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     

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     

Melt‐blowing thermoplastic polyurethane and polyether‐block‐amide elastomers: Effect of processing conditions and crystallization on web properties

Melt‐blown webs from ester and ether thermoplastic polyurethanes and polyether‐block‐amide (PEBA) elastomers were produced at different die‐to‐collector distances (DCD) to study the correlation between the polymer type and hardness, melt‐blowing process conditions, and web properties. An experimental set up was built to measure the air temperature and velocity profiles below and across the melt‐blowing die to correlate the fiber formation process and polymer crystallization behavior to process conditions and web properties. It was shown that air temperature and velocity profiles follow similar trends with increasing distance below the melt‐blowing die: both drop rapidly until reaching a plateau region approximately 5–6 cm below the die. Thereafter, they remain relatively constant with further increasing distance. It was found that crystallization onset and peak temperatures of all block copolymers in this study fall within this region of rapid velocity and temperature drop. This suggests that the polymers have already started to crystallize and solidify before reaching the collector, the extent of which depends on the crystallization kinetics of the polymer. The strong influence of the crystallization kinetics on web strength was clearly demonstrated in the PEBA series. In particular, the hardest grade produced the lowest web strength mainly because of its high crystallization rate and crystallization onset temperature. It is concluded that the melt‐blown web strength is strongly dependent on the degree of fiber‐to‐fiber adhesion within the web, which is determined by the amount of fiber solidification that occurs prior to the collector. The crystallization kinetics of the polymer and the distances traveled between the die and collector or the exposure time of the polymer melt to process and ambient air were shown to be critical in the amount of fiber solidification attained. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Experimental investigation of adhesive meltblown web production using accessory air

Using a low‐melting‐point polymer, copolyamide, as raw material, adhesive meltblown webs were formed on the ordinary melt‐blowing line by using the accessory air and the accessory air chamber. The webs thus produced exhibit narrower fiber diameter distribution and a more uniform pore structure. At the same time, four main melt‐blowing parameters, the primary air pressure, the accessory air pressure, the melt throughput rate, and the die‐to‐collector distance, are discussed in terms of their influence on geometric mean diameter of fibers and fiber diameter distribution. POLYM. ENG. SCI., 46:1–7, 2006. © 2005 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     

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     

滤材用聚对苯二甲酸丁二酯熔喷非织造布的研制

利用熔喷非织造成网系统,制备了滤材用高熔融指数的聚对苯二甲酸丁二酯(PBT)熔喷非织造布,分析了空气压力、接收距离、泵供量等成网工艺参数对产品性能的影响。结果表明:工艺参数对纤网中PBT纤维的形态和结构,对PBT熔喷非织造布的纤维直径、面密度、断裂强力以及孔隙直径都产生了很大的影响。     

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     

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     

The effect of process parameters on the properties of elastic melt blown nonwovens: Air pressure and DCD

An elastic masterbatch and elastic melt blown nonwovens are prepared based successively on styrene-ethylene/butylene-styrene (SEBS) and polypropylene (PP) blend. The phase separation morphology, rheological properties and crystal structure of the elastic masterbatch are investigated. The results show that a compatible and stable structure is obtained in molten SEBS and PP blend with excellent mobility in the temperature range of 210–230°C. The crystallization of PP slows down resulting in a finer structure due to the restriction of the SEBS network structure with rarely change of crystalline structure. The relationship between process parameters and properties of the elastic nonwoven is also studied in detail. Air pressure and die to collector distance (DCD) have discernible effects on fiber diameter and bonding between fibers, further influencing the performances of nonwovens including porosity, tensile strength and elastic recovery. Elastic recovery is shown to be significantly more affected by DCD than by air pressure.     

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     

Numerical computation of the fiber diameter of melt blown nonwovens produced by the inset die

Melt blowing is used commercially as a one‐step process for converting polymer resin directly into a nonwoven mat of microfibers. The inset die is often used to produce polymeric fibers in the melt blowing process. The air jet flow field model for the dual slot inset die is established. The flow field model is solved by using the finite difference method. The numerical computation results of the air velocity distribution coincide with the experimental data. Then the air drawing model of polymers in the melt blowing process established in our previous research is solved with the aid of simulation results of the air jet flow field. The final fiber diameter of the nonwoven fabrics predicted by the air drawing model of polymers tallies with the experimental data. The results show the great potential of this research for the computer assisted design of melt blowing technology and equipment. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

Lyocell熔喷非织造布纤网结构及纤维直径的研究

以纤维素/NMMO/水溶液为原料,制备了Lyocell熔喷非织造布。采用扫描电子显微镜分析了该熔喷纤网的形态结构,并研究了成网方式、气流初始温度及模头温度等对纤维形貌及直径的影响。结果表明,Lyocell熔喷纤网呈三维网状结构,存在"shots"、纤维间的融合与枝化现象,且得到的熔喷Lyocell纤维具有光滑的表面;成网方式和气流初始温度显著地影响熔喷Lyocell纤维的形貌;在一定的温度范围内,提高气流初始温度和模头温度,都能制备更细的熔喷Lyocell纤维。     

Strength properties of melt blown nonwoven webs

A method to obtain the tenacity and Young's modulus of nonwoven webs without direct measurement of web thickness is proposed. This has been tested with several series of samples with different basis weight. It was found that these properties were nearly Independent of the sample gage length, and both tenacity and modulus generally decreased with increase in the die temperature, the air pressure at the die, or the die to collector distance [DCD]. The web stiffness as measured by bending rigidity followed similar trends. The elongation Lo break also decreased as die temperature and air pressure at The die increased, but it increased with increasing DCD. The average filament diameter in the web decreased with increasing die temperature or air pressure at the die. The single filament strength was measured and compared with strength properties of web and of high-speed melt spun filament prepared from the same resins. The strength of single filaments in the web lie in between those of the web and high-speed spun filaments. The mechanical properties of melt blown web were interpreted in terms of the changes in Fiber diameter, the level of interfilament bonding, the molecular orientation developed in the filament, the diameter uniformity along the individual filaments in the web, and the presence of voids in the filament.     

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     

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     

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。     

The effects of processing parameters on the morphology of PLA/PEG melt electrospun fibers

Electrospinning of a polymer melt is an ideal technique to produce highly porous nanofibrous or microfibrous scaffolds appropriate for biomedical applications. In recent decades, melt electrospinning has been known as an eco‐friendly procedure as it eliminates the cytotoxic effects of the solvents used in solution electrospinning. In this work, the effects of spinning conditions such as temperature, applied voltage, nozzle to collector distance and collector type as well as polyethylene glycol (PEG) concentration on the diameter of melt electrospun polylactic acid (PLA)/PEG fibers were studied. The thermal stability of PLA/PEG blends was monitored through TGA and rheometry. Morphological investigations were carried out via optical and scanning electron microscopy. Based on the results, blends were almost stable over the temperature range of melt electrospinning (170 ? 230 °C) and a short spinning time of 5 min. To obtain non‐woven meshes with uniform fiber morphologies, experimental parameters were optimized using ANOVA. While increasing the temperature, applied voltage and PEG content resulted in thinner fibers, PEG concentration was the most influential factor on the fiber diameter. In addition, a nozzle to collector distance of 10 cm was found to be the most suitable for preparing uniform non‐woven PLA/PEG meshes. At higher PEG concentrations, alterations in the collector distance did not affect the uniformity of fibers, although at lower distances vigorous bending instabilities due to polarity augmentation and viscosity reduction resulted in curly fibrous meshes. Finally, the finest and submicron scale fibers were obtained through melt electrospinning of PLA/PEG (70/30) blend collected on a metallic frame. © 2017 Society of Chemical Industry     

Physical and thermal characterization of polylactic acid meltblown nonwovens

A series of polylactic acid (PLA) nonwovens were prepared by the melt blowing process using micro and nano dies. The nonwovens were characterized for structural, thermal, and mechanical properties. These properties varied with the type of die, airflow, and die to collector distance (DCD). The mean pore size for PLA microfiber ranged between 1.82 and 10.48 micrometers, and nanofiber nonwovens ranged between 452 and 818 nanometers. The tensile modulus and strength of PLA nonwovens increased with airflow at a given DCD, but decreased with increased DCD for a given airflow. Thermograms from calorimetry showed microfiber mats had a larger composition of beta‐form crystals than the nanofiber mats. The results showed that a wide range of nonwovens can easily be generated with properties tailored to the specific application. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40593.