Experimental study and numerical simulation the air jet flow field of a dual slot sharp blunt die in the melt blowing nonwoven process

In this work, the physical model of a polymer in a melt blowing process is established and solved by introducing the numerical computation results of the air jet flow field of the dual slot sharp inset die. The influence of the melt blowing processing parameters and the die design parameters on the fiber diameter is also studied. A lower polymer throughput rate, higher polymer melt initial temperature, higher air initial temperature, higher air initial velocity, smaller angle between slot and axis of the spinneret, smaller width of the die head, and larger width of the slot can all produce finer fibers. At the same time, the air jet flow field model of the dual slot sharp inset die of polypropylene polymer nonwovens fabrics in melt blowing process was also established. The air jet flow field model was solved by using the finite difference method. The computational simulation results of the distributions of the z‐components of air temperature and air velocity along the spinline during melt blowing process are in accordance with the experimental data. The air drawing model of melt blowing process was simulated by means of the numerical simulation results of the air jet flow field. The predicted fiber diameter agree with the experimental data. The effects of the air initial velocity and air initial temperature on the fiber diameter were studied and discussed. The results demonstrate that a higher air initial velocity and a higher air initial temperature are beneficial to the air drawing of the polymer melt and thus to reduced fiber diameter. The results show the great potential of this research for computer assisted design in melt blowing nonwoven process and technology. POLYM. ENG. SCI., 57:417–423, 2017. © 2016 Society of Plastics Engineers     

熔喷工艺参数和喷嘴设计参数对纤维直径的影响

引　言熔喷法是 2 0世纪 5 0年代发展起来的一种制备超细纤维非织造布的方法 ,其纤维直径仅 1～10 μm.熔喷非织造布是高效精细过滤材料 ,过滤效率可达 99 9%以上 ,广泛用于医疗和环保等领域 .熔喷是依靠高速高温气流喷吹聚合物熔体使其迅速拉伸而形成超细纤维的 .数学模型对于     

A physical–mathematical model for the prediction of fiber diameter of the polyethylene terephthalate (PET) spunbonding nonwoven fabrics

A mathematical model of air drawing of a polyethylene terephthalate (PET) polymer in a spunbonding nonwoven process was established and solved by introducing the numerical computational results of the air jet flow field of the attenuator. The predicted fiber diameters, crystallinities, and birefringences agreed well with the experimental data. The air jet flow field model was solved and simulated by means of the finite difference method. The numerical simulation computation results of distributions of the air velocity matched quite well with the experimental data. The air drawing model of the polymer was solved with the help of the distributions of the air velocity measured by a particle image velocimetry. The effects of the processing parameters on the fiber diameters, measured with the aid of an image analysis method, are further discussed. A lower polymer throughput rate, higher polymer melt initial temperature, higher air initial temperature, higher air initial speed, lower venturi gap, higher air suction speed, and higher quench pressure can all produce finer filament fibers. The results demonstrated the great prospects for this research in the field of computer‐assisted design (CAD) in the spunbonding technology field. POLYM. ENG. SCI., 58:1213–1223, 2018. © 2017 Society of Plastics Engineers     

Numerical modeling,simulation, and experimental validation of predicting fiber diameter in wide‐slot positive‐pressure spunbonding process

An air‐drawing model of polypropylene (PP) polymer and an air jet flow field model in wide‐slot positive‐pressure spunbonding process are established. The influences of the density and the specific heat capacity of polymer melt at constant pressure changing with polymer temperature on the fiber diameter have been studied. The predicted fiber diameter agrees with the experimental data as well. The effects of the processing parameters on the fiber diameter have been investigated. The air jet flow field model is solved by means of the finite difference method. The numerical simulation computation results of distribution of the fiber diameter match quite well with the experimental data. The air‐drawing model of polymers is solved with the help of the distributions of the air velocity. It can be concluded that the higher air velocity and air temperature can yield the finer fibers diameter. The higher inlet pressure, longer drawing segment length, smaller air knife edge, longer exit length, smaller slot width, and smaller jet angle can all cause higher air velocity and air pressure along z‐axis position, which are beneficial to the air drawing of the polymer melt and thus to reduce the fiber diameter. The experimental results show that the agreement between the predicted results and the experimental measured data is very better, which verifies the reliability of these models. Also, they reveal great prospects for this work in the field of computer‐assisted design (CAD) of spunbonding process. POLYM. ENG. SCI., 58:1371–1380, 2018. © 2017 Society of Plastics Engineers     

Computational fluid dynamics simulation and theoretical study the air jet flow field of a wide slot positive pressure drawing assembly in the spunbonding nonwoven process

The polymer air‐drawing model of polyethylene terephthalate spunbonding nonwovens and the air jet flow field model in wide slot positive pressure spunbonding process have been established. The influence of the density and the specific heat capacity of polymer melt at constant pressure changing with polymer temperature on the fiber diameter have been studied, which is solved by introducing the numerical computation results of the air jet flow field of attenuator. It is simulated by means of the finite difference method. The predicted fiber diameter agrees with the experimental data. The effects of the processing parameters on the fiber diameter with the help of the image analysis method have been investigated. A higher inlet pressure, smaller slot width, and smaller jet angle will all cause higher z‐axis position of air velocity and air pressure, which are beneficial to the air drawing of the polymer melt and thus to reducing the fiber diameter. The experimental results show that the agreement between the results and experimental data is better, which verifies the reliability of these models. The results present great prospects for this research in the field of computer assisted design of spunbonding process, technology, and equipment. POLYM. ENG. SCI., 55:231–242, 2015. © 2014 Society of Plastics Engineers     

Fiber diameter of polybutylene terephthalate melt‐blown nonwovens

A polymer air‐drawing model of Polybutylene Terephthalate (PBT) melt‐blown nonwovens has been established. The predicted fiber diameter coincides with the experimental data. The effects of the processing parameters on the fiber diameter have been investigated. A lower polymer flow rate, a higher initial air velocity, and a larger die‐to‐collector distance can all produce finer fibers, whereas too high an initial air velocity and too large a die‐to‐collector distance contribute little to the polymer drawing of PBT melt‐blown nonwovens. The results show the great potential of this research for the computer‐assisted design of melt‐blowing technology. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1750–1752, 2005     

A numerical computation and experimental study of air drawing model of polymers in spunbonding nonwoven process

The air drawing model of polyethylene terephthalate polymer and the model of the air jet flow field in spunbonding process are established. The air jet flow field model is simulated with the help of the finite difference method. The numerical simulation computation results of distributions of the air velocity and air temperature are in agreement with the experimental data. The air drawing model of polymer is solved with the aid of the distributions of the air velocity measured by a particle image velocimetry. The predicted fiber diameters tally with the experimental data well. It can be concluded that the higher initial air temperature can generate finer filament fiber diameter, and the higher initial air velocity can yield the finer fiber diameter as well. The experimental results show that the agreement between the predicted results and the experimental data is very good, which confirms the reliability and the accuracy of these mathematical models. Also, they reveal great prospects for this work in the field of computer assisted design of spunbonding process. POLYM. ENG. SCI., 2013. ©2012 Society of Plastics Engineers     

Impact force of water jets in the hydroentanglement nonwoven process: Numerical simulation and experimental verification

The water jet flow model in the hydroentanglement nonwoven process is established and solved numerically. The impact force of water jets is calculated with aid of the model and verified with the experimental data. The numerical simulation results of the impact force coincide with the experimental data, which confirms the effectiveness of the two‐dimensional model established. Computer simulations and experiments show that higher water jet pressure, smaller water jet inclination angle, and smaller standoff distance will yield larger impact force. The results show that there is great potential for this research in field of computer‐assisted design in hydroentanglement technology and equipment. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers.     

熔喷法气流拉伸机理与喷射流场的研究进展

介绍了熔喷法非织造布的气流拉伸机理和空气喷射流场的研究进展,评价了聚合物熔喷气流拉伸的数学模型和空气喷射流场等对纤维直径的影响。指出今后的研究应探索建立熔喷法的三维拉伸模型和喷嘴气流喷射流场理论。     

Computer‐aided mathematical modeling and numerical simulation and theoretical analysis of the polypropylene polymer air drawing in spunbonding nonwoven process

In this article, as a nonlinear mathematical problem, the air‐drawing model and the air jet flow field model of the polymer during spunbonding process are also presented, because the continuous filament fiber not always occurs in the spunbonding process, therefore, there exists the filament fiber breakage, the broken fibers occur in the flow field of spunbonding process is a two‐phase flow problem, we suggested a new model called the sphere–spring model that can best described the broken fibers movement features. At the same time, the air‐drawing model of the polypropylene polymer in a spunbonding process is presented and solved by introducing the numerical computation results of the air jet flow field of aerodynamic device. The model's predictions of the filament fiber diameters, crystallinities, and birefringences are coincided well with the experimental data. The effects of the processing parameters on the filament fiber diameter are discussed. A lower polymer throughput rate, lower quench air temperature, higher polymer melt initial temperature, higher air initial temperature, higher air initial speed, medium smaller venturi gap, higher air suction speed, higher quench air pressure, higher air suction speed, higher extrusion temperature, higher quench air pressure, higher cooling air temperature, and so on can all produce finer filament fiber. The results show great prospects for this research in the field of computer‐assisted design of spunbonding technology. POLYM. ENG. SCI., 54:481–492, 2014. © 2013 Society of Plastics Engineers     

Numerical approach to modeling fiber motion during melt blowing

Melt blowing involves applying a jet of hot air to an extruding polymer melt and drawing the polymer stream into microfibers. This study deals with the dynamic modeling of the instabilities and related processes during melt blowing. A bead‐viscoelastic element model for fiber formation simulation in the melt blowing process was proposed. Mixed Euler‐Lagrange approach was adopted to derive the governing equations for modeling the fiber motion as it is being formed below a melt‐blowing die. The three‐dimensional paths of the fiber whipping in the melt blowing process were calculated. Predicted parameters include fiber diameter, fiber temperature, fiber stress, fiber velocity, and the amplitude of fiber whipping. The mathematical model provides a clear understanding on the mechanism of the formation of microfibers during melt blowing. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

纺粘法扁平狭缝牵伸器喷射流场的数值模拟

采用标准K-ε模型描述了纺粘法扁平狭缝流道牵伸器喷射流场的湍流运动,利用有限差分法对该模型求解。通过对6种纺粘法牵伸器喷嘴的喷射流场进行数值模拟,得到了相应的流场矢量图。分析流场矢量图发现,适当减小拉伸段宽度,增加喷射喷口长度,适当选择牵伸器喷口宽度和牵伸器的拉伸段长度,有利于提高气流速度,从而有利于对聚合物熔体进行气流拉伸,使纤维直径变细,提高纺粘法成网的质量。     

Study on airflow field and fiber motion with new melt blowing die

In this study, a new melt‐blowing die was studied with the computational fluid dynamic approach. A bead‐viscoelastic element fiber model was established to model three‐dimensional paths of the fiber motion with the standard linear solid (SLS) constitutive equation in different airflow fields. The effects of this newly designed die on the velocity field, temperature field, and turbulence fluctuation field at the centerline were studied and compared with the traditional melt blowing die. The fiber motion was simulated and compared with the airflow field of different dies. The simulations results demonstrated that the new die was able to reduce the velocity fluctuations of the air flow near the outlet of the polymer capillary and generate the higher centerline air velocity and temperature. The fiber attenuation and motion were related to the centerline air velocity, temperature, and turbulent fluctuation in the melt blowing process. POLYM. ENG. SCI., 59:1182–1189 2019. © 2019 Society of Plastics Engineers     

Study on the flow field of the air jet from dual slot die in the melt blowing process

The possibility of describing the jet from the dual slot die in the melt blowing process with a vortex pair was studied according to the nature of the vortex. A model of the synthesis of two jets was developed. The reliability of the model was confirmed by experimental data cited from literature. The prediction of the fiber diameter using this model coincided with that using the fitted equation with the data advanced by Harpham and Shambaugh. The effects of the equipment parameters, such as the angle between the air flow and the axis of the spinneret, the width of the die head and the width of the slot were also discussed.     

Empirical formulas for distributions of air velocity/temperature along the spinline of a dual slot die

Empirical formulas, which describe the air velocity and air temperature decays along the spinline of a dual slot die, are improved by introducing the influence of the ratio of die end width to air slot width. The thus‐improved empirical formulas include more die geometry parameters and are more accurate than the existing ones. The fiber diameters of nonwoven web are predicted by incorporating these new empirical formulas into a one‐dimensional theoretical model for melt‐blowing process. The agreement between the predicted results and the experimental data cited from literature is very good, which confirms the reliability and the accuracy of these new formulas. POLYM. ENG. SCI., 45:1092–1097, 2005. © 2005 Society of Plastics Engineers     

纺粘工艺参数和牵伸器设计几何参数对纤维直径的影响

建立了纺粘聚合物气流牵伸模型,采用计算机数值模拟方法求解牵伸器的喷射流场,分析了纺粘工艺参数和牵伸器设计几何参数对纤维直径的影响,得出了影响规律。     

Dynamics of air drawing in the melt blowing of nonwovens from isotactic polypropylene by computer modeling

The dynamics of stationary air drawing in the melt blowing of nonwovens were determined on the basis of a single‐filament model in a thin‐filament approximation that accounts for polymer viscoelasticity, heat of viscous friction in the polymer bulk, and surface energy. Predetermined distributions of the air velocity and temperature along the melt blowing axis were assumed. Axial profiles of the polymer velocity, temperature, elongation rate, filament diameter, tensile stress, and extrapressure were computed for the melt blowing of isotactic polypropylene. The effects of the air‐jet velocity, die‐to‐collector distance, and polymer molecular weight are discussed. We predicted that the filament attenuation and velocity at the collector located in the air‐drawing zone would increase with increasing die‐to‐collector distance. The air‐drawing zone was shorter for higher air velocities and lower molecular weights. No online crystallization was predicted before the achievement of the collector, and melt bonding of the filament in the web should have occurred during cooling on the collector, accompanied by spherulitic crystallization. Significant online extrapressure in the filament was predicted in the case of supersonic air jets as resulting from polymer viscoelasticity, which could have led to longitudinal splitting of the polymer into subfilaments. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of processing parameters on fibers diameter and web evenness of polypropylene spunbonding nonwoven fabrics in wide slot positive pressure drafting assembly of spunbonding process

The air drawing model of polymer polypropylene (PP) spunbonding nonwovens has been established. The influences of the density and the specific heat capacity of polymer melt at constant pressure changing with polymer temperature on the fiber diameter have been studied. The air drawing model of polymer in spunbonding is confirmed by the experimental results obtained with our university's equipment. The effects of the processing parameters on fibers web evenness of PP spunbonding nonwoven fabrics in wide slot positive pressure drafting assembly of spunbonding process have also been investigated. The predictions of the filament fiber diameters, crystallinities, and birefringences are coincided well with the experimental data. It is found that a medium polymer melt temperature, monomer suction wind speed, drawing pressure, cross air blow speed, and air control distance have a significant influence on the web evenness and quality, which are beneficial to produce more uniformity fibers web. The experimental results show that the agreement between the results and experimental data is very better, which verifies the reliability of these models. At the same time, the results also reveal the great potential of this research for the computer‐assisted design (CAD) of spunbonding technology. POLYM. ENG. SCI., 58:1268–1277, 2018. © 2017 Society of Plastics Engineers     

熔喷/干法纤网在线复合汽车吸音棉的生产工艺

为了实现熔喷/干法纤网复合汽车吸音棉的在线生产,以开发300 g/m2的复合吸音棉为例,对熔喷工艺、干法纤网工艺以及熔喷/干法纤网在线复合等内容进行了分析介绍。结果表明:采用熔融指数150 g/min的聚丙烯切片,并控制好模头温度、热空气喷射角、热空气压力、接收距离等熔喷工艺参数,采用纤度为3.3 dtex的三维卷曲涤纶中空短纤维和阻燃涤纶短纤维组成的干法纤网,纤网加入熔喷丝的角度在75～83°之间时,能够得到较好的复合吸音棉材料。     

Effects of processing parameters on the filament fiber diameter of spunbonded nonwoven fabrics

The air drawing model of polymer in spunbonding is established. The air drawing model of polypropylene polymer in spunbonding is confirmed by the experimental results obtained with the help of our university's equipment. The predicted filament fiber diameter is in accordance with the experimental data. The effects of the process parameters on the filament fiber are investigated in this article. It is found that a lower polymer throughput rate, a higher polymer melt temperature, a higher primary air temperature, a higher air suction speed, a higher quench pressure, a higher venturi gap can all yield finer fiber, whereas the effect of the web basis weight is not significant. The results show great prospects for this research in the field of computer assisted design of spunbonding technology. POLYM. ENG. SCI., 47:510–515, 2007. © 2007 Society of Plastics Engineers.