Quantitative analysis for polymer degradation in the extrusion process / H. Kometani in INTERNATIONAL POLYMER PROCESSING, Vol. XXI, N° 1 (03/2006)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXI, N° 1 (03/2006) . - p. 24-31 Titre : Quantitative analysis for polymer degradation in the extrusion process Type de document : texte imprimé Auteurs : H. Kometani, Auteur ; T. Kanai, Auteur ; T. Suga, Auteur ; T. Matsumura, Auteur Année de publication : 2006 Article en page(s) : p. 24-31 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Analyse quantitative (chimie) Matières plastiques -- Extrusion:Polymères -- Extrusion Polymères -- Détérioration Index. décimale : 668.9 Polymères Résumé : Polymer degradation in the extrusion process decreases quality and productivity. For this reason, it is necessary to prevent polymer degradation. In the extrusion process, polymer degradation is caused by oxidation. It depends on the processing temperature and the amount of dissolved oxygen in the molten polymer. Therefore, a quantitative analysis of these factors is required. As for the degradation characteristics of the material used in this study, temperature and oxygen concentration dependency of the oxidation rate could be quantitatively characterized with an apparatus to evaluate polymer degradation which utilized chemiluminescence generated by an oxidation reaction. Moreover, an online measuring apparatus to analyze dissolved gas in the extruded molten polymer was developed. With this apparatus, the volume ratio of dissolved gases (N2, O2 etc.) to the extruded molten polymer could be quantitatively analyzed and the quality of the extruded molten polymer evaluated. With this apparatus, dissolved nitrogen (an index of entrained air) was analyzed with a full-flight screw and a barrier screw. Furthermore, observation of cross sectional views in the screw channel obtained from the cooling experiment under the operating conditions was carried out for the full-flight screw and the barrier screw. With the full-flight screw, break up phenomenon (collapse of solid polymer) occurred in the screw channel and the amount of nitrogen increased. With the barrier screw, the amount of nitrogen decreased because of prevention of the break up phenomenon in the screw channel. Consequently, it is shown that the use of the barrier screw is suitable for oxygen reduction in the molten polymer, which is a factor in causing polymer degradation. DOI : 10.3139/217.0092 En ligne : https://drive.google.com/file/d/1QAWMdNQU0jcOmKDuPGX9UubeDi2FhIV0/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=2926 [article]

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Visualization of flow instabilities for high density polyethylene / H. Kometani in INTERNATIONAL POLYMER PROCESSING, Vol. XXI, N° 1 (03/2006)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXI, N° 1 (03/2006) . - p. 32-40 Titre : Visualization of flow instabilities for high density polyethylene Type de document : texte imprimé Auteurs : H. Kometani, Auteur ; T. Kanai, Auteur ; T. Suga, Auteur ; T. Matsumura, Auteur ; H. Kitajima, Auteur Année de publication : 2006 Article en page(s) : p. 32-40 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Polyéthylène haute densité Rhéologie Index. décimale : 668.9 Polymères Résumé : Two typical flow instabilities of “Shark Skin” and “Melt Fracture” for high density polyethylene were investigated in this report. Experimental measurements were carried out methodically in a wide flow region from the reservoir (entry region) to the die land with a specific slit die. Especially the flow pattern was visualized with a high speed camera and the frequency of the flow instability was analyzed. Corresponding to the visualization analysis, the pressure fluctuation in the slit die and the surface roughness at the die exit were measured simultaneously and these frequency characteristics were analyzed with a FFT (Fast Fourier Transform) analyzer. As for “Shark Skin” region, the irregularity of the surface roughness in the broad frequency band was recognized at the die exit. In spite of this surface roughness, the pressure fluctuation and the fluctuation of the flow pattern at the wall vicinity in the die land were not observed. These results indicate that “Shark Skin” occurs at the die exit. As for “Melt Fracture” region, the periodical oscillation of the flow pattern and the periodical pressure fluctuation which corresponded to the periodical distortion of the extrudate was recognized in the die land. However the periodical oscillation of the flow pattern and the periodical pressure fluctuation could not be recognized in the reservoir (entry region of the die land). These results indicate that “Melt Fracture” is initiated at the die entry and occurs in the die land. Consequently it is clarified that “Shark Skin” occurs at the die exit and the flow instability which lead to “Melt Fracture” is initiated at the die entry and occurs in the die land. DOI : 10.3139/217.0057 En ligne : https://drive.google.com/file/d/1JpHl1oJWg93Nc_BwHSAlDwFuiFkWjJsW/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=2927 [article]

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