Effect of molding history on molecular orientation relaxation during physical aging of polystyrene injection moldings / Kousaku Tao in INTERNATIONAL POLYMER PROCESSING, Vol. 38, N° 2 (2023)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. 38, N° 2 (2023) . - p. 233-243 Titre : Effect of molding history on molecular orientation relaxation during physical aging of polystyrene injection moldings Type de document : texte imprimé Auteurs : Kousaku Tao, Auteur ; Koji Yamada, Auteur ; Seiji Higashi, Auteur ; Keitaro Kago, Auteur ; Shiho Kuwashiro, Auteur ; Hiroshi Hirano, Auteur ; Hiroki Takeshita, Auteur ; Katsuhisa Tokumitsu, Auteur Année de publication : 2023 Article en page(s) : p. 233-243 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Matières plastiques -- Détérioration Matières plastiques -- Moulage par injection Orientation moléculaire (matériaux) Phénomènes de relaxation (matériaux) Polystyrène Index. décimale : 668.4 Plastiques, vinyles Résumé : This work examined the effect of changing molding conditions on the physical aging of polystyrene injection moldings. First, we investigated the relationship between the molecular orientation and the molding conditions. The molecular orientation near the surface changed with changing injection rate, so we hypothesized that this molecular orientation might form during the filling stage. Because this molecular orientation did not relax under heat treatment below the glass transition temperature (Tg), the oriented molecules near the surface were thought to be elongated owing to the high strain rate during the filling stage. On the other hand, the molecular orientation in the core layer changed with changing holding pressure and relaxed under heat treatment below Tg. Thus, the molecules in the core layer might become oriented during the holding stage and not be elongated owing to the slow strain rate. Furthermore, the molecular orientation in the core layer decreased with increasing mold temperature, and the physical heat resistance improved with increasing mold temperature. Meanwhile, the excess enthalpy did not change with changing molding conditions. Therefore, the improvement in physical heat resistance with increasing mold temperature was likely caused by the decrease in the molecular orientation in the core layer. Analyzing the relaxation behavior of the molecular orientation suggested that increasing mold temperature reduced the number of oriented molecules with large deformation in the core layer. Note de contenu : - EXPERIMENTAL PROCEDURE : Material - Injection molding - Heat treatment - Evaluation of molecular orientation by laser Raman spectroscopy - Raman mapping of cross sections - Comparison of enthalpy relaxation behaviors - Determination of heat distortion temperature - RESULTS AND DISCUSSION : Effect of molding conditions on molecular orientation - Effect of molding conditions on enthalpy relaxation - Effect of molding conditions on physical heat resistance - Effect of mold temperature on the structure of oriented molecules DOI : https://doi.org/10.1515/ipp-2022-4264 En ligne : https://drive.google.com/file/d/1RkYjnHka-5hUU9fMmnn3Qb1HmaDdJfpG/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=39504 [article]

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