2 edition of study of the extensional flow behaviour of low density polyethylenes found in the catalog.
study of the extensional flow behaviour of low density polyethylenes
D. G. Smoker
Written in English
Thesis(Ph.D.) - Loughborough University of Technology 1984.
|Statement||by D.G. Smoker.|
If extensional flow properties are poor due to too strong plasticization, reduced foam extrusion behavior of the polymer can be the consequence. Therefore, when discussing the suitability of CA for foam extrusion it is necessary to investigate the influence of plasticizer on thermal and rheological properties, especially on extensional flow. A high‐pressure, nitrogen‐driven capillary viscometer has been used to study the extrusion flow properties of polyethylene samples which differed in molecular weight, molecular weight distribution and density.
The melt fracture phenomena of three linear low-density polyethylenes are investigated as a function of die geometry (capillary, slit, and annular) and molecular weight and its distribution. The onset of melt fracture instabilities is determined by using capillary rheometry, mainly studying the extrudate appearance using optical microscopy. This study focuses on some recent experimental results on the effects of the addition of glass beads to the linear and non‐linear rheology, and hence melt processability, of two commercial shear‐matched polyethylenes: an LDPE which shows strong strain hardening in elongational flow and an HDPE which does not. The beads were coated with a commercial coupling agent prior to blending .
Low-density polyethylenes (LDPE) were synthesized in a laboratory-scale autoclave under high pressure. These samples were found to possess a high molar mass tail, resulting in a distinctly bimodal molar mass distribution and a lower concentration of long-chain branching than typical of commercial LDPEs. Rheological experiments in elongation showed that these samples exhibit a . The remaining two resins are deemed controls and include a highly branched low-density polyethylene and a linear low-density polyethylene. Together, the effects of long-chain branching are considered with respect to the shear and extensional rheological properties, the melt fracture behavior, and the ability to accurately predict the flow.
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(i) SYNOPSIS Extensional flow is an important component of the major commercial polymer shaping operations. In processes such as fibre spinning and film blowing, it is believed to. This study focus on the rheological behaviour of polyethylene polymer. The effect of molecular weight for three different types of polyethylene were study; high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and low density polyethylene (LDPE).
To find the rheological behaviour of the polymer, melt flow indexer and capillary rheometer was : Raza Muhammad Khan, Asim Mushtaq, Amina Israr, Asra Nafees. A study of the extensional flow behaviour of low density polyethylenes Author: Smoker, David G.
ISNI: Several commercial low density polyethylene resins have been studied using the Extensional Rheometer. The polyethylene grades were chosen to provide a range of melt flow indices, processing behaviour and molecular characteristics Cited by: 3.
The nonlinear rheology of three selected commercial low-density polyethylenes (LDPE) is measured in uniaxial extensional flow. The measurements are performed using three different devices.
A study of the extensional flow behaviour of low density polyethylenes. Extensional flow theory is as\ud well advanced as that for shear flow. However, it is\ud only in the last 15 years that instruments capable of\ud measuring extensional flow characteristics have been\ud developed by various workers.
Several commercial low density Author: David G. Smoker. and linear low density polyethylenes. At a second critical used to study the role of extensional melt flow in An experimental investigation of the surface melt fracture behavior of linear. Two linear low density polyethylenes (LLDPE) with a different melt flow index (MI) are selected to blend with a low density polyethylene (LDPE) in molten state by means of a screw extruder.
The flow behaviour of the blend melts is studied by using capillary rheometry under rear practical processing conditions.
To enable this study to be performed, a series of four very low‐density polyethylenes (VLDPEs) (film and blow molding grades) with different parameters of molecular weight (M W), molecular weight distribution (MWD), and degree of long‐chain branching (LCB) will be used. Experiments in shear flow (steady state and oscillatory regime) are.
This paper describes a comprehensive experimental study of the extrudate swell behavior of high-density (HDPE) and linear low-density polyethylenes.
The contributions from bulk melt elasticity, entry extensional flow, and exit boundary discontinuity are each explicitly investigated as a function of molecular weight and its distribution.
The elusive apparent molecular weight dependence of the. The nonlinear rheology of three selected commercial low-density polyethylenes (LDPE) is measured in uniaxial extensional flow.
The measurements are performed using three different devices including an extensional viscosity fixture (EVF), a homemade filament stretching rheometer (DTU-FSR) and a commercial filament stretching rheometer (VADER).
The flow curves of linear (linear-low and high density) and branched polyethylenes are known to differ significantly. At increasing shear rates, the linear polymers exhibit a surface melt fracture. Two such linear low-density polyethylenes were studied by using both constant-stress and capillary rheometry, in order to assess their rheological and processing behavior, as well as to identify.
The elongational behavior of two polyethylenes with different structures, namely, a low-density polyethylene and a linear low-density polyethylene, has been investigated by isothermal melt spinning.
The influence of sparse long-chain branching and molecular weight distribution on the melt fracture behavior of polyethylene melts was investigated. Four commercial polyethylene resins were employed for this study: a conventional low-density polyethylene, a conventional linear low-density polyethylene, a linear metallocene polyethylene, and a sparsely branched metallocene polyethylene.
Stress-optical measurements at a flow stagnation point in confined geometries such as the cross-slot provide an elegant way to perform extensional testing for polymer melts.
This technique is especially useful for samples which have a steady-state that cannot be reached (easily) in standard elongational rheometry, for example, highly branched polymers which show a non-homogeneous. The transient uniaxial elongational viscosity for binary blends composed of polypropylene (PP) and low-density polyethylene (LDPE) was evaluated.
A strain hardening behavior. Abstract. The flow curves of linear (linear-low and high density) and branched polyethylenes are known to differ significantly. At increasing shear rates, the linear polymers exhibit a surface melt fracture or sharkskin region that is followed by an unstable oscillating or stick-slip flow regime when a constant piston speed capillary rheometer is used.
The main aim of this work is to study the flow, failure, and rupture dynamics of a benchmark low-density polyethylene (BASF Lupolen H) in true tensile creep conditions in both the viscoelastic and elastic deformation regimes. For this, we used a novel extensional rheometer that for the first time allows real controlled-stress conditions to be applied to the materials (as opposed to.
Results of an industrial case study on measurements of the low strain rate extensional flow properties of polyethylene materials using the NPL extensional rheometer and a modified melt flow rate instrument. () Measuring the extensional flow behaviour of polyethylenes for plastics processing.
NPL Report. MATC(MN)27 Text MATC_MNpdf. 4. Rheological testing and determination of materials functions Flow curves. Experimental flow curves, with values of the pressure applied versus the mass flow rate, have been obtained for polyethylenes PE1 and PE2 in a Modular Flow Indexer CEAST at a temperature of °C, using different loads between 2 and 40 kg, and a die with a capillary ratio of ( mm of.
Low concentrations of peroxide generate materials with flow activation energies similar to that of low-density polyethylenes.
The peroxide modification process produce changes in the molecular structure of linear polyethylene that is mainly reflected in the slow relaxation processes, i.e. the large-scale molecular structure.Megan Heitkemper, Lakshmi Prasad Dasi, in Principles of Heart Valve Engineering, Linear low-density polyethylene.
Linear low-density polyethylene (LLDPE) is a hydrophillic polymer with a high tensile and tear strength and relatively low bending stiffness [61,62].An interpenetrating network (IPN) between hyaluronan (HA) and LLDPE has been shown to increase the material strength.
This paper explores shear and extensional rheological behavior of unimodal, metallocene-catalyzed polyethylenes with low contents of long-chain branching (LCB).
The polymers were produced in semibatch slurry polymerizations with methylaluminoxane (MAO) activated metallocene catalysts bis(n-butylcyclopentadienyl)hafnium dichloride (1), rac-[ethylenebis(2-tert .