Effects of injection molding holding pressure on the replication of surface microfeatures / T. R. Tofteberg in INTERNATIONAL POLYMER PROCESSING, Vol. XXV, N° 3 (07/2010)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXV, N° 3 (07/2010) . - p. 236-241 Titre : Effects of injection molding holding pressure on the replication of surface microfeatures Type de document : texte imprimé Auteurs : T. R. Tofteberg, Auteur ; H. Amédro, Auteur ; F. Grytten, Auteur ; E. Andreassen, Auteur Année de publication : 2010 Article en page(s) : p. 236-241 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Matières plastiques -- Moulage par injection Moulage par injection -- Défauts Polycarbonates Tags : Polycarbonate  'Moulage  par  injection'  'Interférométrie  de  lumière  blanche'  (WLI)  à  haute  résolution  verticale'  (HDVSI)  Recuisson  'Pression  possession'  'Lignes  flux'  'Défauts  d'injection' Index. décimale : 668.9 Polymères Résumé : The injection molding of an optical grating was studied using two different polycarbonates. The grating had period 10 μm and peak-to-valley distance ∼1 μm. Parts were molded using different holding pressures and mold temperatures. After production, the parts were annealed at 100°C. The replication was investigated using white light interferometry (WLI) before and after annealing. WLI was performed using high definition vertical-scanning interferometry (HDVSI) to resolve the details of the molded gratings with a noise level below 2 nm. It was observed that increasing the holding pressure could have either a positive or a negative effect on the replication. When the microfeatures were not fully filled, an increased holding pressure improved the definition of the features. However, for both polymers, it was observed that the replication as a function of holding pressure started to drop when the holding pressure was increased above an optimal value. This could be due to an elastic recoil occurring after releasing the holding pressure. The peak-to-valley distance of the grating was reduced after annealing. This effect was larger for parts molded using a low mold temperature. This is probably due to a higher cooling rate giving higher internal stresses, which will relax during annealing. DOI : 10.3139/217.2340 En ligne : https://drive.google.com/file/d/1Jr8pmzkZ8ZrKvyMacqDsvjly-jPSoUt-/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=9739 [article]

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Multiscale simulation of injection molding of parts with low aspect ratio microfeatures / T. R. Tofteberg in INTERNATIONAL POLYMER PROCESSING, Vol. XXV, N° 1 (03/2010)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXV, N° 1 (03/2010) . - p. 63-74 Titre : Multiscale simulation of injection molding of parts with low aspect ratio microfeatures Type de document : texte imprimé Auteurs : T. R. Tofteberg, Auteur Année de publication : 2010 Article en page(s) : p. 63-74 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : This article presents a simulation study of the injection molding of a macroscopic part with microfeatures; an optical grating with amplitude 0.6 µm and period 3 µm. The aim of the simulations is to develop a procedure capable of predicting the replication of optical gratings based on the injection molding processing parameters. Three coupled simulations are performed. 1.) A macroscopic simulation of the flow in the part without microfeatures. 2.) A microscale flow simulation in a domain around a single microfeature using the pressure from the macroscopic simulation as input. 3.) A thermal simulation of the mold wall coupled to the microscale simulation. In the simulations the polymer melt is treated as a generalized Newtonian fluid. Shear viscosity and thermal properties were characterized as part of the study. Other physical effects such as wall adhesion and elasticity are discussed, but not included in the present model. The simulation results agree well with the experimental replication data, and correctly describe how small changes in the mold temperature can lead to large changes in the replication. DOI : 10.3139/217.2318 En ligne : https://drive.google.com/file/d/1ubhK8LMFOrMlF9I-KYX8eM26KGis6ZV8/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=8584 [article]

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