Properties of wheat straw particleboards bonded with different types of resin

Wheat straw particleboard bonded with a urea–formaldehyde (UF) resin, usually employed in the manufacture of wood-based particleboards, or with a resin based on epoxidised oil was manufactured using a compression molding machine. The effects of resin type on internal bond strength, flexural modulus, and thickness swelling were examined. The properties of boards using UF resins were poor. Internal bond strength and thickness swelling, linked to adhesion quality, were especially low. The high compatibility between straw particles and oil-based resin was explained in terms of straw surface free energy. In straw, this parameter exhibits a much lower polar component than wood species and leads to higher compatibility with resins based on oil than with water-soluble systems like UF.     

Waste paper–wood composites bonded with isocyanate

Waste paper could potentially be used as raw material for fiber- or particle-based composites without resorting, deinking and decontamination required for paper manufacturing. The objective of this study was the evaluation of one-layer boards made of various ratios (0:100,15:85, 25:75, 50:50, 75:25 and 100:0) of waste paper flakes to wood particles mixtures (wt:wt). Three types of waste paper (newspaper, office paper and magazine paper) in pure form or mixed all together were used for board manufacture. PMDI resin at three different levels of 5, 8 and 10% without or with the addition of various amounts of wax (0.7, 1.0, 1.5 and 2.0%) were applied. The participation of waste paper flakes in boards made their appearance more attractive than ordinary particleboards and fiberboards made of wood. In contrast to internal bond, screw-holding strength and thickness swelling, properties that deteriorated substantially as the waste paper percentage increased, the bending strength was only slightly affected. By increasing the resin content all properties of boards and particularly internal bond and thickness swelling were improved. The addition of wax reduced considerably the thickness swelling of boards containing waste paper; however, even at a 2.0% level, it remained greater than the maximum permitted value specified by the relevant standard. Among the three types of waste paper tested, newspaper proved to be the most appropriate for board manufacture, and magazine paper the least appropriate. With the exception of screw-holding strength, the substitution of wood particles by mixed waste paper flakes in amounts up to 50% resulted in acceptable mechanical properties for specific applications in interior uses.     

硅烷偶联剂对稻草板力学性能的影响

以稻草为原料生产人造板,成为高效利用稻草资源、缓解木材供需矛盾的一条有效途径。本文通过硅炕偶联剂（SCA）改善稻草表面润湿性,用脲醛树脂胶黏剂（UF）胶结制戍稻草板,分析SCA用量和UF用量对稻草板力学性能的影响。结果表明：施胶量为16％、SCA添加量为1％时,板子的静曲强度和内结合强度达到GB／T4897．4—2003中A类刨花板优等品的要求。     

Effect of nanoclay on some applied properties of oriented strand board (OSB) made from underutilized low quality paulownia (Paulownia fortunei) wood

In this study, the effect of nanoclay on some applied properties of oriented strand board (OSB) made from underutilized low quality paulownia wood was investigated. Organo-modified montmorillonite (MMT) at four levels (0, 1, 3 and 5?%) was added to urea formaldehyde (UF) resin. Some chemical properties of paulownia wood (holocellulose, cellulose, lignin and ash contents, pH value and hot and cold water solubility), mechanical [modulus of rupture (MOR), modulus of elasticity (MOE), internal bond strength, screw and nail withdrawal strengths], physical (water absorption and thickness swelling) properties and formaldehyde emission of the strand boards were evaluated. Mechanical properties of all panels complied with the general-purpose OSB minimum property requirements of European Norm. With increasing 5?% nanoclay to UF resin, mechanical and physical properties of the resulting panels improved and formaldehyde emission decreased. However, none of the panels satisfied the thickness swelling and water absorption requirement. The results of X-ray diffraction and transmission electron microscope analysis confirmed the good dispersion of nanoclay in the resulting OSBs. Using paulownia as a fast-growing underutilized species not only can sustain the forests but also can supply raw material to countries facing shortage of wood.     

Utilization of pine (Pinus pinea L.) cone in manufacture of wood based composite

Physical and mechanical properties of medium density fiberboards (MDF) made from various mixtures of wood fibers and stone pine (Pinus pinea L.) cones were evaluated using European standards. MDF panels were manufactured using standardized procedures that simulated industrial production at the laboratory. Six panel types were made from mixtures of wood fiber/cone flour, 100/0, 90/10, 80/20, 70/30, 60/40, and 50/50 percents, respectively. Addition of the cone flour into the MDF significantly reduced formaldehyde emission from the panel. In addition, the addition of 10% cone flour also improved water resistance of the MDF panels made using urea–formaldehyde (UF) resin. However, further addition of the cone flour into the panel negatively influenced their water resistance. Flexural properties and internal bond strength decreased with the increase of cone flour content in the panel. The UF resin is the main source of formaldehyde emission from the UF-bonded wood-based panels. Depending on addition of the cone flour in the panels, the formaldehyde emission values ranged from 2.6% to 55.3% lower than the panels made from 100% wood fiber. Based on the findings obtained from this study, pine cone can be used as a renewable biological formaldehyde catcher as an alternative to the traditional formaldehyde catchers for E1 Class MDF manufacture.     

改性胶粘剂对稻壳-木材复合材料性能影响的研究

稻壳的外表面覆盖有二氧化硅膜,使用传统的脲醛树脂(UF)和酚醛树脂胶(PF)生产的100％的稻壳板难以达到木质刨花板的质量指标。本研究采用以异氰酸酯(ISO)改性的脲醛树脂和酚醛树脂胶制造稻壳-木材复合材料。稻壳与木片的混合比例为1:1,施胶量为7％,设计密度0.8g/cm3。试验结果表明,3:4的ISO/UF、2:5的ISO/PF、改性胶粘剂制备的板材的物理力学性能达到国标刨花板二等品的要求;用3:4的ISO/PF改性胶粘剂制备的板材达到优等品的要求。     

改性脲醛树脂胶低密度稻壳-木材复合材料制造工艺的研究

采用异氰酸酯(ISO)改性的脲醛树脂胶制造低密度稻壳-木材复合材料。稻壳与木质刨花的混合比例为1:1,施胶量为7%,试验结果表明,异氰酸酯改性的脲醛树脂胶黏剂适用于低密度稻壳-木材复合材料,其物理力学性能明显优于使用传统的脲醛树脂胶黏剂。低密度稻壳-木材复合材料的物理力学性能随着改性剂异氰酸酯用量的增加而提高。密度是稻壳-木材复合材料物理力学性能的重要影响因素,低密度稻壳-木材复合材料的物理力学性能随着密度的增加而提高。在设定密度为0.45g/m~3和0.5g/cm~3的条件下,3:4的ISO/UF的稻壳-木材复合材料的物理力学性能均达到日本刨花板工业标准(JIS A5908)的要求。     

The influence of silane coupling agent and poplar particles on the wet-tability,surface roughness,and hardness of UF-bonded wheat straw （Triticum aestivum L.）/poplar wood particleboard

We used silane coupling agents to improve the bonding ability between wheat straw particles and UF resin, and investigated surface properties （wettability and surface roughness） and hardness of parti-cleboard made from UF-bonded wheat straw （Triticum aestivum L.） combined with poplar wood as affected by silane coupling agent content and straw/poplar wood particle ratios. We manufactured one-layered particleboard panels at four different ratios of straw to poplar wood par-ticles （0%, 15%, 30% and 45% wheat straw） and silane coupling agent content at three levels of 0, 5% and 10%. Roughness measurements, average roughness （Ra）, mean peak-to-valley height （Rz）, and root mean square roughness （Rq） were measured on unsanded samples by using a fine stylus tracing technique. We obtained contact angle measurements by using a goniometer connected to a digital camera and computer sys-tem. Boards containing greater amounts of poplar particles had superior hardness compared to control samples and had lower wettability. Panels made with higher amounts of silane had lower Rq values.     

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.     

稻草中密度纤维板用改性脲醛树脂的研究

对比三聚氰胺、二甲基硅油、硅树脂和偶联剂KH-550四种改性剂改性的脲醛(UF)树脂性能的差别及其对稻草中密度纤维板性能的影响,并进行经济评价,最终确定适用于稻草纤维板的改性UF树脂的工艺条件,同时借助于红外光谱(FT-IR)和差热扫描分析(DSC)研究最佳改性UF树脂的结构和固化特性.结果表明,三聚氰胺改性脲醛(MUF)树脂不论是对树脂性能、板性能改善还是从成本分析方面均为稻草纤维板最佳的胶黏剂,FT-IR显示出与未加三聚氰胺相比,加入三聚氰胺后树脂的羟甲基含量降低了10 %,DSC分析则表明其峰值温度有较大幅度的提高,但放出的热量较少.加入三聚氰胺改性的UF树脂其表面张力变小.     

一种脲醛树脂胶粘剂的设计

鉴于对文献的分析和实验验证,本文提出一种脲醛树脂胶粘剂的设计原则。即:1)脲醛树脂最终摩尔比应取1.40～1.20:1,这样可以使制成的板材具有足够的胶接强度;2)为了使人造板的甲醛释放量达到10mg/100g(穿孔法)以下,树脂中的游离尿素应在10%以上;3)在脲醛树脂的分子中引入尿素的环状衍生物,如三嗪环或Uron。环状化合物含量最好在10%左右。按此原则合成了三种树脂,在试验室按标准刨花板和中密度纤维板工艺制成板材,其甲醛释放量在10mg/100g左右,板材物理力学性能均超过国家标准和企业标准。     

稻草刨花板制造工艺的初步研究

探讨了以腺醛(UF)胶和以异氰酸酯(PMDI)改性的UF胶制造稻草刨花板的可行性。结果表明,用UF胶很难制造出较高强度的刨花板,以PMDI改性可明显提高UF胶对稻草的胶着力。通过对改性胶的施胶方式、固化利用量与板判性能关系的研究,以及对制板主要工艺参数的正交试俭,提出了制造稻草刨花阪的工艺条件。     

Chemical modification and wetting of medium density fibreboard panels produced from fibres treated with maleated polypropylene wax

Medium density fibreboard (MDF) was produced from fibres treated with maleated polypropylene wax. The objectives of this study were to investigate the effect of fibre treatment with maleated polypropylene wax on the advancing and receding contact angle and wicking of MDF panels by the Wilhelmy plate method; to verify the chemical reactions occurring between fibres and maleated polypropylene wax by infrared spectroscopy, and to verify if there are relationships with the water absorption of panels. Three maleated polypropylene wax contents (0, 3, 5%) and two resin types (urea–formaldehyde, UF and melamine–urea–formaldehyde, MUF) were considered in this study. Our results showed that the treatment increased the advancing contact angle of panels bonded with UF resin. The receding contact angles of MDF panels produced from treated fibres with 5% maleated polypropylene wax content were also increased by the treatment. Also, the wicking was reduced by the treatment independent of the maleated polypropylene wax content. Reductions of the wicking were 59% for panels bonded with UF resin and 73% for panels bonded with MUF. Relationships between the wicking and water absorption were observed. Chemical analysis realized by infrared spectroscopy did not detect the presence of an esterification reaction between wood fibres and anhydride groups of the maleated polypropylene wax. This suggests, therefore, that an esterification reaction did not take place or that chemical modifications were so small that they are not visible by infrared spectroscopy.     

游离甲醛和人造板释放甲醛

甲醛是室内空气污染源，它常与甲醛系统粘接连在一起，本文根据国内外资料评述人造板甲醛释放量，分析了脲醛树脂的水解和人造板释放甲醛的机理，还介绍了甲醛的毒害，各国政府的有关法规以各种降低甲醛释放量的方法。     

Upgrading of urea formaldehyde-bonded reed and wheat straw particleboards using silane coupling agents

Reed and wheat straw particleboards bonded with urea formaldehyde (UF) resin were manufactured from two different material configurations (i.e., fine and coarse particles). The board densities were in the range of 0.550–.90g/cm³. The effects of particle size and board density on the board properties were examined. The properties of particleboard produced from fine particles were better than those made from coarse particles. An increase in board density resulted in a corresponding improvement in the board properties. The properties of OF bonded reed and wheat straw particleboards were relatively lower than those of commercial particleboards. Three silane coupling agents were used to improve the bondability between the reed and wheat particles and OF resin. Results of this study indicate that all the board properties were improved by the addition of silane coupling agent. The degree of improvement achieved from each coupling agent was different; epoxide silane was found to be more effective for reed straw particleboard, and amino silane was better for wheat straw particleboard.     

Particleboard made from hammer milled black spruce bark residues

Summary  The disposal of bark residues is an important problem for the forest industry. An important proportion of the bark produced by the paper and lumber industries is used for energy production, but a significant amount of bark is still unused. The objective of this study was to determine the technical feasibility of making particleboards from black spruce bark residues bonded with urea formaldehyde resin and meeting the indoor performance requirements for wood particleboards. In the positive case, this would define a new use for black spruce bark residues. Fresh black spruce bark residues were obtained from a sawmill located in the northeast part of the province of Quebec, Canada. The bark was kiln-dried at 60 °C, the particles were generated from a hammermill and sieved. Particles from 0.02 to 2.0 mm were used in the surface layers and particles from 2.0 to 6.0 mm were used in the core layer. Particleboards of 540 × 560 × 16 mm were made with a laboratory hot press following a factorial design with two manufacturing variables at three levels: (1) wood particles content of the surface layers (0, 25, 50 percent); and (2) UF resin content of the surface layers (12, 14 and 16 percent) with a UF resin content in the core of 8 percent. This resulted in a factorial design of 9 different combinations repeated 3 times for a total of 27 boards. It was observed that the heating kinetics varied according to the wood particles content in the surface layers. The compression ratio of the mat and the board internal bond, modulus of elasticity, modulus of rupture, linear expansion and thickness swell were determined. The results show that it is technically possible to make particleboard from bark residues meeting the American National Standard Institute indoor requirement for wood particleboard under certain conditions. The modulus of rupture of the boards was the most critical property in this study. The best mechanical properties were obtained with a 50 percent wood content and 14 percent resin content in the surface layers. The particleboards produced in this study did not meet the minimal requirements for linear expansion. The temperature measurements performed in the core of the mat during hot pressing show that heat transfer improves with an increase in wood particles content in the surface layers. Received 15 June 1998     

浅析木材酸性及其对MDF生产的影响

本文对福州人造板厂生产用木片的ｐＨ值、缓冲性能及其对ＵＦ胶固化时间的影响进行了研究，结果表明：木片的ｐＨ值与缓冲性能是影响ＵＦ胶固化的重要因素，煮沸回流后的木片ｐＨ值与ＵＦ胶的固化时间相关性最大；在ｐＨ值相近的情况下，木粉与胶的混合物固化时间随木材缓冲性能的增加而缩短；树皮对胶固化的阻碍大大超过相同ｐＨ值的木材；作为主要原料的马尾松，其地域不同、ｐＨ值不同而呈现出对ＵＦ胶固化的影响也不同。     

刨花板用环保胶黏剂的制备与性能研究

将工业化生产的生物油与聚合4,4’-二苯基甲烷-二异氰酸酯(PMDI)按不同比例混合,并加入一定量的稀释剂形成稳定的PMDI/生物油胶合体系,以此体系作为胶黏剂压制单层结构刨花板,探讨胶黏剂施加量、PMDI/生物油混合比、稀释剂加入量等对刨花板内结合强度、静曲强度、弹性模量、吸水厚度膨胀率、吸水率等物理力学性能的影响。结果表明:加入稀释剂有效地降低了PMDI/生物油体系的黏度,提高了体系在施胶过程中的雾化效果;PMDI/生物油混合比为25∶75的胶黏剂压制的刨花板具有与纯异氰酸酯胶黏剂压制刨花板相似的性能。     

Physical and mechanical properties of particleboard from roselle (Hibiscus sabdariffa) stalks and eucalyptus (Eucalyptus camaldulensis) wood particles

Abstract

The objective of this work was to evaluate the performance of particleboard manufactured from roselle (Hibiscus sabdariffa) stalks and eucalyptus (Eucalyptus camaldulensis) wood. The manufacturing parameters were various roselle (Hibiscus sabdariffa) ratios in the mixture (0, 25, 50, 75 and 100%) and press time (3, 5 and 7 min). Modulus of elasticity (MOE), modulus of rupture (MOR), internal bonding (IB) strength values and thickness swelling (TS) after 24-hour water soaking of the panels were determined according to the procedure of European Union (EN) Standard. The results of the study demonstrate that roselle stalks can be an alternative raw material source for particleboard industry. With an increase of roselle particles from 0% to 100%, the TS was reduced, and the IB, MOR and MOE were increased. The highest MOE, MOR, IB strength and TS values of the samples were found as 2754.18, 16.81, 0.89 N/mm² and 15.26% for the panels made using 100% roselle with a 7-min press time, respectively.     

国际人造板工业研究和开发的进展及趋势(续篇)

本文对国际人造板工业的原料、环境保护问题的研究和开发,以及新技术的应用作了简要回顾,并对其社会背景及前提条件作了分析。其中特别是对于原料的开拓,提出了我国应如何吸取发达国家的经验的看法。