Accurate determination of a deformation measure in the screw extrusion process

It is important to evaluate the deformation process accurately in analyzing mixing in extrusion. This paper discusses numerical methods to determine a representative deformation measure over the entire cross-section of the extruder channel accurately and efficiently. Two different numerical methods are introduced to determine a deformation measure over the entire cross-section of the extruder channel efficiently: (i) the first method based on the mapping sequence of the deformation gradient tensor; and (ii) the second method which does not require the evaluation of velocity gradient fields. These two methods are applied to the extrusion process of a single-screw extruder and are compared with respect to their numerical accuracy. It is found that trajectories of fluid particles are difficult to obtain especially near the screw flight and barrel surface, which causes numerical inaccuracies with respect to obtaining a deformation measure. In this paper an inverse mapping method is employed to overcome such a numerical problem. For computational efficiency and accuracy, the second method was found to be more powerful compared with the first one, especially when there are singular points as in an extruder channel.     

双组分纤维的开发及应用

介绍部分双组分纤维的主要产品、技术特点、产品风格及商业化应用实例。     

Mixing selectivity in bicomponent,bipolar aggregation

The selectivity of aggregation in mixtures of two charged aerosols containing chemically dissimilar nanoparticles is studied by means of a newly developed direct simulation Monte Carlo method. This method allows to trace changes in complex multidimensional systems, in this case describing particle size, charge and aggregate composition. A new procedure was developed for estimating the effective collision diameter of an aggregate composed of primary particles of any size. Three model systems were studied: polydisperse aerosols with initially bipolar charge distribution, unipolarly charged polydisperse aerosols and quasi-monodisperse oppositely charged aerosols. The study is focused on the aggregate composition's dependence on the initial size and charge distribution. It was found that the use of bipolarly charged aerosols does not increase the selectivity of mixing whereas unipolarly, oppositely charged aerosols reach more rapidly a more homogeneous distribution of components within the aggregates. In the last case, the addition of one more elementary charge to the particles roughly doubles the fraction of bicomponent, $\text{1}\text{:}\text{1}$ mixed nanoaggregates and accelerates the process.     

Preferential wetting phenomenon in bicomponent polymer melt flow

For two polymer melts spun in a side-by-side configuration through a capillary, interface shape and spinneret exit angle data are presented as a function of viscosity ratio, spinneret dimensions, and relative polymer-steel wettability. Nylon-nylon versus nylon-polyurethane bicomponent flow systems are compared. A surface tension phenomenon is postulated to be significant in controlling the bicomponent fiber interface shape for capillary length-to-diameter ratios of the order of unity.     

Microphotometric inline determination of polymer blend morphologies during extrusion processing

A novel inline method using microphotometric measuring principle is able to determine mean particle sizes of polymer blends directly during extrusion processing. This process‐micro‐photometer (PMP) is adapted on a special slit die at the extruder head. Refractive indices needed for particle size calculation have been measured by an inline refractometer for all the involved polymers at molten state. For investigation, blends have been made from polystyrene (PS), polypropylene (PP), polyamide (PA6), and polymethylmethacrylate (PMMA); and the resulting blend morphologies are found to be smaller than 1 μm in all cases. Sensor calculations show good correlation to microscopic reference measurements. Because of multiple scattering effects at larger particle number concentrations an exact particle size calculation is limited to low volume concentrations of that polymer blends because of the small blend particle sizes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 258–262, 2007     

双组分环氧胶粘剂在我厂的应用

简单介绍了双组分环氧胶粘剂的特点、组成及固化反应机理 ,并且详细叙述了我厂双组分环氧胶粘剂的组分、配制工艺和灌胶工艺以及讨论了双组分环氧胶粘剂在我厂的应用情况 ,为我厂的军品及民用电器产品的灌封胶接提供了广泛的前景     

Piezoelectric polymeric bicomponent fibers produced by melt spinning

Melt spinning of a novel piezoelectric bicomponent fiber, with poly(vinylidene fluoride) as the electroactive sheath component, has been demonstrated. An electrically conductive compound of carbon black (CB) and high density polyethylene was used as core material, working as an inner electrode. A force sensor consisting of a number of fibers embedded in a soft CB/polyolefin elastomer matrix was manufactured for characterization. The fibers showed a clear piezoelectric effect, with a voltage output (peak‐to‐peak) of up to 40 mV under lateral compression. This continuous all‐polymer piezoelectric fiber introduces new possibilities toward minimal single fiber sensors as well as large area sensors produced in standard industrial weaving machines. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

皮芯复合纤维及其成形理论

主要介绍了复合纤维及皮芯复合纤维的概况,纤维成形及皮芯复合纤维成形理论的研究及最新进展。介绍了模拟成形所采用的模型和方法。     

The fine structure of bicomponent polyester fibers

The application of alkaline hydrolysis to study the change in the fine structure of bicomponent polyester fibers as their surface is removed progressively was explored. The samples were prepared with a poly(butylene terephthalate) (PBT) sheath and a poly(ethylene terephthalate) (PET) core. The reagent used to hydrolyze the PBT was 1M NaOH in 75/25 methanol to water since it appeared to react topochemically with the fiber. The solution reacted more rapidly with PET than with PBT. Thus, when necessary to retard the weight loss of the bicomponent fibers, after a 2‐h hydrolysis with this reagent to remove PBT, it was replaced with aqueous 1M NaOH solution containing 0.1% cetrimmonium bromide. Unlike homofil PET or PBT fibers, where alkaline attack appeared to be confined to the surface and left the residue relatively smooth, the bicomponent fiber was attacked unevenly, and penetration to the PET core occurred before all the PBT at the surface was removed. Nevertheless, most of the reaction was confined initially to the PBT sheath. The tenacity and extension at break of the PBT–PET fiber passed through a maximum as hydrolysis progressed. The fall in tenacity at high weight losses is ascribed to increasing surface defects in the fiber surface. After removal of the PBT by the hydrolysis, the birefringence of the residue became progressively higher. The synergistic effect of the PBT sheath on the properties of the PET core and the possible causes of the nonuniform hydrolysis at the PBT surface are discussed. An equation is proposed that includes an interaction parameter, which can be utilized to determine which property is affected most by the hydrolysis of a bicomponent fiber. In this instance, it appears from the parameters that the order is strength > extension at break ≈ birefringence. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1163–1173, 1999     

流变剪切粘度测量不确定度的评定

建立了热塑性塑料毛细管挤出流变试验中测量剪切粘度的数学模型,根据模型分析其测量不确定度的来源,并以高密度聚乙烯为例分别计算各分量的标准不确定度,以及合成标准不确定度和扩展不确定度,最终报告出不同剪切速率下的剪切粘度的相对扩展不确定度以及扩展不确定度。     

Attenuating PP/PET bicomponent melt blown microfibers

This research investigated the attenuation of polypropylene (PP)/poly(ethylene terephthalate) (PET) bicomponent (bico) filaments during the melt blowing (MB) process. It was found that both mono‐ and bi‐component filaments attenuated from several hundred micrometers to a few micrometers in the first 5 centimeters from the die. However, fiber diameter distributions were found to be broad in these regions. The filaments were attenuated much slower but exhibited narrower diameter distributions as they moved further from the die. The diameters of bico MB filaments were between those of 100% PP and 100% PET filaments. The PET component in a bico filament controls the final fiber diameter. During melt blowing, filaments were aligned orderly with the airflow direction in a short distance near the die. Filament entanglements started at about 2.5 cm from the die and became more and more randomly oriented as the distance‐from‐the‐die (DFD) increased. The fiber diameter distribution of bico filaments was broader than that of 100% PP filaments. A higher airflow rate led to a narrower fiber size distribution for bico filaments.     

Fabrication of segmented cladding fiber by bicomponent spinning

Fabrication of segmented cladding fiber (SCF) by bicomponent spinning was proposed in this article. In the new designed spin pack, we considered the high refractive component of cladding and core as a whole to control the cross section of the fiber. Quenching system in current bicomponent melting spinning system was modified according to the requirement of quenching fiber with a large size. The polymer SCF with required cross section was successfully fabricated using polycarbonate and polymethyl methacrylate. The transmission loss in the wavelength of 500–1000 nm was tested by the cut‐back method. The result showed that the transmission loss of the obtained fiber was comparatively high, being up to 30 dB/m. The output light pattern of the obtained fiber of 60 cm was collected by using a charge‐coupled device camera with laser light of 532 nm as the input. The output light pattern for the far field was a uniform circle and that for the near field was similar to the cross‐section designed. The results showed that the obtained fiber was still a multimode optical fiber because of the comparatively large refractive index difference between the two materials used. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

双组分聚酯纤维技术和产品应用进展

综述了赋予双组分聚酯纤维热熔黏、水溶性、卷曲弹性、超细纳米化、功能化等性能的皮芯复合纺丝、海岛复合纺丝、并列复合纺丝及裂片复合纺丝技术.指出双组分聚酯纤维在"用即弃"非织造布和耐久性合成革非织造布领域的应用将进一步增长,在传统和功能性纺织品领域保持一定市场份额,在技术纺织品领域中承担了重要角色,其发展空间值得期待.在光...     

Application of ultrasound in the determination of fundamental extrusion performance: Residence time distribution measurement

By means of new probe design and rapid data acquisition, we have succeeded in in‐line ultrasonic monitoring of residence time distribution (RTD) at the melting, mixing, and pumping zones as well as at the die exit of a Werner & Pfleiderer 30‐mm twin‐screw extruder by mounting the ultrasonic probes on the extruder barrel over the screw elements and at the die. The experimental systems were LDPE, CaCO₃‐filled LDPE, and a Kraton/LDPE blend. The ultrasonic data at each of the extruder functional zones are presented. The ultrasonic results have been used to evaluate an opical RTD measurement method by using an optical sensor side by side with one ultrasonic probe at the mixing zone of the extruder. The comparison of the ultrasonic and optical results has shown that the presented ultrasonic technique could be a good complement to the optical technique in the monitoring and understanding of RTD during polymer extrusion processes.     

双组分纤维用HDPE 1508S的开发

以乙烯为主要原料,1-丁烯为共聚单体,氢气为相对分子质量调节剂,己烷为溶剂,在齐格勒-纳塔型高效催化剂作用下,按一定的工艺条件进行淤浆聚合,并按特定的配方添加专用助剂,生产出双组分纤维用高密度聚乙烯1508S,满足国内市场需求。     

复合超细纤维的开发与发展

阐述了复合超细纤维的生产工艺、性能和应用 ,介绍了复合超细纤维的发展历程和开发现状及我国复合超细纤维的生产状况 ,并指出发展我国复合超细纤维应注意逐步完善国有技术 ,提高产品开发能力 ,形成一条龙开发