Preparation and crosslinking of oligoesterified woods based on phthalic anhydride and glycidyl methacrylate

Summary Oligoesterification reaction of wood with phthalic anhydride and glycidyl methacrylate (GMA) was investigated. The reaction proceeded smoothly at 90°C. The products obtained consisted of acetone-insoluble and soluble parts. The insoluble parts were novel oligoesterified woods with oligoester chains having methacrylate double bonds. The soluble parts were viscous liquids consisting mainly of free oligoesters not linked with the wood matrix, and contained small amounts of GMA and oligoesterified wood components which were dissolved out. The products (the oligoesterified wood-containing mixtures), when subjected to hotpressing, gave plasticized crosslinked wood boards whose surfaces are smooth, glossy, and plasticlike. In this case, plasticization of wood components and thermal polymerization of the methacrylate double bonds in the oligoester chains occurred simultaneously even in the absence of radical initiator. The soluble parts worked as a plasticizer for the wood components. The crosslinked wood boards exhibited outstanding properties in tensile strength (ca. 700 kg/cm²), flexural strength (ca. 900–1030 kg/cm²), and Rockwell hardness (ca. 120).     

Preparation and crosslinking of oligoesterified woods based on maleic anhydride and allyl glycidyl ether

Summary Oligoesterification of wood was investigated by alternately adding esterification reactions of wood with maleic anhydride and allyl glycidyl ether. The products obtained consisted of acetone-insoluble and soluble parts. The insoluble parts were novel oligoesterified woods with oligoester chains having polymerizable double bonds. The oligoester chain length showed a tendency to decrease with increase in wood content in feed. The soluble parts were free oligoesters which were not linked with the wood matrix. The products (the oligoesterified wood-containing mixtures), when subjected to hot-pressing in the presence of a peroxide, gave plasticized crosslinked wood boards whose surfaces are smooth, glossy, and plasticlike. In this case, the free oligoesters which were hardening worked as a plasticizer for the wood components and were combined, by the crosslinking, with the oligoesterified woods, resulting in the formation of the network structure. The crosslinked wood boards exhibited outstanding properties in heat distortion temperature (>165°C) and compressive strength (ca. 1,600–2,300 kg/cm²).     

乙酸酐对大豆基木材胶粘剂的改性研究

用乙酸酐改性大豆基木材胶粘剂,研究了乙酸酐为不同浓度时,双因素(pH值和温度)对耐水胶合强度的影响。试验结果得到4个不同浓度下pH值和温度的最佳组合值为:乙酸酐体积分数为1.2%、1.8%、2.4%、3.0%时对应的pH值/温度是8/55℃、8/55℃、7/70℃、7/70℃,最佳耐水胶合强度可提高到0.72 MPa。以乙酸酐体积分数为1.8%为例,采用茚三酮法测得大豆蛋白质的酰化程度,分析不同温度下pH值对酰化程度的影响,结果显示:耐水胶合强度与酰化程度不成正相关。由红外光谱分析可知,乙酸酐与大豆蛋白的游离氨基发生了交联反应,从而提高了大豆基木材胶粘剂的耐水胶合强度。     

Preparation,physical properties and ultraviolet resistance of wood nanocomposites based on modified soybean oil and bentonite

ABSTRACT

Safer environmental requirements have resulted in significant interest in natural polymer-based materials to increase sustainability. In this perspective, wood polymer nanocomposites are of particular interest. Wood polymer nanocomposites were prepared from modified soybean oil, wood flour and cetyl trimethylammonium bromide modified bentonite using the compression-molding technique. Fourier transform infrared spectroscopy and X-ray diffractometric studies were used to confirm the successful modification of bentonite. Incorporation of 3?wt% of bentonite in the composites produced significant improvement in properties compared to those of 1 and 5?wt%. Furthermore, in comparison to the unfilled nanocomposites, nanoclay-filled ones showed an enhanced UV resistance property as judged by lower weight loss and carbonyl index. The decrease in mechanical properties of UV-exposed unfilled composites was more significant compared to those of nanoclay-filled composites. Scanning electron microscope and transmission electron microscope were used to study the surface morphology and distribution of the bentonite into the composites. In addition, with the incorporation of bentonite, significant increase in thermal, mechanical and flame-retarding properties was observed.     

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     

Oleothermal modification of fir wood with a combination of soybean oil and maleic anhydride and its effects on physico-mechanical properties of treated wood

This research work aimed at studying the effects of oleothermal modification of fir wood by using combined soybean oil with maleic anhydride (OHT–MA) to achieve lower treatment temperatures and enhance physico-mechanical properties. Wood blocks were oleothermally treated with soybean oil and OHT–MA at five different treatment temperatures (100, 120, 140, 160 and 180 °C) for three different holding times (30, 60 and 180 min). Afterward, physical and mechanical properties of the treated samples were determined, i.e., density, water absorption and volumetric swelling as the physical properties and bending strength, compression parallel to grain and impact load resistance as the mechanical properties. Results revealed increases in densities and reduction in water absorption as well as volumetric swelling of all treated samples. The mechanical properties were affected by OHT–MA treatment at different temperatures. Bending modulus of elasticity as well as compression parallel to grain was increased due to OHT–MA treatment. In addition, there was less reduction in impact load resistance of the treated samples. It was revealed that the OHT–MA enhanced wood properties at low treatment temperatures as well as shorter holding times.     

Modelling elastic and shrinkage properties of wood based on cell structure

Summary In a previous article of the authors a model was developed for estimating elastic and shrinkage properties of a softwood cell-wall. In the present article this model is enlarged to simulate the elastic properties of defect-free softwoods. The wood model consists of earlywood, latewood and ray cells, each of which have a different cell-wall structure. In the model the ratio of earlywood to latewood is defined by a given wood density. The calculated elastic properties are in good agreement with test results.     

Interaction between Epicoccum purpurascens and xylophagous basidiomycetes on wood blocks

Epicoccum purpurascens, a component of the bark micromycota, was evaluated as a potential biocontrol agent for three decay‐causing hymenomycetes frequently found in Buenos Aires city trees, Ganoderma platense, Inonotus rickii and Rigidoporus ulmarius. Treatments consisted of dual cultures of E. purpurascens and xylophagous fungi on box elder (Acer negundo) wood blocks. Two inoculation sequences were tested: (i) the biocontrol agent as the first microorganism inoculated followed by the pathogen; and (ii) the xylophagous fungus as the first microorganism inoculated followed by the biocontrol agent. After 3 months of incubation, percentage dry weight loss was calculated. When E. purpurascens was allowed to colonize wood blocks before the introduction of the xylophagous fungus, dry weight loss was significantly reduced in all instances. However, as a secondary colonizer, E. purpurascens mildly reduced the weight loss caused by G. platense, had no effect on degradation by I. rickii and increased wood weight loss by R. ulmarius.     

Stand,stem and log segregation based on wood properties: a review

There are many log and wood properties of interest to wood processors. There is also high variability in important attributes between and within growing regions and between and within individual stems which influence financial returns to wood processors. This review summarises recent studies of segregation technologies and techniques which have shown that:

• regional or stand level attribute models will facilitate a coarse level of segregation but not account well for the between and within stem variation;

• many tools and techniques are available for segregating wood based on internal properties but few have been implemented commercially. Some are better suited for application in mills than in forests;

• the benefits of segregating stands, stems and logs based on wood properties are not clear due to high variability in wood properties, poor market signals (in terms of price) for wood with superior properties, and poor understanding of the costs across the value chain; and

• most of the existing economic models tend to look at the economics of segregation from the perspective of a single participant in the value chain, e.g. a structural mill or a central processing yard. Only a few models look across the value chain and these have limitations often poorly representing some participants in the value chain.

     

Chemical kinetics of stress relaxation of compressed wood blocks

Summary Methods of chemical kinetics are used to study stress relaxation behaviour of wood blocks made fromPinus sylvestris and compressed parallel to grain at 20°C and 65% relative humidity. The effect of stress levels on stress behaviour is investigated. It is found that both activation volume and activation energy decrease with increasing stress level. The results prove the validity of the chemical kinetics approach in describing stress relaxation of wood blocks in compression. Suggestive explanations are given for the variations in activation energy and activation volume with stress level.Part of this work was carried out at the School of Agriculture and Forestry Sciences, University of North Wales, Bangor, UK through an ODA TCT fellowship granted to one of the authors (SPSR). He would like to thank Director General, ICFRE (India) and Director, IWST, Bangalore (India) for providing him with the opportunity to work in UK. He would also like to acknowledge the help received from Mrs. Helen Simpson and Dr. Robert Brooke of School of Agriculture and Forestry Sciences, University of North Wales, Bangor, U.K     

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.     

Dimensional stability of wood acetylated with acetic anhydride solution of glucose pentaacetate

Five wood species were acetylated with acetic anhydride (AA) solution of glucose pentaacetate (GPA) at 120°C for 8h, and the effect of GPA on the dimensional stability of the acetylated wood was investigated. Some GPA was introduced into the wood cell wall during acetylation. The GPA remaining in the cell lumen penetrated the cell wall effectively after heating to more than 140°C for 10min. The bulking effects of GPA resulted in a 10%–30% increase in the anti-swelling efficiency of the acetylated wood with 20% GPA/AA solution in place of AA. Hydrophobic GPA did not deliquesce under highly humid conditions and it remained in the cell wall after boiling in water.Part of this paper was presented at the 51st Annual Meeting of the Japan Wood Research Society, Tokyo, April 1988     

浙江桂幼龄材的生长特性及主要材性

以3株6年生浙江桂幼龄材为试材,研究了其生物量、材积、基本物理力学性能及生长轮的宽度、纤维长度、宽度、微纤丝角和结晶度的径向变异规律。结果表明,浙江桂幼龄材单株平均总生物量27.93 kg,平均材积0.0124 m3,生长轮平均宽度9.15 mm（3.12~10.57 mm）,基本密度为0.414 g/ cm3,除髓心外其余各生长轮宽度和密度无明显差异,反映浙江桂生长较为稳定;顺纹抗压强度、抗弯强度和弹性模量等物理力学综合性能中上等;纤维长度为830.6μm（581~1043μm）,纤维宽度为23.6μm（21~24μm）,结晶度为38.46％~58.43％,微纤丝角为13.6°~24.6°;纤维长度、宽度和结晶度自髓心向外逐渐增加,微纤丝角自髓心向外逐渐减小,结晶度与纤维长度、宽度间相关性极显著。     

Mechanical properties of wood materials using near-infrared spectroscopy based on correlation local embedding and partial least-squares

This study used near-infrared(NIR)spectroscopy to predict mechanical properties of wood.NIR spectra were collected in wavelengths 900–1700 nm,and spectra averaged by radial and tangential surface spectra were used to establish a partial least square(PLS)model based on correlation local embedding(CLE).Mongolian oak(Quercus mongolica Fisch.ex Ledeb.)was used to test the eff ectiveness of the model.The cross-validation method was used to verify the robustness of the CLE–PLS model.Ninety samples were tested as the calibration set and forty-fi ve as the validation set.The results show that the prediction coeffi cient of determination(R2 p)is 0.80 for MOR,and 0.78 for MOE.The ratio of performance to deviation is 2.23 for MOR and 2.15 for MOE.     

Development of wood and wood ash-based hydroxyapatite composites and their fire-retarding properties

For making efficient use of waste wood ash emitted from wood biomass plant, the wood and wood ash-based hydroxyapatite (HAp) composite was produced and their flammability characterization was studied by thermogravimetric (DTA-TG) analysis, oxygen index (OI) measurement and cone calorimeter test. The results show that the exothermic and weight loss peaks in DTA-TG combustion profiles due to their significant thermal decomposition were weakened by the HAp agent impregnation. In addition, the OI value of HAp composites was increased by the HAp combining and the OI showed a correlation with the HAp contents. Also, the cone calorimeter study revealed that the heat release rates were decreased with increasing amount of HAp injection and accordingly their total heat release has an inverse relationship to the HAp contents. These results indicate that the treatment with wood ash-based HAp agents can enhance the flame retardancy of the treated woods.     

Preparation and characterization of wood/montmorillonite nanocomposites

With montmorillonite (MMT) organically modified as organophilic MMT (OMMT) and water-soluble phenol formaldehyde resin (PF) as intermediate, Chinese fir (Cunninghamia lanceolata) wood/MMT nanocomposites (WMNC) were prepared via nano intercalation compounding and characterized by XRD, SEM and FTIR. Results show that: 1) the preparation of OMMT is very successful; 2) the self-made PF can effectively intercalate into MMT to increase markably its gallery distance and even exfoliate its nano silicate laminae; 3) the XRD analysis indicates that some exfoliated MMT enters the non-crystallized region of microfibrils in wood cell walls and the crystallinity degree of wood in WMNC decreases; 4) the SEM graphs show that multiform MMT exists in WMNC. Some grains block in wood cell lumen, some layers adhere to the wood surface of the inner cell wall and some exfoliated nanolaminae even insert into wood cell walls; and 5) the FTIR analysis suggests that MMT and wood in WMNC perhaps interact via certain chemical bonding.     

Methods for the determination of wood properties,Kraft pulp yield and wood fibre dimensions on small wood samples.

A trial set-up with methods for sampling, treatment and analysis of small wood chips are presented in this paper, to determine important wood and fibre properties, like basic density, dry density, volume swelling of wood, Kraft pulp yield, fibre length, fibre coarseness, fibre width, lumen width and fibre wall thickness. The required time for one sample is about 1.5 man-hour, but this requires relatively larger series and trained personnel. Acceptable measurement accuracy is achieved when the volume of the wood sample is at least 1.5 ml, except that of wood volume swelling. To gain acceptable measurement accuracy for volume swelling, the wood volume should be increased to at least 3 ml, and preferably more than 5–6 ml per sample. The level of pulp yield and wood density do not show a significant effect on the measurement accuracy for fibre cross-section dimensions. Fibre coarseness, on the other hand, has a significant influence on these accuracies. A double measurement of fibre coarseness will improve the accuracy to an acceptable level. The method presented here may, together with information about trees and growth locations, form the basis for greater insight into the mechanisms involved in development of wood and fibre properties in trees, which in turn may provide better control and utilisation of wood for pulp and paper production.Abbreviations CWD cell wall density in dry wood=1500 kg/m³ - Ww dry weight of wood (kg) - Vmax green (wet) volume of wood (m³) - Vmin dry volume of wood (m³) - BD basic wood density (kg/m³) - DD dry wood density (kg/m³) - VS maximum volume swelling of wood (%) - Wp dry weight of pulp (kg) - PY pulp yield (%) - C fibre coarseness, the average weight of a unit length of fibre (g/m) - CL average chip length (mm) - CWT average cell wall thickness (m) - FW average fibre width (m) - l average native fibre length in solid wood - L chip length - lc average fibre length in wood chip (mm) - Lc length-weighted fibre length in wood chip (mm) - lw native average fibre length in wood (mm) - Lw native length-weighted fibre length in wood (mm) - LW average lumen width (m) - llw average native fibre length, length weighted, in wood - X average fibre length in chip - Xlw average fibre length, length weighted, in chip     

Sorption properties of torrefied wood and charcoal

Abstract

Pre-treating biomass by torrefaction is assumed to improve the material's storage properties because of reducing hydrophilicity. In order to assess the effect of sorption on storage properties, the adsorption of water vapour and capillary absorption of liquid water in torrefied and charred spruce and birch were studied. In addition, the chemical changes were evaluated through Fourier Transform Infrared (FT-IR) spectroscopy. Adsorption decreased notably as severity of treatment increased, as was expected due to degradation of the wood constituents, namely hemicelluloses and amorphous cellulose. Capillary absorption increased with increasing severity in spruce samples while birch showed less change, but the maximum volume for absorption increased with both species. FT-IR results showed an increase in aromatic structures that have a role in forming crystalline structures, possibly leading to increased porosity. Torrefied and charred material should not be stored outside, as liquid water absorbs readily into the material, turning it into a suitable substrate for fungi.