Relationship between molecular orientation relaxation during physical aging and heat resistance of polystyrene injection moldings / K. Tao in INTERNATIONAL POLYMER PROCESSING, Vol. 36, N° 5 (2021)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. 36, N° 5 (2021) . - p. 577-585 Titre : Relationship between molecular orientation relaxation during physical aging and heat resistance of polystyrene injection moldings Type de document : texte imprimé Auteurs : K. Tao, Auteur ; K. Yamada, Auteur ; S. Higashi, Auteur ; K. Kago, Auteur ; H. Takeshita, Auteur ; K. Tokumitsu, Auteur Année de publication : 2021 Article en page(s) : p. 577-585 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Basses températures Hautes températures Matières plastiques -- Moulage par micro-injection Orientation moléculaire (matériaux) Polystyrène Résistance thermique Viscoélasticité Index. décimale : 668.4 Plastiques, vinyles Résumé : This work examined the relationship between changes in molecular orientation and the heat resistance (heat distortion temperature) of polystyrene injection moldings following heat treatment below the glass transition temperature. Molecular orientation around the core layer of the injection moldings was found to be relaxed by the heat treatment. Also, in the untreated specimen, the molecular orientation around the core layer was relaxed from 60°C during the heating process. Since loss tangent (tanδ) also increased from 60°C during the heating process in the untreated specimen, it was considered that the increase in tanδ occurred with the molecular motion due to the relaxation of molecular orientation from 60°C. After the heat treatment, because of the relaxation of molecular orientation around the core layer by the heat treatment, the relaxation of molecular orientation from 60 °C did not occur during the subsequent heating process, and the tanδ of the polymer between 60 and 90 °C was decreased. Because this decrease in the tanδ over this temperature range improved the heat resistance of the material, the enhanced heat resistance by the heat treatment was attributed to the suppression of the relaxation of molecular orientation from 60°C during the heating process. Furthermore, relaxation of molecular orientation and enthalpy relaxation were related to improvement in the heat resistance. Note de contenu : - EXPERIMENTAL PROCEDURE : Material - Injection molding - Low temperature heat treatment - High temperature heat treatment - Observation of optical distortion - Evaluation of molecular orientation by laser Raman spectroscopy - Raman mapping of cross sections - Measurement of dynamic viscoelasticity - Determination of heat distortion temperature - Comparison of enthalpy relaxation behaviors - RESULTS AND DISCUSSION : Effect of heat treatment on molecular orientation - Effect of heat treatment on dynamic viscoelasticity - Relationship between molecular orientation and dynamic viscoelasticity - Enthalpy relaxation by heat treatment - Relationship between relaxation of molecular orientation and heat resistance DOI : https://doi.org/10.1515/ipp-2020-4093 En ligne : https://drive.google.com/file/d/1DpG0tvJJ0lDM4WQBVe6Gyf5UNpuBMOZ5/view?usp=shari [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=36524 [article]

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