Influence of crystal structure on thermo-mechanical properties of injection molded B-nucleated iPP / A. Hamza in INTERNATIONAL POLYMER PROCESSING, Vol. 36, N° 5 (2021)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. 36, N° 5 (2021) . - p. 545-556 Titre : Influence of crystal structure on thermo-mechanical properties of injection molded B-nucleated iPP Type de document : texte imprimé Auteurs : A. Hamza, Auteur ; R. K. Arya, Auteur ; A. D. Palsodkar, Auteur ; G. R. Bhadu, Auteur ; S. J. A. Rizvi, Auteur Année de publication : 2021 Article en page(s) : p. 545-556 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Agent de nucléation Caractérisation Matériaux -- Propriétés thermomécaniques Matières plastiques Matières plastiques -- Moulage par injection Mélange Polymères -- Propriétés thermomécaniques Polymères isotactiques Polypropylène greffé anhydride maléique Structure cristalline (solide) Thermodurcissables -- Propriétés thermomécaniques Index. décimale : 668.4 Plastiques, vinyles Résumé : Isotactic polypropylene (iPP) was nucleated in-situ with calcium pimelate during melt compounding. Calcium pimelate is a highly effective β-nucleator for isotactic polypropylene (iPP). The β-nucleated iPP was characterized by wide angle x-ray diffraction (WAXD) and differential scanning calorimetry (DSC) for its crystallinity and crystal structure. In addition, the injection-molded samples were tested for thermo-mechanical properties. It is found that very low quantity (< 0.1 wt. %) of β-nucleator is required to produce sufficiently high β-crystal fraction (Kβ) in isotactic polypropylene. β-nucleated iPP shows increment of 11 to 14 °C in its heat deflection temperature (HDT). It was also observed that slow cooling rate of β-nucleated iPP promotes the formation of β-crystals and that tensile stretching leads to complete transformation of β crystals into a-crystals at room temperature. It was also revealed that the presence of maleic anhydride grafted polypropylene (PP-g-MA), a well-known coupling agent (or compatibilizer), may reduce the (Kβ) value to a marginal extent. It was also observed that the thermo-mechanical properties were not much affected by the presence of PP-g-MA. Therefore, calcium pimelate may be used as β-nucleator in case of neat as well as reinforced polypropylene containing maleic anhydride as coupling agent. Note de contenu : - EXPERIMENTAL : Materials - Melt compounding - Injection molding - Testing of molded specimens - RESULTS AND DISCUSSION : Effect of concentration of β-nucleator on thermo-mechanical properties of iPP - Effect of coupling agent (PP-g-ma) on the efficiency of β-nucleator - Stretching induced (β-α) transformation in β-iPP - Table 1 : Injection molding parameters - Table 2 : Crystallinity of neat and 𝛽-iPP at different concentrations of 𝛃-nucleator (calculated from WAXD data) - Table 3 : Crystallinity of neat- and 𝛃-iPP at different concentrations of 𝛃-nucleator (calculated from DSC first heating data) - Table 4 : Results of DSC second heating scan for neat and 𝛃-nucleated iPP - Table 5 : Crystallinity values of 𝛃-iPP with different concentration (wt.%) of PP-g-MA - Table 6 : DSC-second melting and crystallization parameters for 𝛃-nucleated iPP containing coupling agent (PP-g-MA) - Table 7 : Effect of stretching on crystallinity and crystal structure DOI : https://doi.org/10.1515/ipp-2020-4106 En ligne : https://drive.google.com/file/d/1fBkbI5UTQhKXftRExRvGTPuJb7sNbvIl/view?usp=shari [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=36521 [article]

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Microcellular PP vs. microcellular PP/MMT nanocomposites : a comparative study of their mechanical behavior / S. J. A. Rizvi in INTERNATIONAL POLYMER PROCESSING, Vol. XXVI, N° 4 (09/2011)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXVI, N° 4 (09/2011) . - p. 375-382 Titre : Microcellular PP vs. microcellular PP/MMT nanocomposites : a comparative study of their mechanical behavior Type de document : texte imprimé Auteurs : S. J. A. Rizvi, Auteur ; Naresh Bhatnagar, Auteur Année de publication : 2011 Article en page(s) : p. 375-382 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Anhydride maléique Azote Copolymères greffés Extrudeuse bi-vis Fluides supercritiques Matières plastiques -- Moulage par injection microcellulaire Montmorillonite Mousses plastiques -- Extrusion Mousses plastiques -- Propriétés mécaniques Nanoparticules Nucléation Polypropylène Index. décimale : 668.9 Polymères Résumé : Microcellular foams have attracted interest in both scientific and industrial communities. Injection molding is perhaps the most versatile industrial method of polymer processing. Microcellular injection molding is a newcomer variant in this class. It is capable to produce microcellular structure. The mechanical behavior of a microcellular polymer is different than conventional foams. Although they exhibit much improved mechanical properties than conventional foams still they are inferior to solid polymer. Incorporation of nanoparticles in matrix may affect the nucleation and bubble growth process. Further, nanoparticles will enhance the performance (stiffness, strength etc.) of matrix. In present study an effort has been made to quantitatively analyze the improvements in mechanical properties of microcellular foam with the addition of nanoclay (MMT). Nanocomposite of polypropylene and nanoclay was prepared in a co-rotating twin screw extruder. Maleic anhydride grafted polypropylene (PP-g-MA) was used as compatibilizer. PP/nanocomposites were foamed in a microcellular injection molding machine, where supercritical nitrogen (SCF-N2) was mixed with plasticized PP/ nanocomposite inside the screw – barrel assembly. The molded foamed samples were tested for various mechanical properties. Experimental results show that a considerable improvement occur in the property of microcellular polypropylene by the addition of 2 wt.% nanoclay (MMT). DOI : 10.3139/217.2375 En ligne : https://drive.google.com/file/d/1f6-1RrQ1xrQyO-cb5JWkYXr4szFJ_G6i/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=12435 [article]

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Optimization of microcellular injection molding parameters / S. J. A. Rizvi in INTERNATIONAL POLYMER PROCESSING, Vol. XXIV, N° 5 (11/2009)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXIV, N° 5 (11/2009) . - p. 399-405 Titre : Optimization of microcellular injection molding parameters Type de document : texte imprimé Auteurs : S. J. A. Rizvi, Auteur ; Naresh Bhatnagar, Auteur Année de publication : 2009 Article en page(s) : p. 399-405 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : Microcellular foamed polymeric products have found various applications depending upon their cell morphology. The microcellular injection molding process parameters have effect on the cell size, cell density and cell distribution. In order to develop desired cell morphology for a particular application, the set of injection molding parameters is required to be optimized for achieving a correct process window. In this paper an effort is made to study the effect of various injection molding processing parameters on cell morphology. Series of experiments were conducted for each of the processing parameter and the samples were observed under Scanning Electron Microscope (SEM). The trends of cell size and cell density with respect to the processing parameters were qualitatively analyzed. The results are useful for the processors who are interested in building up an understanding of this novel process and also to enable optimization of the set of processing parameters so that the desired microstructure of a foamed polymer can be obtained. DOI : 10.3139/217.2263 En ligne : https://drive.google.com/file/d/1CEZlSlySVbloDR9Rj7HTKTa5l4c9I1OB/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=6362 [article]

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