Carbon nanotube conductive networks through the double percolation concept in polymer systems / A. Abbasi in INTERNATIONAL POLYMER PROCESSING, Vol. XXIX, N° 1 (03/2014)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXIX, N° 1 (03/2014) . - p. 13-27 Titre : Carbon nanotube conductive networks through the double percolation concept in polymer systems Type de document : texte imprimé Auteurs : A. Abbasi, Auteur ; A. Derdouri, Auteur ; Pierre J. Carreau, Auteur Année de publication : 2014 Article en page(s) : p. 13-27 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Butylène téréphtalate cyclique Conduction électrique Matériaux hybrides Matières plastiques -- Moulage par micro-injection Nanotubes de carbone à parois multiples Un nanotube de carbone multifeuillet est constitué de plusieurs feuillets de graphènes enroulés les uns autour des autres. Il existe deux modèles pour décrire la structure des nanotubes multifeuillets : - le modèle poupée russe: les plans de graphène sont arrangés en cylindres concentriques ; - le modèle parchemin: un seul feuillet de graphène est enroulé sur lui-même, comme une feuille de papier. Percolation Polybutylène téréphtalate Polypropylène Index. décimale : 668.4 Plastiques, vinyles Résumé : We investigated the electrical conductivity and percolation behavior of binary and ternary nanocomposites based on multiwalled carbon nanotubes (MWCNs) using polypropylene (PP) and a blend of PP with cyclic butylene terephthalate (CBT). The nanocomposites were prepared by diluting a commercial 20 %wtMWCNT PP masterbatch using optimized melt-mixing conditions. The concentration of carbon nanotubes in the diluted PP samples was as low as 0.5 % and as high as 15 % in weight. For the PP/CBT blend CBT concentration was varied up to 40 %wt while the loading of CNT was from 0 to 5 %wt. SEM and TEM techniques were used to examine the quality of the dispersion and the formation of nanotube networks within the polymer matrix. TEM and Raman spectroscopy results showed that for the diluted PP/MWCNT composites the nanotubes are well aligned in samples obtained the microinjection molding process, although the level of alignment is less with crystalline PP than in an amorphous matrix such as polycarbonate (PC). FTIR and XRD results revealed that the orientation of both polymer chains and crystals decreased with the incorporation of nanotubes into PP. The electrical conductivity was also significantly altered by the nanotube alignment in a PP matrix, as was previously observed for PC/MWCNT composites; the conductivity decreased and the percolation threshold rose in highly sheared samples; however, the presence of a crystalline phase improved the conductivity even for high shear conditions through the phenomenon of double percolation threshold. This last concept refers to the requirement that the filler-rich phase be continuous and conductive and not to the existence of two percolation thresholds at two different CNT concentrations. The electrical conductivity of PP/CBT blends was also improved through a double percolation that is the basic requirement for the conductivity of the ternary nanocomposites. Note de contenu : - EXPERIMENTAL : Materials - Nanocomposite preparation and molding - Morphological characterization - Nanotube alignment - Polymer chain and crystal orientation - Rheological measurements - RESULTS : PP nanocomposites - PP/CBT blend nanocomposites DOI : 10.3139/217.2778 En ligne : https://drive.google.com/file/d/1ZJZlKx49qryLnfqR7g8IQdi6ph2N2o-a/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=20571 [article]

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Design sensitivity analysis applied to injection molding for optimization of gate location and injection pressure / K. K. Kabanemi in INTERNATIONAL POLYMER PROCESSING, Vol. XVII, N° 3 (09/2002)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XVII, N° 3 (09/2002) . - p. 254-264 Titre : Design sensitivity analysis applied to injection molding for optimization of gate location and injection pressure Type de document : texte imprimé Auteurs : K. K. Kabanemi, Auteur ; J.-F. Hétu, Auteur ; A. Derdouri, Auteur Année de publication : 2002 Article en page(s) : p. 254-264 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : In this work, we develop a numerical simulation method to optimize the injection molding process using the design sensitivity analysis (DSA). The optimization concerns the filling stage and focuses on the location of gates in the mold cavity as well as the injection pressure profile, in order to minimize the fill time. Since the problem to be solved involves transient flow with free surface (flow front), the direct differentiation method is used to evaluate the sensitivities of the Hele-Shaw, filling fraction and energy equations with respect to the design variables used in the analysis. The search domain parameterization is coped with using B-spline functions. Sensitivity and state equations are solved by means of finite element method. The proposed numerical approach is combined with the sequential linear and quadratic programming method of the design optimization tools (DOT) to find new design variables at the end of each complete filling simulation. Starting from any initial gate locations and injection pressure profile, the iterative optimization procedure enables us to find the optimal gate locations together with the optimal injection pressure profile. Finally, numerical results involving complex mold geometries are presented and discussed to assess the validity and robustness of the proposed method. Note de contenu : - Basic equations of injection molding : Hele-Shaw approximation - Numerical discretization - DSA-based approach and optimization - Algorithm DOI : 10.3139/217.1692 En ligne : https://drive.google.com/file/d/14svlimdPnr4Ek-a1nrP-shtFqs7qfyoL/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=16012 [article]

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Flow and thermal history effects on morphology and tensile behavior of poly(oxymethylene) micro injection molded parts / Musa R. Kamal in INTERNATIONAL POLYMER PROCESSING, Vol. XXXII, N° 5 (11/2017)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXXII, N° 5 (11/2017) . - p. 590-605 Titre : Flow and thermal history effects on morphology and tensile behavior of poly(oxymethylene) micro injection molded parts Type de document : texte imprimé Auteurs : Musa R. Kamal, Auteur ; R. El Otmani, Auteur ; A. Derdouri, Auteur ; J.-S. Chu, Auteur Année de publication : 2017 Article en page(s) : p. 590-605 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Analyse thermique Calorimétrie Diffraction des rayons X à grand angle Essais dynamiques Fluides, Mécanique des Matières plastiques -- Moulage par micro-injection Microscopie Morphologie (matériaux) Traction (mécanique) Index. décimale : 668.4 Plastiques, vinyles Résumé : The micro injection molding process is a rapidly growing area in plastics processing technology. In this process, the polymer is exposed to both high shear rates and large thermal gradients. In view of the versatility of the process, both commodity and engineering polymers have been used in micro injection molded products. In the present work, poly(oxymethylene) (POM), a partially crystalline engineering polymer, was employed to evaluate the relationships between processing conditions, on one hand, and the morphology and properties of the final part, on the other hand. An unsymmetrical mold cavity to make parts in the form of stepped plaques was used in the study. This resulted in substantial differences in morphology, crystallinity and shrinkage of the zones of different constant thicknesses in the micro parts. Depending on the molding conditions and the location on the micro-part, the microstructure can display up to five crystalline layers. Of particular interest, shish-kebab crystalline structures were observed within the skin of the step with the smallest thickness. Differential scanning calorimetry (DSC) tests are used to distinguish between the melting points of the shish and kebab components of this particular structure. The degree of crystallinity as determined by wide angle X-ray diffraction (WAXD) and shrinkage across the thickness were also found to be highest in the step with the smallest thickness. Note de contenu : - EXPERIMENTAL : Materials and equipments - CHARACTERIZATION METHODS : Polarized light microscopy - Scanning electron microscopy - Mechanical analysis - Differential scanning calorimetry - Shrinkage measurement - Wide angle X-ray diffraction - RESULTS AND DISCUSSION : Morphology along the flow and transverse directions - Differential scanning calorimetry (DSC) - Wide angle X-ray diffraction - Measurement of 3-D shrinkage - Tensile modulus DOI : 10.3139/217.3472 En ligne : https://drive.google.com/file/d/1LbPNfA_cGnBsKJJjhpKJdTCldmb6ca5j/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=29426 [article]

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Micro replication by injection-compression molding / M. Rohde in INTERNATIONAL POLYMER PROCESSING, Vol. XXIV, N° 3 (07/2009)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXIV, N° 3 (07/2009) . - p. 288-297 Titre : Micro replication by injection-compression molding Type de document : texte imprimé Auteurs : M. Rohde, Auteur ; A. Derdouri, Auteur ; Musa R. Kamal, Auteur Année de publication : 2009 Article en page(s) : p. 288-297 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : The replication of polymeric microstructures on a flat surface is not easily achieved by conventional injection molding, because of the required micro-dimensional control and the stringent tolerances of most applications. Moreover, the flow behaviour of melts in micro cavities remains not well understood and challenging. On the other hand, injection-compression molding is an established process for the manufacturing of optical storage media, like compact discs (CD) or digital versatile discs (DVD), with grooves and pits at the micro-scale. The difficulties arise mainly from two sources: lack of adequate filling because of premature freezing of features with very small thicknesses and excessive deformation during ejection due to high friction at the polymer-metal interface. In this work, a study is carried out to investigate the effect of process parameters on the replication of various microstructures on a flat disk using microinjection-compression molding. A commercial microinjection molding machine has been used in the study. Two optical grade polymers poly(methyl methacrylate) (PMMA) and cyclic olefin polymer (COP) were used in conjunction with various mold inserts to reproduce the embedded microstructures. The dimensions of the microstructures on the inserts and molded parts were measured with a confocal profiler. A transcription ratio was defined to assess the quality of the replication. The design of experiment (DOE) method was used to obtain correlations between the process parameters and the development of the microstructure during injection-compression molding. DOI : 10.3139/217.2264 En ligne : https://drive.google.com/file/d/1BovX7_ewXmMt3K3Zi8JPa9csMPSVfFPx/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=5933 [article]

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