Breakage and buckling of fibrous reinforcements during fabrication of thermoplastic matrix composites / A. Cohen in INTERNATIONAL POLYMER PROCESSING, Vol. XIV, N° 3 (09/1999)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XIV, N° 3 (09/1999) . - p. 276-281 Titre : Breakage and buckling of fibrous reinforcements during fabrication of thermoplastic matrix composites Type de document : texte imprimé Auteurs : A. Cohen, Auteur ; M. E. Adams, Auteur ; G. A. Campbell, Auteur Année de publication : 1999 Article en page(s) : p. 276-281 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : The paper addresses the buckling of fibrous reinforcements which occurs due to motion of the amorphous matrix material during solidification. The motion of the matrix material is caused by a variation in cooling rate in different portions of a composite while the sample is cooling. In the course of this study, samples were prepared with a fiber reinforcement sandwiched between premolded sheets of polycarbonate. Samples were either processed in a two-cavity, 'dogbone' shape mold or in a rectangular, single-cavity mold matched die compression mold. In order to visualize the motion of the molten matrix material, strands of polycarbonate blended with carbon black were mounted into the matrix. The buckling behavior demonstrated sensitivity, to the amount of reinforcement observed with single and multiple filaments of carbon and Kevlar and bundles of carbon fiber tows. This paper provides scaling considerations indicating the sensitivity of the observed effects to processing conditions and concludes with a discussion of the implications for load carrying capabilities of composites. Note de contenu : - EXPERIMENTAL : Outline of the experimental program - Sample preparation procedure - A REVIEW OF THE EXPERIMENTAL OBSERVATIONS : "Dogbone" experiments - Experiments with rectangular samples - EVALUATION OF THE EXPERIMENTAL OBSERVATIONS - GOVERNING EQUATIONS - SIMPLIFICATION AND MODIFICATION OF THE CONTINUITY CONDITION - EVALUATION OF THE COOLING RATES - INTERPRETATION OF THE MOMENTUM BALANCE - APPLICATION OF THE THEORETICAL MODEL DOI : 10.3139/217.1555 En ligne : https://drive.google.com/file/d/15Dc353i_6ODjhFo8HREOJNapOn7PJ0oA/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=16138 [article]

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Crystallization studies of LLDPE during tubular blown film processing / M. D. Bullwinkel in INTERNATIONAL POLYMER PROCESSING, Vol. XVI, N° 1 (03/2001)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XVI, N° 1 (03/2001) . - p. 39-47 Titre : Crystallization studies of LLDPE during tubular blown film processing Type de document : texte imprimé Auteurs : M. D. Bullwinkel, Auteur ; G. A. Campbell, Auteur ; D. H. Rasmussen, Auteur ; J. Krexa, Auteur ; C. J. Brancewitz, Auteur Année de publication : 2001 Article en page(s) : p. 39-47 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : The final physical properties of semi-crystalline blown films are highly dependent on the crystalline morphology and orientation of polymer chains within the film. Simultaneous on-line SALS (Small Angle Light Scattering) and IR (Infrared) temperature measurements were successfully used to study crystallization during tubular blown film extrusion of LLDPE. SALS patterns were recorded at various vertical positions along the bubble. For LLDPE an undeformed spherelulitic structure is formed if the stress level during processing is not too high. The change in average scattered intensity with axial position can be described using multiple step Avrami kinetic processes in parallel. the first step accounts for crystal growth and corresponds to the well-known temperature plateau. The later processes start with the impingement of the growing spherulites and may reflect secondary crystallization and orientation processes. Because the magnitude of the average intensity is responsive to changes in process conditions, the on-line SALS system is potentially a useful tool for monitoring process-property interactions. Note de contenu : - Experiments - Process data analysis - SALS image analysis - Temperature profile - SALS-analysis - Effect of process conditions DOI : 10.3139/217.1624 En ligne : https://drive.google.com/file/d/1Y_XBRZpYXsYj7wpyU1625EJCvqWmDhqw/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=15883 [article]

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Investigation of flow rate and viscous dissipation in a single screw pump-extruder / G. A. Campbell in INTERNATIONAL POLYMER PROCESSING, Vol. XVI, N° 4 (12/2001)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XVI, N° 4 (12/2001) . - p. 323-333 Titre : Investigation of flow rate and viscous dissipation in a single screw pump-extruder Type de document : texte imprimé Auteurs : G. A. Campbell, Auteur ; C. Wang, Auteur ; M. Bullwinkel, Auteur ; M. A. Te-Riele, Auteur ; H. Cheng, Auteur Année de publication : 2001 Article en page(s) : p. 323-333 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : The focus of this investigation was to determine the effect of barrel rotation and screw rotation on the flow rate and viscous dissipation inside the screw pump-extruder. The screw pump-extruder was built to allow for barrel rotation and screw rotation independently. A Newtonian fluid, Polypropylene glycol, was chosen as the working fluid. The experimental results can be summarized by noting that the pumping capacity of the device was independent of which element was rotated at constant angular velocity and that barrel rotation generated higher temperature rise than screw rotation for the two screws evaluated. Also this analysis suggested that a large amount of viscous dissipation inside this extruder arises from clearance flow. A new analytical model was proposed to evaluate the viscous dissipation for screw rotation. calculations using this new mathematical model provided good agreement with the experimental data for both barrel and screw rotation. Note de contenu : - THEORETICAL ANALYSIS : Constant temperature screw rotation and barrel rotation theory - SCREW AND BARREL ROTATION THEORY : Fluid flow - Energy dissipation and temperature rise - RESULTS AND DISCUSSIONS : Fluid flow - Energy dissipation DOI : 10.3139/217.1663 En ligne : https://drive.google.com/file/d/1FWqLuaBj-h_mTQ6j7tTp9AnBe33NTNjW/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=15916 [article]

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Investigation of the effect of filler concentration on the flow characteristics of filled polyethylene melts / G. A. Campbell in INTERNATIONAL POLYMER PROCESSING, Vol. XXXIII, N° 5 (11/2018)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXXIII, N° 5 (11/2018) . - p. 619-633 Titre : Investigation of the effect of filler concentration on the flow characteristics of filled polyethylene melts Type de document : texte imprimé Auteurs : G. A. Campbell, Auteur ; M. D. Wetzel, Auteur Année de publication : 2018 Article en page(s) : p. 619-633 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Charges (matériaux) Dispersions et suspensions Fluides newtoniens Matières plastiques -- Extrusion Matières plastiques -- Moulage par injection Polyéthylène Rhéologie Index. décimale : 668.4 Plastiques, vinyles Résumé : All polymeric slurries that have a high concentration of filler are shear thinning. Shear thinning is an important characteristic of polymers, filled and unfilled, because it enables an increase in the throughput, shear rate in a die or an injection molding system without having to use substantially more power to increase the flow rate. Newtonian fluid-based slurries show an increase in shear thinning as the concentration of "filler" increases above the percolation threshold. As particle maximum packing concentration is approached the slurries begin to approach a perfect pseudoplastic fluid. In some cases, the shear thinning characteristics of a filled polymer do not increase substantially as the filler loading is increased. This is a quite different response that is newtonian fluid-based slurry. Therefore, it is important to understand the materials engineering interactions that control shear thinning so that process flow models can better predict the performance of filled polymer system. Highly filled polymers can have processing issues, including high screw shaft torque, energy consumption, die pressure and melt temperature rise. Previous theoretical developments and experimental evaluations of highly filled polymer melts showed that the rheology can be effectively described with a percolation model. In this work, capillary rheometer measurments using several low-density polyethylene resins, calcium carbonate and titanium dioxyde fillers are reported using percolation theory concepts. The theoretical treatment of the rheology as a particulate percolating system with power-law behavior is used to analysed capillary rheometer data. The observed effects of resin molecular weight, filler type and size on rheology are described. Engineers that design and debottleneck polymer processes need to utilize the polymer viscosity at the minimum process shear rate to determine the smallest motor that will allow the process to run ; in addition, the shear thinning characteristics of the polypmer are used to indicate how much increased production may be possible with a given motor size. Thus, some examples of expected effects on melt processing are also presented. Note de contenu : - POWER LAW THEORY DEVELOPMENT : Power law index, n - EXPERIMENTAL PROCEDURES : Application of the power law theory to newtonian fluid-based slurries - APPLICATION OF THEORY TO FILLED POLYMER MELTS : Implications for extrusion and molding processes DOI : 10.3139/217.3571 En ligne : https://www.degruyter.com/document/doi/10.3139/217.3571/pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=31392 [article]

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A study of concentrated suspensions in polyethylene melts and the impact on viscosity and polymer processing operations / Marc D. Wetzel in INTERNATIONAL POLYMER PROCESSING, Vol. XXXIII, N° 4 (08/2018)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXXIII, N° 4 (08/2018) . - p. 574-587 Titre : A study of concentrated suspensions in polyethylene melts and the impact on viscosity and polymer processing operations Type de document : texte imprimé Auteurs : Marc D. Wetzel, Auteur ; G. A. Campbell, Auteur Année de publication : 2018 Article en page(s) : p. 574-587 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Carbonate de calcium Le carbonate de calcium (CaCO3) est composé d'un ion carbonate (CO32-) et d'un ion calcium (Ca2+), sa masse molaire est de 100,1 g/mole. C'est le composant principal du calcaire et de la craie, mais également du marbre. C'est aussi le principal constituant des coquilles d'animaux marins, du corail et des escargots. Charges (matériaux) Dioxyde de titane Etat fondu (matériaux) Malaxeurs et mélangeurs Mélanges-maîtres (chimie) Percolation Polyéthylène basse densité linéaire Rhéologie Viscosité Index. décimale : 668.4 Plastiques, vinyles Résumé : Filled polymer compounds can present processing challenges, including poor dispersive mixing, high screw shaft torque and energy consumption, flow instabilities, and significant increases in melt pressures and temperatures. Previous theoretical development and experimental evaluations of polymer melts filled with particulate solids showed that the viscosity can be described with a model based on percolation theory concepts. This paper describes a batch mixer characterization method developed to measure the effects of filler concentration and operating conditions on the melt viscosity and process response. Experimental results are compared with capillary rheometer measurements using several low-density polyethylene resins, calcium carbonate and titanium dioxide. The theoretical treatment of the viscosity as a particulate percolating system with power-law behavior was used to analyze and compare rheometer and batch mixer data. The effects of resin molecular weight, filler type and size on viscosity and melt processing were examined and there was good agreement between rheometer and mixer viscosity trends, and percolation model predictions. The laboratory experiments and model estimates provide quantitative information that can be used to develop and troubleshoot extrusion compounding, single screw extrusion and low-shear forming processes. Note de contenu : - MATERIAL SYSTEMS AND MASTERBATCHES - RHEOLOGY MEASUREMENTS AND MODELS : Modified percolation-based filler concentration viscosity model - LDPE/TiO2 system - LLDPE/CaCO3 system - BATCH MIXER EXPERIMENTS : LLDPE/CaCO3 system - EFFECTS OF POLYMER TYPE, FILLER TYPE AND SIZE : LDPE/TiO2 system - DISCUSSION AND IMPACTS ON POLYMER PROCESSING DOI : 10.3139/217.3577 En ligne : https://drive.google.com/file/d/13HWzo5EDjdthp4Dlsr4ZA3LacgS15Ksj/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=30897 [article]

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