Understanding softening of amorphous materials for FFF applications / José Luis Colon Quintana in INTERNATIONAL POLYMER PROCESSING, Vol. 37, N° 1 (2022)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. 37, N° 1 (2022) . - p. 120-138 Titre : Understanding softening of amorphous materials for FFF applications Type de document : texte imprimé Auteurs : José Luis Colon Quintana, Auteur ; Tim Osswald, Auteur Année de publication : 2022 Article en page(s) : p. 120-138 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Chimie analytique Chlorure de polyvinyle Etat fondu (matériaux) Polyamide 6 Polyamides Un polyamide est un polymère contenant des fonctions amides -C(=O)-NH- résultant d'une réaction de polycondensation entre les fonctions acide carboxylique et amine. Selon la composition de leur chaîne squelettique, les polyamides sont classés en aliphatiques, semi-aromatiques et aromatiques. Selon le type d'unités répétitives, les polyamides peuvent être des homopolymères ou des copolymères. Polymères amorphes Polymères cristallins Polypropylène Rhéologie Transition de phase En physique, une transition de phase est une transformation du système étudié provoquée par la variation d'un paramètre extérieur particulier (température, champ magnétique...). Cette transition a lieu lorsque le paramètre atteint une valeur seuil (plancher ou plafond selon le sens de variation). La transformation est un changement des propriétés du système. Transition vitreuse Index. décimale : 668.4 Plastiques, vinyles Résumé : The work explores the fundamentals of the softening process for amorphous materials expanding on the work presented by Stammers and Beek (Stammers, E. and Beek, W.J. (1969). The melting of a polymer on a hot surface. Polym. Eng. Sci. 9). The pressure induced melt removal process was studied in detail. The process, although fundamental, allows for an understanding of the phase transition of materials during the fused filament fabrication (FFF) process. Experimental results were analyzed using state-of-the-art equipment. A total of four materials were tested. PVC and PC are amorphous materials, and PA6 and PP are semi-crystalline materials. A setup was built to allow the application of a constant force. The resulting melt film was analyzed using computed tomography technology. The experimental results were compared with numerical simulation results originating from COMSOL Multiphysics and the analytical solution derived by Stammers and Beek. Rheological and thermo-mechanical tests were used to find the softening temperature of amorphous materials. Results showed a straightforward transition for the melting temperature of semi-crystalline materials and softening temperature of amorphous materials. It is suggested that for amorphous materials, the glass transition temperature can be used as the softening temperature (T s = T g ). When comparing all three results (experimental, analytical, and numerical), values are within the same range and magnitude. A good approximation was achieved for PA6 and PVC, which have semi-crystalline and amorphous structures, respectively. Results provide insights into the phase transition process and phase change mechanisms during the extrusion of materials in the fused filament fabrication process. Note de contenu : - EXPERIMENTAL : Materials - Setup - Experimental procedure - Micro computed tomography (µ-CT) of melt film - Pressured induced melt removal solution - Thermogravimetric analysis (TGA) - Differntial scanning calorimetry (DSC) - Double shear test - COMSOL multiphysics - Rheological properties - PRESSURE INDUCED MELT REMOVAL PROCESS INCLUDING CONVECTION TERM : Mathematical derivation - RESULTS AND DISCUSSION : TGA results - DSC results - DMA results - DSC versus DMA - Rheological properties - Experimental results - Analytical model - Numerical solution : COMSOL multiphysics - Comparison of methods - Table 1 : Processing temperatures in °C - Table 2 : Compression molding parameters - Table 3 : Temperature range for double shear test - Table 4 : Rheometer temperatures - Table 5 : Melting temperature and heat of fusion of PA6 and PP - Table 6 : Glass transtition temperature of PC and PVC - Table 7 : Complex shear modulus model parameters (modulus with units of MPa) - Table 8 : Carreau - Yasuda parameters DOI : https://doi.org/10.1515/ipp-2021-4155 En ligne : https://drive.google.com/file/d/1OTuW0XxLIBbnXjss8QsmMh0aOlV8ZUQb/view?usp=share [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=38446 [article]

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