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Auteur H. Yokoi |
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Ajouter le résultat dans votre panier Affiner la rechercheEffects of cavity conditions on transcription molding of microscale prism patterns using ultra-high-speed injection molding / X. Han in INTERNATIONAL POLYMER PROCESSING, Vol. XXI, N° 5 (11/2006)
Titre : Effects of cavity conditions on transcription molding of microscale prism patterns using ultra-high-speed injection molding Type de document : texte imprimé Auteurs : X. Han, Auteur ; T. Takahashi, Auteur ; H. Yokoi, Auteur Année de publication : 2006 Article en page(s) : p. 473-479 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : Ultra-high-speed injection molding has been reported to be a very effective method for improving transcription molding. In this study, by using stampers with V-grooves having pitches of 25 lm and 100 lm, we investigated the effects of cavity conditions, including cavity thickness, groove layout, and groove pitch size, on transcription molding. These experiments were also conducted under various molding conditions such as injection rates, melt and mold temperatures, and holding pressure, etc. As a result, it was found that the groove layout of a stamper remarkably affects transcription fidelity and these effects do not disappear when the molding is performed with a cavity-vacuum process. This phenomenon was explained using the well-known molecular orientation by the extensional flow during injection molding.When transcription molding was performed with cavities of different thicknesses (0.5 mm, 1.0 mm, and 2.0 mm), the effect of holding pressure on transcription was inversely related to the cavity wall thickness. This result indicates that, in the molding with a thin cavity wall, the transcription mainly completed during the filling stage. In addition to the shortening of cavity filling time and decrease in viscosity by shear heating, an accelerated increase in cavity pressure during the cavity filling stage was also found to be important for explaining the improvement in transcription with ultrahigh-speed injection molding. DOI : https://doi.org/10.3139/217.0112 En ligne : https://drive.google.com/file/d/1iG7URau_vkI5P7y3I1tTnpBXqCouNNF4/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=2801
in INTERNATIONAL POLYMER PROCESSING > Vol. XXI, N° 5 (11/2006) . - p. 473-479[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 005699 - Périodique Bibliothèque principale Documentaires Disponible
Titre : Visualization analysis of asymmetric fountain flow phenomenon in injection molding of filler-reinforced resins by rotary runner exchange system Type de document : texte imprimé Auteurs : H. Yokoi, Auteur ; Y. Kanetoh, Auteur Année de publication : 2005 Article en page(s) : p. 157-161 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : In this study, we attempted to visualize the flow patterns inside molded samples of glass-fibers or talc reinforced GPPS and PP especially in the vicinity of the flow front, using a rotary runner exchange system which instantaneously switches melt flowing into the cavity. From the visualization results, an extremely characteristic flow behavior was seen at the flow front area for resins with fillers which was not observed for those without fillers. Especially in the case of resins with 40 wt.% talc or 30 wt.% GF, a-symmetric zigzag fountain flows were generated alternately upward and downward along the cavity width direction. Moreover along the outer layer of the flow front, one observed a large amount of residual resin remaining for a long time during the cavity filling process, in the case of 40 wt.% GF, primarily due to the increase of viscosity which restricts the occurrence of diverging flow. Based on the above visualization results, we proposed a generic model of zigzag fountain flow; an a-symmetric upward flow in a certain area starts preventing the fountain flow in the upper side of the adjacent area, causing the diverging center to sink. This phenomenon subsequently causes an a-symmetric flow in the opposite direction in the next adjacent area, which continuously propagates along the cavity width direction. DOI : 10.3139/217.1875 En ligne : https://drive.google.com/file/d/1VqXzreoqEXJDat_AznmBOZpOFGuW5Y-r/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3075
in INTERNATIONAL POLYMER PROCESSING > Vol. XX, N° 2 (06/2005) . - p. 157-161[article]Réservation
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Titre : Visualization analysis of a multilayer foam development process in microcellular injection molding Type de document : texte imprimé Auteurs : T. Yamada, Auteur ; Y. Murata, Auteur ; H. Yokoi, Auteur Année de publication : 2012 Article en page(s) : p. 299-309 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Construction sandwich
Matières plastiques -- Moulage par injection microcellulaire
Mousses plastiques
Polystyrène
Revêtements multicouchesIndex. décimale : 668.4 Plastiques, vinyles Résumé : In this study, cross-sectional analyses were performed on microcellular injection-molded high-impact polystyrene products. The results confirm that the following five types of layers were formed: Skin layers I (the silver streak layer) and II (a nonfoamed layer), Core layers I (cell diameter, d > 150 µm), II (d < 50 µm), and III (d > 100 µm). As the maximum in-mold pressure (Pmax) was increased from 5 to 30 MPa, the thickness of Skin layer II remained nearly constant. However, the foam types in the core layers changed from I and II to II and III or III only, resulting in an increase in cell diameter and a decrease in cell density. The process of cellular structure formation was observed using a glass-inserted mold, which revealed that this process consists of a flow (with a burst of cells at the melt front and the subsequent flow of the melt containing the cells), an end of the filling (involving elastic compression or the dissolution and disappearance of cells formed in the flow stage), and a cooling (new cell generation and growth and cooling solidification). Based on these cross-sectional observations, in concert with meltpressure measurements and visualizations, we developed a model describing the formation process of Skin layer II and the core layers including a new concept that considers the melt pressure inside the cavity. The following layers are incorporated into the model: Skin layer II: A nonfoamed layer is formed in the area of the melt front where gases diffuse out from within the melt during the filling stage, and this nonfoamed layer moves to from melt front to the surface of the product due to fountain flow. Core layers I and II: A multilayer is formed containing a distribution of cells preserved from the flow stage due to the low compression forces, Core layer III: cells are dissolved in the melt due to strong compression forces at the end of the filling stage and then reform and grow in the cooling stage. DOI : 10.3139/217.2443 En ligne : https://drive.google.com/file/d/1dVnoo3jHmY1a6xZXcNmshaz-sdzkH-C-/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=15575
in INTERNATIONAL POLYMER PROCESSING > Vol. XXVII, N° 3 (07/2012) . - p. 299-309[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 13995 - Périodique Bibliothèque principale Documentaires Disponible
Titre : Visualization analysis of resin flow behavior around a flow front using a rotary runner exchange system Type de document : texte imprimé Auteurs : Y. Kanetoh, Auteur ; H. Yokoi, Auteur Année de publication : 2012 Article en page(s) : p. 310-317 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Ecoulement visqueux
Fluides, Mécanique des
Matières plastiques -- Moulage par injection -- Appareils et matériel
Moulage par injection -- Défauts
Moules d'injection
PolystyrèneIndex. décimale : 668.4 Plastiques, vinyles Résumé : In plastic injection molding, external defects such as flow marks are serious problems. These external defects are known to occur during cavity filling processes inside the mold, and are closely related to resin flow behavior in the flow front area. In this study, the authors propose a new method for visualizing in-mold resin flow behavior using a glass-inserted mold and rotary runner exchange system capable of instantaneously switching two types of melt at the runner just before the gate. This method is capable not only of dynamic visualization, but also static visualization by the observation of cross-sections of a sample, because colored resins switched multiple times at the gate spread in layers inside the sample and freeze. Using this method and general purpose polystyrene, visualization analysis of the flow behavior of inner layer resins near the flow front in simple rectangular cavities was carried out. As a result, it was found that resins reaching the flow front are not exposed at the molded product surface immediately after the fountain-flow process, but remain along the circumference of the flow front for a long period of time, and then stretch out into a thin filmlike shape to form the surface of the molded product. In addition, the inner layer resins near the flow front form a converging flow just before reaching the flow front and then form a fountain flow. It was also confirmed that this is a general phenomenon in the fountain-flow process during injection molding regardless of whether the resin is crystalline or noncrystalline. Based on these results, we built a model on the flow of inner layer resins near the flow front of general resins. DOI : 10.3139/217.2457 En ligne : https://drive.google.com/file/d/12C-9v6b6ma__sKVLqopueoqxp7OW7vvm/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=15576
in INTERNATIONAL POLYMER PROCESSING > Vol. XXVII, N° 3 (07/2012) . - p. 310-317[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 13995 - Périodique Bibliothèque principale Documentaires Disponible
Titre : Visualization of melt-flow behavior inside the runner in ultra high speed injection molding Type de document : texte imprimé Auteurs : S. Hasegawa, Auteur ; H. Yokoi, Auteur Année de publication : 2006 Article en page(s) : p. 464-472 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : Ultra-high-speed injection molding is a highly effective technique for realizing very thin-walled molded parts; its application to the production of new high value-added products is anticipated. The melt-flow behavior in ultra-high-speed injection molding is expected to differ from that in conventional molding. However, thus far, very few studies pertaining to the phenomena occurring within cavities and runners at such high filling speeds have been reported, thus necessitating the direct observation of melt-flow behavior inside the molds. In this study, we attempted to dynamically visualize the meltflow behavior at the runner split portion, especially under ultra-high-speed injection molding. Visualization experiments were conducted using a glass-inserted mold, which was modified from the original visualization mold structure in order to improve the pressure endurance of the glass-inserted visible area. This paper discusses the visualization analyses of meltflow behavior in two types of experimental split runner systems (three inclined split runners and cross-shaped runners in a cascade layout). The behavior at the runner split area was studied under low to ultra-high-filling rates. The analyses clarified the effects of inertia at the runner branching point, which has not been verified in general injection molding, and the consequent changes in the filling behavior. DOI : https://doi.org/10.3139/217.0997 En ligne : https://drive.google.com/file/d/1SttkV178jpaTfR20bVuN3FeALuvqWQqu/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=2800
in INTERNATIONAL POLYMER PROCESSING > Vol. XXI, N° 5 (11/2006) . - p. 464-472[article]Réservation
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