperature decreased and changed suddenly near 0 °C,consistent with the experimental observations.The prediction error of the model was relatively large when the temperature of the wood was above the freezing point,probably due to an overestimation of the effect of the liquid water content on the acoustic velocity and the limited variables of the model.The high correlation between the predicted and measured acoustic velocity values in frozen wood samples revealed the mechanisms of temperature,MC,and water status and how these affected the wood(particularly its acoustic velocity below freezing point of water).This result also verified the reliability of a previous experimental model used to adjust for the effect of temperature during field testing of trees.     

Influence of pre-treatment in citric acid solution on physical and mechanical properties of thermally compressed oil palm board

Oil palm trunk is an excellent raw material for thermally compressed wood board.However,improvements to dimensional stability during water absorption and reduced thickness swelling has been tied to losses in other mechanical properties,especially as the compression temperature is increased.Toward solving this trade-off,we analyzed the effects of a 48 h pre-soak in citric acid solutions(0,5,15,25,or 35%w/v in distilled water)on the physical and mechanical properties of oil palm board compressed at 140℃.The reference benchmark case was compressed at 200℃without pretreatment.The oil palm board raw materials were obtained from outer,middle and inner parts of trunk.The results showed that the oven-dry density of compressed oil palm board made from different parts of trunk increased with thermal compression(maximum pressure 12.26 MPa for 8 min).The citric acid pretreatment improved water absorption and thickness swelling properties of oil palm board thermally compressed at 140℃,consistent with the citric acid concentration.The carboxyl groups in citric acid cross-link with the hydroxyl groups in the wood.However,no significant difference was found between the benchmark(200℃)and pretreatments with 5 or 15%citric acid.The citric acid altered the wood chemistry during hot compressing at 140℃.Static bending strength,modulus of rupture(MOR),and modulus of elasticity(MOE)slightly decreased with the citric acid pretreatment,matching the effects of high temperature compression at 200℃.     

Biological performance,water absorption,and swelling of wood treated with nano-particles combined with the application of Paraloid B72~

We evaluated fungal decay and mold resistance,leaching, and water absorption of nano-compounds and Paraloid B72~(PB72) in treated wood specimens to develop new methods of consolidation by combining nanoparticles and consolidants. Scots pine wood specimens were treated with dispersions of nano-Cu O, nano-Zn O,nano-B_2O_3, nano-Ti O_2, and nano-Ce O_2. PB72 treatments of nano-particle-treated wood specimens were then carried out by either vacuum or immersion for 24 h. Previously,decayed wood specimens were also consolidated with the nano-compounds and PB72. PB72 treatments reduced element release from treated wood specimens. Nearly all nano-compounds ? PB72 treatments increased the biological performance of treated wood specimens against decay fungi tested. PB72-only treated wood specimens had the highest weight losses in decay tests. No improvements were obtained in mold resistance tests when the nanocompounds and PB72 were combined. In nano-compoundonly treatments, unleached specimens showed slightly lower water absorption values compared to untreated control specimens. Incorporation of PB72 into nano-compound-treated wood specimens resulted in considerably lower water absorption and volumetric swell. In previously decayed specimens treated with the nano-compounds and PB72 solution, water absorption after 2-h immersion declined compared to control specimens.     

A Potential Criterion to Evaluate Copper Adsorption in Wood Cell Wall

A gcometrical definition, fractal dimension, was introduced in this study to evaluate copper adsorption in wood treated with copper-containing preservatives. It is based on the assumption that some copper would compete the hydroxyl groups in wood cell wall with water molecules, and therefore influence the fractal dimension of internal wood surfaces revealed by the moisture adsorption in wood. Southern yellow pine (Pinus spp.) specimens were treated with different concentrations of copper ethanolamine (Cu-EA) solution to obtain different copper retention levels. Then the adsorption isotherms of untreated and Cu-EA treated specimens were determined at 4, 15, 30, and 40℃ to provide the source data for fractal dimension calculation. The results showed that, at all temperatures, the fractal dimension of the internal wood surfaces had a decreasing trend with increasing copper retention. That is, the internal spaces in wood become “thinner“ due to the copper adsorption on some hydroxyl groups in wood cell wall. The correlation between the fractal dimension and adsorbed copper ions makes it possible to evaluate the copper adsorption in wood cell wall.     

Effects of Natural Weathering on A Wood Fiber/HDPE Composite and Application of Additives

In this study,the durability of rubber wood(Hevea brasiliensis) which was thermally treated at 170,185,200,and 215℃for 3 h respectively was investigated.The results showed that the durability of heat-treated rubber wood was improved,and the improvement became more obvious with the increase of the treating temperature. When treated at 185℃or lower temperature,the decay resistance of treated wood had no significant improvement.The lowest weight losses were 21.6%and 6.8%after attack by brown rot fungi(Gloeophyllum trabeum) and white rot fungi (Coriolus versicolor) respectively,which were reached by the specimens treated at 215℃.Their resistance to mold fungi was not improved,but the heat-treated wood performed better than untreated wood when both were painted.In field test,the heat-treated specimens exhibited no advantage in termite resistance compared to untreated.     

Vapor phase reaction of wood with maleic anhydride (I): dimensional stability and durability of treated wood

Reaction between maleic anhydride (MA) and wood specimens was carried out in a vapor phase reaction system. Reaction conditions such as the ratio of supplied MA to wood, initial moisture content, and reaction temperature were optimized. The MA supplied to the reaction system was effectively absorbed by the wood, and a satisfactorily high dimensional stability was achieved even at a low MA/wood ratio. The dimensional stability increased with rising initial moisture content. When the reaction was conducted at an elevated temperature (180°C), high dimensional stability was attained without remarkable weight increase and bulking. The mechanism of dimensional stabilization was discussed on the basis of the dimensional changes at high humidity and during repeated water soaking and drying. It was shown that the dimensional stabilization arises mainly from a decrease of hygroscopicity. When the reaction was conducted at 180°C, the formation of cross-links in the cell wall was apparent. Following the MA treatment, the antifungal property was remarkably enhanced and met the Japanese Industrial Standard K1571. Therefore, MA treatment in the vapor phase is an effective method to attain antifungal properties as well as high dimensional stability with a small amount of nontoxic reagent.     

甘油预处理对热处理材尺寸稳定性的影响

为提高木材的尺寸稳定性,采用甘油水溶液对毛白杨和云杉进行预处理,然后再进行热处理.通过检测处理材的密度、平衡含水率、吸水和吸湿抗胀率等,结果表明:与未预处理的热处理材相比,经甘油水溶液预处理后,热处理材的密度增加率提高;平衡含水率先降低后增加;吸水和吸湿抗胀率均显著增加.     

阻燃剂WFRJ1改性木材的体积稳定性和涂饰性能

用阻燃剂ＷＦＲＪ１处理大青杨木材并对处理材的阻燃性能、涂饰性能和体积稳定性进行测定。结果表明：ＷＦＲＪ１可用于木制品的阻燃处理。当ＷＦＲＪ１浓度为１０％时,氧指数可达到５０％以上,与水溶性ＲＦ树脂复配,可大幅度提高处理材的抗胀缩率和阻湿率,增加体积稳定性。经ＷＦＲＪ１处理后杨木单板的涂饰性能未受影响。     

Influence of treatment temperature and duration on selected biological, mechanical, physical and optical properties of thermally modified timber

The impact of heat-treatment temperature (180, 200, 210, 220 and 240°C) and various heat-treatment durations on selected biological, mechanical, optical and physical properties of thermally modified timber (TMT) was determined. The suitability of different measures for prediction of the treatment intensity was also investigated. Resistance to impact milling (RIM), lightness L*, equilibrium moisture content (EMC), and antiswelling efficiency (ASE) were correlated with corresponding fungal resistance achieved by heat treatments. The results show that the decrease in mass by heat treatments is a suitable measurand to describe the treatment intensity, which is a product of treatment temperature and duration, where the impact of temperature is dominant over the impact of time. The properties examined showed a strong reciprocally proportional relationship with the decrease in mass. Different correlations were found for the various treatment temperatures: the higher the temperature applied, the lower the decrease in mass required for an equivalent improvement in certain wood properties, e.g. biological durability, EMC and dimensional stability. However, mass loss by Poria placenta correlated well with RIM, lightness L*, EMC and ASE of the different heat-treated specimens, depending on the heat-treatment temperature. Consequently, a reliable estimation of improved fungal resistance of TMT, as well as quality control of TMT in general, requires certain process information.     

The modification of wood by treatment with low molecular weight phenol-formaldehyde resin: a properties enhancement with neutralized phenolic-resin and resin penetration into wood cell walls

To enhance dimensional stability and biological properties, low molecular weight phenolic resins of a conventional alkaline type and neutralized type were impregnated into Japanese cedar wood (Cryptomeria japonica D. Don) and heat-cured. The treatment with the neutralized type resin retained the original wood color, whereas the alkaline treatment changed the color of wood to red-brown. The concentrations of the resin solutions and the weight gains due to the resin loading of wood after treatment were highly correlated, and the target resin loading could be assessed from the solution concentration. A high dimensional stability of 60% antiswelling efficiency was attained when both types of resins were impregnated at about 30% resin loading and no significant difference was recognized between the two. To suppress decay attack from brown-rot and white-rot fungi, 15% and 10% resin loading due to treatment was required for the neutralized and alkaline types of phenolic resins, respectively. The penetration of resin into wood cell walls was investigated by means of light microscopy, Scanning Electron Microscopy (SEM), and Electron Probe X-ray Microanalysis (EPMA). A m-Bromophenol-formaldehyde resin of three levels of an average molecular weight was used to detect the presence of resin by bromine signals. The phenolic resins with low and medium molecular weights (290 and 470) were shown to penetrate into the cell walls the furthest, thereby contributing to the enhancement of dimensional stability and decay resistance in the resin-impregnated wood. Also, for phenolic resin with a high molecular weight (820), only the resin components of low molecular weight appeared to be present in the walls, making very little contribution to the dimensional stability.     

Chemical modification of wood by non-formaldehyde cross-linking reagents

Summary The probability of bond between wood components and glyoxal was examined by means of a mechanical method, infrared (IR) spectrometry, and solid state ¹³C-nuclear magnetic resonance (NMR) spectrometry. The successive fixation of a compressed wood by the glyoxal treatment suggested the formation of cross-linkings between wood components and/or wood structures. The IR spectra showed that ester bond as well as ether bond was formed between wood components and glyoxal. The existence of linkages between glyoxal and cellulose was indicated also from the NMR spectra. The addition of glycol to the glyoxal solution was investigated from the viewpoint of stabilizing effect of the linkages. When 0.2 mole ratio of glycol was added to 5–10% glyoxal solution, weight gain and antiswelling efficiency (ASE) were largest, however the addition of excessive amount of glycol did not advance further the weight gain and ASE. When an appropriate amount of glycol was added to the impregnation solution, both weight and ASE did not largely reduce even by the repeated hot water soaking. By the treatment without glycol, the dimensional stability after water soaking was attributed to only restraint of the swelling. On the other hand, when the glycol was added, the dimensional stability was developed not only by the restraint of the swelling but also by the buckling effect.We would like to thank Associate Professor Dr. Umezawa, Wood Research Institute, Kyoto University, for his invaluable support in NMR analysis. Thanks are also due to Dr. Inoue, Wood Research Institute, Kyoto University, for his preparing the wood specimens.     

Effect of oil impregnation on water repellency,dimensional stability and mold susceptibility of thermally modified European aspen and downy birch wood

Conventional chemical wood preservatives have been banned or restricted in some applications due to human and animal toxicity and their adverse impact on the surrounding environment. New, low-environmental-impact wood treatments that still provide effective protection systems are needed to protect wood. Thermal modification of wood could reduce hygroscopicity, improve dimensional stability and enhance resistance to mold attack. The aim of this study was to investigate if these properties enhanced in thermally modified (TM) wood through treatments with oils. In this study, TM European aspen (Populus tremula) and downy birch (Betula pubescens) wood were impregnated with three different types of oil: water-miscible commercial Elit Träskydd (Beckers oil with propiconazole and 3-iodo-2-propynyl butylcarbamate, IPBC), a pine tar formulation and 100% tung oil. The properties of oil-impregnated wood investigated were water repellency, dimensional stability and mold susceptibility. The treated wood, especially with pine tar and tung oil, showed an increase in water repellency and dimensional stability. However, Beckers oil which contains biocides like propiconazole and IPBC showed better protection against mold compared with pine tar and tung oil. To enhance the dimensional stability of the wood, pine tar and tung oil can be used, but these oil treatments did not significantly improve mold resistance rather sometimes enhanced the mold growth, whereas a significant anti-mold effect was observed on Beckers oil treated samples.     

Preparation and properties of oligoesterified wood blocks based on anhydride and epoxide

Summary Preparation and properties of oligoesterified woods in the form of block are reviewed. The oligoesterified wood blocks are prepared by stepwise addition reactions of dicarboxylic acid anhydride and epichlorohydrin (EpCl), or one-step chemical treatment with reactant solution of the anhydride and EpCl. Among the preparation methods investigated, the heating-suction method is industrially advantageous. In this method, wood blocks impregnated with the reactant solution are heated and then subjected to suction under reduced pressure and heating, to remove unreacted reactant solution. The oligoesterified wood blocks thus obtained contain oligoester chains formed by the alternate additions of the anhydride and EpCl to OH groups of wood. They also contain small amounts of free oligomers not linked with the wood matrix. Their dimensional stabilities against moisture and water become greater with increase in the apparent total weight increase due to the oligoester chains and the free oligomers. The oligoesterified wood blocks based on phthalic anhydride-EpCl are industrially promising, and exhibit higher compressive and flexural strenghts, greater chemical resistance, electric insulation, and much lower water absorption than untreated wood block. Furthermore, excellent resistances are observed against weathering and biodeterioration.     

Improvement of wood properties by urea-formaldehyde resin and nano-SiO2

In order to improve wood properties of triploid clones of Populus tomentosa, urea-formaldehyde (UF) resin was compounded with nano-SiO₂, coupling agents and flame retardants in different ways to prepare five kinds of modifiers. The poplar wood samples were impregnated with the modifiers and heated to prepare UF-SiO₂-wood composites. The antiswelling efficiency, resistance of water absorption, oxygen index and hardness of the composites were measured. Results show that all of the modifiers reduced water absorption of poplar wood and enhanced flame resistance and hardness. Nano-SiO₂ showed a marked effect in improving the hardness of wood. In addition, all of the modifiers, except UF-C-SiO₂-polymer, improved the dimensional stability of poplar wood. The UF resin and nano-SiO₂ compound improved general properties of poplar wood. __________ Translated from Journal of Beijing Forestry University, 2006, 28(2): 123–128 [译自: 北京林业大学学报]