Crystallization behavior of polyvinyl alcohol with 1,2-diol side-chains / Mitsuo Shibutani in INTERNATIONAL POLYMER PROCESSING, Vol. XXXIII, N° 2 (05/2018)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXXIII, N° 2 (05/2018) . - p. 234-244 Titre : Crystallization behavior of polyvinyl alcohol with 1,2-diol side-chains Type de document : texte imprimé Auteurs : Mitsuo Shibutani, Auteur ; T. Yamamoto, Auteur ; K. Inoue, Auteur ; K. Tokumitsu, Auteur Année de publication : 2018 Article en page(s) : p. 234-244 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Additifs Alcool polyvinylique Analyse thermique Calorimétrie Cristallisation Index. décimale : 668.4 Plastiques, vinyles Résumé : The crystallization behavior of a newly developed polyvinyl alcohol with 1,2-diol side-chains (DPVA) was investigated for different 1,2-diol side-chain, magnesium acetate, and sodium acetate contents. Crystallization by stepwise cooling, isothermal and non-isothermal crystallization (the actual cooling process in melt molding) experiments were conducted. Upon crystallization analysis by stepwise cooling, the end surface energy of DPVA increased as the 1,2-diol side-chain content was increased. The isothermal crystallization process exhibited longer half crystallization times at high 1,2-diol side-chain and magnesium acetate contents. Upon Kissinger analysis of the non-isothermal crystallization results, the effect of the acetate salts was found to be smaller than that for isothermal crystallization, while the smaller number of repeating units in the lamellar structure, reflecting a higher side-chain 1,2-diol content, resulted in a smaller activation energy for DPVA crystallization. In addition, analyses by the Ozawa method and the Kissinger Plot suggested possible changes in the mode and dimension of the crystal growth of DPVA. Note de contenu : - EXPERIMENTAL : Preparation of DPVA - Additives for DPVA - DPVA additive mixing conditions - Crystallization by stepwise cooling - Isothermal differential scanning calorimetry (DSC) analysis - Non-isothermal DSC analysis - RESULTS AND DISCUSSION : DPVA crystallization by stepwise cooling - Isothermal crystallization conditions : Tm - 14°C - Non-isothermal DSC anaysis DOI : 10.3139/217.3479 En ligne : https://drive.google.com/file/d/1pUHqFKyjaHKRK1Wn_KnwIiZYmuVxRHcu/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=30572 [article]

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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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