Properties of medium density fiberboards made from renewable biomass

The goal of this study was to determine the comparative properties of dry-formed medium density fiberboards (MDF) made from renewable biomass (wheat and soybean straw) and those from conventional soft wood fiber. The MDF properties evaluated were modulus of elasticity, modulus of rupture, internal bond strength, thickness swell, and screw holding capacity. The results show that MDF made from wheat straw fiber and soy straw fiber have weaker mechanical and water resistance properties than those made from softwood fiber. Soybean straw is comparable to wheat straw in terms of both mechanical and water resistance properties to make MDF. Water resistance of MDF decreased drastically with increasing straw fiber composition. Wheat straw fiber and soybean straw fiber should be physically or chemically treated to increase their water resistance property for MDF production.     

杉木人工林木材力学性质与纤维形态关系的研究

应用正交试验设计方法对不同林龄、立地条件和林分密下杉木人林木材力学性质,纤维形态的测定结果为基础,采用多元线性回归方法,对杉木人工林木材力学性质与纤维形态的关系进行相关分析和回归分析,结果表明：杉木人工林木材顺纹抗压强度,抗弯强度等十一项力学性质指标与纤维长度,纤维宽度、壁厚、腔径、壁腔比之间存在极显著的相关关系。     

Laccase mediator systems for eco-friendly production of medium-density fiberboard (MDF) on a pilot scale: physicochemical analysis of the reaction mechanism

Increasing prices of petrochemical resins and possible harmful formaldehyde emissions from conventionally produced wood composites have resulted in increased interest in enzymatic binder systems as environmentally friendly alternatives for gluing lignocellulosic products. In this study, laccase mediator systems (LMSs) were used to activate lignin on wood fiber surfaces in the pilot-scale production of medium-density fiberboard (MDF) using a dry process. Three different mediators were applied: 4-hydroxybenzoic acid (HBA), 1-hydroxybenzotriazole (HBT), and acetosyringone (AS) of which HBA performed best. The mechanical properties of the manufactured boards produced with thermomechanical pulp (TMP) fibers, laccase, and HBA fulfilled all required European standards for wood-based panels. Oxygen consumption rates of the different LMSs and (13)C NMR spectroscopy results for treated TMP fibers were obtained for qualitative and quantitative analysis of lignin activation. The results show that reactions were most effective within the first 30 min of incubation. Oxygen consumption was fastest and highest for the LMS using HBA. (13)C NMR spectroscopy indicated the highest decrease of aromatic groups in the wood fiber lignin with this LMS. The data correlated well with the quality of the MDF. The required enzymatic reaction times allowed direct integration of the LMS into standard MDF production techniques. The results indicate that application of LMSs has a high potential for environmentally friendly MDF production.     

Performance of oak,beech and spruce beams after more than 100 years in service

The aim of this study was to investigate differences in the mechanical and fungicidal properties of three different wood species (English oak (Quercus sp.), common beech (Fagus sylvatica) and Norway spruce (Picea abies)) that had been in indoor use for several decades, compared to control specimens of freshly cut timber. The collected material was cut into smaller samples prior to further analysis. Extractive content, mechanical, fungicidal and sorption properties were determined according to standard procedures. The obtained results showed that the mechanical properties of oak wood do not deteriorate over the investigated time frame. On the other hand, the resistance of oak wood against fungi decreases over time. The reason for this is yet to be confirmed; it may be due to degradation of secondary metabolites. Similar results have been reported for spruce wood. There were no statistically significant differences in the mechanical properties of old and new spruce wood. In contrast to oak wood, there were also no significant differences in fungicidal properties, bearing in mind that spruce wood has lower durability than oak wood. Aging of beech wood resulted in a considerable decrease in the tested mechanical properties but showed no significant differences in fungicidal properties. Old beech wood specimens were moderately deteriorated by insects and fungi, which was the reason for the loss of bending and compressive strength. Our results confirm that most of the relevant properties do not deteriorate with time and that wood can be reused for a variety of other applications even after decades in service.     

Some of the properties of flame retardant medium density fiberboard made from rubberwood and recycled containers containing aluminum trihydroxide

The flame retardancy of medium density fiberboard (MDF) made from mixture of rubberwood fibers and recycled old corrugated containers was studied. Aluminum trihydroxide (ATH) was used as a fire retardant additive and mixed with the fibers to manufacture experimental MDF panels using wet process. Phenol formaldehyde (PF) resin in liquid, 2% based on oven dry weight of fibers, was used along with 0%, 10%, 15% and 20% of ATH. The flame retardant test was done using the limiting oxygen index (LOI) test. The other properties investigated include internal bond strength, thickness swelling and water absorption. The results showed that ATH loading increased as the LOI of MDF increased. This demonstrated that ATH could improved the fire retardant property of MDF at sufficient loading. An increase in concentration of ATH showed an increase in the IB values of MDF made without resin. MDF panels made without resin showed a progressive increase in internal bond as the composition of recycled old corrugated containers fiber increased. Addition of resin improved internal bond strength and reduced thickness swelling, and water absorption. Thickness swelling of panel increased as the composition of recycled old corrugated containers fiber increased. Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) showed that there is indication of ATH and resin filling the void space in between fibers.     

Spatial patterns of wood traits in China are controlled by phylogeny and the environment

Aim Wood properties are related to tree physiology and mechanical stability and are influenced by both phylogeny and the environment. However, it remains unclear to what extent geographical gradients in wood traits are shaped by either phylogeny or the environment. Here we aimed to disentangle the influences of phylogeny and the environment on spatial trends in wood traits. Location China. Methods We compiled a data set of 11 wood properties for 618 tree species from 98 sampling sites in China to assess their phylogenetic and spatial patterns, and to determine how many of the spatial patterns in wood properties are attributable to the environment after correction for phylogenetic influences. Result All wood traits examined exhibited significant phylogenetic signal. The widest divergence in wood traits was observed between gymnosperms and angiosperms, Rosids and Asterids, Magnoiliids and Eudicots, and in Lamiales. For most wood traits, the majority of trait variation was observed at genus and species levels. The mechanical properties of wood showed correlated evolution with wood density. Most of the mechanical properties of wood exhibited significant latitudinal variation but limited or no altitudinal variation, and were positively correlated with mean annual precipitation based on both Pearson's correlation analysis and the phylogenetic comparative method. Correlations at family level between mean annual temperature and wood density, compression strength, cross‐section hardness, modulus of elasticity and volumetric shrinkage coefficient became significant after correction for phylogenetic influences. Main conclusions Phylogeny interacted with the environment in shaping the spatial patterns of wood traits of trees across China because most wood properties showed strong phylogenetic conservatism and thus affected environmental tolerances and distributions of tree species. Mean annual precipitation was a key environmental factor explaining the spatial patterns of wood traits. Our study provides valuable insights into the geographical patterns in productivity, distribution and ecological strategy of trees linking to wood traits.     

Inducing β-sheets formation in synthetic spider silk fibers by aqueous post-spin stretching

As a promising biomaterial with numerous potential applications, various types of synthetic spider silk fibers have been produced and studied in an effort to produce man-made fibers with mechanical and physical properties comparable to those of native spider silk. In this study, two recombinant proteins based on Nephila clavipes Major ampullate Spidroin 1 (MaSp1) consensus repeat sequence were expressed and spun into fibers. Mechanical test results showed that fiber spun from the higher molecular weight protein had better overall mechanical properties (70 KD versus 46 KD), whereas postspin stretch treatment in water helped increase fiber tensile strength significantly. Carbon-13 solid-state NMR studies of those fibers further revealed that the postspin stretch in water promoted protein molecule rearrangement and the formation of β-sheets in the polyalanine region of the silk. The rearrangement correlated with improved fiber mechanical properties and indicated that postspin stretch is key to helping the spider silk proteins in the fiber form correct secondary structures, leading to better quality fibers.     

Whipping and Emulsifying Properties of Soybean Products

Both whipping and emulsifying properties, the characteristic functional properties of soybean products, were investigated by using the commercial products in Japan. Whipping properties of the soybean products, expressed by foam expansion and foam stability, were found to correlate with water dispersible nitrogen, and the resultant foams were stable when the dissolved proteins were native. Thus, the native defatted soybean flour which contained native and soluble protein exhibited excellent whipping property. Emulsifying properties correlated positively with protein and negatively with fiber contents. As soybean protein isolate and soybean protein extract are rich in protein and poor in fiber contents, both of them show good emulsifying functions.     

高温杀菌对预浸泡豆杆的杀菌效果及品质影响

本研究以预浸泡豆杆为研究对象,研究高温杀菌对预浸泡豆杆中微生物的杀灭效果及其品质的影响,以期获得具有良好感官品质和理化品质的产品。结果表明:当温度≥105℃和时间≥10 min时,样品的菌落总数由初始的8.72×108cfu/g减少到50 cfu/g以内,样品的大肠菌群从1.6×105MPN/g减少到3 MPN/g以内,致病菌均未检出。杀菌温度和杀菌时间对预浸泡豆杆中脂肪含量、pH、弹性影响差异不显著(p>0.05),对水分含量、蛋白质、色差、硬度和咀嚼性影响显著(p<0.05),综合微生物、理化指标、色泽、质构的变化结果,经105℃、15 min和110℃、10 min处理后的预浸泡豆杆既能满足产品卫生要求也可以较好的保留产品原有的品质。     

香椿木材解剖构造及其物理力学性质

为扩大和培育香椿资源和填补国内经济建设及人民生活对优质木材的需求,为其开发和利用提供一定的基础数据及科学的理论指导,依照GB1927-91实验方法对其木材的解剖和物理力学性质做了系统研究。结果表明：香椿纤维13年生后形态均匀,长宽比46.18,双壁厚11.00μm,纤维壁腔比0.56,腔径比0.76;导管分子平均长度383.52μm,宽度143.98μm;基本密度和气干密度分别为0.415g/cm3和0.475g/cm3,属“轻”型;差异干缩为1.93;木材的抗弯强度、抗弯弹性模量和顺纹抗压强度分别为67.85MPa、6179.82MPa和38.23MPa,综合强度106.08MPa,均属“低”级,香椿的综合品质系数为2556.1×105 Pa,为高等级材。综合分析表明香椿材质优良。     

Utilizing peanut husk (Arachis hypogaea L.) in the manufacture of medium-density fiberboards

The main objective of this study was to investigate the potential of peanut husk (Arachis hypogaea L.) as a fiber–peanut mixture to produce fiberboards for general purposes. For panel production, the addition of peanut husk at various percentages to the wood fiber was the only variable. Panels produced utilizing peanut husk were compared to panels produced using 100% wood fiber. The chemical properties of peanut husk; holocellulose and lignin content, alcohol–benzene, hot and cold water, and dilute alkali (1% NaOH) solubility, were also determined. Results indicated that panels could be produced utilizing up to 30% peanut husk without affecting the usability of the panels. It was not possible to meet the minimum IB strength standards when peanut husk was added to the mixture. Higher additions resulted in panels having lower elastic and rupture moduli than the minimum requirements according to TS-EN standards.     

Effect of adding nano‐titanium dioxide on the microstructure,mechanical properties and in vitro bioactivity of a freeze cast merwinite scaffold

In the present research, merwinite (M) scaffolds with and without nano‐titanium dioxide (titania) were synthesized by water‐based freeze casting method. Two different amounts (7.5 and 10 wt%) of n‐TiO₂ were added to M scaffolds. They were sintered at temperature of 1573.15°K and at cooling rate of 4°K/min. The changes in physical and mechanical properties were investigated. The results showed that although M and M containing 7.5 wt% n‐TiO₂ (MT7.5) scaffolds had approximately the same microstructures in terms of pore size and wall thickness, these factors were different for sample MT10. In overall, the porosity, volume and linear shrinkage were decreased by adding different weight ratios of n‐TiO₂ into the M structure. According to the obtained mechanical results, the optimum mechanical performance was related to the sample MT7.5 (E = 51 MPa and σ = 2 MPa) with respect to the other samples, i.e.: M (E = 47 MPa and σ = 1.8 MPa) and MT10 (E = 32 MPa and σ = 1.4 MPa). The acellular in vitro bioactivity experiment confirmed apatite formation on the surfaces of all samples for various periods of soaking time. Based on cell study, the sample which possessed favorable mechanical behavior (MT7.5) supported attachment and proliferation of osteoblastic cells. These results revealed that the MT7.5 scaffold with improved mechanical and biological properties could have a potential to be used in bone substitute. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:550–556, 2015     

Decay and termite resistance of medium density fiberboard (MDF) made from different wood species

Medium density fiberboard (MDF) production worldwide is increasing due to the development of new manufacturing technologies. As a result, MDF products are increasingly utilized in traditional wood applications that require fungal and insect resistance. This study evaluated the ability of white and brown rot fungi and termites to decompose MDF consisting of different wood species by measuring weight loss. Furnish in the boards was prepared from heart and sapwood portions of pine (Pinus nigra Arnold var. pallasiana), beech (Fagus orientalis Lipsky), and European oak (Quercus robur L.) species. Fungal decay resistance tests were performed according to ASTM D 2017-81 standard method using two brown-rot fungi, Gloeophyllum trabeum (Pers. ex Fr.) Murr. (Mad 617), Postia placenta (Fries) M. Larsen et Lombard (Mad 698), and one white-rot fungus, Trametes versicolor (L. ex Ft.) Pilat (Mad 697). MDF and wood specimens were also bioassayed against the eastern subterranean termite, Reticulitermes flavipes (Kollar) in order to determine termite resistance of the specimens. MDF specimens containing oak and mixed furnish demonstrated increased durability against decay fungi. Only pine, oak, and mixed MDF specimens met the 25% or less weight loss limit to be classified resistant according to ASTM D 2017-81 standard method. Overall, MDF specimens made from oak showed better performance than oak solid wood specimens. Accelerated aging according to ASTM D 1037-96a standard method before fungal bioassay decreased fungal resistance of the specimens. In contrast to the fungal bioassay, MDF specimens made from beech and mixed furnish showed decreased weight losses from termite attack after 4 weeks. However, none of the MDF specimens were resistant to termite attack. In severe conditions, the MDFs may require the incorporation of chemical biocides prior to board production for increasing the resistance of MDF to termite attack.     

响应面法优化低温豆粕大豆分离蛋白提取工艺

采用响应面分析法(RSM)对低温豆粕大豆分离蛋白(soybean protein isolated,SPI)的碱提工艺进行优化。在单因素实验的基础上,选取了影响SPI提取率的4个关键因素(pH、温度、时间和液料比)进行四因素五水平的中心组合旋转实验设计(CCRD)。通过RSM建立了响应值(SPI提取率)与各影响因素之间的回归方程,并获得了SPI的最优提取条件:pH 8.5,提取温度55℃,提取时间42.8 min,料水比1∶9.7(g/mL),此条件下SPI提取率预测值为37.12%,与实验值(36.69%)的误差为1.16%。将一次碱提后残渣进行二次碱提,二次提取率为10.16%。2次碱提上清液等电点沉淀的蛋白沉淀率分别为84.03%和85.84%。     

Esterification crosslinking structures of rayon fibers with 1,2,3,4-butanetetracarboxylic acid and their water-responsive properties

1,2,3,4-Butanetetracarboxylic acid (BTCA) was applied to crosslink amorphous regions of cotton-type rayon fibers via anhydride-mediated esterification for the purpose of enhanced mechanical properties. Crosslinking was conducted under a series of curing temperature with the presence of sodium hypophosphite (SHP) as the effective catalyst for anhydride formation. The conversion rate based on Fourier transform infrared (FTIR) spectra was in good agreement with that from the direct calculation based on titrated carboxyl groups and ester linkages. Crosslinking degree increased linearly with the curing temperature. The optimal tensile properties were derived from the curing temperature of 180 °C with an intermediate crosslinking degree. Moreover, the crosslinked structures of the rayon fibers had a great impact on absorption of liquid and gaseous water. The liquid water retention capacity diminished substantially with the crosslinking degree, while interaction between moisture and the fibers revealed that sorption–desorption cycles and concomitant hystereses were scarcely affected by the crosslinked fiber structures.     

Liquid hot water and alkaline pretreatment of soybean straw for improving cellulose digestibility

Soybean straw was pretreated with either liquid hot water (LHW) (170-210 °C for 3-10 min) or alkaline soaking (4-40 g NaOH/100 g dry straw) at room temperature to evaluate the effects on cellulose digestibility. Nearly 100% cellulose was recovered in pretreated solids for both pretreatment methods. For LHW pretreatment, xylan dissolution from the raw material increased with pretreatment temperature and time. Cellulose digestibility was correlated with xylan dissolution. A maximal glucose yield of 70.76%, corresponding to 80% xylan removal, was obtained with soybean straw pretreated at 210 °C for 10 min. NaOH soaking at ambient conditions removed xylan up to 46.37% and the subsequent glucose yield of pretreated solids reached up to 64.55%. Our results indicated LHW pretreatment was more effective than NaOH soaking for improving cellulose digestibility of soybean straw.     

Inflammatory response and genotoxicity of seven wood dusts in the human epithelial cell line A549

Exposure to wood dust is common in many workplaces. Epidemiological studies indicate that occupational exposure to hardwood dusts is more harmful than to softwood dusts. In this study, human epithelial cell line A549 was incubated with well-characterized dusts from six commonly used wood species and from medium density fibreboard (MDF), at concentrations between 10 and 300microg/ml. After 3 and 6h of incubation, genotoxicity was assessed by measurement of DNA damage with the single-cell gel electrophoresis (comet) assay and inflammation was measured by the expression of IL-6 and IL-8 mRNA and by the amount of IL-8 protein. There was a 1.2-1.4-fold increase in DNA strand breaks after incubation with beech, teak, pine and MDF dusts compared with the levels in untreated cells, but after 6h only the increase induced by the MDF dust remained. Increased expression of cellular IL-6 and IL-8 mRNA was induced by all of the wood dusts at both times. Similar to IL-8 mRNA expression, the amounts of secreted IL-8 protein were elevated, except after incubation with oak dust, where a marginal reduction was seen. On the basis of the effects on IL-8 mRNA expression, the wood dusts could be divided into three groups, with teak dust being the most potent, MDF, birch, spruce and pine being intermediate, and beech and oak being the least potent. The induction of DNA strand breaks did not correlate well with the interleukin response. In conclusion, all wood dusts induced cytokine responses, and some dusts induced detectable DNA damage. The inflammatory potency seemed intermediate for dusts from the typical softwoods spruce and pine, whereas the dusts from species linked to cancer, beech and oak, were the least inflammatory. The variation of the effects induced by different wood dusts over time indicates that the DNA damage was not secondary to the cytokine response. Although hardwoods are often considered more harmful than softwoods by regulatory agencies, the current experiments do not provide evidence for a clear-cut distinction between toxicities of hardwood and softwood dust.     

Preparation and characterization of surface crosslinked TPS/PVA blend films

Surface crosslinked thermoplastic starch (TPS)/PVA blend films were prepared by applying ultra violet (UV) irradiation. Sodium benzoate was used as photosensitizer and induced onto film surface layer by soaking the TPS/PVA films in the photosensitizer aqueous solution. The effects of concentration of photosensitizer aqueous solution, soaking time and UV irradiation dose on the surface photocrosslinking reaction were investigated. Physical properties, such as water contact angle, moisture absorption, swelling degree and solubility in water as well as mechanical properties of the films were measured to characterize the influence of the surface photocrosslinking modification. The obtained results showed that the surface modification considerably reduced the surface hydrophilic character of the TPS/PVA films, enhanced the film’s water resistance and also increased tensile strength and Young’s modulus but decreased elongation at break of the films.     

The effects of heat treatment on physical and technological properties and surface roughness of Camiyani Black Pine (Pinus nigra Arn. subsp. pallasiana var. pallasiana) wood

Heat treatment is often used to improve the dimensional stability of wood. In this study, the effects of heat treatment on physical properties and surface roughness of Camiyani Black Pine (Pinus nigra Arn. subsp. pallasiana var. pallasiana) wood were examined. Samples obtained from Yenice-Zonguldak Forest Enterprises, Turkey, were subjected to heat treatment at varying temperatures and for varying durations. The physical properties of heat-treated and control samples were tested, and oven-dry density, air-dry density, and swelling properties were determined. The mechanical properties of heat-treated and control samples were tested, and compression strength, and Janka-hardness were determined. A stylus method was employed to evaluate the surface characteristics of the samples. Roughness measurements by the stylus method were made in the direction perpendicular to the fiber. Four main roughness parameters, mean arithmetic deviation of profile (Ra), mean peak-to-valley height (Rz), root mean square roughness (Rq), and maximum roughness (Ry) obtained from the surface of wood were used to evaluate the effect of heat treatment on the surface characteristics of the specimens. Significant difference was determined (p=0.05) between physical and technological properties, and surface roughness parameters (Ra, Rz, Ry, Rq) for three temperatures and three durations of heat treatment. Based on the findings in this study, the results showed that density, swelling, compression strength, Janka-hardness and surface roughness values decreased with increasing treatment temperature and treatment times. Increase in temperature and duration further diminished technological strength values of the wood specimens. Camiyani Black Pine wood could be utilized by using proper heat treatment techniques without any losses in strength values in areas where working, stability, and surface smoothness, such as in window frames, are important factors.     

Clonal consistency of wood technological properties in canker-resistant <Emphasis Type="Italic">Cupressus sempervirens</Emphasis> clones at two contrasting sites

Cupressus sempervirens L. (Mediterranean cypress) has been traditionally used as a multipurpose tree. In the past, its wood was extensively used as a highly durable raw material in the Mediterranean, but nowadays, production of cypress wood is constrained by the lack of exploitable woods and plantations and by the spread of bark canker. In this study, the wood properties of canker-resistant clones specifically meant for timber production were assessed in two different locations. The aim was to evaluate the effect of genotype and environment on physical and mechanical properties of wood and its bonding quality. Four ramets of each of 10 clones were sampled in both sites, wood density, shrinkage, hardness, and the bonding strengths when glued together with two different adhesives were determined, and clonal repeatabilities and genetic correlations were also estimated. Clonal consistency for wood traits was moderate to high within and across environments, far higher than for growth- and morphological traits. Indications are that selection based exclusively on tree height would result in a lower wood density and hardness. Bonding strength reflected the combination of the material properties and the selected adhesive: For adhesive M (polyvinyl acetate dispersion), it was negatively correlated with density, whilst for adhesive E (emulsion polymerization isocyanate), it was not as influenced. Thus, even favouring higher-density wood (and therefore not only hardness but also higher shrinkages), adhesive E would give excellent bonding.