固化工艺对玻璃纤维织物增强材料摩擦性能的影响

针对石棉摩擦材料的分解产物致癌且严重污染环境的问题,以力学性能优异的玻璃纤维织物为基体,以酚醛缩醛黏合剂为固化剂,制成新型无石棉复合摩擦材料。研究了固化温度和固化时间、玻璃纤维织物的纤维方向以及酚醛缩醛黏合剂对该材料摩擦性能的影响。结果表明：当固化温度为180°C,固化时间为1h 时,该复合材料表现出优异的摩擦磨损性能,摩擦因数为0.25,且磨损最小;复合摩擦材料中垂直于纤维方向的磨损量比平行于纤维方向的少;该玻璃纤维复合材料摩擦磨损性能符合使用要求,又因其成本较低、耐热性好、机械强度良好等优点,可被广泛应用于各个领域。     

Thermal properties of wood-gypsum boards

Transient simultaneous measurements of thermal conductivity, volume heat capacity and thermal diffusivity of laboratory wood-gypsum boards have been performed with ISOMET 2104 at room temperature. The influences of wood particle content, density and moisture content on thermal properties were investigated. The measurements were performed in a direction perpendicular to the board plane. The effect of density and wood particle content on the thermal properties may be related to the presence of voids both between and inside particles. It seems, that the dominant mechanism of heat transfer across the board is the heat conduction through the voids. Wood-gypsum boards with a density of 850–1300 kg/m³, a moisture content of 2–11% and a wood particle content of 0–35% have the following thermal conductivity of 0.189–0.753 W m^-1 K^-1, volume heat capacity of 0.683–1.43×10⁶ J m^-3 K^-1 and thermal diffusivity of 0.171–0.367×10^-6 m² s^-1; their magnitudes are higher than those ones of OSB, MDF, particleboard and plywood.     

Thermal properties of wood-gypsum boards

Transient simultaneous measurements of thermal conductivity, volume heat capacity and thermal diffusivity of laboratory wood-gypsum boards have been performed with ISOMET 2104 at room temperature. The influences of wood particle content, density and moisture content on thermal properties were investigated. The measurements were performed in a direction perpendicular to the board plane. The effect of density and wood particle content on the thermal properties may be related to the presence of voids both between and inside particles. It seems, that the dominant mechanism of heat transfer across the board is the heat conduction through the voids. Wood-gypsum boards with a density of 850–1300 kg/m³, a moisture content of 2–11% and a wood particle content of 0–35% have the following thermal conductivity of 0.189–0.753 W m^-1 K^-1, volume heat capacity of 0.683–1.43×10⁶ J m^-3 K^-1 and thermal diffusivity of 0.171–0.367×10^-6 m² s^-1; their magnitudes are higher than those ones of OSB, MDF, particleboard and plywood.     

Performance of cement bonded boards made from maple particles

Cement bonded particleboards were manufactured from maple (Acer platanoides L.) wood particles. The results revealed that the mixture of maple-cement can be classified as moderate inhibition, as determined by the hydration tests. Two wood:cement ratios were applied in this study, namely 1:3 and 1:4, for the board manufacture. An increase in the cement-wood ratio resulted in an increase in all, but MOR values. Boards were exposed to brown and white rot fungi, Coniophora puteana, Trametes versicolor, respectively. Overall, both fungi failed to attack the cement-bonded boards.     

Performance of cement bonded boards made from maple particles

Cement bonded particleboards were manufactured from maple (Acer platanoides L.) wood particles. The results revealed that the mixture of maple-cement can be classified as moderate inhibition, as determined by the hydration tests. Two wood:cement ratios were applied in this study, namely 1:3 and 1:4, for the board manufacture. An increase in the cement-wood ratio resulted in an increase in all, but MOR values. Boards were exposed to brown and white rot fungi, Coniophora puteana, Trametes versicolor, respectively. Overall, both fungi failed to attack the cement-bonded boards.     

聚苯酯填充聚四氟乙烯复合材料的导热及摩擦学性能研究

采用聚苯酯对PTFE进行改性,并对改性后复合材料的导热及摩擦学性能进行研究.结果表明：当m（聚苯酯）∶m（PTFE）=5∶100时,复合材料的热扩散系数可达2.646 mm2/s,导热性能有显著提高,材料的耐磨性能提高了20倍,有效改善了材料的摩擦学性能.     

Effect of the densification process on properties of commercial oriented strand boards

The objective of this work was to evaluate the effects of the densification on the physical and mechanical properties of OSB panels. A single-opening hot-press was used to perform the densification process. Four treatments were applied to densify the boards combining two temperatures (170 and 190 °C) and two pressures (25 and 50% of the compression strength perpendicular to the board plane). The properties of densified and undensified boards were assessed and the effect of temperature and pressure of the densification process was studied. It was found that undensified boards presented lower thickness swelling but higher water absorption and equilibrium moisture content than densified boards. Densified boards presented higher values of bending properties, parallel compression strength and hardness than undensified ones. The comparison within densified boards showed that in general the temperature was the most influential variable to modify the physical properties, while the mechanical properties were more affected by the pressure used. It can be concluded that the proposed densification process promoted remarkable changes on the OSB boards mainly regarding mechanical properties and water absorption. However, the thickness swelling remained as issue to be specially addressed in future works.     

On the tribological properties of extremely different wood materials

Three different woods (lignum vitae; black fiber palm; spruce) were investigated regarding their friction and wear properties under abrasion and sliding. For the abrasive wear against silicon carbide paper, the palm wood gave the lowest removal of material, especially under an orientation of the black fibers normal to the contact region (on R–T-plane in R-direction). At the same time, this material had the highest anisotropy. Slightly less abrasion resistant was lignum vitae, whereas spruce was most easily abraded. This can be considered as an indication that spruce can easily be machined. Under sliding conditions against smooth steel, a similar tendency, but at much lower wear rates compared to abrasion, was found. The relatively high coefficient of friction under dry sliding allows the use of these woods as friction materials, for example in brakes. Additional lubrication of the two best woods, lignum vitae and black fiber palm, by soaked sunflower oil brought the coefficient of friction to a much lower level, so that the use of these woods as bearing materials in various applications is promising.

     

Comparative properties of bagasse, canola and hemp particle boards

Residues of Bagasse (Saccharum officinarum L.), canola (Brassica napus L.) and hemp (Cannabis sativa L.) as well as industrial wood chips in various proportions from 0–100% were used as raw materials for the main component of the middle layer in urea formaldehyde bonded particle boards. The results reveal that most of the investigated mechanical-technological properties of the boards achieved the requirements of EN 312-2 (2003). Only increasing the percentage of canola chips usage in the middle layer to more than 30% negatively affect the internal bond (IB) properties. Comparing the water absorption (WA) and thickness swelling (TS) values, the boards containing up to 50% bagasse and hemp reach similar values to the ones of the reference boards, while increasing the amount of canola leads to more and more disadvantageous WA and TS. In summary, the results reveal that agri-fibers can be used for making composite panels conforming to the standards (EN 312-2 2003). One possible application for these panels could be the production of furniture.     

An experimental investigation on mechanical and tribological properties of Himalayan nettle fiber composite

The main focus of the present research work was to explore mechanical and tribological properties of Himalayan nettle fiber and unsaturated polyester resin (GP) using hand lay-up method. Four composite laminates were prepared by adding the Himalayan nettle fibers by weight percentage (5%–20%). The various properties (e.g., tensile strength, hardness, impact strength, and abrasion wear) were calculated for the composite laminates. It was found that the significant variation in properties was observed when fiber addition was in the range 15%. The change in the properties was negligible when fiber addition was increased from 15% by weight.     

酶法改性环氧大豆油的流变学与摩擦学性能研究

为扩大大豆油的应用范围,采用脂肪酶Novozym435催化大豆油环氧化改性合成环氧大豆油,对环氧大豆油进行了红外光谱和核磁共振氢谱表征,并考察其流变学和摩擦学性能。结果表明：成功合成了环氧大豆油;相较于大豆油,环氧大豆油的黏度指数增大,黏温性能更优异;相较于矿物润滑油和大豆油,环氧大豆油的平均摩擦系数及磨损体积减少率分别为21.6%、17.0%和71.2%、64.9%,减摩抗磨性能显著提升。环氧大豆油可在摩擦表面形成致密、厚实的物理化学吸附膜,从而有效减摩抗磨,提高润滑性。     

Characterization of properties of oriented strand boards from beech and poplar

The aim of this study was to evaluate the possibility of using European beech and poplar species to manufacture oriented strand boards (OSB). Beech and poplar strands with three different combinations of face/core ratios at densities of 650 and 720 kg/m³ were examined. Poly methylene diphenyl diisocyanate glue at 5 % was used with press conditions of 180 °C and 240 s. Findings showed that with increasing density the physical and mechanical properties of the different OSB combinations generally improved. Panels made of 60 % beech in face layers showed higher modulus of rupture and modulus of elasticity. Internal bond strength rose as the amount of beech strands in the core layer increased. Panels with 75 % beech strands in the core layer showed the maximum internal bond strength at 720 kg/m³. It was also observed that increasing the amount of beech in the core layer from 40 to 75 % decreased thickness swelling at both densities.     

Density related properties of bark insulation boards bonded with tannin hexamine resin

Building owners are increasingly interested in a healthy and sustainable living environment, which is a trend favoring ecological building materials with outstanding structural physical parameters. Insulation boards from particles of larch bark (Larix decidua Mill.) bonded with a formaldehyde-free tannin resin were pressed and evaluated for their mechanical and physical properties. It could be shown that light (target density 250 kg/m³) boards can be pressed, and their thermal conductivity is low (0.065–0.09 W/(m*K)). With regard to mechanical characteristics, the influence of panel density was studied, and it was found that a certain compaction (ρ ≥ 400 kg/m³) is necessary to meet the requirements of the relevant standard. Interestingly, the resin amount did not influence the mechanical board properties as strongly as expected, and panel density is the most important variable in this respect. The study proved that tree bark cannot only be used for substantially upgraded insulation panels but can also be bonded with a formaldehyde free tannin resin.     

Tensile strength properties of particle boards at different temperatures and moisture contents

The equilibrium tensile properties of urea-formaldehyde (UF)- and phenol-formaldehyde (PF)-bonded particle boards have been studied at moisture contents between 1 and 33% and at temperatures between ?15°C and +45°C. These conditions may occur e.g. during exterior use of the boards. The tensile strength and the modulus of elasticity decrease slightly while the strain at rupture increases slightly between 1% and 7% moisture content. These effects are similar for UF- and PF-bonded boards. Above 7% moisture content the tensile strength and the modulus of elasticity decrease markedly while the stretch at rupture increases with increasing moisture content. These changes are more pronounced for UF-bonded boards. The bending stiffness is less affected than the modulus of elasticity since the board thickness increases with increasing moisture content. The tensile properties are not significantly affected by the temperature at low moisture contents, but at high moisture contents the combined effects are more pronounced. The effect of moisture is generally stronger than that of temperature, in the range studied.     

Separating and recovering Pb from copper-rich particles of crushed waste printed circuit boards by evaporation and condensation

Waste printed circuit boards (WPCBs) are treated by crushing and electrostatic separation to obtain the copper-rich particles. However, the copper-rich particles contain a certain content of solder, which may cause Pb contamination if improperly treated. The separation behaviors of Pb from single solder and solder mixed with Cu particles under vacuum are studied in this work. Due to the presence of Cu particles in the copper-rich particles, it becomes much easier to separate Pb from mixed particles than from single solder. On the basis of the experiments, the rules and phenomena different from previous studies are concluded, including the multilayer evaporation effect, the formation of Cu-Sn intermetallic compound and so on. Mechanisms of these phenomena are also explored. Pb is separated and recovered from copper-rich particles of crushed WPCBs at 1123 K for 90 min under 0.1-1 Pa. The metals including Cu, Pb, Sn in WPCBs are all efficiently recovered. This work enriches separating rules for recovering Pb by evaporation and condensation, and also points out an efficient and promising method for recovering toxic heavy metals from WPCBs.     

油酸合成酸性磷酸酯胺盐及其摩擦性能研究

油酸经氨化、加氢合成油胺,进而与P2O5、异癸醇合成的酸性磷酸酯进行反应以合成酸性磷酸酯胺盐。对酸性磷酸酯胺盐的合成条件进行了优化,并对其结构和性能进行了表征和测试。结果表明,酸性磷酸酯胺盐的最佳合成条件为:n(P_2O_5)∶n(异癸醇)∶n(油胺)=1∶3∶0. 9,总反应时间12. 5 h。在最佳合成条件下,产物的pH在5. 5左右,收率可达92. 76%。通过红外、核磁和VPO相对分子质量表征,确定产物为目标产物。通过四球实验、抗腐蚀性测试及油溶性的考察表明,合成的酸性磷酸酯胺盐不仅有良好的油溶性、抗腐蚀性,且在极压抗磨性上有很大的提高,在加剂量2. 0%时效果最佳。     

聚电解质用量对模板微粒和微胶囊性能的影响

以掺杂不同浓度聚苯乙烯磺酸钠(PSS)的碳酸钙(CaCO3)微粒为模板,将聚丙烯胺盐酸盐(PAH)和PSS在模板表面进行层层组装,研究PSS掺杂量对模板微粒形貌尺寸及微胶囊负载性能的调控作用。通过扫描电镜与透射电镜观察其表观形貌和中空结构,利用热失重分析和紫外分光光度法对微胶囊的性质进行表征。结果表明,掺杂PSS的碳酸钙微粒为规则球体,较高的PSS浓度可获得粒径较小的CaCO3微粒,CaCO3微粒中含有PSS量为2.73%~5.12%,微胶囊内截留的PSS含量对其形貌和结构没有影响,冷冻干燥的微胶囊较热风干燥效果更好,所得的微胶囊对带正电荷的罗丹明B具有自沉积效应,最大负载效率可达75.42%。     

几种复合材料的简介

介绍几种主要复合材料的性能和使用情况,对我国的木材利用提供一些参考。     

关于刨花板质量问题的探讨

通过分析刨花板质量缺陷产生的原因,提出了解决刨花板质量缺陷的措施。