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.     

Characterization of urea–formaldehyde resin penetration into medium density fiberboard fibers

The amount of UF resin penetration into fibers, used for the production of medium density fiberboard (MDF), is unknown. To evaluate the relationship between resin viscosity and resin penetration depth, an experimental procedure involving confocal laser scanning microscopy (CLSM) and a Toluidine Blue O staining system was performed. The results indicate that CLSM in combination with a Toluidine Blue O staining system is a good way to characterize UF resin penetration into wood fibers. The main penetration direction is toward the fiber lumen. For wet fibers, whose moisture content is about 88%, the effect of resin viscosity with a range of 80 cps – 340 cps on penetration is very similar, with all adhesives reaching or almost reaching the fiber lumen after 60 min at room temperature. For MDF industrial samples, the highest depth of penetration of the adhesive was attained in the second dryer stage. After the second dryer stage, the resin penetration into the fiber did not increase.     

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.     

Sesbania aegyptiaca as promising biomass for manufacturing of MDF

Sesbania fiber is a fast-growing wood species that has been investigated for medium-density fiberboard (MDF) production. To assess the possibility of applying the local industrial defibration parameters of sugar-cane bagasse (SCB) on defibration of sesbania, the chemical constituents of unfibrated and defibrated sesbania, as well as their thermal stability and scanning electron micrographs, were estimated. Different preparation variables of MDF, such as density, level of urea-formaldehyde (UF) resin (with 0.19% free-formaldehyde [HCHO]), and pressing time were studied, in comparison with that produced by using SCB fibers. The results showed that most of the tested sesbania-based MDFs have mechanical properties that fulfill the minimum requirements of MDF ANSI standard. Additionally, applying 12% UF and pressing for 240 sec provided sesbania-based MDF with optimum reduction in thickness swelling (reached ～7%). It is important to note that the sesbania-based MDF produced under these conditions is characterized by a lower TS property, than that obtained from SCB, or that reported in standards. The preliminary feasibility study revealed that using sesbania fibers will be an added economical potential for MDF production.     

LLM型UF树脂制造橡胶木和赤桉中密度纤维板

通过使用ＬＬＭ型ＵＦ树脂制造橡胶木和赤桉中密度纤维板的研究,评价用该树脂制造橡胶木和赤桉中密度纤维板的适应性。橡胶木和赤桉各５０％比例温和后施以ＬＬＭ型ＵＦ树脂,按照ＭＤＦ常规工艺压制９,１２,１６ｍｍ的试验板。结果表明：板材物理力学性能及甲醛释放量指标均达到ＧＢ１１７１８．２－８９标准规定的要求。     

Medium-density fiberboard performance as affected by wood fiber acidity, bulk density, and size distribution

The properties of medium-density fiberboard (MDF) panels as affected by wood fiber characteristics were investigated. Wood chips from three softwood and one hardwood species were refined under the same refining conditions to make four different types of fibers. The resulting fibers were characterized by fiber size distribution, bulk density, pH value, and buffering capacity. Using the same resin system and hot-pressing parameters, MDF panels were produced and evaluated for internal bonding (IB), modulus of rupture (MOR), modulus of elasticity (MOE), thickness swelling, and linear expansion. The pH values and alkaline buffering capacities of raw materials were reduced considerably after refining. IB was strongly related to the pH value of fibers. The mechanical properties increased with alkaline buffering capacity. IB, MOR, and MOE increased with the bulk density of fibers. Increased proportions of coarse fibers had negative effects on the panel mechanical properties.     

稻草原料酸碱性及稻草中密度纤维板的性能

测试分析了稻草原料的ｐＨ值和缓冲容量，分别使用脲醛树脂胶和异氰酸酯胶在特定工艺条件下压制了稻草中密度纤维板，并测试了板材性能。结果表明：１）稻草秸秆原料呈弱碱性，缓冲容量远高于普通木材；经热磨处理获得的稻草纤维呈弱酸性，其缓冲容量虽较稻草秸秆有一定幅度的下降，但仍高于普通木材；２）脲醛树脂或异氰酸酯稻草中密度纤维板的性能都明显优于相应的碎料板；在密度０．８０ｇ／ｃｍ３和施胶量１７％的条件下，脲醛树脂稻草中密度纤维板性能达到国标ＧＢ／Ｔ１７６５７－１９９９一等品的要求，在密度０．８０ｇ／ｃｍ３和施胶量６％的条件下，异氰酸酯稻草中密度纤维板性能达到国标ＧＭ／Ｔ１７６５７－１９９９优等品要求。     

Quantification of urea formaldehyde resin in wood fibers using X-ray photoelectron spectroscopy and confocal laser scanning microscopy

The potential merits of X-ray photoelectron spectroscopy (XPS) technique for the quantification of nitrogen on the wood fiber surface before and after resination with UF resin was investigated and the resin content was calculated. The bulk nitrogen content of the fibers obtained by XPS after grinding was compared with those obtained by combustion and Kjeldahl methods. Four different fluorescence staining agents were tested by UV spectroscopy. Their λ_max shifted to longer wavelengths when reacted with UF resin. Appropriate analysis conditions were tested for a satisfactory analysis of wood fibers by the confocal laser scanning microscopy (CLSM). The result obtained by CLSM was compared with that obtained by XPS.     

Measurement of urea-formaldehyde resin distribution as a function of MDF fiber size by laser scanning microscopy

A technique has been developed to show the extent of the distribution of the adhesive on the fiber surface. This involves treatment of the resinated fibers with the dye Toluidine blue O, to quench the autofluorescence of the wood materials, to show only the fluorescence of the UF resin in the presence of the dye. The results indicate that this method is a simple and practical way to understand UF resin coverage on wood fibers. With image analysis, the adhesive has been shown to cover a small percentage (3.5%) of the fiber surface, although the percent by weight (based on wood fiber) of resin is much more (13%). The fiber size strongly affects the resin coverage ratio and the chance to collect resin droplets, but it is not significant in the resin-droplets size distribution. Decreasing the proportion of shorter fibers is beneficial in improving resin coverage uniformity. A model for calculating the resin-coverage ratio was developed. The resin coverage is about 4.8% for the resin content of 13% by the model.     

Effect of thermo-mechanical refining on properties of MDF made from black spruce bark

The effects of thermo-mechanical refining conditions on the properties of medium density fiberboard (MDF) made from black spruce (Picea mariana) bark were evaluated. The bark chips were refined in the MDF pilot plant of Forintek Canada Corporation under nine different refining conditions in which preheating retention time was adjusted from 3 to 5 to 7 min and steam pressure was set at either 0.6, 0.9 or 1.2 MPa. The resulting bark fibers were blended with 12% UF resin (based on oven-dry fiber weight) using a mechanical blender. The resinated fibers were manually formed into fiber mats and hot-pressed into MDF panels using consistent parameters. Two panels for each refining condition were produced, resulting in a total of 18 panels. Analysis of variance (ANOVA) was used to analyze the significance of factors. Regression coefficients and 3D contour plots were used to quantify the relationship between panel properties and the two test factors. The results from this study indicated that the preheating retention time was a significant factor for both modulus of rupture (MOR) and modulus of elasticity (MOE), the steam pressure was a significant factor for internal bond strength (IB), MOR and MOE, whereas both factors were insignificant for thickness swelling, water absorption and linear expansion. The properties of MDF panels were quadratic functions of retention time and steam pressure. Compared to the ANSI standard for 120-grade MDF, most panels with a nominal density of 950 kg/m³ had very high IB (>1 MPa) and acceptable MOR, MOE and dimension stabilities. These results suggest that black spruce bark residues can be considered as a potentially suitable raw material for manufacturing MDF products.     

15mm厚中密度纤维板不同装饰后耐老化性能研究

研究了加速老化试验对经不同装饰后的脲醛胶中纤板物理力学性能的影响.结果表明,未经装饰的中纤板经加速老化处理后力学强度降低较快,吸水厚度膨胀率明显增大.选用的4种装饰中纤板中,三聚氰胺板的力学性能降低最大,油漆板耐久性能最好.     

热磨条件对麦秸中密度纤维板性能的影响

在不同的热磨条件下(蒸汽压力为0.4、0.6、0.8、1.0MPa,磨盘转数为2 500r/min和3 000r/min),将麦秸原料分离成纤维,并试制了相应的麦秸中密度纤维板,对比分析了不同的热磨条件对麦秸中密度纤维板的内结合强度、弯曲性能、吸水性能、表面硬度和边部握螺钉力的影响。结果表明,不同的热磨条件下分离得到的麦秸纤维形态存在差异,纤维的强度和形态对麦秸中密度纤维板的物理力学性能影响较大。当蒸汽压力为0.8MPa,磨盘转数为3 000r/min,麦秸中密度纤维板的各项性能得刮改善。     

Effect of wood species,digester conditions,and defibrator disc distance on wettability of fiberboard

Wettability of medium density fiberboard (MDF) surface affects paint or adhesive application and is, thus, of importance in the course of furniture manufacturing. This study investigated the effects of wood species, digester conditions and defibrator disc distance on the wettability properties. It was found that the wettability of the MDF significantly decreased with increasing the defibrator disc distance and increased with the increment in the severity of the digestion conditions. The highest wettability was found for samples made of beech wood having an average contact angle value of 74.5°, followed by poplar wood (76.5°), birch wood (79.7°), the mixture (1:1) of scots pine and beech wood (82.9°), and scots pine wood (86.4°), respectively.     

Effects of surface laminate type and recycled fiber content on properties of three-layer medium density fiberboard

ABSTRACT

High global production of medium-density fiberboard (MDF) in recent years could generate an equal quantity of waste MDF at the end of its service life, requiring recycling of waste MDF instead of landfilling or incineration. This study investigated effects of the addition of recycled fiber (RF) obtained from surface laminated MDFs with three different materials to the properties of three-layer recycled MDF (rMDF). Three types of surface laminates such as low-pressure laminate, polyethylene terephthalate, and polyester coating were hammer milled, and then went through a patent-pending fiber recovery system to obtain the resultant RFs that were added to the core layer of rMDF. These RFs at three contents (10, 20, and 30%) were blended with 12% of urea-formaldehyde (UF) resin prior to hot-pressing. Statistical analysis showed that the best internal bonding strength, modulus of rupture, and modulus of elasticity of rMDF panels were obtained for LPL-rMDF with a 20% RF content. Thickness swelling, water absorption, and formaldehyde emission of rMDF were reduced by increasing the RF content. These findings suggest that a minimum RF content of 20% can be replaced with virgin fibers for the rMDF manufacture, indicating the feasibility of recycling waste laminated MDF into three-layer rMDF.     

Comparison of protein-based adhesive resins for wood composites

The search for new value-added uses for oilseed and animal proteins led us to develop protein-based wood adhesives. Low-fat soy and peanut flours and blood meal were hydrolyzed in an alkaline state, and PF-cross-linked protein resins were formulated by reacting the protein hydrolyzates with phenol-formaldehyde (PF) in solid-tosolid ratios ranging from 70% to 50% hydrolyzates and 30% to 50% PF. Physical properties of medium density fiberboard (MDF) bonded with protein-based phenolic resins were compared to those of boards bonded with ureaformaldehyde (UF) and PF resins, and flakeboard bonded with soy protein-based phenolic resin was compared to PF-bonded board. As MDF binders, adhesive properties of protein-based phenolic resins depended upon protein content of proteinacious materials. MDF board bonded with blood-based phenolic resin was comparable to PF-bonded board and met the requirements for exterior MDF. Boards bonded with soy-protein-based phenolic resin met requirements for interior MDF, while peanut-based phenolic failed to meet some of the requirements. Flakeboard bonded with soy-protein-based phenolic resins was inferior to PF-bonded board but outperformed PF-bonded board in accelerated aging tests. Although they exhibit a slow curing rate, the cost effectiveness and superior dimensional stability of protein-based phenolic resins may make them attractive for some uses.     

Development of high-performance UF-bonded reed and wheat straw medium-density fiberboard

Urea formaldehyde resin-bonded reed and wheat straw fiberboards were produced from the fibers made under different steam cooking conditions in refining processes at densities of 500 and 700kg/m³. The effect of steam cooking conditions on the board properties was examined. The steam pressure and cooking time for reed and wheat straws were 0.4MPa/10min and 0.4MPa/5min, respectively, and 0.6MPa/3min and 0.6MPa/10min for both straws. The effect of steam cooking treatment before the fiber refining process on the wettability and weight losses of the straws was also investigated. The results indicated that the mechanical properties and linear expansion of the straw medium-density fiberboard (MDF) were improved with increasing steam cooking pressure and time during the refining process, whereas the thickness swelling (TS) did not vary much. The wettability of the straws was improved by cooking treatment. The steam cooking conditions had little effect on the wettability of the straw surfaces. For reed and wheat straws, the weight losses increased with increasing steam pressure and cooking time. In addition, it was found that the properties of MDF were significantly higher than those of particleboard, especially the internal bond (IB), where the IB values of MDF were more than 10 times higher than those of particleboard. All the properties of the straw MDF, except the TS of wheat board, can meet the requirement of JIS fiberboard standard. The high performances of MDF could be due to the improved wettability and the removal of extractives during the refining process.     

防潮型中密度纤维板的研制

研究了以脲醛胶为主，三聚氰胺胶为辅制造防潮型中密度纤维板的工艺条件，讨论了热压时间、热压压力、热压温度、施胶量、配胶比例对中密度纤维板物理力学性能的影响。结果表明：配胶比例是重要的影响因子。采用试验所得的优选工艺制得的产品各项指标均达到或优于防潮型中密度纤维板国家标准。     

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。     

生物酶预处理对秸秆中密度纤维板性能的影响

针对稻草和麦秸原料的特点,分别用木聚糖酶、漆酶／碳源系统(LCS)和脂肪酶对原料进行生物酶预处理用机械磨浆方法制备纤维,以木质纤维板用脲醛树脂作胶黏剂,压制秸秆中密度板,并探讨酶处理对秸秆纤维板性能的影响。结果表明:各种生物酶预处理对稻草和麦秸纤维板的性能都有一定的改善,同软化处理相比,经三种生物酶处理后的长纤维的比例明显增加,而细小纤维的含量则明显降低,IB均有不同程度的改进,其中木聚糖酶对此两项指标的改进效果更好。经木聚糖酶预处理后压制的密度达到0．8 g／cm3以上的纤维板的性能如下:麦草纤维板的IB为0．75 MPa,MOE为3 960 MPa,MOR为37．60 MPa,TS为21．29％。除TS外,均优于GB／T11718-1999标准要求。而稻草纤维板的IB为0．73 MPa,MOE为2 618 MPa,MOR为21．35 MPa,TS为21．19％,其中MOR与TS均离标准要求还有一定的差距。     

MF—97三聚氰胺—甲醛树脂对中密度纤维板（MDF）耐湿性能影响初探

本文着重介绍了用ＭＦ－９７三聚氰胺－甲醛树脂制备准耐水级ＭＤＦ的结果。