Effect of processing parameters on the uniformity of adhesive meltblown web

The influence of the main processing parameters, including the primary air pressure, the accessory air pressure, the melt throughput rate, and the die‐to‐collector distance, on the uniformity of adhesive meltblown web produced on the pilot‐scale melt‐blowing equipment with the added accessory device is investigated using weight measurement and thickness measurement. The effects of the process parameters on the web weight unevenness and the web thickness unevenness are similar, so both the weight unevenness and the thickness unevenness can be used to analyze the web unevenness. The results show that the web unevenness increases with the increasing melt throughput rate and the accessory air pressure; the web unevenness decreases firstly and increases later with the increasing primary air pressure and the die‐to‐collector distance. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Experimental investigation on compressed air drying performance using pressurized liquid desiccant

As a new compressed air-drying method, the compressed air dehumidification using a pressurized liquid desiccant was proposed in our previous study. The pressurized dehumidifier is a complex and core component of the drying system. The mass transfer performance between the compressed air and LiCl aqueous solution is experimentally studied in a counter-flow pressurized dehumidifier filled with structured packing. The humidity ratio of outlet compressed air, vapor removal of processed compressed air, moisture removal rate, and dehumidification efficiency were selected as the performance indices. The results show that the minimum humidity ratio of processed compressed air could reach 0.23 g/kg under 0.71 MPa. Compressed air-drying performance could be remarkably enhanced through increasing the air pressure and liquid desiccant inlet concentration while the influence of liquid desiccant temperature is negative. Furthermore, in order to ensure high compressed air-drying performance, reduce the power consumption of the air compressor and liquid desiccant pump, and the possibility of carryover, the optimum ratio of liquid to compressed air flow rate is recommended to be around 1.5 under pressure around 0.50 MPa. Meanwhile, the energy consumption for per-gram moisture removal of a liquid-desiccant-based compressed air-drying system can reach 1.42 kJ/g lower than cooling dehumidification under 0.3 MPa, which is 16.0% lower than a compressed air-cooling dehumidification system.     

Boron carbide combustion in solid-fuel ramjets using bypass air. Part I : Experimental investigation

The effects of bypass air on the combustion of highly loaded boron carbide/HTPB fuel grains in a solid-fuel ramjet motor were investigated experimentally. It was found that combustion efficiency can be significantly increased by employing high bypass rations with low dump momentum. The results indicated that high bypass dump momentum causes the particles to collide with the wall and extinguish. Increasing pressure increased efficiency, apparently through the resulting increased residence time. Increased overall equivalence ratio (grain length) also was found to be beneficial, the result of a smaller percentage of larger particles which are generated in the recirculation zone. Some of the reduction in combustion efficiency was determined to be due to incomplete combustion of the HTPB rather than just to the incomplete burning of the boron carbide particles.     

Mechanical behavior of adhesive anchors under high temperature exposure: Experimental investigation

The improvement in mechanical and adhesion properties of polymer resins have allowed to progressively substitute cast-in place rebars by polymer-based anchors in some applications, by providing equivalent or even higher mechanical properties at ambient temperature. However, a temperature increase has the effect of weakening the bond and leads to a significant decay in the bearing capacity of the adhesive anchors.This paper presents a study of the phenomena that occur at high temperature in an adhesive anchor when exposed to high temperatures by means of two pull-out test procedures and by thermomechanical characterization of the polymer resin. Results showed that the resin glass transition is the responsible for the decay in the fire resistance of adhesive anchors. The paper highlights the non-conservative aspect of the current design method used to calculate the fire resistance of chemical anchors and proposes to consider the pull-out curves as input data.     

高速空气循环制冷机转速性能的试验研究

采用新型气体润滑轴承替代滚动轴承的空气循环制冷机轴系结构,针对制冷机转速性能进行了试验研究。研究结果表明:在满足转速裕度的前提下,能够有效提高转子稳定运行的工作转速和制冷机冷、热联供的能力。     

An investigation of fiber splitting of bicomponent meltblown/microfiber nonwovens by water treatment

Meltblowing is a most versatile and cost‐effective process commercially available worldwide to produce microfiber nonwovens directly from thermoplastic resins. The new bicomponent (bico) meltblown technology opens a great possibility to make even finer microfibers by subsequently fiber splitting. Water‐dispersive Eastman AQ polymers were initially introduced to the meltblown process to make the mono‐ and bicomponent meltblown webs at Textiles and Nonwovens Development Center (TANDEC), University of Tennessee, Knoxville. The postwater treatment was performed on the fabrics, which resulted in the dispersive part (AQ polymer) being dispersed in water and only the other part remaining in the bico web. A process–structure–property study is provided toward the research reported in this article. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1218–1226, 2004     

Experimental investigation and numerical modelling of the mechanical response of a semi-structural polyurethane adhesive

The use of adhesives in load-carrying structures and components has increased recently, especially in the automotive industry. There has been many studies on structural adhesives, but when it comes to semi-structural adhesives, there is a lack of literature. In this article, a semi-structural two component polyurethane adhesive has been studied experimentally and modelled numerically. It was performed uniaxial tension tests at rates ranging from 10^-3s^-1 to 10^-1s^-1. The tests were monitored by two perpendicular digital cameras and a thermal camera. Similarly, uniaxial compression tests were performed at rates ranging from 10^-3s^-1 to 350s^-1, where a split Hopkinson pressure bar (SHPB) was used for the highest rates. The low-rate tests were recorded with high-resolution digital cameras, while a high-speed camera and a thermal camera were used for the SHPB tests. In addition, it was performed notched tensile tests at a low rate to study failure. These tests also served as a validation case for the numerical simulations. A high-resolution camera was used, such that the local strains in the notch could be captured using digital image correlation. The experiments indicated that the adhesive behaved similar as rubbers. Therefore, the Bergström-Boyce constitutive model was applied in the numerical simulations. The overall prediction of the test results was seen to be satisfactory, but the initial stiffness was too high compared to the response measured from the experiments. An investigation of the numerical results indicated that this mismatch was likely linked to the formulation of the inelastic shear rate.     

Rheological investigation of cure kinetics and adhesive strength of polyurethane acrylate adhesive

In this work, we used rheological techniques to study both the cure characteristics and the degree of cure of polyurethane acrylate adhesive, a type of reactive adhesive used in hard disk component assembly. These results were then correlated with the tensile shear strengths of adhesives. Here, the cure characteristics of polyurethane adhesive were investigated at isothermal conditions ranging from 25 to 120°C. From the rheological results, the gelation time, the vitrification time, as well as the time required to reach the maximum degree of cure, decreased when increasing the curing temperature. The cure rates of adhesive increased with temperature in three temperature ranges, which were retardation zone, vitrification zone, and reaction‐controlled zone. The cure rates in these zones were controlled by slow diffusion, fast diffusion, and the rate of reaction, respectively. From the temperature sweep of fully‐cured adhesives, we found that the crosslinking level of adhesives increased with curing temperatures at different rates depending on the temperature zones as well. Moreover, the adhesive strength measured by tensile shear test was found to also increase correspondingly with the adhesives' T_g, indicating that the crosslinking level directly affected the adhesive strength. The strong dependence of adhesive strength with crosslinking level indicates that the crosslinking level was essential for high adhesive strength. The correlation of cure characteristics and adhesive strengths at various curing temperatures performed in this study can further provide useful information for planning appropriate curing schemes of polyurethane acrylate adhesives used in electronic and other industries. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Experimental investigation of liquid-fuel atomization using Hartmann acoustic generator

The Hartmann acoustic generator has been used in the present experiments to atomize high-speed diesel oil, aviation kerosene and light furnace oil. The effects of upstream air pressure (196–490 kPa), nozzle diameter, and frequency of sound field (5000–22000 Hz) on the mean droplet size of the spray have been investigated. The experiments showed that the degree of fuel atomization was much more sensitive to a variation in the upstream air pressure than to a variation in the acoustic frequency. Atomization was almost independent of fuel viscosity; thus burners incorporating these acoustic generators should prove particularly suitable for the atomization and combustion of heavy fuel oils. It was dependent mainly on surface tension and fuel density. A single correlation has been obtained for all three fuels, within the range of experimental conditions investigated, but attempts to develop a dimensionless expression incorporating surface tension and density were unsuccessful, partly because of the small range of these properties examined.     

Experimental investigation on two-phase air/high-viscosity-oil flow in a horizontal pipe

The flow of very-viscous-oil and air through a horizontal pipe (inner diameter 22 mm) is experimentally studied. We first build and analyze the flow pattern map; a comparison between the air–water and the air–oil flow pattern maps shows a strong influence of the fluid properties. The experimental flow maps are compared with empirical and theoretical ones – Baker (1954), Mandhane et al. (1974), and Petalas and Aziz (1998) – showing a poor agreement. Experimental pressure gradients are also reported and compared with theoretical model, but also in this case the agreement is not very satisfactory. Finally, the elongated bubble velocity and length are measured and compared to model present in the literature. We conclude that the high viscosity of the liquid phase has a strong influence on the results and that the current models are not able to predict the flow features satisfactorily.     

Experimental investigation into the process of fixed-bed coal gasification with reversed air blowing

The fixed-bed of brown coal with reversed air blowing is experimentally studied. A definition of the rate of the gasification process with reversed air blowing is given. Dependences of the basic characteristics of gasifier operation (rate of the process, heat-wave velocity, and production rates for the combustible gas and low-temperature coke) on the fractional composition of the initial coal and the air flow rate are obtained. The correlation between the technological characteristics and control parameters of the process is analyzed. Commercially attractive modes of gasifier operation are determined, and methods of its intensification are formulated.     

Fabrication of micro‐meltblown filtration media using parallel plate die design

Meltblown fibers are typically produced using a die technology based on the slot concept, an extension of the sheet die technology with a series of holes substituting the center rectangular slot of the sheet die. While this prevalent technology has met with considerable success, an economical, facile design would be desirable. In this study a new parallel plate die concept to fabricate micro‐meltblown fibers that offers simplicity, ease of use, and low cost was examined. The new die concept had parallel plates forming channels for polymer melt to flow through with a set of air holes surrounding them. This die design produced meltblown fibrous media with fibers in the range of 3–10 μm with pore size between 20 and 60 microns. The underlying mechanisms leading to such large fiber size formation and its implication in air filtration performance has been discussed. While conventional meltblown die generates fibers of smaller diameter and webs with higher filtration efficiency than the parallel plate geometry, design modifications could enhance the parallel plate meltblown die performance and make it a viable alternative. These die adaptations that include reducing air flow resistance, increasing the number of air nozzles around the polymer nozzles, recessing the polymer spinnerets above the die face, and having inclined air channels to increase the drag force on the fibers has been discussed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42998.     

航空硅橡胶用热硫化型胶粘剂的性能研究

研究了热硫化型胶粘剂XY-931S和XY-601S的性能，试验结果表明，胶粘剂XY-931S具有较好的常温和高温粘合性能，耐热空气老化性能及耐油性能，可用于三氟丙基甲基乙烯基硅橡胶与金属的热硫化粘合；胶粘剂XY-601S具有良好的粘合性能和耐热性，在300℃下的耐热空气老化性能稳定，可用于甲基乙烯基硅橡胶和低苯基甲基乙烯基硅橡胶与金属的热硫化粘合。     

注乙二醇溶液分解甲烷水合物的实验研究

在甲烷水合物一维分解模拟系统上,进行了模拟注乙二醇溶液分解甲烷水合物的实验研究。使用甲烷气体与纯水在一定温度、压力条件下,在沉积物中合成水合物。通过以不同速率注入不同浓度的乙二醇溶液,研究了化学法分解水合物过程中甲烷气体和水生产规律。实验结果表明,水合物分解产出甲烷气体的过程主要分为4个阶段：初始注入段、化学剂稀释段、水合物分解段和残余气体产出段。整个分解过程中,水的生产速率几乎保持恒定。通过对实验结果的能量分析表明,本实验条件下分解综合效率在0.20～0.88之间,并且受注入速率和化学剂浓度影响。在恒定注入速率条件下,分解效率在化学剂质量分数为60%时达到最大值。     

空气取水用套管式吸附床的吸附特性

为提升吸附式空气取水吸附床吸附性能,对套管式吸附床吸附性能的影响因素(风机功率和传质通道直径大小)进行实验分析。利用称重法分别测量不同因素影响下吸附床吸附量随时间变化情况。结果表明,为满足吸附床吸附要求,需对吸附床进行风机送风;吸附床吸附量随着风机功率增加而增加,最大提升约14.5%;随着传质通道直径加大而变大,最低提升约39.66%;相比于提升风机功率,提升传质通道直径能更好地提高吸附量,效果为提升风机功率的3倍以上。     

新型微波高温热风系统实验研究

介绍了一种新型的微波高温热风系统,测试分析了微波功率、风机风速、吸波材料等对热风温度及保温箱内温度分布的影响。研究结果表明:设计合理的微波高温热风系统结构紧凑、换热强度大、洁净环保,并能满足各种工业应用对热风温度的要求。     

Experimental investigation on the enhancement of Mode I fracture toughness of adhesive bonded joints by electrospun nanofibers

ABSTRACT

The use of an electrospun nylon nanofibrous mat at the interface between adjacent plies of a composite laminate is a promising mean to improve the delamination strength, as the nanomat acts a reinforcing web enabling a ply-to-ply bridging. This kind of reinforcement can be potentially used in other applications, such as adhesive bonding, where it may also work as adhesive carrier. The present work is therefore aimed at analysing the potential of an electrospun polymeric nanomat as adhesive carrier and reinforcing web in adhesive bonding. The adhesive is used to pre-impregnate a nylon nanofibrous mat that is then placed at the interface between two metal pieces and cured. The effectiveness of this procedure is evaluated by comparing of the mode-I fracture toughness measured 2024-T3 aluminum alloy DCB (Double Cantilever Beam) specimen bonded using a two-part epoxy resin with and without the nanomat.     

Experimental investigation of the autoignition process during fuel injection into a heated air flow

Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 25, No. 1, pp. 9–12, January–February, 1989.     

热空气脉冲喷吹法拆卸废旧印刷电路板的试验

电子元器件的拆卸对于废旧印刷电路板(waste printed circuit boards,WPCBs)的资源化利用具有重要意义,是废旧印刷电路板回收利用必不可少的环节。文章利用热空气作为预热气源和脉冲喷吹气源,采用自主设计的WPCBs拆卸设备进行拆卸实验,运用正交试验方法研究了拆卸工艺参数对电路板拆卸率的影响,优化了工艺参数,并对影响原因进行了分析。实验结果表明:小贴片元器件拆卸率与元器件总拆卸率随喷吹次数增加先增大后减小;当进气温度为240℃、加热时间为5min、喷吹次数为10次时,插槽元器件、通孔元器件、大贴片元器件拆卸率大部分在95%以上,小贴片元器件拆卸率最高达80%以上,且元器件总拆卸率达85%以上。利用热空气作为预热气源和喷吹气源拆卸WPCBs的最优实验参数为:进气温度为240℃,加热时间为5min,喷吹次数为10次。