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.
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Applied Rheology
Crystallization of Shape Memory Polymer Blends
Olivier B. Arnoult, Patrick T. Mather, May 2007
Shape Memory Polymers (SMP) blends are of particular interest because they are easily processible, commercially available and recyclable. In this paper we study blends of PVDF (semi-crystalline, Tg=-35 °C, Tm=173 °C) and PVAc (amorphous, Tg=33 °C) which are miscible at all blending ratio (presence of a single Tg). Effects of composition as well as thermal histories on crystallization were investigated via differential scanning calorimetry (DSC), parallel plate rheology and polarizing optical microscopy (POM). For the first time, evidence for two distinct crystalline forms was observed in a blend with PVAc and PVDF crystallized for all blending ratios. Rheological measurements show that the rubber plateau of the blend decreases with lower PVDF content because of lower density of physical crosslinks. Surprisingly, in the case of 30:70 PVDF:PVAc the highest rubber plateau was achieved by isothermal crystallization at temperature close to, but above, the crystallization point measured by DSC. Comparing rheological and optical results for crystallization kinetic, it can be inferred that PVDF crystallizes faster near a solid interface than in the bulk.
Rheology-Based Pore Size Estimation in Polyacrylamide Hydrogels for DNA Analysis
Jian Wang, Victor M. Ugaz, May 2007
The physiochemical properties of polyacrylamide hydrogels have made them important in a variety of biomedical applications including drug delivery, tissue engineering, and electrophoresis of charged biomolecules. In this paper, we perform a series of in-situ dynamic small-amplitude oscillatory shear measurements during photopolymerization of crosslinked polyacrylamide electrophoresis gels to investigate the relationship between rheology and parameters associated with the gelation process including UV intensity, monomer and crosslinker composition, and reaction temperature. These results are then combined with a simple model based on classical rubber elasticity theory to obtain estimates of the average gel pore size.
Organoclay Networking in Polypropylene-Clay Nanocomposites
Mark A. Treece, James P. Oberhauser, May 2006
This report discusses the networking of organoclays and its influence on the rheology of polymer-clay nanocomposites. Small amplitude (SAOS) and steady state rheological experiments are systematically performed to study the effect of flow and thermal history on solid-like formation dynamics in a 3wt% polypropylene-clay sample. Results indicate that the kinetics of network formation increase with temperature, while the application of a sufficiently large deformation will irreversibly weaken the clay network.
Rheology and Properties of Linear and Branched Polypropylene Blends
Tara McCallum, Chul B. Park, May 2006
The rheological, thermal and mechanical properties of linear and branched polypropylene blends with varying melt flow rates are characterized. These blends are miscible in the melt state and have high melt elasticity while retaining good flow and mechanical properties.
Scale Up of Polypropylene Vis-Breaking for Industrial Application
Franco Guastaferro, Iván Fernández, May 2006
A statistical experimental design was used to find the required concentration of a novel additive in order to obtain the same rheological behavior of higher priced, commercial controlled-rheology polypropylenes. A lab extruder was used to perform the experimental design, minimizing the amount of material needed. According to the results, recommendations were given to process two different lower priced polypropylenes with the additive in an industrial extruder with very good agreement with lab predictions.
Rheology of High Molecular Weight Polyethylenes with SCCO2
Matthew D. Wilding, Donald G. Baird, May 2006
The effects of using supercritical carbon dioxide (SCCO2) to melt process high molecular weight polyethylene are studied. High molecular weight polyethylene (HDPE) is studied in an effort to produce high strength fibers and materials in a melt extrusion process. Dynamic, capillary, and slit-die rheometry are used to quantify the effect SCCO2 has on the melt viscosity of high Mw HDPEs. Carbon dioxide uptake is quantified using mass flow measurements.
Reactive Extrusion of PBT for Low Density Foaming
B. Jeong, M. Xanthos, K. Hyun, May 2006
Branching or partial cross-linking of polybutylene terephthalate (PBT) resins by reactive modification with multi-functional epoxides was investigated. The rheology of the PBT products could be controlled by varying material and operational conditions of the reactive extrusion process. The modified PBT was adaptable to low density foam extrusion, where higher melt strength is necessary.
Shape Memory Binary Blends: Compositionally Tailored Fixing and Recovery
Cheryl J. Campo, Patrick T. Mather, May 2006
Semicrystalline-amorphous blends exhibit shape memory due to (1) the elastomeric nature imparted by crystallites that act as physical crosslinks and (2) temporary shape fixing made possible by the vitrification of a continuous, miscible amorphous phase. PVDF-containing binary blends were studied using calorimetry and rheology in order to characterize the morphological control afforded by subjecting such materials to different thermal histories. The sensitivity of the aforementioned techniques to changes in blend morphology will also be discussed.
Film-Casting Behavior as a Function of Molecular Structure and Rheology
Christopher W. Seay, Donald G. Baird, May 2006
Polyethylene resins with different molecular structures and rheological properties are investigated in terms of their performance in film-casting. Four metallocene catalyzed polyethylene resins with different degrees of long-chain branching and two conventional polyethylene resins are analyzed in terms of their dimensional changes during film production. With an increase in long-chain branching, and thus strain hardening-behavior, an increase in the necking phenomenon is observed during film-casting.
Measurement of Surface Properties of Polymeric Materials Using Nanosphere Embedment Measurements
Stephen A. Hutcheson, Gregory B. McKenna, May 2006
Here we report results from our ongoing investigation of the surface properties of polymers using a nanoparticle embedment method that was originally pioneered by Teichroeb and Forrest. We describe a viscoelastic contact mechanics solution that includes surface adhesive forces and a time dependent Poisson's ratio. The results show that, with properly designed experiments, both the surface adhesion properties and the surface rheological properties can be extracted from nanosphere embedment measurements.
Modeling the Transient Rheology of a Polypropylene Melt Reinforced with Long And Short Glass Fibers
Aaron P.R. Eberle, Donald G. Baird, Peter Wapperom, May 2006
In this paper we investigate the transient shear rheology of a polypropylene containing long fibers (2.75 to 11 mm, L/D > 150) and short fibers (1 mm, L/D < 50). The objectives of this work are to determine the relationship between stress growth and relaxation behavior of fiber orientation and determine the feasibility of extending Doi's theory for the rheology of rod-like molecules to fiber reinforced materials.
Structure and Performance of ABS-Clay Nanocomposites by Melt Compounding
E.H. Qua, I.F.M. Major, C.Y. Lew, G.M. McNally, A.H. Clarke, May 2006
ABS layered-silicate nanocomposites were manufactured by melt compounding. X-ray diffraction and transmission electron microscopy analysis confirmed the achievement of hybrid intercalated and exfoliated structures, giving significant improvement in the mechanical, thermal and rheological properties.
Rheology Phenomena of Nano-Extrudate Flow
Jiann-Shing Wu, Huan-Chuang Tseng, Rong-Yeu Chang, May 2006
The purpose of this paper is to study the die swell phenomena in a nano-extrudate flow from the molecular dynamics simulation. We have studied a polyethylene (PE) melt extruding into vacuum surrounding through a 4-to-1 nano-extrusion die. The results indicate the extrusion velocity has a strong influence on the stability of extrudate with the die swell. Also, there is a particularly noteworthy surface effect that some molecules are adsorbed on the outer surface of capillary under the lower extrusion velocity.
Partially Oxidized Graphite in Polypropylene Grafted Maleic Anhydride
P.E. Poirier, D.J.Y.S. Pagé, N. Cunningham, May 2006
Natural graphite flakes (NGF) were partially oxidized with potassium permanganate (KMnO4) in order to increase their dispersion during melt mixing in polypropylene (PP) grafted maleic anhydride (MA) (PPg- MA). Electrical conductivity of the composite, as well as X-ray diffraction, Fourier transform infrared spectrometry, and rheological properties were assessed against the level of oxidation.
Rheology and Thermoforming of Rigid Medical Packaging Materials
A. Costa, G. Zeller, May 2006
Rheological properties were measured on two materials to evaluate their behavior in the thermoforming process. An impact-modified acrylic-based terpolymer compound displayed higher extensional viscosity and melt strength measurements versus a copolyester. The findings in this study showed that lower extensional viscosity and melt strength led to higher molded-in-stress and thinner walls of thermoformed parts.
Electrorheological Properties of Carbon Black Filled PDMS
Michael Kaufman, Marianna Kontopoulou, Aristides Docoslis, May 2006
The electrical conductivity and rheological properties under steady shear flow of carbon black-filled PDMS are measured as a function of filler loading, matrix viscosity and shear rate, upon application of an AC electric field. The effects of electric field are most notable at low filler loadings and low matrix viscosities.
Pressure Profile in Annular Die Using PP/CO2 Solution Viscosity
Jing Wang, Chul B. Park, May 2006
In this paper, a rheological die with a slit channel was designed to determine the solution viscosity of supercritical CO2 in non-crosslinked high-melt-strength (HMS) polypropylene (PP). The shear viscosity was modeled as a function of temperature, pressure, gas content, and shear rate. With interest in producing highly expanded foam sheets using an annular die, an analysis of the annular die pressure profile using the measured viscosity data was also conducted.
Compatibilization of Natural Fibers/PP Composites
K. Jarukumjorn, Y. Ruksakulpiwat, W. Sutapun, J. Kluensamrong, May 2006
The effect of maleic anhydride grafted polypropylene (PP-g-MA) as a compatibilizer on mechanical, rheological, and morphological properties of rossells/PP and sisal/PP composites was investigated. The fiber loading was 20wt% and the compatibilizer contents were varied from 1-10 phr. The tensile strength and unnotched impact strength of the composites increased with increasing the compatibilizer content.
The Processing and Performance of Nylon 12/PEBAX Blends
A.C. Ruddy, G.M. McNally, G.M. Walker, May 2006
This work studied the effect of a polyether block amide (PEBA) on the rheological, mechanical and thermal properties of nylon 12 polymers. The results showed significant differences in melt viscosity, tensile properties and phase transition temperatures (tan ?) with varying PEBA concentration.
Rheological Modeling of Plug-Assist Thermoforming
Hosseini Hossein, Berdyshev Boris Vasilivich, May 2006
Solving problems for thermoforming processes in production of axisymmetric thin walled plastics is investigated in this research work. A non-linear viscoelastic rheological model with a new strain energy function is suggested for improvement of physical properties of final product. For model validation, a quantitative relation between stress and technical parameters of plug-assist thermoforming is determined by comparison of theoretical and experimental results. This process with the proposed rheological model could be suggested for prevention from some technical defects such as wall thickness variations, physical instability during inflation-shrinkage, and warpage exhibited in the final part of a polymeric sheet thermoforming.
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