Analysis of shrinkage development of injection moulded PS samples / R. Pantani in INTERNATIONAL POLYMER PROCESSING, Vol. XIV, N° 2 (06/1999)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XIV, N° 2 (06/1999) . - p. 183-190 Titre : Analysis of shrinkage development of injection moulded PS samples Type de document : texte imprimé Auteurs : R. Pantani, Auteur ; G. Titomanlio, Auteur Année de publication : 1999 Article en page(s) : p. 183-190 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : Molding - Modern approaches to the phenomenon of dimensional accuracy in injection moulding link the evolution of shrinkage from the moment of first solidification to a force balance between restraining and constraining forces which sets in inside the mould before ejection. Such an approach needs a complete understanding of what happens inside the cavity during the moulding cycle. In a recent paper [9], a new technique has been presented, by which it is possible to follow the shrinkage development of an injection moulded sample from the moment it starts solidifying to soon after ejection. In this work, with reference to a simple rectangular cavity, shrinkage curves measured by strain gages in different moulding conditions are analysed by means of a simple thermomechanical model recently proposed. Results show that the model satisfactorily predicts the moment shrinkage starts inside the mould and reveal the existence of a restraining force not due to pressure, which builds in gradually in a few seconds from the instant of first solidification. Knowing the value of this force - which can be drawn by Hooke's law from the strain jump at mould opening - the model gives a good description of both shrinkage development inside the mould and ejection shrinkage. DOI : 10.3139/217.1529 En ligne : https://drive.google.com/file/d/1zjvr4-f_hNxp_5Pvp9_dXcZeJhnddnvO/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=16102 [article]

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A criterion for the formation of fibrillar layers in injection molded parts / R. Pantani in INTERNATIONAL POLYMER PROCESSING, Vol. XXXIII, N° 3 (07/2018)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXXIII, N° 3 (07/2018) . - p. 355-362 Titre : A criterion for the formation of fibrillar layers in injection molded parts Type de document : texte imprimé Auteurs : R. Pantani, Auteur ; Vito Speranza, Auteur ; G. Titomanlio Année de publication : 2018 Article en page(s) : p. 355-362 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Matières plastiques -- Moulage par injection Polypropylène Simulation par ordinateur Structures fibrillaires Index. décimale : 668.4 Plastiques, vinyles Résumé : It is quite well known that the morphology of an injection molded part made by a semicrystalline polymer presents several layers. In particular spherulitic structures are found in the core region, a layer characterized by highly oriented fibrillar morphology (the shear layer) usually follows and a skin layer is often observed at the sample surface. The thickness of the fibrillar layer deeply influences the mechanical properties of the part. In this work, a criterion to predict the thickness of the fibrillar layer is proposed and verified. The criterion is essentially based on the amount of viscous work done when the molecular stretch is higher than a critical value: the molecular stretch should be above a critical value while a critical amount of viscous work is accumulated. In order to tune the parameters, and to validate the criterion, a well characterized polypropylene was chosen as test material, and four different injection molding conditions were analyzed. The criterion is verified by comparing some experimental results with the prediction of the UNISA code (an injection molding software developed at the University of Salerno), good comparison between software predictions and experimental data confirms the suitability of the criterion. Note de contenu : - INJECTION MOLDING DATA AND PROCESS SIMULATION - INJECTION MOLDING SIMULATIONS : Definition of the molecular stretch parameter - Final distributions of stretch and work and their evolutions - APPLICATION OF THE SIMULTANEITY CRITERION DOI : 10.3139/217.3543 En ligne : https://www.degruyter.com/document/doi/10.3139/217.3543/pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=30804 [article]

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Crystallinity and linear rheological properties of polymers / G. Lamberti in INTERNATIONAL POLYMER PROCESSING, Vol. XXII, N° 3 (07/2007)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXII, N° 3 (07/2007) . - p. 303-310 Titre : Crystallinity and linear rheological properties of polymers Type de document : texte imprimé Auteurs : G. Lamberti, Auteur ; G. Titomanlio, Auteur ; G. W. M. Peters, Auteur Année de publication : 2007 Article en page(s) : p. 303-310 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : The crystallization of a polymer melt, taking place during transformation processes, has a great impact on the process itself, mainly because it causes a large increase in the viscosity (hardening). Knowledge of the hardening kinetics is important for modeling and controlling the transformation processes. In this work, first an overview is given of the experimental and modeling work on the hardening of crystallizing polymers. Next, we present isothermal crystallization experiments using differential scanning calorimetry (DSC) and rotational rheometry to measure the dynamic viscosity. The evolution of the relative crystallinity and normalized complex viscosity are correlated by a novel technique which allows simultaneous analysis of several runs, even if they are not carried out at same temperatures; the main requirement with the traditional technique. The technique, described in detail in this paper, provides an experimental relationship between the crystallinity and the hardening, i.e. the increase in the viscosity. Moreover, by measuring the dynamic viscosity at different frequencies, surprisingly, a master curve is obtained which combines the effects of shear rate, temperature and the level of crystallinity. DOI : 10.3139/217.2006 En ligne : https://drive.google.com/file/d/1k6Wv4JH11chxsFT9c65tRgm1ZvmdmpNz/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=2708 [article]

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Evolution of morphology of iPP in processing conditions / I. Coccorullo in INTERNATIONAL POLYMER PROCESSING, Vol. XX, N° 2 (06/2005)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XX, N° 2 (06/2005) . - p. 186-190 Titre : Evolution of morphology of iPP in processing conditions : Relevance of solidification pressure Type de document : texte imprimé Auteurs : I. Coccorullo, Auteur ; G. Titomanlio, Auteur ; R. Pantani, Auteur Année de publication : 2005 Article en page(s) : p. 186-190 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : A model for crystallization kinetics that accounts for the formation of different crystalline phases and is able to describe the morphological characteristics of samples solidified under quiescent conditions, has been enriched to account for the effect of solidification pressure. The effect of pressure was considered by assuming a linear increase of melting and glass transition temperatures (which are involved in the description of the growth rate and nucleation density of the alpha phase). Moreover, pressure was incorporated in the kinetic constant adopted to describe the evolution of the mesomorphic phase. The parameters of the model were identified on the basis of literature data on the distribution of crystalline phases in samples solidified under different pressures. The modified model also satisfactorily described PVT curves up to 100MPa, and is now able to describe the evolution of morphology during solidification at cooling rates as fast as several hundreds of Kelvin degrees per second and under pressures of as high as 100MPa. DOI : 10.3139/217.1877 En ligne : https://drive.google.com/file/d/1MU0nmmxwVQ7tBh-DdIgxGkunDd7jIRT1/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3079 [article]

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Polymer solidification under pressure and high cooling rates / Valerio Brucato in INTERNATIONAL POLYMER PROCESSING, Vol. XV, N° 1 (03/2000)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XV, N° 1 (03/2000) . - p. 103-110 Titre : Polymer solidification under pressure and high cooling rates Type de document : texte imprimé Auteurs : Valerio Brucato, Auteur ; Vincenzo La Carrubba, Auteur ; G. Titomanlio, Auteur ; S. Piccarolo, Auteur Année de publication : 2000 Article en page(s) : p. 103-110 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : Polymer solidification under processing conditions is a complex phenomenon in which the kinetics of flow, high thermal gradients and high pressures determine the product morphology. The study of polymer structure formed under pressure has been mainly made using conventional techniques such as dilatometry and differential scanning calorimetry under isothermal conditions or non isothermal conditions but at cooling rates several orders of magnitude lower than those experienced in industrial processes. A new equipment has been recently developed and improved to study the crystallization of polypropylene when subjected to pressure and cooled rapidly. An experimental apparatus essentially constituted of a special injection mould has been employed. Polymer samples can be cooled at a known cooling rate and under a known pressure. Micro Hardness (MH), Wide angle x-ray diffraction (WAXD), Polarised Optical Microscopy (POM) and density measurements are then used to characterize the sample morphology. The results of rapid cooling experiments under pressure on an iPP sample display a lower density and a lower density dependence on cooling rate for increasing pressure. Micro hardness confirms the trend. A deconvolution technique of WAXD patterns is used to evaluate the final phase content of samples and to assess a crystallization kinetics behaviour. Phase distribution results indicate that the decrease of alpha phase with pressure is balanced by an increase of the mesomorphic phase leaving unaffected the amorphous phase content. This peculiar behaviour can be easily related to a negative influence of pressure on the kinetics of the crystallization of alpha phase. Note de contenu : - EXPERIMENTAL : Apparatus development - Material employed - Sample preparation - Sample characterization - Heat-transfer modelling of cooling inside the polymer - RESULTS AND DISCUSSION : Density and microhardness dependence on cooling rate and pressure - Properties-structure relationships DOI : 10.3139/217.1572 En ligne : https://drive.google.com/file/d/1ewmLxSkxdwt6FVg-Y8NCLwNzMQfwP6bT/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=16089 [article]

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Relevance of crystallisation kinetics in the simulation of the injection molding process / R. Pantani in INTERNATIONAL POLYMER PROCESSING, Vol. XVI, N° 1 (03/2001)  

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Solidification criterion on shrinkage predictions for semi-crystalline injection moulded samples / A. J. Pontes in INTERNATIONAL POLYMER PROCESSING, Vol. XV, N° 3 (09/2000)  

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Thirty years of modeling of injection molding. A brief review of the contribution of UNISA code to the field / R. Pantani in INTERNATIONAL POLYMER PROCESSING, Vol. XXXI, N° 5 (11/2016)  

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