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Rheology
SPE Library content related to rheology
Melt Rheology and Processability of Conventional and Metallocene Polyethylenes
Choon K. Chai, May 1999
The melt rheology and film processing behaviours of conventional high pressure-LDPE and LLDPE are compared with both linear and long chain branched (LCB) metallocene polyethylenes. The effects of molecular structure on melt behaviours of these different types of polymers will be discussed in terms of an improved melt strength measurement. Two new parameters: ?(MS)/?P the melt strength pressure derivative and ?(MS)/?(log?), the melt strength shear rate derivative, have been defined.
Product Design with High Value Recyclable Plastic Waste Streams
K.A. Narh, J. Guo, M. Xanthos, U. Yilmazer, V. Tan, May 1999
As part of on-going studies on the manufacturing of re-engineered materials from waste plastic streams, rheological, mechanical and thermal characterization of recyclable plastics from old computer housings and used carpet materials were carried out, with anticipated use in thin-walled products. A combined stress and mold cavity flow analysis has been used to obtain optimum design and process parameters for the anticipated products.
Investigation of the Rheological Properties of Rotomolding Resins
Alvin Spence, May 1999
There are many influential factors and processing variables that can impact the mechanical and aesthetic properties of a rotomolded part. One of the main variables is the resin being processed and its associated rheological properties. The manner by which the polymer powder sinters and fuses together needs to be understood to ensure the correct processing cycle is used to obtain an optimum cured part. The influence of bubbles that form during the sintering phase and the melt index of the material, contribute to the quality of the part being produced.
Extrusion of LLDPE through Polypropylene Coated Dies
Gifford Shearer, Costas Tzoganakis, May 1999
Polypropylene (PP) coated dies were used in an attempt to decrease the die pressure and eliminate surface melt fracture during the extrusion of linear low density polyethylene (LLDPE). The investigated coatings were: controlled-rheology PP, hydrosilylated PP, amorphous PP wax, and maleic anhydride grafted PP. Extrusion stability, die pressure, and extrudate appearance were used to compare the effectiveness of the different coatings.
Prediction of Viscoelastic Behaviour of Thermorheologically Complex Polymeric Materials
Naba K. Dutta, N. Roy Choudhury, Janis Matisons, G.H. Edward, May 1999
A simplified numerical computational technique based on a Gaussian spectral distribution model developed by Dutta and Edward [1] has been used to describe the stress relaxation behavior of polystyrene (PS) and isotactic polypropylene (iPP) over a wide range of, time and temperature. An excellent fit between experimental data and the mathematical model is observed. The method may be applied generally for any linear viscoelastic property and for any polymer.
Difference in Integral Aggregate Structure for Co-Neutralized Carboxylate Ionomers
Brian P. Grady, May 1999
The purpose of this study was to determine the arrangement of atoms inside ionic aggregates for ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers neutralized with a combination of sodium and zinc. Significant qualitative differences were found as a function of sodium:zinc ratio. The implications of the differences in aggregate structure on the rheological behavior of these mixed-cation systems is discussed.
Effects of Lubricants on Processing of Metallocene LLDPE
Joe B. Williams, Kenn S. Geick, May 1999
Fatty acid ester and amide lubricants were evaluated as processing aids in a 1.0 MI film grade mLLDPE. The effect of the lubricants on extruder energy and output of laboratory extruders fitted with a capillary rheology die and with a two inch film die were determined. Additives were found that reduced the amount of extruder energy required to process the mLLDPE. These additives also increased the output of the extruders per unit of extruder energy.
Rheological Properties and Numerical Simulation of S-PVC Formulations in Extrusion Dies
T. Glomsaker, E.L. Hinrichsen, Å. Larsen, P. Thorsteinsen, May 1999
We report effects of formulation and sample preparations on measured rheological properties relevant for constitutive modelling of die flow in PVC extrusion. Numerical simulations are performed in order to separate non-isothermal and viscoelastic effects in the extrusion experiments as well as self-consistency between constitutive models and measurements.
Processing Trends of Metallocene Linear Low Density Polyethylenes and Their Influence on Single Screw Design
K.R. Slusarz, C.A. Ronaghan, J.P. Christiano, May 1999
New families of polyolefin resins using single site catalysis technology, are being produced to enhance resin properties. The changes to the molecular architecture of these resins effect the rheological, thermal, frictional, and elastic properties; all of which play a significant role in screw design. This paper will investigate several polyolefin plastomers and compare them to a conventional linear low density polyethylene (LLDPE) to determine their impact on screw design.
Computing an Injection Fill Speed from a Relative Viscosity Curve
J.R. Wareham, J.D. Ratzlaff, May 1999
On-machine rheology is a methodology of determining the flow characteristics of a material at a given temperature with a specific mold and machine. [5] This methodology can be used to help determine the best injection fill speed to be used for a given material, machine and mold combination. This study presents a mathematical method to obtain an injection fill speed starting point when setting up a new mold, machine and material combination.
Polymer Melt Formation and Densification in Rotational Molding
M. Kontopoulou, E. Takács, J. Vlachopoulos, May 1999
Polymer melt densification, involving particle coalescence followed by the formation and dissolution of bubbles, has been studied in order to evaluate how it is affected by powder properties, chemical structure, thermal properties and rheology. A variety of rotomolding grade resins have been tested, in an effort to understand the mechanisms involved in the melt formation and its subsequent densification.
Effect of Formulation and Processing Conditions on the Viscosity of Masterbatches
Bob Zeller, May 1999
Adding colorants and additives in masterbatches may affect the rheological properties of the resins into which they are mixed, but the extent of this effect has not been fully investigated. This paper reports on a design of experiments (DOE) study of the effect of 3 common colorants, 2 lubricants, a filler, an antioxidant, and 2 processing parameters (melt temperature and screw speed), on the viscosity of a linear low-density polyethylene (LLDPE) masterbatch. The series of experiments determined that only the lubricant and filler had a significant impact on resin rheology.
Improvement of the Simulation of Shrinkage and Warpage by Characterizing the Material Behaviour More Exactly
Peter Niggemeier, Walter Michaeli, May 1999
Caused by the demand on shorter development times for technical products the use of simulation programs for the rheological, thermal and geometrical mould design increases. Up to the present, the prediction of shrinkage and warpage of semi-crystalline polymers is difficult because of the complex material behavior during the crystallization [1-3]. Therefore the influence of the thermal material data und parameters on the prediction of temperature profiles is intensively discussed at the IKV. The cooling rate is also considered in the pvT-behaviour.
Quality Improvement of Foamed Seals for the Automotive Industry
Annette Krusche, Edmund Haberstroh, May 1999
Automotive body seals are becoming increasingly complex. As there is still little knowledge about the manufacturing process, extensive investigations are done to analyze the influence of the rheological behavior of the materials, the parameters of the extrusion process and the foaming/vulcanization on the quality properties of the foamed seals. The evaluation allows a better process understanding which in combination with improved test methods leads to an increased product quality and reduced manufacturing costs.
Linear Viscoelastic Properties of Polymeric Suspensions
Goknur Bayram, Ulku Yilmazer, Nese Orbey, May 1999
Linear viscoelastic properties of a model suspension containing hydroxyl terminated polybutadiene (HTPB) and glass beads with filler concentration up to 30% by volume were investigated by using a Haake parallel disk rheometer. For all the suspensions, it was observed that the rheological properties such as the storage modulus, G', loss modulus, G and complex viscosity ?* increases with the filler content ?. The relaxation spectra was calculated by using G' and G". The relaxation moduli Gi(?i?) decreased with the relaxation time ?i but increased with the filler content ?."
Modeling of Rheological Behavior of Immiscible Polymer Blends Undergoing High Deformation Flows
Mokhtar Aouina, Mosto Bousmina, Robert Guénette, May 1999
Non linear rheology of a mixture of two immiscible viscoelastic fluids undergoing high deformation flow was considered. Using Grmela's approach of compatibility of dynamics with thermodynamics, we derived a set of highly non-linear governing equations that take into account particles breakup, coalescence and the time evolution of the complex interface between the two mixture components. The proposed model recovers previous models such as Doi-Otha, Grmela and Ait-Kadi and Lee and Park models.
Effect of Formulation Variables on Rheology of Rigid PVC
Virginia Odle Hayes, May 1999
The effect of lubricants, impact modifier, and process aid on the processing and physical properties of a rigid PVC compound have been modeled using a Central Composite designed experiment. Capillary rheology was used to evaluate the flow properties of the various formulations in the study. By modeling the rheological properties it is possible to simultaneously optimize flow, extruder conditions, and final part properties.
Rheological Study of Soy Protein-Based PRF Wood Additives
John D. Clay, Bhima Vijayendran, Jan Moon, May 1999
The gelling of soy protein-based PRF wood adhesives is studied. Soy protein isolate, in combination with phenol resorcinol formaldehyde (PRF) resins is useful in the finger joining of lumber. This unique technology has several advantages including an ability to bond green lumber, very rapid set at room temperature, excellent water resistance, and reduced formaldehyde emissions. The goal of this study is to quantify the effect of soy protein hydrolysis conditions and amine functionality on the gelling and ultimate modulus of soy-derived wood adhesives.
A New Generation of Materials for the Calendering Industry
Teresa P. Karjala, Brian W. Walther, Alastair S. Hill, Ronald Wevers, May 1999
While polyvinyl chloride (PVC) has been employed in the calendering industry for many years, other polymers have not been as widely used. Ethylene styrene interpolymers (ESI) demonstrate the requisite rheological properties and thermal stability to be successfully used in the calendering process. Commercial scale validations were performed on ESI based formulations. Examples of the applicability of ESI to calendering are discussed.
Film Casting of a Low Density Polyethylene Melt
Kathleen Canning, Baigui Bian, Albert Co, May 1999
Film casting is one of the major commercial film manufacturing processes. Although various investigators have studied the process, no comprehensive set of data is available. In this study, film casting experiments of a LDPE polymer melt are conducted. The rheological properties of the melt, the film tension, the velocity profile, and the film width profile due to necking in will be presented. The thickness profile of the solidified film and the edge bead profile will also be reported. These experimental data will be useful for process analysis and verification of film casting simulation.


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