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Rheology
SPE Library content related to rheology
TRITICALE STARCH BASED BIOPLASTICS
Triticale is being developed and aimed as an industrial crop and biorefinery feedstock for the Canadian manufacturing industry within the CTBI networking. In this paper the potential of triticale starch for the TPS/polymer blend fabrication was explored in terms of the starch morphology, crystallization structure, and the TPS (thermoplastic starch) rheology properties. The possibility of using triticale to make 100% biobased blown film was investigated using a small lab-scale film blown line. Film thickness of 25 um was obtained successfully for the triticale starch based PLA/TPS blends.
SELF-NUCLEATED CRYSTALLIZATION OF A BRANCHED POLYPROPYLENE
Long chain branched polypropylene (LCBPP) crystallizes rapidly and with high nucleation density. The origin of this fast crystallization process of is not well understood. It has been attributed to its complicated molecular architecture. In this research, we explore isothermal crystallization of LCBPP through rheological, thermal, and optical measurements. The time resolved mechanical spectroscopy technique was used to predict the liquid-to-solid transition (gel point) of LCBPP.
RHEOLOGICAL MORPHOLOGICAL RELATIONSHIP IN IMMISCIBLE AND REACTIVELY COMPATIBILIZED SAN/EPDM BLENDS
In uncompatibilized SAN/EPDM blend a coarse morphology is formed. Viscosity of the components drops below that of individual components. In reactive blends formation of graft at the interface causes fine droplet morphology and viscosity increases. Favis equation shows at 17 wt% of graft, the size of EPDM is minimum. The relaxation spectra of the uncompatibilized blends show a combination of phases and an additional relaxation time. The interfacial tension shows minimum value at 1 phr initiator.The droplet morphology is changed to composite in two step blending. A higher apparent volume fraction of EPDM obtains by Kerner equation for composite morphology.
RHEOLOGICAL PROPERTIES OF BRANCHED POLYMER FENE MODELS
FENE bead-spring chain model for branched polymer molecules in a Newtonian solvent is employed to describe the bead-bead interaction within a molecule. Brownian dynamics simulation is used to capture the steady state and transient rheological behavior of branched polymer. The simulations include examination of the effects of viscosity depending on length of the branching chain, spring parameter, and shear rate. The results of shear flow simulation show that the shear viscosity value increases with the increasing length of branch chain, and displays shear-thinning. Moreover, a large difference on the rheological response to different spring parameter is observed in this study.
EFFECT OF MICRO-VISCOSITY AND WALL SLIP ON POLYMER MELT RHEOLOGY INSIDE MICRO-CHANNEL
The rheological model for polymer melt flow in micro-channels is vital for the accurate simulation of micro-injection molding. In this study, the governing equations for mlet flow in micro-channel were in terms of viscous, incompressible 1D flow. The simulated rheological difference between macro model and micro model becomes significant when the micro channel is smaller than 100?¬m, and increases with the diameter decrease. The simulated results indicate the combined micro-viscosity and wall slip model can improve the simulating precision.
EVALUATION OF FOAMING OF PHARMACEUTICAL POLYMERS BY CO2 and N2 TO ENABLE DRUG PRODUCTS
Gas mediated foaming of extrudate is of interest to the pharmaceutical industry as a method to improve milling performance, to increase surface area for dissolution of molded parts, and to increase the processing window of thermally labile active ingredients via gas-assist extrusion. Pharmaceutical polymers were characterized via rheology and gas solubility measurements for their ability to support a foamed architecture. Finally, batch foaming studies were conducted and the materials characterized for density and cell size.
MORPHOLOGY, MECHANICAL, AND RHEOLOGICAL BEHAVIOR OF MICROCELLULAR INJECTION MOLDED EVA-CLAY NANOCOMPOSITES
Ethylene Vinylacetate (EVA)/montmorillonite (MMT) nanocomposites diluted from master batch (50 wt%) with EVA and EVAgMA was used in this study. The organoclay EVA nanocomposites were then injection molded by conventional and microcellular methods. Nitrogen was used as the blowing agent. The effect of organoclay content and high/low MA grafted EVA on the mechanical, rheological properties of the EVA-clay nanocomposites was investigated. The results showed that the mechanical properties (tensile and impact) increased as the clay content increased. The high MA grafted EVA nanocomposites had better mechanical properties than that of low MA grafted EVA nanocomposites.
RHEOLOGICAL MEASUREMENTS OF LOW DENSITY POLYETHYLENE (LDPE)/SUPERCRITICAL NITROGEN (N2) WITH A SLIT-DIE RHEOMETER AND THE USE OF NUMERICAL SIMULATION
In this study, the rheological behaviors of single-phase LDPE/N2 solutions at various gas contents are measured using a high-pressure slit-die rheometer. The resulting rheology data of LDPE/N2 are curve fit using the Cross-WLF model, which were then used in simulation of microcellular injection molding processes. The pressure effect on the shear viscosity is also studied. In addition, A 3D plot of viscosity as a function of shear rate, pressure and temperatures has been constructed, which is more profound at high pressures, low temperatures, and low shear rates.
EXTENSIONAL RHEOLOGY OF RAW NATURAL RUBBER FROM NEW CLONES OF HEVEA BRASILIENSIS
Natural rubber (NR) is a biopolymer whose properties depend on the structure of the 1,4-cis polyisoprene chains, non-rubber constituents, environmental conditions. NR has been characterized by traditional methods, but these cannot effectively account for clone's differences. The aim of this work is to use extensional rheology to characterize and differentiate NR samples as for clone type and season of the year. Three IAC 300 series and RRIM 600 clones of Hevea brasiliensis tapped between October 2006 and August 2008 were investigated. The extensional viscosity varied considerably and was more sensitive than any other traditional property, being fundamental for monitoring purposes.
EVALUATION OF BIODEGRADABLE COPOLYESTER RESINS WITH INCREASED GREEN CONTENT
Three different biodegradable copolyesters with increased green content (starting from 31 %) made from recycled post consumer poly(ethylene terephthalate) (PET) were evaluated in comparison to commercial poly(butylene terephthalate-co-adipate) (PBAT) in terms of thermal, rheology, and physical properties. The melting temperature of the resins is lower compared to commercial PBAT due to the presence of isophthalate and traces of diethylene glycol (DEG) linkages from PET. The melt flow values are 2.5 times higher than those of commercial PBAT, which has extensive branching. New resins show low crystallinity, high flexibility, and no break at maximum elongation compared to commercial PBAT.
THE LIQUID-LIQUID SEPARATION AND RHEOLOGY OF BINARY STRONG INTERACTION SYSTEM
It is important to discern the liquid-liquid phase separation (LLPS) and crystallization from UHMWPE- liquid paraffin solution in order to control the membrane forming process. Since the UHMWPE- liquid paraffin solution belongs to a binary strong interaction system, accustomed methods such as DSC, light scattering, and optical microscopy (OM) are not so suitable. By adopting an inversing quenching rheological method we successfully obtained LLPS temperature of the polymer solution. The results show that viscoelastic properties are more sensitive to concentration fluctuation of L-L phase separation at the early stages than other methods.
DEVELOPMENT OF REACTIVE BLEND WITH SUPERCRITICAL CARBON DIOXIDE
A reactive extrusion process for immiscible PP/PS blend with peroxide and multifunctional agent in the presence of supercritical carbon dioxide was studied. Supercritical carbon dioxide was used in reactive extrusion to assist the diffusion of agent into polymer matrix. The PP/PS blends were investigated by rheological measurement, scanning electron microscopy and thermal property. The results indicate that complex viscosity and storage modulus of blend are increased by adding peroxide and multifunctional agent. Moreover, analysis of the products revealed that the use of supercritical carbon dioxide led to improved compatibility.
STUDY ON RHEOLOGICAL BEHAVIOR OF ULTRA HIGH SPEED INJECTION MOLDING
In this study, the high-speed experiment was conducted to verify moldex3D simulation technology. Mold and melt temperature were kept at 200, 215 and 230 C in the maximum injection pressure condition. The experimental method changed the injection speed from 100 to 1500 mm/s and obtained the pressure drop and flow rate. The experimental results were calculated using some equations and compared with Moldex3D simulation results. Both simulation and experimental results demonstrated that the second Newton area appears starting from 1000 mm/s injection speed. With the increase of melt and mold temperature, the shear rate increases and the viscosity value decreases.
SEAL LAYER MATERIALS CHARACTERIZATION IN TERMS OF CRYSTALLINITY AND RHEOLOGY
A series of commercial seal layer grades ethylene vinyl acetate (EVA) resins were investigated in terms of thermal and rheological properties. The effect of vinyl acetate (VA) content in Differential scanning calorimetry (DSC) experiments revealed that the increase of VA content leads to decrease in melting point and heat of fusion. In oscillatory shear measurements the effect of long-chain branching on high shear sensitivity and long relaxation time of resins was revealed. In addition, a significant strain hardening behavior in extensional viscosity measurements was observed which indicated high melt strength of these resins.
PREDICTION OF CRAZING AND BIREFRINGENCE IN ORIENTED GLASSY POLYMERS
A study has been made of prediction of crazing stress and birefringence in oriented glassy polymers. The ROLIEPOLY (RP) polymer rheological model proposed by Likhtman and Graham (2003) was employed, together with the Kramer theory of crazing (1983). Predictions were tested by comparison with results of a new experimental study of crazing and birefringence in monodisperse grades of polystyrene, following model melt-stretching histories. The RP model produced accurate predictions of birefringence, provided orientation occurred on a time-scale slower than the entanglement Rouse relaxation time. Crazing stress was predicted successfully with the model under the same conditions.
RHEOLOGICAL EFFECTS ON FOAM PROCESSING IN ROTATIONAL MOLDING
Rheological properties of several polypropylene polymers were measured and the foam processing of these materials using chemical blowing agent was studied. Foaming was carried out in monolayer and skin-foam layer moldings. The uniaxial extensional viscosity was quantified and the foam characterized based on bulk density, bubble size, and bubble concentration. It was found that the foam processing window is determined and bounded by melt viscosity and melt elasticity. Melt strength and strain-hardening can substantially improve the foaming performance and play significant role in determining the developed morphological structure.
PRELIMINARY RESULTS IN RHEOLOGICALLY OBTAINING MODEL PARAMETERS FOR THE PURPOSE OF PREDICTING THE ORIENTATION OF CONCENTRATED LONG GLASS FIBERS IN PROCESSING FLOWS
The purpose of this research is to understand the transient fiber orientation of long glass fiber (> 1mm) reinforced polypropylene, in a well-defined simple shear flow (using a sliding plate), by determining unambiguous model parameters from rheological experiments, and to ultimately predict fiber orientation in complex processing flows. Two fiber orientation models were investigated. One model, the Folgar-Tucker model, has been particularly useful for short glass fiber systems and was used in this paper to assess its performance with long glass fibers. A second fiber orientation model, one that accounts for the flexibility of long fibers, was also investigated.
RHEOLOGICAL CHARACTERIZATION OF POLYPROPYLENE MIXED WITH SPECIALLY MODIFIED CALCIUM CARBONATE
The rheological properties of polypropylene filled with specially coated calcium carbonate were investigated in this study. CaCO3 fillers were coated in order to further improve the mechanical and flow properties of the filled polymer. A fluid energy mill (FEM) was used to simultaneously mill and coat the calcium carbonate particles. Both rotational and capillary rheometers were utilized to study the rheological impact of the coated particles. The rheological properties of the specially coated particles were compared with non-coated particles at similar concentration. Shear viscosity, dynamic viscosity and also melt flow index were determined at three different temperatures.
RHEOLOGICAL CHARACTERIZATION OF POLYCARBONATE RESINS AND ITS APPLICATIONS
We show results of rheological testing of polycarbonate resind and its applications. Rheological characterization provides indirect measurements of materials properties, such as molar mass and molar mass distribution. Dynamic storage Gƒ?? and loss Gƒ? modulus represent elastic and viscous properties of the material. Viscosity curves give information about materials behavior under different temperatures and shear rates. Dynamic mudulus and zero shear viscosity can be used as qualitative parameters to characterize and distinguish different materials, and to predict materials performance. Rheological data can be used for process optimization and quality control.
ORDERING KINETICS OF BLOCK COPOLYMER SOLUTIONS DURING SOLVENT REMOVAL
The ordering kinetics of block copolymers in solution are studied during a solvent removal process. The kinetics of styrenic block copolymers in a neutral solvent, toluene, are tracked at various concentrations along a drying path to determine the effect of concentration on phase separation. The ordering process is modeled with the Avrami equation. Small angle X-ray scattering has been used to determine that the structures developing during solvent removal are cylinders. Scattering data also indicates that the concentrations studied by the rheology experiments are limited by the conditions under which samples are dried.
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