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Capillary Rheometer (capillary + rheometer)
Selected AbstractsThermoplastic silicone elastomer lubricant in extrusion of polypropylene wood flour compositesADVANCES IN POLYMER TECHNOLOGY, Issue 2 2007Velichko Hristov Abstract A possibility of using a thermoplastic silicone elastomer (TPSE) for reduction of surface defects in the extrusion of wood-filled metallocene polypropylene (mPP) has been investigated in this work. A capillary rheometer and a single-screw extruder have been utilized to study the effect of the additive on the extrudate distortions. Maleated syndiotactic metallocene polypropylene was also used as an adhesion promoter in mPP/wood flour composites. At loadings of 50 wt% wood flour in the mPP, the extrudates come out of the die with significant tearing and surface roughness. The surface rupture mechanism is similar to that of sharkskin in neat polymers; however, the defect is much more exaggerated in the case of wood fiber-filled composites. It was found that TPSE at low concentrations (1 wt%) was able to reduce or even completely eliminate extrudate surface tearing. Increasing the extrusion speed yielded better results. Addition of a coupling agent also provides improvement in the extrudate appearance. © 2007 Wiley Periodicals, Inc. Adv Polym Techn 26:100,108, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20090 [source] Estimation of elongational viscosity of polymers from entrance loss data using individual parameter optimizationADVANCES IN POLYMER TECHNOLOGY, Issue 2 2002Mahesh Gupta The elongational viscosity model proposed by Sarkar and Gupta (Journal of Reinforced Plastics and Composites 2001, 20, 1473), along with the Carreau model for shear viscosity is used for a finite element simulation of the flow in a capillary rheometer. The entrance pressure loss predicted by the finite element flow simulation is matched with the corresponding experimental data to predict the parameters in the elongational viscosity model. To improve the computational efficiency, various elongational viscosity parameters are optimized individually. Estimated elongational viscosity for a Low Density Polyethylene (Dow 132i) is reported for two different temperatures. © 2002 Wiley Periodicals, Inc. Adv Polym Techn 21: 98,107, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/adv.10017 [source] The rheological properties of modified microcrystalline cellulose containing high levels of model drugsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2009Paul E. Knight Abstract The rheological properties of different types of microcrystalline cellulose (MCC) mixed with model drugs and water have been evaluated to identify the influence of sodium carboxymethylcellulose (SCMC) added to the cellulose during preparation. A ram extruder was used as a capillary rheometer. The mixtures consisted of 20% spheronizing agent (standard grade MCC or modified types with 6% or 8% of low viscosity grade SCMC) and 80% of ascorbic acid, ibuprofen or lactose monohydrate. The introduction of SCMC changed all rheological parameters assessed. It produced more rigid systems, requiring more stress to induce and maintain flow. Degree of non-Newtonian flow, angle of convergence, extensional viscosity, yield and die land shear stress at zero velocity, and static wall friction were increased, but recoverable shear and compliance were decreased. The presence of SCMC did not remove the influence of the type of drug. The mixture of ibuprofen and standard MCC had the lowest values for shear stress as a function of the rate of shear, extensional viscosity, and angle of convergence, but the highest values for recoverable shear and compliance. The findings indicate that the system has insufficient rigidity to form pellets. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:2160,2169, 2009 [source] Studies on rheology and morphology of POE/PP thermoplastic elastomer dynamically crosslinked by peroxideJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 2 2008Bo Yuan An ethylene-octene copolymer (POE)/polypropylene (PP) thermoplastic elastomer was prepared through dynamically crosslinking by 2,5-dimethyl-2,5-dilbuty (Peroxy) hexane (DHBP). The effects of DHBP concentration, POE/PP ratio, melt flow index (MFI) of PP, and mixer rotation on rheology and morphology of the thermoplastic elastomer were studied. The results showed that with increasing DHBP concentration or POE content, the size of crosslinked particles as well as the melt viscosity increased. Furthermore, agglomerates or a network structure formed as the size of crosslinked particles increased. The melt viscosity also increased as MFI of PP decreased, while the size of crosslinked particles decreased under the same condition. Research on the morphology of dynamically crosslinked POE/PP thermoplastic elastomer flowing through a capillary rheometer at different shear rates show that the reprocessing had little effect on the morphology of dynamically crosslinked elastomer. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers. [source] Rheological behavior of LDPE/CaCO3 blends containing EAAPOLYMER COMPOSITES, Issue 9 2009Aiqin Dong Calcium carbonate (CaCO3) filler particles were surface treated with organic titanate (TTS), a coupling agent. The composites were prepared by blending low-density polyethylene (LDPE) with the surface-modified fillers at various weight ratios. Ethylene-acrylic acid copolymer (EAA) was added to improve the adhesion of LDPE to fillers. A capillary rheometer was used to evaluate rheological properties of the LDPE/CaCO3/EAA blends. The blends were shown to be pseudoplastic with shear thinning behavior. When CaCO3 was modified by TTS (<2 wt%), the viscosity of the blends decreased quickly, and, addition of a small amount of EAA (<6 wt%) could also decrease the viscosity of the blends. The thermal behavior of these materials is evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The addition of a small amount of EAA and TTS enhances the stabilization of the blends, which could be explained by the "ball belling" action. The effects of temperature, TTS content, CaCO3 granule size, and content on the rheological property were also studied. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Rheological characterization of HDPE/sisal fiber compositesPOLYMER ENGINEERING & SCIENCE, Issue 10 2007Smita Mohanty The present paper summarizes an experimental study on the molten viscoelastic behavior of HDPE/sisal composites under steady and dynamic mode. Variations of the melt viscosity and die swell of the composites with an increase in shear rate, fiber loading, and coupling agent concentration have been investigated using capillary rheometer. The shear rate , at the wall was calculated using Rabinowitsch correction applied to the apparent shear rate values. It was observed that the melt viscosity of the composites increased with the addition of fibers and maleic anhydride-grafted PE (MAPE). Die swell of HDPE also decreased with the addition of sisal fibers and MAPE. Further, the dynamic viscoelastic behavior of the composites was measured employing parallel plate rheometer. Time,temperature superposition was applied to generate various viscoelastic master curves. Temperature sweeps were also carried out to study the flow activation energy determined from Arrhenius equation. The fiber,matrix morphology of the extrudates was also examined using scanning electron microscopy. POLYM. ENG. SCI., 47:1634,1642, 2007. © 2007 Society of Plastics Engineers [source] Effect of diatomite/polyethylene glycol binary processing aid on the melt fracture and the rheology of polyethylenesPOLYMER ENGINEERING & SCIENCE, Issue 7 2005Xiaolong Liu The influence of polyethylene (PE) glycol (PEG), diatomite, and diatomite/PEG binary processing aid (BPA) on the rheological properties and the sharkskin melt fracture of three PEs was studied using a capillary rheometer. When diatomite or PEG is added to the PE matrix, they have little effect on the viscosity reduction of PEs, while the diatomite/PEG BPA shows a synergetic effect on the viscosity reduction of PEs. The incorporation of small amount of BPA was found to increase the shear-thinning behavior and decrease the melt viscosity significantly. Meanwhile, the critical apparent shear rate for the onset of sharkskin melt fracture of PEs is increased. The mechanism for BPA to improve the rheological properties and the melt flow instability of PEs was discussed. POLYM. ENG. SCI., 45:898,903, 2005. © 2005 Society of Plastics Engineers [source] A parallel coextrusion technique for simultaneous measurements of radial die swell and velocity profiles of a polymer melt in a capillary rheometerPOLYMER ENGINEERING & SCIENCE, Issue 10 2004N.-T. Intawong This article proposes a new experimental technique to simultaneously measure radial die swell and velocity profiles of polystyrene melt flowing in the capillary die of a constant shear rate rheometer. The proposed technique was based on parallel coextrusion of colored melt-layers into uncolored melt-stream from the barrel into and out of the capillary die. The size (thickness) ratio of the generated melt layers flowing in and out of the die was monitored to produce the extrudate swell ratio for any given radial position across the die diameter. The radial velocity profiles of the melt were measured by introducing relatively light and small particles into the melt layers, and the times taken for the particles to travel for a given distance were measured. The proposed experimental technique was found to be both very simple and useful for the simultaneous and accurate measurement of radial die swell and velocity profiles of highly viscous fluids in an extrusion process. The variations in radial die swell profiles were explained in terms of changes in melt velocity, shear rate, and residence time at radial positions across the die. The radial die swell and velocity profiles for PS melt determined experimentally in this work were accurate to 92.2% and 90.8%, respectively. The overall die swell ratio of the melt ranged from 1.25 to 1.38. The overall die swell ratio was found to increase with increasing piston speed (shear rate). The radial extrudate swell profiles could not be reasoned by the shear rate change, but were closely linked with the development of the velocity profiles of the melt in the die. The die swell ratio was high at the center (,1.9) and low (,0.9) near the die wall. The die swell ratio at the center of the die reduced slightly as the piston speed was increased. Polym. Eng. Sci. 44:1960,1969, 2004. © 2004 Society of Plastics Engineers. [source] On the effect of pressure on the shear and elongational viscosities of polymer meltsPOLYMER ENGINEERING & SCIENCE, Issue 7 2004Tomas Sedlacek The effect of pressure and temperature on the shear and elongational deformation rate,dependent viscosities has been experimentally investigated for several polymers (HDPE, LDPE, LLDPE, PP, PC, PMMA, and PS) on a capillary rheometer with a back-pressure device. Pressure, ,, and temperature, ,, coefficients have been determined through simultaneous fitting of the shear and extensional viscosity data by the modified White-Metzner model. The dependence of , and , on temperature and pressure, respectively, was investigated and it has been found that simple relationships exist between pressure and temperature sensitivity coefficients for individual polymers. Polym. Eng. Sci. 44:1328,1337, 2004. © 2004 Society of Plastics Engineers. [source] Measurement and prediction of LDPE/CO2 solution viscosityPOLYMER ENGINEERING & SCIENCE, Issue 11 2002Surat Areerat When CO2 is dissolved into a polymer, the viscosity of the polymer is drastically reduced. In this paper, the melt viscosities of low-density polyethylene (LDPE)/supercritical CO2 solutions were measured with a capillary rheometer equipped at a foaming extruder, where CO2 was injected into a middle of its barrel and dissolved into the molten LDPE. The viscosity measurements were performed by varying the content of CO2 in the range of 0 to 5.0 wt% and temperature in the range of 150°C to 175°C, while monitoring the dissolved CO2 concentration on-line by Near Infrared spectroscopy. Pressures in the capillary tube were maintained higher than an equilibrium saturation pressure so as to prevent foaming in the tube and to realize single-phase polymer/CO2 solutions. By measuring the pressure drop and flow rate of polymer running through the tube, the melt viscosities were calculated. The experimental results indicated that the viscosity of LDPE/CO2 solution was reduced to 30% of the neat polymer by dissolving CO2 up to 5.0 wt% at temperature 150°C. A mathematical model was proposed to predict viscosity reduction owing to CO2 dissolution. The model was developed by combining the Cross-Carreau model with Doolittle's equation in terms of the free volume concept. With the Sanchez-Lacombe equation of state and the solubility data measured by a magnetic suspension balance, the free volume fractions of LDPE/CO2 solutions were calculated to accommodate the effects of temperature, pressure and CO2 content. The developed model can successfully predict the viscosity of LDPE/CO2 solutions from PVT data of the neat polymer and CO2 solubility data. [source] Response of a concentrated monoclonal antibody formulation to high shearBIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009Jared S. Bee Abstract There is concern that shear could cause protein unfolding or aggregation during commercial biopharmaceutical production. In this work we exposed two concentrated immunoglobulin-G1 (IgG1) monoclonal antibody (mAb, at >100 mg/mL) formulations to shear rates between 20,000 and 250,000 s,1 for between 5 min and 30 ms using a parallel-plate and capillary rheometer, respectively. The maximum shear and force exposures were far in excess of those expected during normal processing operations (20,000 s,1 and 0.06 pN, respectively). We used multiple characterization techniques to determine if there was any detectable aggregation. We found that shear alone did not cause aggregation, but that prolonged exposure to shear in the stainless steel parallel-plate rheometer caused a very minor reversible aggregation (<0.3%). Additionally, shear did not alter aggregate populations in formulations containing 17% preformed heat-induced aggregates of a mAb. We calculate that the forces applied to a protein by production shear exposures (<0.06 pN) are small when compared with the 140 pN force expected at the air,water interface or the 20,150 pN forces required to mechanically unfold proteins described in the atomic force microscope (AFM) literature. Therefore, we suggest that in many cases, air-bubble entrainment, adsorption to solid surfaces (with possible shear synergy), contamination by particulates, or pump cavitation stresses could be much more important causes of aggregation than shear exposure during production. Biotechnol. Bioeng. 2009;103: 936,943. © 2009 Wiley Periodicals, Inc. [source] | |||||||||||||