家具漆底擦色及修色剂的研制及应用

介绍了家具漆用底擦色及修色剂的主要组成,并结合家具厂的实际应用,对其配方进行优选,最终使其产品与本厂PU系列家具漆配合使用,达到国内出口家具的涂装要求。本文仅对影响产品研制的主要因素进行了讨论。     

Analytical and numerical assessments of local overpressure from hydrogen gas explosions in petrochemical plants

Accurate prediction of pressure rise is important for safety assessments of a petrochemical plant in the event of an explosion accident. The sudden pressures arising from gas explosions at various hydrogen concentrations in air have been predicted analytically and numerically. These solutions were compared against experimental data. The analytical solution, based on the self‐similar solution for pointwise strong explosions in an open space, which assumed no energy loss and premixed fuel‐air mixture, reasonably predicted the explosive‐ignition detonation case while the numerical solutions were more suitable to model spark‐ignition deflagration cases that accounted for the effect of turbulence arising from three‐dimensionality and presence of obstacles in the computational domain. Comparison of both analytical and numerical results against experimental data indicates that their differences are within a 30% margin. The analytical model presented herein can be useful for field engineers who want conservative estimates of the overpressure resulting from explosive‐ignition detonation. Copyright © 2016 John Wiley & Sons, Ltd.     

The massive formation of hybrid shish‐kebab structures in HDPE/PA6 microfibril blend subjected to melt second flow

During the melt second flow process, the synergetic effect of intense shear and polyamide 6 (PA6) microfibrils finally results in the massive formation of highly oriented crystalline structures in the entire thickness of high‐density polyethylene (HDPE)/PA6 microfibril blend. Interestingly, not only does the small microfibril induce HDPE crystallization to form typical hybrid shish–kebab structure, but the large microfibril (about 2 μm in diameter) also induces the formation of local hybrid shish–kebab structure. For the small PA6 microfibril, the oriented HDPE chains caused by the intense shear are absorbed on the whole surface of the microfibril and then a complete polymer underlayer is formed. Subsequently, the crystal nuclei appear on the underlayer, and then the other oriented HDPE chains overgrow from the nuclei in the form of folded chains and grow perpendicular to the microfibril. Finally, the typical hybrid shish–kebab structure is formed. While for the large PA6 microfibril, a few HDPE chains can be still absorbed on the microfibril surface due to the high surface energy of PA6. However, the driving force is insufficient to absorb largely oriented HDPE chains to form complete hybrid shish but only local adsorption layer, so the local hybrid structure is formed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45274.     

多丝束碳纤维湿法缠绕系统研究

研究了多丝束碳纤维湿法缠绕机工艺,对影响张力的摩擦张力调节环节、碳纤维放卷辊及缠绕辊环节、同步运动环节分别进行了分析。在此基础上,研究了系统控制策略、设计PID张力控制系统和目标跟随式的同步运动控制系统,保证了缠绕的高质量。对碳纤维预浸缠绕机的控制系统软硬件进行设计和实现。结果表明:采用以上算法后,碳纤维张力达到±1N;缠绕精度达到±0.1mm。研究了触摸屏与远端监控相结合的双上位控制结构,设计了触摸屏本地人-机接口,利用RS-485总线传输,实现了碳纤维湿法缠绕机远端监控。     

锰系固体超强酸催化合成苯甲醛乙二醇缩醛

在微波辐射下,自制的固体超强酸SO2-4/MnO2为催化剂,以乙二醇和苯甲醛为原料催化合成苯甲醛乙二醇缩醛。考察了微波辐射的时间、微波输出的功率、催化剂的焙烧温度、催化剂的焙烧时间因素的影响。实验结果显示:当醇醛物质的量之比为2∶1、微波输出的功率为550 W、微波辐射的时间5 min、催化剂用量为0.5 g时,苯甲醛乙二醇缩醛的产率为76.3%。     

Morphologies and dynamic mechanical properties of core‐shell emulsifier‐free latexes and their copolymers for P(BA/MMA)/P(MMA/BA) and P(BA/MMA)/PSt systems in the presence of AHPS

Different poly(methyl methacrylate/n‐butyl acrylate)/poly(n‐butyl acrylate/methyl methacrylate) [P(BA/MMA)/P(MMA/BA)] and poly(n‐butyl acrylate/methyl methacrylate)/polystyrene [P(BA/MMA)/PSt] core‐shell structured latexes were prepared by emulsifier‐free emulsion polymerization in the presence of hydrophilic monomer 3‐allyloxy‐2‐hydroxyl‐propanesulfonic salt (AHPS). The particle morphologies of the final latexes and dynamic mechanical properties of the copolymers from final latexes were investigated in detail. With the addition of AHPS, a latex of stable and high‐solid content (60 wt %) was prepared. The diameters of the latex particles are ～0.26 μm for the P(BA/MMA)/P(MMA/BA) system and 0.22–0.24 μm for the P(BA/MMA)/PSt system. All copolymers from the final latexes are two‐phase structure polymers, shown as two glass transition temperatures (T_gs) on dynamic mechanical analysis spectra. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3078–3084, 2002     

Enhanced light emission of nano-patterned GaN via block copolymer thin films

We demonstrate that the nanoscopic block copolymer patterns on GaN can enhance light extraction efficiency of GaN-based light emitting diodes. Nanoporous patterns were fabricated on a bare GaN substrate via self-assembly of poly(styrene-b-methyl methacrylate) block copolymers from which PMMA microdomains were selectively removed later on. A bare GaN surface was treated with a photo-crosslinkable thin layer of poly(styrene-r-methyl methacrylate) random copolymers to tune the cylindrical microdomain orientations. The nanoporous block copolymer thin film was controlled to be thicker than its typical repeat period in bulk by incorporating PMMA homopolymer into block copolymer. Consequently, the light extraction efficiency in photoluminescence spectra could be tuned with the thickness of nanopatterned thin film on GaN. This paper is dedicated to Professor Chul Soo Lee on the occasion of his retirement from Korea University.     

Influence of tempering temperature on both the microstructural evolution and elemental distribution in AISI 4340 steels

In the present study, the influence of tempering temperature on the microstructural evolution and prior austenite grain boundary segregation of AISI 4340 steels was investigated by transmission electron microscope and atom probe. The transmission electron microscopy results showed a variation in the microstructure and the morphology of carbides with a change in tempering temperature. Additionally, the chemical compositions of the prior austenite grain boundaries and carbides were quantified by atom probe tomography. An increase in the tempering temperature led to a decrease in the amount of carbon segregated at the prior austenite grain boundary from 7.9 to 1.3 at.%. It was found that a higher tempering temperature can accelerate the diffusion of carbon from the prior austenite grain boundary into carbide. However, phosphorus atoms were segregated mainly at the prior austenite grain boundary in steel tempered at 400°C (up to 0.18 at.%). It was found that formation of film-like carbide and phosphorus segregation along the prior austenite grain boundary is the main cause of embrittlement in steel tempered at 400°C.     

Effects of intermetallic compound on the electrical and mechanical properties of friction welded Cu/Al bimetallic joints during annealing

Al/Cu metal joints applied for the electrical connector was joined by the friction welding method to limit the formation of intermetallic compound under optimum friction welding condition. To guarantee the reliability of the Al/Cu joints in service requirement, the effects of the intermetallic compound layer on the electrical and mechanical properties have been investigated under various annealing conditions. Two kinds of intermetallic compounds layer were formed in the joints interface and identified by AlCu and Al₂Cu. The growth kinetic of these intermetallics during the annealing can be followed by volume diffusion process. The activation energy of Al₂Cu, AlCu and total intermetallic compound (AlCu + Al₂Cu) represented 107.5, 98.42 and 110.22 kJ/mol, respectively. A thicker intermetallic compound layers could seriously degrade the electrical resistivity and tensile strength. The electrical resistivity with 21 μm thickness of intermetallic compound was 45 μΩ cm and increased to be 85 μΩ cm with 107 μm of intermetallic compound. Tensile strength remarkably decreased from 85 MPa to near zero at the annealing condition of 773 K and 129.6 ks and fracture occurred through the intermetallic compound layers.     

Preparation and electrocatalytic properties of tungsten carbide electrocatalysts

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