细木工板中甲醛释放特征及规律

采用环境测试舱模拟室内环境,测量细木工板中甲醛的释放浓度,考察细木工板结构、温度、相对湿度和空气交换率对甲醛释放的影响,分析细木工板中甲醛气体扩散机理,并建立了灰色预测模型对细木工板中甲醛释放峰值后的过程进行模拟. 结果表明,细木工板中甲醛散发通道主要为端面,端面的甲醛释放量是平面的3倍;细木工板中甲醛气体扩散过程分为3个阶段(初始快速释放、稳定释放和长期缓速释放);空气交换率对细木工板中甲醛释放率影响不大;相对湿度和温度升高,细木工板中甲醛释放率也增大;预测模型的预测数据与实验数据吻合较好,平均相对误差率仅为3.717%,适合进行长期预测.     

永磁场对气体中分子传质过程的影响

在不同磁感应强度的磁场中,研究了磁场对气体中分子传质过程的影响。研究结果表明,磁场对水、甲醇、乙醇、甲酸及乙酸在空气中的分子传质过程具有正效应,即在磁场中的扩散系数增大。定量计算表明,其扩散系数提高4%～7%。磁场对苯、甲苯、丙酮及甲基乙基酮在空气中的分子传质过程基本无影响。对磁场影响气体中分子传质过程的机理进行了探讨。     

有机分散相强化气体吸收的研究

分析了有机分散相强化气体吸收机理,阐述了分散相强化气液传质的意义.以水吸收二氧化碳为研究体系,实验考察了加入辛醇、辛烷对吸收过程影响,运用因次分析法分析有机分散相分散程度对吸收效果的影响,进而确定强化气体吸收的最小搅拌速度,并用插值函数微商法确定体积传质系数KLa.研究结果表明:有机分散相的加入能够显著提高气体吸收速率;适宜的搅拌速度有利于液液体系分散,促进传质;降低界面张力和增加气含率也有利于传质.     

第二液相对气液二相体系传质的影响

以CO2气体-K2CO3/KHCO3水溶液吸收过程为研究体系,用酸解法测量气体被吸收的速率,通过对比试验考察了加入第2液相(有机相)对体系传质速率的影响。经过试验研究证明,第2液相的加入对气液传质过程的影响程度与加入的物质有关,在试验条件下甲苯对体系强化作用高于异辛醇和庚烷对体系的强化作用。当第2液相加入量较小时,随加入量的增加,其对气液传质过程的促进作用增强,但当第2液相加入量较大时,这种作用则不明显。同时第2液相对传质作用的影响与流动场有关,增加流动场的搅动有助于强化气液传质作用。     

三聚氰胺泡沫中甲醛不同检测方法的比较分析

分别采取9-11L干燥器法、水吸收法及水萃取法对蜜胺泡绵中游离甲醛含量进行检测,通过对不同方法的检测结果进行比较分析,探讨各种测试方法的优缺点,旨在为完善我国蜜胺泡绵产品甲醛释放量的检测方法提供一些参考意见。     

金属网波填料用于吸收和脱吸时的特性

在φ86和φ100内径有机玻璃塔内,分别研究了不同结构尺寸的金属网波填料用于CO_2-空气-去离子水系统,在常温、常压下的吸收和脱吸时的流体力学和传质特性;提出了压力降及液泛速度关联式,测定了空气脱吸CO_2水溶液的传质数据,并建立了准数关联式。为网波填料推广用于难溶气体吸收和脱吸提供了依据。     

填料塔中的NaOH水溶液脱除空气中微量CO2的传质动力学

在填料吸收塔中测定了25℃时NaOH水溶液吸收空气中微量CO2的体积传质总系数(KGαv)．并研究了进口气体中CO2的含量、气体流量、吸收液喷淋密度以及NaOH浓度对体积传质总系数的影响。进口气体中CO2的含量、气体流量、吸收液喷淋密度对KGαv的影响较小;NaOH浓度对KGαv的影响较大,随着NaOH浓度的增加,KGαv显著提高。     

基于水电解制氢的梯度多孔传输层中气液流动可视化实验研究

在电解水制氢的过程中,多孔电极内的孔隙会发生气泡阻塞现象,这会妨碍气体扩散以及电解液在多孔电极内的流动,从而导致电极传质电阻的增加,进而影响电解水制氢的速率和能耗。采用3D金属打印技术制备了LSL-PTL、MMM-PTL和SLS-PTL三种规则的镍铁合金电极扩散层,进行了可视化的水电解实验,定量地记录了不同电流密度下梯度多孔传输层中气液两相流动的变化,包括气泡形态、孔隙含气率和气泡脱离速率等参数,研究扩散层梯度对气液传质过程的影响,并分析了不同电极梯度结构对电解过程中阻抗和过电位的影响。实验结果显示,与SLS-PTL和MMM-PTL相比,LSL-PTL的梯度结构从催化层即逐渐增大孔隙尺寸,始终保持较低的容积含气率,可以加速气泡在扩散层中的迁移,使气液交换更加频繁,有效减小气液传质阻力,并获得更低的传质阻抗和电解过电位,三种梯度电极在相同电流密度下的电解电势关系为E_LSLMMMSLS。因此,在水电解中采用LSL-PTL梯度的扩散层可以提高制氢效率,减少能耗损失。这项研究为水电解制氢中气液传质过程的主动控...     

伴有瞬时化学反应微溶固体颗粒的气液传质

为研究瞬时化学反应性固体颗粒对气液传质过程的影响,对伴有瞬时反应性固体颗粒/水浆料体系吸收气体过程进行了理论分析。考虑了固体颗粒在气液界面附近的溶解,以及固体颗粒尺寸对传质的影响,将cell模型融入溶质渗透理论,建立了气液二相间传质模型,并对模型进行了解析求解,得到了液相传质系数的解析表达式。结果显示:固含率、固体颗粒尺寸和溶解度对气液传质过程具有重要影响,液相传质系数随固含率和固体颗粒在液相中饱和浓度的增加而增大,随固体颗粒粒径增大而减小。在搅拌式反应器中利用Mg(OH)2/水浆料吸收SO2气体,对传质模型进行了实验验证。模型计算结果与实验值吻合良好。     

氧在水中传质过程的探讨

曝气是污水处理厂的一个重要工艺环节,在实际应用中我们大多采用氧气传质速率方程来描述曝气池和设备的性能,但此公式不能预测工艺性能。文章将氧在水中的传质过程分为氧气和水接触界面过程与氧在水中的扩散过程两部分,分别进行分析,得出氧在水中传质的模型,最后结合现阶段对氧气在水中传质的各种研究,讨论了气泡半径、压力、温度、溶氧物质、悬浮物颗粒、粘度、水的紊动条件对氧气在水中传质的影响。     

干燥器法测定甲醛释放量的不确定度评定

依据GB/T 17657-1999《人造板及饰面人造板理化性能试验方法》中干燥器法测定甲醛释放量,对装饰单板贴面人造板中甲醛释放量的检测过程进行研究,分析了检测过程的不确定度来源,确定了人造板甲醛释放量的测量结果不确定度,提出了干燥器法甲醛释放量检测不确定度的评定方法。     

Decreasing formaldehyde emission from medium density fiberboard panels produced by adding different amine compounds to urea formaldehyde resin

In this study, medium density fiberboard panels were produced by adding different ratios of some amine compounds to urea formaldehyde resin, which had 1:1.17 mol ratios. The formaldehyde contents, physical, and mechanical properties of medium density fiberboard panels were determined according to EN standard methods.In this study, it was determined that the formaldehyde emission emitted from medium density fiberboard panels decreased by adding urea, propylamine, methylamine, ethylamine, and cyclopentylamine solution. It was found that the water absorption and thickness swelling values increased slightly; however, the internal bond strength, modulus of rupture, and modulus of elasticity of medium density fiberboard panels also increased substantially, but these properties of medium density fiberboard panels decreased by adding higher ratios of urea solution. It was found that the formaldehyde emission of medium density fiberboard panels decreased 16.5% by using a 16% rate of urea formaldehyde resin and 0.8% rate of urea and ethylamine solution. These decreases were determined as 57% for cyclopentylamine solution addition, 41% for propylamine solution addition, and 48% for methylamine solution addition.     

脲醛树脂胶粘剂及其制品低毒化研究新进展

从脲醛树脂胶粘剂的配方改进、胶粘剂合成工艺改进、胶粘剂调胶及人造板热压工艺改进、甲醛吸附材料与人造板等的复合、人造板及其制品的后处理等几个方面,综述了近几年来脲醛树脂胶粘剂及其制品低毒化研究新进展。     

Urea impregnated multiwalled carbon nanotubes; a formaldehyde scavenger for urea formaldehyde adhesives and medium density fiberboards bonded with them

Multiwalled carbon nanotubes (MWCNTs) were subjected to modification by urea to use as formaldehyde scavenger in urea formaldehyde (UF) adhesive and reducing the free formaldehyde emission of the medium density fiberboards (MDFs). Morphological differences besides elemental analysis was investigated using field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy. The effect of urea impregnated MWCNTs filler on the physical, morphological and thermal properties of the UF resin has investigated. Furthermore, characterization of the mechanical properties, free formaldehyde emission and thickness swelling were carried out for the MDF panels. From the results, the free formaldehyde of the UF resins was significantly decreased. The lowest free formaldehyde was belonged to the sample with 3 wt% of scavenger which was about 71% lower than the value for neat UF resin. Accordingly, the formaldehyde emission of the fiberboards was also showed a descending trend by incorporation of MWCNTs-U to the composite structure. It was decreased from 9.67 to 3.89 mg/100 g dried board. These results indicated that the prepared nano modifier was successfully performed as a formaldehyde scavenger for the UF resin and could prevent the hazards of the free formaldehyde emission from MDF panels.     

Properties of plywood panels bonded with ionic liquid-modified lignin–phenol–formaldehyde resin

The aim of this research was to investigate the physical and mechanical properties of plywood panels bonded with ionic liquid-modified lignin–phenol–formaldehyde (LPF) resin. For this purpose, soda bagasse lignin was modified by 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) ionic liquid, and then, various contents of modified lignins (10, 15, and 20 wt%) were added as a substitute of phenol in phenol–formaldehyde (PF) resin synthesis. The properties of the synthesized resin were compared with those of a control PF resin. The changes in curing behavior of the resins prepared were analyzed by differential scanning calorimetry (DSC). The physical properties of the resins prepared, as well as the water absorption, thickness swelling, shear strength, and formaldehyde emission of the plywood panels bonded with these adhesives, were measured according to standard methods. DSC analysis indicated that in comparison with PF resins, curing of the LPF resin occurred at lower temperatures. The physical properties of the synthesized resins indicated that viscosity and solid content increased, while gel time and density decreased by addition of treated lignin to the PF resin. Although the panels containing resins with modified lignin yielded low formaldehyde emission, their dimensional stability was worse than those bonded with a commercial PF adhesive. The plywood prepared using IL-treated lignin PF resins has shear strength, which satisfy the requirements of the relevant standards specifications and significantly better than that of panels prepared with the control PF resin. The mechanical properties of the panels could be significantly enhanced with increased percentage of treated lignin content from 0 to 20 wt%.     

Reduction of formaldehyde emission from plywood

The aim of this work is to evaluate performances of tannin-based resins designed as adhesive in the plywood production. For this purpose, a part of phenol formaldehyde (PF) and melamine formaldehyde (MF) in the classic adhesive formulation was replaced by tannin. The physical properties of the formulated resins (rheological characterization, etc.) were measured. In order to analyze the mechanical performance of tannin-based resins, plywood panels were produced and the mechanical properties including tensile strength wood failure and three-point bending strength were investigated. The performance of these panels is comparable to those of plywood panels made by commercial PF and MF. The results showed that the plywood panels bonded with tannin–PF (PFT) and tannin–MF (MFT) resins exhibited better mechanical properties in comparison to the plywood panels made of commercials PF and MF. The introduction of small properties of tannin in PF and MF resins contribute to the improvement of the water performance of these adhesives. The formaldehyde emission levels obtained from panels bonded with tannin-based resins were lower than those obtained from panels bonded with control PF and MF. Although there are no actual reaction at all between PF, MF, and tannin, addition of tannin significantly improves the water resistance of PF and MF resins. This is a novel finding that manifests the possibility of replacing a convention PF and MF resins by tannin. Modified adhesive is one of the goals in the plywood production without changing any of their production conditions with improvement to their overall properties.     

改性三聚氰胺树脂及其饰面刨花板的制备与研究

为解决人造板甲醛含量普遍超标的现状,文章采用纳米二氧化钛(TiO2)/纳米蒙脱土(MMT)混合液与三聚氰胺树脂复合,并利用改性的三聚氰胺树脂制备三聚氰胺饰面刨花板。再分别利用单组份的纳米粒子改性三聚氰胺树脂,利用这两种改性树脂及未改性的树脂制备三聚氰胺饰面刨花板,将这三组板材设为对照组。参照国家标准《人造板及饰面人造板理化性能试验方法》(GB/T 17657—1999),利用紫外光分光光度计测量板材中的甲醛含量。结果表明,纳米TiO2/MMT改性的三聚氰胺饰面刨花板的甲醛含量最低,仅为0.427mg?L-1,明显符合国家室内使用标准,达到欧洲E0级标准(≤0.5mg?L-1)。且这类板材成本低廉、制备工艺简单,有利于大规模生产,在环保型人造板的研发及生产等领域具有巨大的应用潜力。     

The effect of soda bagasse lignin modified by ionic liquids on properties of the urea–formaldehyde resin as a wood adhesive

The aim of this research was to investigate the influence of lignin modified by ionic liquids on physical and mechanical properties of plywood panels bonded with the urea–formaldehyde (UF) resin. For this purpose, soda bagasse lignin was modified by the 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) ionic liquid and then the various contents of unmodified and modified lignins (10, 15, and 20%) were added at pH=7 instead of second urea during the UF resin synthesis. The physicochemical properties of the prepared resins as well as the water absorption, shear strength, and formaldehyde emission of the plywood panels made with these adhesives were measured according to standard methods. According to Fourier Transform Infrared (FTIR) Spectrometry, by treatment of lignin, the C=O, C–C, and C–H bonds decrease while the content of the C–N bond dramatically increases. Based on the finding of this research, the performance of soda bagasse lignin in UF resins dramatically improves by modification by ILs; as the resins with modified lignin yielded lower formaldehyde emission and water absorption when compared to those made from unmodified lignin and commercial UF adhesives, respectively. The shear strength as well as wood failure percentages are lower for the panels produced with modified lignin than for the panels produced with UF resins alone.     

Low formaldehyde emission particleboard panels realized through a new acrylic binder

The effectiveness of acrylic resins as low formaldehyde emission binders for particleboard production was explored. In particular, a multifunctional methacrylic monomer, ethoxylated bisphenol A dimethacrylate, classified as nonskin and eyes irritant, was selected and tested. In comparison panels realized with classic urea‐formaldehyde (UF) binder were also prepared. No significant differences were found through the morpholocigal analysis of samples prepared with the two different binders. Moreover, particleboard panels realized with the acrylic binder showed better mechanical properties and lower water absorption and thickness swelling in comparison with corresponding panels realized with the UF binders. Furthermore, the replacement of the UF with the acrylic binder did not affect thermal insulation properties of the panels. Formaldehyde release tests revealed that particleboard panels obtained by applying the acrylic binder can be classified as E1 following the European classification and even F**** following the stricter Japanese classification. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Improving the properties of ionic liquid-treated lignin-urea-formaldehyde resins by a small addition of isocyanate for wood adhesive

The aim of this research was to investigate the effect of polymeric 4, 4 diphenyl methane diisocyanate (pMDI) on the physical and mechanical properties of plywood panels bonded with an ionic liquid (IL)-treated lignin-urea-formaldehyde resin. Soda lignin modified by 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) IL was added to a urea formaldehyde (UF) resin during resin synthesis to prepare a lignin-urea-formaldehyde (LUF) resin. pMDI at various contents (2, 4, and 6% on resin solids) was then added to prepare a LUF resin. The thermal and physicochemical properties of the resins prepared as well as the water absorption, shear strength, and formaldehyde emission of the plywood panels bonded with them were measured according to standard methods. DSC analysis indicated that the addition of pMDI decreases the gel onset and curing temperatures of the LUF resin. According to the results obtained, the addition of pMDI significantly increased the viscosity and solid content and accelerated the gelation time of LUF resins. Based on the findings of this research, the addition of pMDI dramatically improves the performance of LUF resins as a new adhesive for wood-based panels. The LUF resins with isocyanate added yielded panels presenting lower formaldehyde emission and lower water absorption content when compared to those bonded with the control LUF resins. Greater dry and wet shear strength can be obtained by a small addition of pMDI to LUF resins.