2 edition of Normal stress differences and die-swell phenomena in polymer melts. found in the catalog.
Normal stress differences and die-swell phenomena in polymer melts.
Peter James Daniels
Written in English
|The Physical Object|
|Number of Pages||96|
Measurable normal stress differences, 1 oo[[ \\normal stress differences. The first and second normal stress differences are material dependent and are defined by 17 [[ \\ [\ oo saaPolymer Melts 1 The yield normal stress Henri de Cagny1, Mina Fazilati1, Mehdi Habibi1,2, Morton M. Denn3, Daniel Bonn1 1 Institute of Physics, University of Amsterdam, Science Park , XH Amsterdam, The Netherlands 2 Laboratory of Physics and Physical Chemistry of Foods, Wageningen University, WG Wageningen, The Netherlands 3 Benjamin Levich Institute and Department of
The measured normal stress difference correlates well with the parison swell - a difference in long chain branching or a small amount of high molecular weight component may be the origin. Due to the increased die swell, the parison is thicker, therefore the increased weight of the › 百度文库 › 行业资料. so called normal stress differences which are the landmark of vis-coelasticity. Despite this accepted view, the devil is in the details and although considerable effort has been carried out since the middle of the last century (see e.g. Refs.1 for historic details) accurate modelling of polymer melts is
where N1 and N2 are the first and second normal stress differences, respectively. Note that θ is not zero for polymer melts, and its usual range is between – and – . The materials considered for simulation in the present co-extrusion system are a high-density polyethylene melt (HDPE-E manufactured by the Korea Constitutive equations for polymer melts and solutions Ronald Larson. Categories: normal stress convected edwards rheol integral rates melts extensional dependence Post a Review You can write a book review and share your experiences. Other readers will always be interested in your opinion of
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In this paper we determine the ability to obtain values of the first normal stress difference, N 1, at relative high shear rates (– s −1) in a slit-die for several polymer melts of varying degrees of fluid elasticity using hole pressure data and the Higashitani–Pritchard–Baird (PHB) te measurements of the hole pressure, P h, which is defined as the difference A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the :// Polymer melts and solutions exhibit an increase in cross-sectional area whenever they emerge from dies or conduits.
Four mechanisms are considered to be responsible for this phenomenon: Newtonian Carbon nanotubes have great potential as polymer additives, but they are difficult to process.
A mixture of nanotubes in a polypropylene melt exhibits enhanced electrical conductivity and an A significant feature of the Leonov model is the capability to describe basic features of the non-linear viscoelastic behavior of polymer melts, i.e. shear thinning, first and especially second normal stress differences, only with the relaxation spectrum, contrary to other differential models (e.g.
Giesekus, PTT, Larson, XPP).On the other hand, the Leonov model’s inability to represent liquids the normal stresses (pressure) are isotropic even in ﬂow, whereas polymeric liquids, upon application of shear ﬂow, begin to develop nor mal stress differences between the ﬂow (τxx) and ﬂow-gradient directions (τyy).
Extrudate or Die Swell This phenomenon is observed when polymeric melts are extruded through a die. The~compflu/Lect-notes/ The vast majority of previous work on extrudate swell directly addresses systems of industrial complexity.
Commercial polydisperse, crystalline, polymer melts in nonisothermal extrusion exhibit swelling strongly controlled by crystallization [1 nti, V.
K., M. Derakhshandeh, M. Ebrahimi, E. Mitsoulis, and S. Hatzikiriakos, “ Non-isothermal extrudate swell,” Phys. Fluids 28 The true shear stress at the wall is discussed. The theoretical result suggests that Bagley's formula holds even if the exit pressure is not negligible in capillary flow of polymer melts.
The importance is emphasized of distinguishing the pressure in the axial direction (driving pressure) from that in the radial direction in cases of flow where primary and secondary normal stress differences such phenomena as die swell.
Low shear Figure 3: Molecular weight distribution differences in polymer melts are easily detected by measuring the complex viscosity η* as a function elasticity of the polymer melts which shows in the normal stress difference and the storage typical of polymer melts is frequently addressed by presenting the storage modu-lus from dynamic-mechanical experiments and the normal stress difference from stressing experiments.
However, these quantities are determined by viscous and elastic properties, and the elastic behavior has to be extracted from them.
This These fluids exhibit a wide variety of flow behaviors, including shear-rate dependent viscosity, non-zero normal stress differences (leading to rod-climbing effects, die swell, etc.), stress overshoot in a start-up of a shear flow, fluid recoils, large elongational viscosity, extrudate instabilities, :// Figure 1 First normal stress differences and die swell properties.
a,Generally,when polymer melts are sheared between parallel plates (one stationary,the other moving with velocity v),they develop tensile stresses along the flow direction and compressive stresses in the cross-stream difference of these stresses ~mp/articles/?origin=publication_detail.
Shear viscosity, elongational viscosity, normal stress differences, stress relaxation, and some other measures and rheological phenomena, of relevance to polymer pro- cessing, are discussed.
The most widely used polymer processing technologies of extrusion and The quantified normal stress variation matches well with the parison swell - a variation in long chain branching or a small quantity of high molecular weight component may be the origin. Owing to the increased die swell, the parison is thicker and hence the increased weight of the ://?ArticleID= While the uniaxial elongational viscosity is widely investigated, and its relevance for processing is described in the literature, much less has been published on the recoverable extensional flow of polymer melts.
This paper presents a short overview of the dependencies of the recoverable elongation on the molecular structure of a polymer, and on some experimental :// The normal stress differences can be very large in high-shear-rate extrusion.
authors suggest a variation for the normal stress difference at the wall in the form N1 w = A τb w The stress ratio SR = N1 w 2 τw () Some () can reach a value of 10 or more › 百度文库 › 语言/资格考试.
Rheology and Rheometry Paula Moldenaers Department of Chemical Engineering Katholieke Universiteit Leuven W. De Croyl B Extrudate or Die Swell POLYOXTM(PEO, PEG) Solution Ejected from a syringe Signiﬁcant increased diameter upon exit Also known as Barus Effect Newtonian ﬂuids diameter does not change signiﬁcantly Due to Normal stress differences psidot, Youtube: KcNWLIpv8g P Sunthar (IIT Bombay) Polymer Rheology ComFlu 17 / 44 Cocchini, F., Nobile, MR.
and Acierno, D. () Letter: About negative first normal stress differences in a thermotropic liquid crystalline polymer. Journal of Rheology, 36 (7), – CrossRef Google Scholar the so-called extrudate swell which can be observed while extruding a melt through a die.
Other phenomena reflecting the elasticity of polymers melts are the occurrence of normal stress differences during shearing and the existence of storage moduli and elastic compliances in dynamic-mechanical experiments.
Recovery experiments after. 由于液体上部的压力较低，因此液体产生了沿轴上升的运动（与重力平衡）。 爬杆效应的原因： Die swell (Barus effect) 挤出胀大(Barus效应) Die swell phenomena When a viscoelastic fluid is extruded, it flows from the die and Web view.
Materials. The polymer used in this study was high-density PE (Japan Polyethylene Corporation, Tokyo, Japan, HD) with a relative density ofa It has a higher zero-shear viscosity, larger power law exponent, larger normal stress differences and larger die swell.
In addition the value of the parameter K in the property correlation proposed by Abdel-)\ The Canadian Journal of Chemicul Engineering, Vol. 55, December, Khalik et a1 was 1 for resins 1 and 9 but closer to 2 for resin