Investigation of a new natural adhesive composed of citric acid and sucrose for particleboard

The development of a natural adhesive composed of materials derived from non-fossil resources is a very important issue. In this study, only citric acid and sucrose were used as adhesive materials for particleboard. A water solution in which citric acid and sucrose were dissolved was used as an adhesive, and the manufacture of particleboard with a target density of 0.8 g/cm³ was attempted under a press condition of 200 °C for 10 min. The optimum mixture ratio of citric acid and sucrose and the optimum resin content was 25–75 and 30 wt%, respectively. The modulus of rupture (MOR) and the modulus of elasticity in bending were 20.6 MPa and 4.6 GPa, respectively. The internal bond strength (IB) was 1.6 MPa, indicating that the adhesive had excellent bond strength. The thickness swelling (TS) after water immersion for 24 h at 20 °C was 11.9 %. The board did not decompose even under more severe accelerated treatments. This meant that the adhesion had good water resistance. The MOR, IB and TS of the board were comparable to or higher than the requirement of the 18 type of JIS A 5908 (2003). Consequently, there is a possibility that a mixture of citric acid and sucrose can be used as a natural adhesive for particleboard.     

LARCH BARK TANNIN ADHESIVE FOR EXTERIOR PARTICLEBOARD

INTR0DUCTI0NChinaisacountrywhichhasnotade-quateforestresources.Itsforestcoverson-lyaboutl3%ofthewh01ecountry.Inor-dertomeetthedevelopmentofnationaleconomy,wemustmakegreateffortstodevelopman-madepanelindustryandmoreefficientlyusetheforestresources.Inthepresent,becauseoftheshortsupplyofchemicalmaterials,thepriceofphenolinthemarketcontinuestogoupwhichledtheincreaseofadhesivemanufacturecost.Findingnewphenolicmateria1sinplaceofphenolisaneffectivemethodtoreducetheadhesivecost.Vegetab1etanninsar…     

豆胶杨木/麦秸复合刨花板制造工艺

研究利用无醛豆胶生产杨木/麦秸复合刨花板的制造工艺。采用正交试验设计方法,探讨了施胶量、杨木/麦秸刨花质量比例、热压温度、热压时间等工艺因素对刨花板的静曲强度、弹性模量、内结合强度、吸水厚度膨胀率等性能的影响。试验结果表明:利用无醛豆胶生产杨木/麦秸复合刨花板是可行的,厚度11 mm复合刨花板的优化工艺参数为施胶量14%、杨木/麦秸刨花质量比70/30、热压时间10 min、热压温度170℃。     

Evaluation of decay resistance of wood products made from borax-impregnated wood and bonded with a formaldehyde-free cornstarch and tannin adhesive

? At present, the production of wood composites mainly relies on the petrochemical-based and formaldehyde-based adhesives such as phenol-formaldehyde (PF) resins and urea-formaldehyde (UF) resins, which are non-renewable and therefore ultimately limited in supply.

? This paper concerns the decay resistance of wood products bonded with a new, environment-friendly adhesive derived from abundant and renewable cornstarch and tannin. To improve the total resistance of the composite against both Coriolus versicolor and Coniophora puteana rot fungi, borax (di-sodium tetraborate) was added in proportions of 0.5%, 1% and 2% (w/w) to the cornstarch-tannin adhesives.

? The results show that increasing the concentration of borax in the adhesive decreased the mechanical properties of the composite. The best way to avoid this problem was to use wood impregnated with borax.

? Biodegradation studies were conducted on new composites, first without any treatment, followed by borax at 0.5% aqueous solution treatment. The results show that wood impregnated with borax, in the presence of tannin and sodium hydroxide in the adhesive improves the total resistance of the wood composite against both Coriolus versicolor and Coniophora puteana rot fungi.

     

Functional genomics analysis of foliar condensed tannin and phenolic glycoside regulation in natural cottonwood hybrids

Regulation of leaf condensed tannins (CT) and salicylate-derived phenolic glycosides (PG) in fast- and slow-growing cottonwood backcrosses was analyzed by metabolic profiling and cDNA microarray hybridization. Seven hybrid lines of Populus fremontii L. and P. angustifolia James exhibiting growth/CT-PG phenotypes ranging from fast/low (Lines 18 and 1979) to slow/high (Lines 1012 and RL2) and intermediate (Lines NUL, 3200 and RM5) were investigated. Methanol-extractable leaf metabolites were analyzed by gas chromatography-mass spectrometry, and the results evaluated by principal component analysis. The hybrid lines formed separate clusters based on their primary metabolite profiles, with cluster arrangement also reflecting differences in CT-PG phenotype. Nitrogen (N) supply was manipulated to alter CT-PG partitioning and to obtain molecular insights into how primary metabolism interfaces with CT-PG accumulation. Three backcross lines (RM5, 1012, 18) exhibiting differential CT-PG responses to a 10-day hydroponic N-deprivation treatment were chosen for metabolite and gene expression analyses. The fast- growing Line 18 showed a minimal CT-PG response to N deprivation, and a reduction in photosynthetic gene expression. Line 1012 exhibited a strong phenylpropanoid response to N deprivation, including a doubling in phenylalanine ammonia-lyase (PAL) gene expression, and a shift from CT accumulation in the absence of stress toward PG accumulation under N-deprivation conditions. Amino acid concentrations were depressed in Lines 18 and 1012, as was expression of nitrate-sensitive genes coding for transketolase (TK), and malate dehydrogenase (MDH). Genes associated with protein synthesis and fate were down-regulated in Line 1012 but not in Line 18. Line RM5 exhibited a comparatively large increase in CT in response to N deprivation, but did not sustain decreases in amino acid concentrations, or changes in PAL, TK or MDH gene expression. Molecular characterization of the variable CT-PG responses shows promise for the identification and future testing of candidate genes for CT-PG trait selection or manipulation.     

Properties of particleboard produced using a sealed press

In this study, different properties of experimental particleboard produced using a sealed press were determined and were compared with those for particleboard produced using a conventional press. Three types of binder, namely urea formaldehyde (UF), melamine formaldehyde (MUF), and polymethylene diphenyl diisocyanate (PMDI), were used for board production. For the UF-bonded boards produced using the sealed press, the modulus of rupture and the internal bond strength (IB) decreased due to the high temperature and steam pressure used in comparison to the conditions in a conventional press. However, MUF- and PMDI-bonded boards had improved IB and thickness swelling (TS). For the PMDI-bonded boards, especially, the TS was further improved and IB was increased by using a sealed press. PMDI is known to possess superior properties and was confirmed to achieve good properties when used as a binder for particleboards produced using a sealed press.     

Cement-bonded particleboard with a mixture of wheat straw and poplar wood

We investigated the hydration behavior and some physical/mechanical properties of cement-bonded particleboard (CBPB) containing particles of wheat straw and poplar wood at various usage ratios and bonded with Portland cement mixed with different levels of inorganic additives. We determined the setting time and compression strength of cement pastes containing different additives and particles, and studied the effects of these additives and particles on thickness swelling, internal bond strength and modulus of rupture of CBPB by using RSM (Response Surface Methodology). The mathematical model equations (second-order response functions) were derived to optimize properties of CBPB by computer simulation programming. Predicted values were in agreement with experimental values (R2 values of 0.93, 0.96 and 0.96 for TS, IB and MOR, respectively). RSM can be efficiently applied to model panel properties. The variables can affect the properties of panels. The cement composites with bending strength > 12.5 MPa and internal bond strength > 0.28 MPa can be made by using wheat straw as a reinforcing material. Straw particle usage up to 11.5% in the mixture satisfies the minimum requirements of International Standard, EN 312 (2003) for IB and MOR. The dose of 4.95% calcium chloride, by weight of cement, can improve mechanical properties of the panels at the minimum requirement of EN 312. By increasing straw content from 0 to 30%, TS was reduced by increasing straw particle usage up to 1.5% and with 5.54% calcium chloride in the mixture, TS satisfied the EN 312 standard.     

一种新型竹木集成材粘着剂问世

CU—3型粘着剂为日本株式会社生产,日本竹协会特别推荐的具有超高水平,超高安全性能的水基乙烯聚氨酯型粘着剂。最适合于竹子集成材及各种木质集成材的粘合。作为竹材特选专用粘着剂,CU—3型粘着剂已经在日本国内广泛使用,并博得用户很高的评价。凡使用CU—3型粘着剂的竹木制品能够顺     

Dimensional stability and strength properties of particleboard produced by a closed-press system

The purpose of this study was to reveal the effects of various levels of mat-moisture content (m.m.c.) and the closed-press system for making single- or three-layer particleboard on the density profile, thickness swelling, specific moduli of elasticity (MOE) and rupture (MOR) and internal bond strength. Internal gas pressure was measured in an enclosed frame; and the larger the m.m.c., the higher the internal gas pressure became. When rising water vapor (steam) struck particles, it plasticized them and cured the adhesive, resulting in improved interparticle contact. The vertical density gradient in the three-layer board was larger than that in the single-layer board. As for thickness swelling by cold-water soaking, the single-layer boards were less affected than the three-layer boards and showed good dimensional stability with increased m.m.c. The open-system boards swelled more than the closed-system boards. The closed-system single-layer board made at high m.m.c. returned nearly to the prime thickness by air-drying after cold-water soaking. Specific MOE and MOR were larger at 15% or 10% m.m.c. than those at other m.m.c. Considerable reductions of specific MOR and MOE of the closed-system three-layer board were observed at 20% or 25% m.m.c.Part of this report was presented at the 45th annual meeting of the Japan Wood Research Society, Tokyo, April 1995 and at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 1998     

Preparation and properties of waste tea leaves particleboard

Urea-formaldehyde (UF) adhesive is the main source of formaldehyde emission from UF-bonded boards. The components in waste tea leaves can react with formaldehyde to serve as a raw material in the production of low formaldehyde emission boards. In our study, waste tea leaves and UF adhesive were employed in the preparation of waste tea leaves particleboard (WTLB). An orthogonal experimental method was applied to investigate the effects of process parameters on formaldehyde emission and mechanical properties of WTLB. The results indicated that: 1) waste tea leaves had the ability to abate formaldehyde emission from boards; and 2) density of the WTLB was a significant factor affecting its modulus of rupture (MOR), modulus of elasticity (MOE) and internal bonding (IB).     

MUF共缩聚树脂的制备及其在防潮型刨花板上的应用

介绍了三聚氰胺改脲醛树脂的主要制备工艺并对该树脂在防潮型刨花板中的使用条件如热压参数、施胶量、板坯含水率等方面进行了探讨。试验表明，采用三聚氰胺改性脲醛树脂压制的刨花板物理力学性能达到或超过相关标准。     

大兴安岭云杉林天然更新调查研究

根据1900个样方和90株幼树解析木调查资料，对大兴安岭云杉林天然更新进行了评定、分析和研究，并对云杉林幼树生长进行了模拟和预测。     

Utilization of sweet sorghum bagasse and citric acid for manufacturing of particleboard II: influences of pressing temperature and time on particleboard properties

Development of environmentally friendly particleboard made from sweet sorghum bagasse and citric acid has recently attracted attention. In this study, we investigated the effects of pressing temperature and time on physical properties, such as dry bending (DB), internal bond strength (IB), and thickness swelling (TS) of particleboard. Wet bending (WB), screw-holding power (SH), biological durability, and formaldehyde emission of particleboard manufactured under effective pressing temperature and time were also evaluated. Particleboards bonded with phenol formaldehyde (PF) resin and polymeric 4,4′-methylenediphenyl isocyanate (pMDI) were manufactured as references. Effective pressing temperature and time were 200?°C and 10 min, respectively. It was clarified that DB, IB, and TS satisfied the type 18 requirements of the JIS A 5908 (2003), and were comparable to those of particleboard bonded with PF and pMDI. The WB and SH of particleboard did not satisfy type 18 of JIS. Particleboard manufactured under effective pressing conditions had good biological durability and low formaldehyde emission. Based on the results of infrared spectra measurement, the degree of ester linkages increased with increased pressing temperature and time.     

Comparison of the pressing behaviour of wood particleboard and strawboard

To improve the understanding of strawboard manufacturing processes, mat pressing behaviour of wood particleboard and strawboard bonded with urea formaldehyde resins were experimentally investigated and compared in terms of mat compressibility, transverse permeability, mat pressure, core temperature, core gas pressure and vertical density profile. The results have shown that straw particles are much more compressible and therefore require less platen pressure for pressing. Compared to wood particle and refined straw particle mats, hammer milled straw mats have low permeability and subsequently show high core gas pressure and high maximum core temperature during hot pressing, in addition to large differential densities between surface and core layers in the final pressed boards. It is recommended that a slower press closing rate and longer press opening time be used to develop the strawboard pressing schedule.     

Preparation and adsorption properties of macroporous tannin resins

1 Introduction Plant polyphenols are a large and diverse class of poly-atomic phenols which occur naturally in some parts of plants. Their molecular weight ranges from 500 to 3,000 g·mol–1. Plant polyphenols are abundant in nature and their production capacity is only second to that of cellulose, hemicellulose and lignin (Sun, 1988). Polyphenols can be divided into two kinds given their chemical constitution: hydrolysable tannin and condensed tannin (Song and Di, 2000). Benzene rings in th…     

Manufacture and properties of low-density binderless particleboard from kenaf core

Low-density binderless particleboards from kenaf core were successfully developed using steam injection pressing. The target board density ranged from 0.10 to 0.30g/cm³, the steam pressure used was 1.0MPa, and the steam treatment times were 7 and 10min. The mechanical properties, dimensional stability, and thermal and sound insulation performances of the boards were investigated. The results showed that the low-density kenaf binderless particleboards had good mechanical properties and dimensional stability relative to their low board densities. The board of 0.20g/cm³ density with a 10-min treatment time produced the following values: modulus of rupture 1.1MPa, modulus of elasticity 0.3GPa, internal bond strength 0.10MPa, thickness swelling in 24h water immersion 6.6%, and water absorption 355%. The thermal conductivity of the low-density kenaf binderless particleboards showed values similar to those of insulation material (i.e., rock wool), and the sound absorption coefficient was high. In addition, the boards are free from formaldehyde emission. Kenaf core appears to be a potential raw material for low-density binderless panels suitable for sound absorption and thermally resistant interior products.Part of this report was presented at the 52th Annual Meeting of the Japan Wood Research Society, Gifu, Japan, April 2002     

新物种——青檀绵叶蚜寄主及天敌种类调查

青檀绵叶蚜是危害青檀的蚜虫新种。该文报道了该虫的寄主和天敌,根据试验结果:青檀是该虫的唯一适合寄主;调查到4科6属8种捕食性天敌,以异色瓢虫Leis axyridis(Pallas)、中华草蛉Chrysoperla sinica Tjeder、大草蛉Chrysopa pallens(Rambur)、黑带食蚜蝇Epistrophe balteata DeGeer、中华狼蛛Lycosa sinensis Schenkel数量大,捕食量大。除1种寄生螨外,未发现其他寄生性天敌。     

陇县天然沙棘资源调查

1陇县概况 　　陕西省陇县位于渭北黄土高原西端,地处东径106°26′32″～107°8′11″,北纬34°35′17″～35°6′45″之间,东连千阳,南邻宝鸡,西、北与甘肃接壤.……     

Effects of air injection on properties of particleboard manufactured using a radio-frequency hot press

The effectiveness of air injection for preventing the blowout of particleboards manufactured using a radio-frequency hot press was investigated by evaluating the board properties under artificially created conditions that were conducive to blowout. For evaluation, 10-mm-thick boards with densities of 0.7 and 0.8 g/cm³ and 20-mm-thick boards with a density of 0.7 g/cm³ were manufactured. Pressing times for the 10-mm-thick boards were 2, 4, 6, and 8 min, and those for the 20-mm-thick boards were 4, 6, 8, and 10 min. Without air injection, blowout occurred in all manufactured boards. With air injection, however, blowout did not occur in the 10-mm-thick boards with a density of 0.7 g/cm³. Moreover, air injection prevented blowout even when the board density and board thickness were increased to 0.8 g/cm³ (for 10-mm-thick boards) and 20 mm (the density was kept at 0.7 g/cm³), respectively. Air-injection radio-frequency pressing reduced the pressing time from 4 to 2 min for 10-mm-thick boards, and from 6 to 4 min for 20-mm-thick boards. Moreover, this reduction in the pressing time was achieved without a large reduction in the internal bond strength of the boards.