Enhanced infrared heating of thermoplastic composite sheets for thermoforming processes / M. Längauer in INTERNATIONAL POLYMER PROCESSING, Vol. 36, N° 1 (2021)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. 36, N° 1 (2021) . - p. 35-43 Titre : Enhanced infrared heating of thermoplastic composite sheets for thermoforming processes Type de document : texte imprimé Auteurs : M. Längauer, Auteur ; G. Zitzenbacher, Auteur ; C. Burgstaller, Auteur ; C. Hochenauer, Auteur Année de publication : 2021 Article en page(s) : p. 35-43 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Chauffage Composites à fibres -- Thermoformage Composites à fibres de carbone Composites à fibres de verre Polyamide 6 Polyamide 66 Rayonnement infrarouge Index. décimale : 668.4 Plastiques, vinyles Résumé : Thermoforming of thermoplastic composites attracts increasing attention in the community due to the mechanical performance of these materials and their recyclability. Yet there are still difficulties concerning the uniformity of the heating and overheating of parts prior to forming. The need for higher energy efficiencies opens new opportunities for research in this field. This is why this study presents a novel experimental method to classify the efficiency of infrared heaters in combination with different thermoplastic composite materials. In order to evaluate this, different organic sheets are heated in a laboratory scale heating station until a steady state condition is reached. This station mimics the heating stage of an industrial composite thermoforming device and allows sheets to slide on top of the pre-heated radiator at a known distance. By applying thermodynamic balances, the efficiency of chosen parameters and setups is tested. The tests show that long heating times are required and the efficiency of the heating is low. Furthermore, the efficiency is strongly dependent on the distance of the heater to the sheet, the heater temperature and also the number of heating elements. Yet, using a full reflector system proves to have a huge effect and the heating time can be decreased by almost 50%. Note de contenu : - Specific heat capacity - Heating tests without reflectors - Heating tests using reflectors - Table 1 : Input parameters for the calculation of the enthalpy and heat flux (a derived from material data sheet) DOI : https://doi.org/10.1515/ipp-2020-3923 En ligne : https://drive.google.com/file/d/1NRCKw4IGMW7OJRvSI5wngwS8omSB2xAy/view?usp=shari [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=36344 [article]

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Modeling and estimation of the pressure and temperature dependent bulk density of polymers / Christian Kneidinger in INTERNATIONAL POLYMER PROCESSING, Vol. XXXV, N° 1 (03/2020)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXXV, N° 1 (03/2020) . - p. 70-82 Titre : Modeling and estimation of the pressure and temperature dependent bulk density of polymers Type de document : texte imprimé Auteurs : Christian Kneidinger, Auteur ; M. Längauer, Auteur ; Gernot Zitzenbacher, Auteur ; S. Schuschnigg, Auteur ; Jürgen Miethlinger, Auteur Année de publication : 2020 Article en page(s) : p. 70-82 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Extrudeuse monovis Masse volumique Mesure Modèles mathématiques Polymères Pression Index. décimale : 668.4 Plastiques, vinyles Résumé : The bulk density of polymers is a crucial factor for the throughput and the pressure build-up of single screw plasticating units. It depends not only on the density of the polymeric material itself, but also on the geometry of the single pellets, on the dimensions of the screw channel and, furthermore, on the temperature and the pressure. A review of the existing models shows that there is potential for improvement, as their applicability is restricted. It is difficult to obtain model parameters, as they can only be determined by experiment, but there are only a few devices which enable temperature- and pressure-dependent bulk density to be measured. Furthermore, these devices are not standardized. This work presents a new model which can be used to calculate the bulk density as a function of pressure and temperature and an adapted approach that considers the dimensions of the single pellets and the screw channel. The model is verified by both, new data derived from experiments and data from the literature. Compared to existing models, this new model fits the experimental data better, requires fewer parameters and shows much better extrapolation behavior as well as a continuous changeover behavior at the melting temperature. Another big advantage of the new model compared to the existing ones is that the model parameters of this new model can be estimated from the stress at yield and from the melting temperature. This enables a rough estimation of the pressure and temperature dependent bulk density without having to measure it. Note de contenu : - INTRODUCTION : Measurement of the bulk density - Existing models - Evaluation of the existing models - PROPOSED MODEL : Material density - Adjustable approach - Simplified approach - Combined approach - Modification by implementation of the volumetric transition temperature - Modifications considering the temperature dependence of the bulk density at zero pressure - Consideration of the screw channel geometry - Benefits of the new model compared to the existing models - Parameter fitting - MATERIALS USED - RESULTS AND DISCUSSION - ESTIMATING MODEL PARAMETERS FROM MATERIAL PROPERTIES DOI : https://doi.org/10.3139/217.3876 En ligne : https://drive.google.com/file/d/1jH3kB_e72-_OymLxouI82g5CYVTN2VzK/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=33780 [article]

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Modeling temperature and time dependence of the wetting of tool steel surfaces by polymer melts / Gernot Zitzenbacher in INTERNATIONAL POLYMER PROCESSING, Vol. XXXII, N° 2 (05/2017)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXXII, N° 2 (05/2017) . - p. 245-252 Titre : Modeling temperature and time dependence of the wetting of tool steel surfaces by polymer melts Type de document : texte imprimé Auteurs : Gernot Zitzenbacher, Auteur ; M. Längauer, Auteur ; C. Holzer, Auteur Année de publication : 2017 Article en page(s) : p. 245-252 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Acier L'acier est un alliage métallique utilisé dans les domaines de la construction métallique et de la construction mécanique. L'acier est constitué d'au moins deux éléments, le fer, très majoritaire, et le carbone, dans des proportions comprises entre 0,02 % et 2 % en masse1. C'est essentiellement la teneur en carbone qui confère à l'alliage les propriétés du métal qu'on appelle "acier". Il existe d’autres métaux à base de fer qui ne sont pas des aciers comme les fontes et les ferronickels par exemple. Angle de contact Etat fondu (matériaux) Métaux -- Surfaces Modèles mathématiques Mouillage (chimie des surfaces) Polyméthacrylate de méthyle Le poly(méthacrylate de méthyle) (souvent abrégé en PMMA, de l'anglais Poly(methyl methacrylate)) est un polymère thermoplastique transparent obtenu par polyaddition dont le monomère est le méthacrylate de méthyle (MMA). Ce polymère est plus connu sous son premier nom commercial de Plexiglas (nom déposé), même si le leader global du PMMA est Altuglas International9 du groupe Arkema, sous le nom commercial Altuglas. Il est également vendu sous les noms commerciaux Lucite, Crystalite, Perspex ou Nudec. Polypropylène Index. décimale : 668.4 Plastiques, vinyles Résumé : Beside the surface properties of the tool material, its temperature is an important parameter influencing the wettability of the tool surface by polymer melts in extrusion technology and injection molding. The temperature and time dependence of the contact angle of a polypropylene and a polymethylmethacrylate melt on polished tool steel was studied in this work at close to process conditions. The experiments were conducted by placing the polymeric sample on the hot tool material substrate in a high temperature chamber and recording the drop shape dependence on time. Based on the experimental results, a novel model was developed which allows a description of the contact angle dependent on temperature and time. The contact angle of the investigated polymer melts exhibits a linear decrease with rising temperature, which means that the wettability of the tool material by the polymer melt is improved with increasing temperature. Furthermore, the model proposed herein enables a complete mathematical description of the contact angle of polymer melts on the tool material dependent on temperature and time. The parameters of this function are the initial contact angle ?0, the contact angle when time approaches infinity ?? and a characteristic material time B. The time dependency is incorporated by an exponential function. The characterizing contact angle parameters (?0, ??) follow a linear decrease with rising temperature. The characteristic material time B obeys an exponential law dependent on the reciprocal value of temperature similar to Arrhenius' law. Note de contenu : - EXPERIMENTAL : Materials - Determination of surface roughness - Determination of the contact angle of the polymer melts - RESULTS AND DISCUSSION : Temperature dependence of the contact angle - Modeling time and temperature dependence of the contact angle DOI : 10.3139/217.3340 En ligne : https://drive.google.com/file/d/12TWebHMjzkjDu-LsGFJvTFTUHe729_qV/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=28522 [article]

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