SPE Library
The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
The SPE Library is just one of the great benefits of being an SPE member! Are you taking advantage of all of your SPE Benefits?
Not an SPE member? Join today!
| = Members Only |
|
Categories
|
Rheology
SPE Library content related to rheology
EFFECTS OF LONG-CHAIN BRANCHING CONCENTRATION OF SUPERCRITICAL CO2 AND PRESSURE ON THE VISCOSITY OF LINEAR AND BRANCHED POLYPROPYLENES
Supercritical carbon dioxide (CO2) is of interest as a physical blowing agent in the manufacture of plastic foam and as a plasticizer to reduce melt viscosity during processing. The combined effects of concentration (C) of dissolved CO2 pressure (P) and temperature (T) on the rheological properties of the melt were determined to achieve optimum processing conditions. Linear and branched polypropylenes and their blends were chosen. A high-pressure sliding plate rheometer in which the shear deformation T P and C are all uniform was used. It was possible to use shift factors for T P and C to obtain a master curve.
STRACTURE AND INTERFACIAL ADHESION OF PP/PBS SANDWICH INJECTION MOLDINGS
Polypropylene (PP) based sandwich injection moldings with biomass based polymers (PBS) in the core were studied. In order to obtain superior surface properties such as high chemical resistance and anti-scratch resistnce improvement of interfacial strength between skin and core parts is important which can be controlled by the additional PP component in the PBS core part. The selection of additional PP and injection conditions were found to be important to improve the interfacial strength of which phenomena was understood by the melt rheology at the injection condition.Scratch tests according to ASTM method was performed to investigate the relationship between scratch behavior and skin/core adhesion. Poor skin/core adhesion caused the skin/core delamination upon the scratch tests.
STRACTURE AND INTERFACIAL ADHESION
OF PP/PBS SANDWICH INJECTION MOLDINGS
Polypropylene (PP) based sandwich injection
moldings with biomass based polymers (PBS) in the core
were studied. In order to obtain superior surface
properties such as high chemical resistance and
anti-scratch resistnce, improvement of interfacial strength
between skin and core parts is important, which can be
controlled by the additional PP component in the PBS
core part. The selection of additional PP and injection
conditions were found to be important to improve the
interfacial strength, of which phenomena was understood
by the melt rheology at the injection condition.
Scratch tests according to ASTM method was
performed to investigate the relationship between scratch
behavior and skin/core adhesion. Poor skin/core adhesion
caused the skin/core delamination upon the scratch tests.
RHEOLOGICAL PROPETIES OF BRANCHED POLYSTYRENE PREPARED BY AN ULTRASOUND ASSISTED INTENSIVE MIXER
By combining ultrasonic energy which can cause chain scission of polymer molecules and a multifunctional agent (MFA) having double bonds at its ends we were able to modify the molecular structure of polystyrene (PS) from linear to a branched structure during melt processing. The three double bonds in chain ends of MFA were expected to act as sites for trapping macroradicals of PS during the course of ultrasound- assisted mixing process. The transformation of molecular structure of PS was confirmed by the measurements of rheological properties of the modified PS. After the ultrasonic irradiation of PS together with MFA increase in complex viscosities and shear-thinning behavior were observed. The Cole-Cole plot revealed the characteristic features of branched structure.
HOW CAN POLYMER RHEOLOGY BE USEFUL TO GUIDE PROCESSING
This presentation discusses the latest developments in
the field of nonlinear rheology of entangled polymeric
liquids resulting from nearly two dozens of publications
from the Polymer Dynamics Interface and Rheology
Group at Akron. The essential findings are that a)
entangled liquids respond to sudden startup flow
elastically and undergo cohesive failure or yielding before
subsequent flow is possible b) the flow field beyond the
yield point is dictated by the characteristics of the yielding
process that can be strongly inhomogeneous c) entangled
liquids possess finite cohesion that can be overcome after
flow cessation by internal elastic restoring forces.
HOW CAN POLYMER RHEOLOGY BE USEFUL TO GUIDE PROCESSING
This presentation discusses the latest developments in the field of nonlinear rheology of entangled polymeric liquids, resulting from nearly two dozens of publications from the Polymer Dynamics, Interface and Rheology Group at Akron. The essential findings are that a) entangled liquids respond to sudden startup flow elastically and undergo cohesive failure or yielding before subsequent flow is possible, b) the flow field beyond the yield point is dictated by the characteristics of the yielding process that can be strongly inhomogeneous, c) entangled liquids possess finite cohesion that can be overcome after flow cessation by internal elastic restoring forces.
RELATIONSHIP BETWEEN STRUCTURE AND RHEOLOGICAL
PROPERTIES IN POLYMER/LAYERED SILICATE
NANOCOMPOSITES
Poly[butylenes succinate-co-adipate] (PBSA)
layered silicate nanocomposite was prepared by
melt extrusion of PBSA and organically
modified montmorillonite (OMMT).
Nanocomposites were prepared at a single clay
loading. Before taking rheological
measurements the nanocomposites were
characterized by X-ray diffraction (XRD) and
transmission electron microscopy (TEM). Stress
growth experiments were performed for both
pure polymer and nanocomposite. Flow reversal
experiments were conducted for
nanocomposites at different predetermined rest
time after cessation of forward flow. The
orientation state of silicate layers were also
investigated by cooling down the sample in the
rheometer before and after the forward flow and
then by performing X-ray in the transmission
mode.
RELATIONSHIP BETWEEN STRUCTURE AND RHEOLOGICAL PROPERTIES IN POLYMER/LAYERED SILICATE NANOCOMPOSITES
Poly[butylenes succinate-co-adipate] (PBSA) layered silicate nanocomposite was prepared by melt extrusion of PBSA and organically modified montmorillonite (OMMT). Nanocomposites were prepared at a single clay loading. Before taking rheological measurements, the nanocomposites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Stress growth experiments were performed for both pure polymer and nanocomposite. Flow reversal experiments were conducted for nanocomposites at different predetermined rest time after cessation of forward flow. The orientation state of silicate layers were also investigated by cooling down the sample in the rheometer before and after the forward flow and then by performing X-ray in the transmission mode.
HIGH-PERFORMANCE-TIE-LAYER RESINS IN FLEXIBLE PACKAGING APPLICATIONS: STRUCTURE–PERFORMANCE RELATIONSHIPS
Interlayer adhesion between tie and barrier layers in
blown and cast film plays a major role in determining the
performance of tie layer resins in barrier applications. In
general tie-layer adhesion increases and film clarity
decreases with increased maleic anhydride functionality
(MAF). The tie resin employed for this investigation
showed reduced adhesion to EVOH even with increased
MAF. Understanding such unusual behavior is an
important aspect of the structure of tie-layer resins to be
used in industrial barrier packaging applications. We
investigated structural factors of the tie resins using
rheological measurements. It was found that dynamic
shear rheological data does not provide useful information
to understand tie layer performance. However extensional
rheological data showed useful information to understand
tie resin performance. The strain-hardening behavior of
the tie-layer resin during the melt extensional process
plays a major role in determining the interfacial adhesion
between tie and EVOH layers and clarity regardless of a
given range of MAF levels.
HIGH-PERFORMANCE TIE LAYER RESINS IN FLEXIBLE PACKAGING APPLICATIONS: STRUCTURE-PEROFRMANCE RELATIONSHIPS
Interlayer adhesion between tie and barrier layers in blown and cast film plays a major role in determining the performance of tie layer resins in barrier applications. In general, tie-layer adhesion increases and film clarity decreases with increased maleic anhydride functionality (MAF). The tie resin employed for this investigation showed reduced adhesion to EVOH even with increased MAF. Understanding such unusual behavior is an important aspect of the structure of tie-layer resins to be used in industrial barrier packaging applications. We investigated structural factors of the tie resins using rheological measurements. It was found that dynamic shear rheological data does not provide useful information to understand tie layer performance. However, extensional rheological data showed useful information to understand tie resin performance. The strain-hardening behavior of the tie-layer resin during the melt extensional process plays a major role in determining the interfacial adhesion between tie and EVOH layers and clarity, regardless of a given range of MAF levels.
POLYMER-POLYMER INTERFACIAL SLIP MEASUREMENTS IN MULTILAYERED FILM
Significant slip can occur during flow of twoimmiscible polymers due to reduced entanglements at theirinterface. The slip is of practical importance because of itseffect on morphology and adhesion of these multi-phasematerials such as disordered two-phase blends andmultilayer films. Using rheological technique we studiedthe interfacial slip in co-extruded multilayer films. Theviscosity drop of a multilayer sample below the averageviscosity of two neat components was observed for bothpolypropylene/polystyrene and polyethylene/fluoropolymer systems indicating interfacial slip.Furthermore the viscosity drop of a multilayer sampleincreased with the number of layers.
POLYMER-POLYMER INTERFACIAL SLIP MEASUREMENTS
IN MULTILAYERED FILM
Significant slip can occur during flow of two
immiscible polymers due to reduced entanglements at their
interface. The slip is of practical importance because of its
effect on morphology and adhesion of these multi-phase
materials, such as disordered two-phase blends and
multilayer films. Using rheological technique, we studied
the interfacial slip in co-extruded multilayer films. The
viscosity drop of a multilayer sample below the average
viscosity of two neat components was observed for both
polypropylene/polystyrene and polyethylene
/fluoropolymer systems, indicating interfacial slip.
Furthermore, the viscosity drop of a multilayer sample
increased with the number of layers.
RHEOLOGICAL PROPERTIES OF LONG CHAIN BRANCHED POLYETHYLENE MELTS AT HIGH SHEAR RATE
Capillary extrusion experiments involving a number
of polyethylenes with emphasis on assessing the effect of
long chain branching are performed. None of the
metallocene catalyzed linear low density polyethylenes
(mLLDPE) produced by Dow Chemicals which are
believed to have some level of long chain branching show
temperature dependence on the viscosity at the gross melt
fracture regime. Furthermore these materials do not show
spurt or stick-slip flow in contrast with most linear
polyethylenes. LDPE and blends of LDPE with linear
polyethylenes also show the absence of stick-slip flow but
temperature dependence on the viscosity. From these
observations we conclude that the stick-slip flow is very
sensitive to the existence of long chain branching and the
behavior of the stick-slip flow can be used as an indicator
of LCB.
RHEOLOGICAL PROPERTIES OF LONG CHAIN BRANCHED POLYETHYLENE MELTS AT HIGH SHEAR
Capillary extrusion experiments involving a number of polyethylenes with emphasis on assessing the effect of long chain branching are performed. None of the metallocene catalyzed linear low density polyethylenes (mLLDPE) produced by Dow Chemicals, which are believed to have some level of long chain branching, show temperature dependence on the viscosity at the gross melt fracture regime. Furthermore, these materials do not show spurt or stick-slip flow, in contrast with most linear polyethylenes. LDPE and blends of LDPE with linear polyethylenes also show the absence of stick-slip flow, but temperature dependence on the viscosity. From these observations, we conclude that the stick-slip flow is very sensitive to the existence of long chain branching, and the behavior of the stick-slip flow can be used as an indicator of LCB.
RHEOLOGY AND STRUCTURE OF FILLED PROPYLENE/ETHYLENE COPOLYMERS
We have studied a new family of propylene/ethylene(P/E) copolymers produced by The Dow ChemicalCompany which allow high filler loadings whilemaintaining good processability. Our goal was to providea fundamental understanding of the unexpectedly lowviscosity exhibited by these materials when filled withparticulates. We propose that in these copolymers interfacial slip (between the particles and the polymermelt) is enhanced by the presence of a thin layer of lowviscosity polymer around the particles. The formation ofthis layer is surface tension driven and can occur insystems such as these copolymers which are homogeneousin the bulk. Such behaviour has been observed with blockcopolymersand blends; this study is the first time it hasbeen observed in an industrial copolymer of this type.
Differentiated Compression Molding: A New Process Innovation Creates Dramatic Cost Savings & Product Improvements for Compression-Molded Applications
Long glass fibre thermoplastics (LGFT) used in compression moulded applications has grown dramatically due to metal replacement by composites and the derived benefits in both cost and weight savings. In order to make thin walled parts from higher viscosity thermoplastic materials as opposed to thermosetting resins machine producers have been challenged in terms of clamp size and tooling. In this paper a revolutionary new process called differentiated compression moulding (DCM) is described and compared with traditional compression moulding. Using new tool designs the process allows for reductions in press sizes of up to 70%. This in turn allows for significant cost savings in machine investment tooling and energy consumption. Larger projected areas and thinner walled investment tooling and energy consumption. Larger projected areas and thinner walled parts can be made on smaller machines. The paper discusses the physics and rheological conditions that allow for this innovation and a test case is compared to current technology.
Modeling and Simulation of the Complex Flows in the Extrusion Process of Plastic Profile with Metal Insert
The extrusion technology of plastic profile with metal insert is recently an advanced plastic processing method. However, its mechanism research work is lagging behind. In this paper, we developed the mathematical model of the extrusion process and simulated the three-dimensional complex flows in the extrusion die by the finite element method based on the CFD theory. The change of the melt rheological properties versus different processing conditions was investigated and some practicable advice on the process operation was accordingly put forward.
Continuous Ultrasonic Process for Preparation of PET/LCP Blends
Wholly aromatic polyester, LCP, was blended with PET to produce self-reinforced composites using an ultrasonically assisted single screw compounding extruder. Ultrasonic intensity was varied to induce in-situ compatibilization in the blends and was found to decrease pressure, and affect morphological, rheological and mechanical properties. PET and LCP homopolymerization, as well as their copolymerization through possible esterification/ transesterification reactions leading to an increase in their viscosities and mechanical properties was observed in the melt state under certain conditions.
Physics of Amorphous Polymers
Amorphous polymers are of continuing great fundamental and practical interest. From the melt state through the glass transition these materials exhibit highly nonlinear properties that are readily interrogated using methods of both linear and nonlinear rheology and mechanics. Here we examine several novel methods developed by the author to investigate swelling in rubber, nonlinear behavior of polymer glasses and the behavior of materials at the nanoscale
Determining the Processability of Multilayer Coextruded Structures
Multilayer coextrusion is a process in which two or more polymers are extruded and joined together in a feedblock or die to form a single structure with multiple layers. This paper will discuss techniques for measuring experimental rheology data for monolayer and multilayer structures and how that data can be used for determining the processability of multilayer coextruded structures.
|
This item is only available to members
Click here to log in
If you are not currently a member,
you can click here to fill out a member
application.
We're sorry, but your current web site security status does not grant you access to the resource you are attempting to view.
.jpg)
.jpg)
.jpg)
.jpg)
