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.
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Michelle M. Mok , Soyoung Kim , Wesley R. Burghardt , John M. Torkelson, May 2010
Gradient copolymers have great versatility in terms ofsequence distribution of monomers along the polymerbackbone for control over their level of nanophaseheterogeneity and flow properties. Using a gradientcomposition rather than a block-type distribution, it ispossible to design longer chains which undergonanophase segregation at lower temperatures yet becomemore homogeneous and melt processible at accessibletemperatures. These behaviors are investigated for a rangeof block and gradient architectures using melt rheologyand small-angle x-ray scattering.
The degree of film-width reduction or necking during
film-casting is analyzed for several metallocene-catalyzed
high density polyethylenes HDPE with varying degrees
of sparse long-chain branching LCB. It is found that the
addition of sparse LCB reduces the degree of necking to a
greater degree than broadening the MWD. Analysis of the
uniaxial extensional and dynamic shear rheology with the
pom-pom constitutive model reveals that a distribution of
branches along shorter relaxation time modes is important
in reducing necking at higher drawdown ratios.
The degree of film-width reduction or necking during film-casting is analyzed for several metallocene-catalyzed high density polyethylenes, HDPE, with varying degrees of sparse long-chain branching, LCB. It is found that the addition of sparse LCB reduces the degree of necking to a greater degree than broadening the MWD. Analysis of the uniaxial extensional and dynamic shear rheology with the pom-pom constitutive model reveals that a distribution of branches along shorter relaxation time modes is important in reducing necking at higher drawdown ratios.
Vandita Pai-Paranjape, André Van Zyl, Jan Pleun Lens, Dake Shen, May 2010
Rheology is used to track the phase separation
kinetics of block copolymer solutions during processing
and then modeled using the Avrami equation. Previous
studies dealt explicitly with disorder-order transitions
following shallow temperature quenches. To make this
work applicable to the processing of solution-cast films,
styrenic block copolymers in solvents of varying
selectivity are cast as thin, dilute samples and dried
isothermally so that various constant-concentration
kinetics can be tracked. Rheology proves to be useful in
tracking both rapid and slow kinetics of diblock and
triblock styrenic copolymers in toluene. It is found that
the diblock copolymer undergoes faster ordering than a
triblock copolymer of comparable molecular weight. A
competition between thermodynamic driving forces and
kinetic suppression of the phase separation exists as
concentration changes. AFM images are provided to
confirm the kinetic data and to understand the meaning
of the Avrami exponent values determined for the
different systems studied.
Jaap den Doelder , Teresa Karjala , Mehmet Demirors, May 2010
LDPE product development is accelerated by understanding the relationships between process, structure, rheology, fabrication, and end-use properties. This paper describes the data analysis of a large set of tubular LDPEs.Focus is put on film optics in relation to structure, including fabrication condition effects. It is found that haze, gloss, and clarity are largely independent in the good-optics range. Good optics is found to be related to narrow molecular weight distribution, whereas melt index and density play a secondary role. It is advised to use topology-generating models to further quantify structural features in relation to optics.
This paper covers the development of an innovative composite material together with a specialized process for 3D formed parts made of Wood-Plastic-Composites (WPC) with genuine wooden surface. Special preprocessed veneers are 3D formed and in-mold laminated with polypropylene-based WPC simultaneously. Questions relating to adhesive strength and warpage of the two components and the injection molding of WPC are analysed and discussed. Another key issue is the scientific derivation of the rheological behaviour of WPC, the optimization of the injection molding process for WPC and the analysis of the warpage between the two materials veneer and WPC
Polypropylene impact copolymers are widely used in
automotive applications. They are required to comply
with many criteria. Customers demand high-performance
materials which also exhibit good aesthetical properties.
The challenge is to balance properties as high impact
strength, good flow ability and absence of surface defects,
like tiger stripes.
It is known that peroxide modification whilst
increasing the flow ability of polypropylene impact
copolymers deteriorates the basic mechanical and
aesthetical properties.
Work was performed in which a PP-impact
copolymer was subjected to peroxide aided chain-scission
under simultaneous presence of the co-agent 1,4-
butanedioldimethacrylate (1,4-BDDMA). Results show
that samples made with 1,4- BDDMA exhibit superior
cold impact resistance and tiger stripe performance
compared to the materials made with only peroxide. In
addition, morphology, molecular weight distribution, and
rheological behaviour of the continuous and dispersed
phases of the modified PP impact copolymer were
studied.
Polypropylene impact copolymers are widely used in automotive applications. They are required to comply with many criteria. Customers demand high-performance materials which also exhibit good aesthetical properties. The challenge is to balance properties as high impact strength, good flow ability and absence of surface defects, like tiger stripes. It is known that peroxide modification whilst increasing the flow ability of polypropylene impact copolymers deteriorates the basic mechanical and aesthetical properties. Work was performed in which a PP-impact copolymer was subjected to peroxide aided chain-scission under simultaneous presence of the co-agent 1,4-butanedioldimethacrylate (1,4-BDDMA). Results show that samples made with 1,4- BDDMA exhibit superior cold impact resistance and tiger stripe performance compared to the materials made with only peroxide. In addition, morphology, molecular weight distribution, and rheological behaviour of the continuous and dispersed phases of the modified PP impact copolymer were studied.
Polyethylene/montmorillonite nanocomposites based on LDPE, HDPE and LLDPE of similar rheological properties were prepared and mechanically tested in tension mode. It was shown that nanocomposites based on LLDPE exhibit a very peculiar behavior, with a significant improvement in toughness (elongation at break). The microstructural features of the various nanocomposites were investigated through scanning and/or transmission electron microscopy. Based on those observations, an explanation for the deformation and fracture mechanisms in LLDPE/montmorillonite nanocomposites was proposed.
Florian Petzold , Marco Thornagel , Kaushik Manek, May 2010
Depending on the material and process parameters
geometrically balanced runners can show rheological
imbalances. In hot runner systems these imbalances are
handled by controlling the nozzle tempering. However this
balancing method leads to high polymer temperatures and
causes a product quality that differs from part to part.
This paper presents and discusses the preferential
polymer flow paths inside hot-runner systems and their
dependency on the plastic system as simulated and
analyzed by SIGMASOFT. It will be shown that a
complex thermal hot-runner tempering layout tweaked by
simulation reduces the imbalances and improves the
product quality at the same time.
Depending on the material and process parameters geometrically balanced runners can show rheological imbalances. In hot runner systems these imbalances are handled by controlling the nozzle tempering. However this balancing method leads to high polymer temperatures and causes a product quality that differs from part to part. This paper presents and discusses the preferential polymer flow paths inside hot-runner systems and their dependency on the plastic system, as simulated and analyzed by SIGMASOFT. It will be shown that a complex thermal hot-runner tempering layout tweaked by simulation reduces the imbalances and improves the product quality at the same time.
This paper describes a study of the mechanical properties of films produced from five different medium molecular weight homopolymer high density polyethylene resins. The machine direction (MD) tear strength and dart impact strength of these films track together. This is due to the tendency of these films to fail during dart impact testing by tearing in the machine direction. The ratio of MD and transverse direction (TD) tear properties correlates with low frequency linear viscoelastic measurements. There is a straightforward relationship between melt index measurements and low frequency rheology for the resins in our study, which relates film properties directly to readily available resin properties and film processing conditions.
Wallace W. Yau , Jian Wang , Rongjuan Cong , David Gillespie , Joe Huang, May 2010
A new GPC polydispersity parameter, MxR, was introduced in this study. The MxR value, based on the GPC-Mx concept originally proposed by Yau [1], was found to be more suitable to account for the effect of different parts of the polymer molecular weight distribution (MWD) on rheology measurements at different shear rates than do the traditional polydispersity index based on the ratio of Mz, Mw and Mn values. By using this Mx-approach on a set of polypropylene homopolymers, we show that a much improved correlation indeed exists and can be achieved between GPC measurement with the rheology polydispersity indices of PDI and ModSep. Also presented in the paper is the improved correlation between melt flow rate (MFR) and molecular weight (MW) by using this Mx approach.
Hesam Ghasemi , Pierre J. Carreau, Musa R. Kamal, May 2010
The purpose of this research is to
understand fiber orientation of long glass fibers
(> 1mm) in polymer melts and the associated
rheology in well-defined simple shear flow.
Specifically, we are interested in associating the
rheological behavior of glass fiber reinforced
polypropylene with the transient evolution of
fiber orientation in simple shear in an effort to
ultimately model fiber orientation in complex
flow. A sliding plate rheometer was designed
to measure stress growth in the startup and
cessation of steady shear flow. Results were
confirmed by independent measurements on
another sliding plate rheometer13. A fiber
orientation model that accounts for the
flexibility of long fibers, as opposed to rigid rod
models commonly used for short fibers, was
investigated and results are compared with
experimentally measured values of orientation.
The accuracy of this model, when used with the
stress tensor predictions of Lipscomb, is
evaluated by comparing against experimental
stress growth data. Samples were prepared with
random initial orientation and were sheared at
different rates. Results show that fiber
flexibility has the effect of retarding transient
fiber orientation evolution. Additionally, it is
shown that the stress growth measurements
provide results that are not fully explained by
the chosen models.
The increasing diversity of commercial polypropylene products in recent years, related to the increase in the production volumes of PP, has led to a high number of studies dealing with structure-specific nucleating agents (NAƒ??s). Experiments on sorbitol-based NAƒ??s suggest that the nucleation function of this group of nucleating agents is a result of hydrogen bonding and self-assembly. So far, nucleation studies have been conducted in an indiscriminate manner with little reference to the exact effect of PP structure on nucleating behaviour of NAƒ??s. However, given the variety of commercial PP structures produced today, the question on the existence of synergy between polypropylene structure and nucleating efficiency of NAƒ??s remains open. The SIST (Stepwise Isothermal Segregation Technique) has been used in this study as a fast and efficient method to characterize a group of random PPƒ??s having different structures, giving the lamellar thickness distribution. In addition, temperature sweep measurements were performed to study the effect of flow on the interaction between NA and PP. In this way, small discrepancies between different materials can be pointed out to assess the nucleating efficiency of the nucleating agent.
We investigated thermal mechanical rheological properties of a binary blend of poly lactic acid (PLA) and Sapindus trifoliatus as additive in it. The blends with different percentages of Sapindus Trifoliatus were extruded and their molded properties were examined. DSC thermograms show improvement in the crystallization. Rheological properties changed drastically with increasing percentage of Sapindus Trifoliatus. Tensile strength and modulus increased by addition of Sapindus Trifoliatus. Immiscibility was measured with thermal data. It is also observed that thermal stability of blends was lower than the pure PLA.
Avinash Baji, Shing-Chung Wong, Todd A Blackledge, Siwei Leng, May 2010
Different compositions of starch/water/plasticizer slurries are prepared in a batch mixer followed by an equilibration time. The slurries were then subjected to different thermal and shear treatments. A rheological technique has been developed to track the influence of shear on the gelatinization process and the results are also supported by DSC and polarized light microscopy for static systems. Shear has a dramatic effect on gelatinization and the dependence of the onset and conclusion temperatures with slurry composition vary widely depending on the type of plasticizer used.
Sergey Lapshin , Sarat K. Swain , Avraam. I. Isayev, May 2010
A continuous ultrasound assisted process using a single screw compounding extruder with an ultrasonic attachment was developed to prepare polyolefin/clay nanocomposites. High density polyethylene (HDPE) and isotactic polypropylene (PP) were compared. The feed rate that controls the residence time of the polymer in the ultrasonic treatment zone was varied. Die pressure and power consumption were measured.Rheological properties morphology and mechanical properties of the untreated and ultrasonically treated nanocomposites were studied. Similarities and differences of obtained nanocomposites are discussed based on their properties and structural characteristics.
Rheological computer experiments, involving small amplitude oscillatory shear flows for liquid n-hexadecane, are performed using non-equilibrium molecular dynamics methodology. In particular, the so-called Cox-Merz rule, which suggests that the magnitude of the complex viscosity with respect to frequency is equal to that of the steady shear viscosity with respect to shear rate, is validated. At different frequencies, the complex viscosity, including both dynamic and out-of-phase parts, varies significantly with respect to temperature.
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The work deals with the influence of content of the untreated wood flour filler (natural pine wood) on rheological behavior of blends with poly(1-butene) matrix. Therefore the blends with 5, 10, 15, 20, 30 and 50 % of wood flour were prepared in microcompounder. The rheological behavior was studied in oscillatory shear regime. Cole-Cole plot was used for determination of differences in molecular weight and distribution. It was found that low content of the wood flour acts as a lubricant agent and decreases zero shear viscosity. On the contrary, increasing content of the wood flour has an opposite effect.
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Any article that is cited in another manuscript or other work is required to use the correct reference style. Below is an example of the reference style for SPE articles:
Brown, H. L. and Jones, D. H. 2016, May.
"Insert title of paper here in quotes,"
ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
Available: www.4spe.org.
Note: if there are more than three authors you may use the first author's name and et al. EG Brown, H. L. et al.
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