Analysis of asymmetric morphology evolutions in iPP molded samples induced by uneven temperature field

Liparoti, Sara; Titomanlio, G.; Sorrentino, Andrea

doi:10.1002/aic.15241

Cited by 20 publications

(14 citation statements)

References 39 publications

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“…The observed distribution of the mesomorphic phase is consistent with the distribution reported in the literature [53]. The formation of the mesomorphic phase took place as a consequence of fast cooling experienced by the melt when contacted the cold surface of the mold [41,54,55]. As a further confirmation that the formation of the mesomorphic phase occurred under fast cooling conditions, the samples A and B, obtained with 150 • C cavity surface temperature, showed only a negligible fraction (smaller than 2%) of the mesomorphic phase since, in those conditions, the cooling rate was smaller than in the passive case.…”

Section: Discussionsupporting

confidence: 88%

Effect of Rapid Mold Heating on the Structure and Performance of Injection-Molded Polypropylene

et al. 2020

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The tailoring by the process of the properties developed in the plastic objects is the more effective way to improve the sustainability of the plastic objects. The possibility to tailor to the final use the properties developed within the molded object requires further understanding of the relationship between the properties of the plastic objects and the process conduction. One of the main process parameters that allow adjusting the properties of molded objects is the mold temperature. In this work, a thin electrical heater was located below the cavity surface in order to obtain rapid and localized surface heating/cooling cycles during the injection molding process. An isotactic polypropylene was adopted for the molding tests, during which surface temperature was modulated in terms of values and heating times. The modulation of the cavity temperature was found able to control the distribution of relevant morphological characteristics, thus, properties along the sample thickness. In particular, lamellar thickness, crystallinity distribution, and orientation were analyzed by synchrotron X-ray experiments, and the morphology and elastic modulus were characterized by atomic force microscopy acquisitions carried out with a tool for the simultaneous nanomechanical characterization. The crystalline degree slightly increased with the cavity temperature, and this induced an increase in the elastic modulus when high temperatures were adopted for the cavity surface. The cavity temperature strongly influenced the orientation distribution that, on its turn, determined the highest values of the elastic modulus found in the shear layer. Furthermore, although the sample core, not experiencing a strong flow field, was not characterized by high levels of orientation, it might show high values of the elastic modulus if temperature and time during crystallization were sufficient. In particular, if the macromolecules spent adequate time at temperatures close to the crystallization temperature, they could achieve high levels of structuring and, thus, high values of elastic modulus.

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Section: Discussionsupporting

confidence: 88%

Effect of Rapid Mold Heating on the Structure and Performance of Injection-Molded Polypropylene

et al. 2020

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“…The strong temperature differences along the sample thickness allow molecular relaxation only over a part of the sample; therefore, some fibrils, that is, those placed at the border of the spherulitic core, are replaced by elongated spherulites. The result of this partial relaxation is the coexistence of different crystal morphologies separated by transition regions [41,61]. Finally, closer to the sample surface, highly oriented fibrillar morphology has been found as reported in the right of Figure 5(a).…”

Section: Mechanical Characterization By Harmonix Afmmentioning

confidence: 62%

“…In this paper, we intend to demonstrate the applicability of HarmoniX AFM technique to the characterization of molded polymer samples with complex, nonuniform morphologies [37][38][39][40][41][42], which could influence the mechanical properties of the final object [28,43,44]. To accomplish this objective, a series of HarmoniX tests have been performed on selected polypropylene molded samples.…”

Section: Introductionmentioning

confidence: 99%

“…To accomplish this objective, a series of HarmoniX tests have been performed on selected polypropylene molded samples. These samples have been chosen to highlight the sensitivity of this technique to the variations in morphologies normally found in molded thermoplastic samples [37,38,41,42,45]. HarmoniX tests have been conducted with different scan sizes and resolutions on samples prepared in different ways (i.e., etching procedures), with the objective of studying the relative influence of the preparation methods on the obtained results.…”

Section: Introductionmentioning

confidence: 99%

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Micromechanical Characterization of Complex Polypropylene Morphologies by HarmoniX AFM

Liparoti

Sorrentino

Speranza

2017

International Journal of Polymer Science

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This paper examines the capability of the HarmoniX Atomic Force Microscopy (AFM) technique to draw accurate and reliable micromechanical characterization of complex polymer morphologies generally found in conventional thermoplastic polymers. To that purpose, injection molded polypropylene samples, containing representative morphologies, have been characterized by HarmoniX AFM. Mapping and distributions of mechanical properties of the samples surface are determined and analyzed. Effects of sample preparation and test conditions are also analyzed. Finally, the AFM determination of surface elastic moduli has been compared with that obtained by indentation tests, finding good agreement among the results.

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“…The use of polycaprolactone (PCL) seems to be particularly promising, because of its biocompatibility and its capability to prolong the drug release. In the last decades, compression molding has been one of the most diffused processes for polymeric part production [20][21][22][23]. High automation, high geometrical accuracy, and the fast cycle time, which means high productivity, are the main reasons for the diffusion of this process.…”

Section: Introductionmentioning

confidence: 99%

PCL/Mesoglycan Devices Obtained by Supercritical Foaming and Impregnation

et al. 2019

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In this work, a one-shot process for the simultaneous foaming of polycaprolactone (PCL) and impregnation of mesoglycan (MSG) into the porous structure was successfully attempted. Supercritical carbon dioxide plays the role of the foaming agent with respect to PCL and of the solvent with respect to MSG. The main objective is to produce an innovative topical device for application on skin lesions, promoting prolonged pro-resolving effects. The obtained device offers a protective barrier to ensure a favorable and sterilized environment for the wound healing process. The impregnation kinetics revealed that a pressure of 17 MPa, a temperature of 35 °C, and a time of impregnation of 24 h assured a proper foaming of PCL in addition to the impregnation of the maximum amount of MSG; i.e., 0.22 mgMSG/mgPCL. After a preliminary study conducted on PCL granules used as brought, the MSG impregnation was performed at the optimized process conditions also on a PCL film, produced by compression molding, with the final goal of producing medical patches. Comparing the dissolution profiles in phosphate buffered saline solution (PBS) of pure MSG and MSG impregnated on foamed PCL, it was demonstrated that the release of MSG was significantly prolonged up to 70 times. Next, we performed functional assays of in vitro wound healing, cell invasion, and angiogenesis to evaluate the biological effects of the PCL-derived MSG. Interestingly, we found the ability of this composite system to promote the activation of human keratinocytes, fibroblasts, and endothelial cells, as the main actors of tissue regeneration, confirming what we previously showed for the MSG alone.

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Analysis of asymmetric morphology evolutions in iPP molded samples induced by uneven temperature field

Cited by 20 publications

References 39 publications

Effect of Rapid Mold Heating on the Structure and Performance of Injection-Molded Polypropylene

Effect of Rapid Mold Heating on the Structure and Performance of Injection-Molded Polypropylene

Micromechanical Characterization of Complex Polypropylene Morphologies by HarmoniX AFM

PCL/Mesoglycan Devices Obtained by Supercritical Foaming and Impregnation

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