MDF长期释放甲醛的FTIR分析

在使用过程中，中密度纤维板（medium density fiberboard，简称MDF）及其产品物理力学强度出现降低，但甲醛释放似乎没有衰减。采用气候箱法，对MDF进行老化处理，跟踪测试MDF的理化指标，并用FTIR测试分析UF树脂的特征峰变化，揭示MDF理化指标的变化规律。红外光谱显示，试验结果表明，经过气候箱法老化处理后，MDF的物理力学性能迅速下降，尔后趋于稳定，而甲醛释放量（如）与循环周期（T）成指数关系。FTIR显示，与UF相比，MDF中的酰胺Ⅰ带含量逐渐降低，纤维与UF之间的结合在逐渐的分解，UF体形结构也开始破坏，导致MDF长期释放较多的甲醛。但老化处理，可以加速MDF中的甲醛释放。     

循环老化中HDF的甲醛释放规律的研究

在使用过程中，HDF的力学强度不仅会降低，而且其甲醛释放量也会发生变化。采用气候箱老化法处理HDF，按照国家标准跟踪测试HDF的理化指标，探索HDF甲醛释放的规律，为消除甲醛污染和改善室内环境提供理论依据。试验结果表明，在湿热作用下，HDF的力学指标下降到一定程度后趋于平稳，而甲醛释放量与老化周期成指数关系，并使HDF甲醛释放量长期保持在较高水平。     

Mechanical and physical properties of medium density fiberboard panels laminated with thermally compressed veneer

The objective of study was to evaluate some of the physical and mechanical properties of medium density fiberboard (MDF) panels laminated with veneer sheets compressed at different levels of pressure and temperature. Rotary peeled veneer samples of European beech (Fagus orientalis Lipsky) were compressed at temperatures of 150 °C, 180 °C, and 200 °C using 4 MPa and 6 MPa pressure for 8 min. Commercially produced MDF samples also were laminated with such compressed veneer sheets. Both modulus of elasticity (MOE) and modulus of rupture (MOR) of the specimens increased with increasing pressure and press temperature. Bending characteristics of the samples tested parallel to the grain orientation resulted in significantly higher values than that perpendicular to the grain orientation for each manufacturing parameter. Thickness swelling of the samples also was influenced by increased pressure but variation in press temperature did not result in any influence on dimensional stability. The findings of this work provide potential to produce sandwich type panels with improved properties. Initial results found in this study could be used to manufacture laminated panels with a fixed rate of adhesive while controlling press parameters as a function of the magnitude of pressure and temperature.     

Some properties of thin medium density fiberboard panels treated with sunflower waste oil vapor

The objective of this study was to investigate the effect of hot waste oil vapor on some of the physical and bending properties of commercially manufactured thin medium density fiberboard (tMDF) panels. The samples were treated with waste oil vapor at a temperature of 220 °C for 10 and 20 min time durations. Based on the findings in this work, the water absorption and thickness swelling of the samples were improved by the treated panels with hot vapor oil and heat. It appears that the samples had some discoloration as a result of treatment processes. It was also observed that modulus of rupture (MOR) and modulus of elasticity (MOE) of the samples were adversely influenced. However, it seems that the thermal conductivity of the samples enhanced by such treatments. Panel products treated with these processes could have some promising potential in various applications including outdoor use.     

Water as a reaction medium for clean chemical processes

Solvent usage is often an integral part of manufacturing process, whether it is chemical or another industrial sector. Thus, this unavoidable choice of a specific solvent for a desired manufacturing process can have profound economical, environmental, and societal implications. Some of the impacts are long lasting especially from an environmental perspective, which has been well documented in the scientific literature. The pressing need to develop alternative solvents for manufacturing processes originates, in part, from these implications and constitutes an essential strategy under an emerging field of green chemistry. Whereas there have been excellent advances in developing several alternative clean solvents, it is unlikely that the one solvent will be a panacea for various chemical protocols. This article provides some examples of using water as an alternative solvent for chemical reactions with wide-ranging possibilities that include direct use of water soluble renewable materials, C–C bond forming reactions using organometallic reagents, and exploiting the use of alternate energy sources such as solar, microwave and ultrasound in accelerating chemical syntheses.The online version of the original article can be found at     

Water as a reaction medium for clean chemical processes

Solvent usage is often an integral part of manufacturing process, whether it is chemical or another industrial sector. Thus, this unavoidable choice of a specific solvent for a desired manufacturing process can have profound economical, environmental, and societal implications. Some of the impacts are long lasting especially from an environmental perspective, which has been well documented in the scientific literature. The pressing need to develop alternative solvents for manufacturing processes originates, in part, from these implications and constitutes an essential strategy under an emerging field of green chemistry. Whereas there have been excellent advances in developing several alternative clean solvents, it is unlikely that the one solvent will be a panacea for various chemical protocols. This article provides some examples of using water as an alternative solvent for chemical reactions with wide-ranging possibilities that include direct use of water soluble renewable materials, C–C bond forming reactions using organometallic reagents, and exploiting the use of alternate energy sources such as solar, microwave and ultrasound in accelerating chemical syntheses.An erratum to this article can be found at     

The fracture toughness of medium density fiberboard (MDF) including the effects of fiber bridging and crack–plane interference

The fracture toughness of medium density fiberboard (MDF) as a function of crack length (R curve) was measured. Fracture toughness was determined from force–displacement and crack length data using a new energy analysis procedure that avoids the scatter of prior discrete analysis methods. Because crack lengths were difficult to observe, they were measured using digital image correlation (DIC). The R curves for two different densities of MDF, two thicknesses, and for both in-plane and through-the-thickness cracks all increased linearly with crack length. The increase was interpreted as the development of a fiber-bridging process zone. Numerical modeling methods were used to determine the cohesive stress of the fiber-bridging zone.     

The effect of surface roughness on tensile strength of the medium density fiberboard (MDF) overlaid with polyvinyl chloride (PVC)

The objective of this study is to determine the effect of the surface roughness on the tensile strength perpendicular to the surface of medium density fiberboard (MDF) overlaid with polyvinyl chloride (PVC). The surfaces of the MDF panels were sanded with four different grit abrasives, 220, 240, 280 and 320-grit, to create different roughness values. The roughness of the panel surfaces were determined in accordance with ISO 4288. The MDF panels were laminated with polyvinyl chloride (PVC) using a polyurethane-based adhesive. A total of 70 samples having the dimensions of 50 × 50 mm from the panels were prepared based on EN 326-1. The universal test machine was used for tensile strength. The test results were statistically analyzed and it was found that the sanding process decreases the surface roughness of the MDF and as the grit size of the abrasives increases, the surface roughness decreases. The surface roughness influences the tensile strength perpendicular to the surface of the overlaid samples. The most suitable surfacing type for lower cost and the highest tensile strength is the sanding with the 240-grit abrasive.     

工业废碱渣高密度纤维板制备与阻燃性能

以工业废碱渣(主要组分为氢氧化铝(Al(OH₃)))、 硼酸锌(2ZnO·3B₂O₃·3.5H₂O)、 硼酸(H₃BO₃)等为阻燃剂, 制备出具有良好阻燃性能的阻燃高密度松木纤维板(HDF), 对其物理及力学性能、 阻燃性能、 残炭形貌等进行了分析表征。结果表明: 在满足物理及力学性能的条件下, 废碱渣Al(OH₃)与2ZnO·3B₂O₃·3.5H₂O和H₃BO₃之间具有良好的阻燃协效性, 提高了纤维板的成炭性, 残炭量达到22.2%, 降低了总释热量, 降低幅度为32%, 使其氧指数提高到36.4%, 垂直燃烧等级达到V-0级。      

The simulation of a gas-liquid chemical reactor with dispersed medium

It is suggested to develop a gas-liquid reactor in which heterogeneous exothermal reactions will proceed, with cumene selected as fuel. The temperature field and the yield of reaction product are given as functions of flow rate and initial temperature of mixture. The case is considered of the mass content of fuel components, at which the detonation occurs. Calculation is preformed of the cooling system for preventing the ignition and maintaining the temperature conditions of reaction. The calculation of chemical reaction is performed in the approximation of model of eddy dissipation which is valid at high values of Reynolds number.     

Shrinkage as a measure of the deformation efficiency of ultra-oriented high density polyethylene

A simple test is described that allows the evaluation of the molecular extension in solid state extruded high density polyethylene at maximum extrusion draw ratio 36. The samples, which were prepared by shaving the extrudates to films of average thickness 0.4 mm, were melted very rapidly and shrunk at 160° C. Experimental evidence shows that at high heating rates (800° C min⁻¹) all the molecular extension is recovered elastically. The variation of shrinkage with molecular weight indicates a difference in the molecular extension produced during the extrusion, and a simple relationship between molecular draw ratio and modulus is considered.     

Light-scattering efficiency of starch acetate pigments as a function of size and packing density

We study theoretically the light-scattering efficiency of paper coatings made of starch acetate pigments. For the light-scattering code we use a discrete dipole approximation method. The coating layer is assumed to consists of roughly equal-sized spherical pigments packed either at a packing density of 50% (large cylindrical slabs) or at 37% or 57% (large spheres). Because the scanning electron microscope images of starch acetate samples show either a particulate or a porous structure, we model the coatings in two complementary ways. The material can be either inside the constituent spheres (particulate case) or outside of those (cheeselike, porous medium). For the packing of our spheres we use either a simulated annealing or a dropping code. We can estimate, among other things, that the ideal sphere diameter is in the range 0.25-0.4 microm.     

Properties of a diffused photon-pair density wave in a multiple-scattering medium

A novel diffused photon-pair density wave (DPPDW) composed of correlated polarized photon pairs at different temporal frequencies and orthogonal linearly polarized states is proposed. A theory of DPPDWs is developed. A DPPDW selected by coherence gating and polarization gating that satisfies the diffusion equation has been verified experimentally. The sensitivity of amplitude and phase detection of the heterodyne signal has been improved by the properties of synchronized detection and common-path propagation of polarized pair photons in a multiple-scattering medium. Both reduced scattering coefficient micro2s' and absorption coefficient micro2alpha of the scattering medium in terms of the measured phase and amplitude of the heterodyne signal have been obtained. The detection sensitivity of micro2s' and micro2alpha and the properties of a DPPDW in a multiple-scattering medium are discussed and analyzed.     

Measurement of diffuse photon-pairs density wave in a multiple-scattering medium

As a continuation of the previously developed theory of a diffuse photon-pairs density wave (DPPDW) [Appl. Opt.44, 1416-1425 (2005)APOPAI0003-693510.1364/AO.44.001416], this research experimentally studies and verifies the DPPDW theory in a heterogeneous multiple-scattering medium. The DPPDW is generated by collecting the scattered linear polarized photon pairs (LPPPs) in the multiple-scattering medium. Theoretically, the common-path propagation of LPPPs not only provides common phase noise rejection mode but also performs coherence technique via heterodyne detection. In addition, the polarization gating and spatial coherence gating of LPPPs would suppress the severe scattered photon in the multiple-scattering medium. In the experiment, the amplitude and phase wavefronts of DPPDWs, which are distorted by a small object embedded in a homogeneous multiple-scattering medium, are measured in one dimension or two dimensions by scanning the source detector pair. The measured distortion of DPPDW wavefronts are detected precisely and are consistent with the theoretical calculation of DPPDW. It implies an improvement on the detection sensitivity of a small object compared with the conventional diffuse photon density wave (DPDW).     

The motion of a particle in a viscous medium discharging as a jet

Motion of a particle is examined during jet discharge of a viscous liquid in the region Re 300 with a hydrodynamic resistance coefficient which takes account of all the inertial terms.     

Stability of a monodispersed droplet flow in a gaseous medium of variable density

Experimental studies are performed of the effect of gaseous medium pressure on the stability of a flow of monodispersed droplets. The dependence of particle angular scattering upon gas density is obtained. It is shown that scattering increases with pressure of the gaseous medium.Translated from Inzhenerno-fizicheskii Zhurnal, Vol. 60, No. 4, pp. 668–670, April, 1991.     

Mode I and mode II initiation fracture toughness and resistance curve of medium density fiberboard measured by double cantilever beam and three-point bend end-notched flexure tests

Using specimens of medium density fiberboard, double cantilever beam and three-point bend end-notched flexure tests were conducted to obtain the mode I and mode II initiation fracture toughness and resistance curve for in-plane and through-the-thickness systems. The mode I initiation fracture toughness was smaller than that of mode II for the in-plane crack systems, but this tendency was inverse for the through-the-thickness systems. The fracture toughness increased during the crack propagation because of the significant fiber bridgings induced between the crack surfaces, but the increase of the mode I propagation fracture toughness was moderated after the crack reached a certain length. In contrast, the mode II propagation fracture toughness continuously increased during the crack propagation.     

Energy transmission through a medium with low optical density

The transmission of radiant energy through a medium with low optical density is analyzed here. The radiative thermal conductivity of thin porous fiber layers was measured, and the results are shown.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol.22, No. 5, pp. 907–912, May, 1972.