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  • 1
    Online-Ressource
    Online-Ressource
    Experimental analysis of the influence of pellet shape on single screw extrusion
    Wiley ; 2015
    In:  Journal of Applied Polymer Science Vol. 132, No. 13 ( 2015-04-05)
    Details
    In: Journal of Applied Polymer Science, Wiley, Vol. 132, No. 13 ( 2015-04-05)
    Kurzfassung: Extrusion technology is one of the most prominent methods for processing polymers. The shape of polymer pellets plays an important role in conveying solid material through the extruder and thus directly influences the mass flow rate. In the course of this article, the influence of the pellet shape of a polypropylene homopolymer on the processing conditions using a smooth barrel single‐screw extruder is evaluated. Especially the mass flow rate, the melt temperature, and the pressure build up in the barrel are investigated. It can be shown that processing long cylindrical pellets leads to a higher mass flow rate than comparable experiments with virgin pellets or short cylinders. Additionally, screw cool and pull‐out tests, measurements of the external coefficient of friction as well as the bulk density of the different pellet geometries are performed. The interaction of the screw geometry and the pellet shape is found to have the biggest influence. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132 , 41716.
    Materialart: Online-Ressource
    ISSN: 0021-8995 , 1097-4628
    URL: Issue
    URL: Article
    DOI: 10.1002/app.v132.13
    DOI: 10.1002/app.41716
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2015
    ZDB Id: 1491105-X
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  • 2
    Online-Ressource
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    Wetting behavior of polymer melts on coated and uncoated tool steel surfaces
    Wiley ; 2016
    In:  Journal of Applied Polymer Science Vol. 133, No. 21 ( 2016-06-05)
    Details
    In: Journal of Applied Polymer Science, Wiley, Vol. 133, No. 21 ( 2016-06-05)
    Kurzfassung: The wettability of steel and coatings used for tools and screws in polymer processing is often determined at room temperature. However, it has to be taken into account that polymeric materials are processed at higher temperatures. Contact angle measurements of melted PP, HDPE, PMMA, and PA 6.6 on steel and on TiN, TiAlN, CrN, DLC, and PTFE were performed in this work to investigate the wetting behavior under closer‐to‐processing conditions. The contact angle is dependent on time and the ambient atmosphere. Oxidation and degradation of the polymer melts influence wetting significantly. TiN, TiAlN, CrN, and DLC exhibit a rather good wettability, whereas the highest contact angle of the polymer melts was observed with PTFE. Higher roughnesses of the surfaces lead to an increase in the contact angle. It was also shown that a higher temperature causes a better wetting of the solid surfaces. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133 , 43469.
    Materialart: Online-Ressource
    ISSN: 0021-8995 , 1097-4628
    URL: Issue
    URL: Article
    DOI: 10.1002/app.v133.21
    DOI: 10.1002/app.43469
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2016
    ZDB Id: 1491105-X
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  • 3
    Online-Ressource
    Online-Ressource
    Calculation of the Contact Angle of Polymer Melts on Tool Surfaces from Viscosity Parameters
    MDPI AG ; 2017
    In:  Polymers Vol. 10, No. 1 ( 2017-12-30), p. 38-
    Details
    In: Polymers, MDPI AG, Vol. 10, No. 1 ( 2017-12-30), p. 38-
    Materialart: Online-Ressource
    ISSN: 2073-4360
    URL: Article
    DOI: 10.3390/polym10010038
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2017
    ZDB Id: 2527146-5
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  • 4
    Online-Ressource
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    Influence of thermal deconsolidation on the anisotropic thermal conductivity of glass fiber reinforced, pre‐consolidated polypropylene sheets used for thermoforming applications
    Wiley ; 2022
    In:  Polymer Composites Vol. 43, No. 4 ( 2022-04), p. 2264-2275
    Details
    In: Polymer Composites, Wiley, Vol. 43, No. 4 ( 2022-04), p. 2264-2275
    Kurzfassung: Modeling how thermoplastic composites are processed using thermoforming is a challenging task, and not only due to the heterogenic nature of the material. During the thermoforming processes, the polymeric matrix has to be heated above the softening temperature, enabling the composite to be formed into three‐dimensional parts. As the system mobility increases, thermal deconsolidation takes place, and voids are created or expand within the composite sheet. These voids alter the sheet's material properties and aesthetic characteristics. The formation of gas‐filled voids in the material hinders the heat transport, resulting in longer heating times and inefficient processes. Moreover, such voids invalidate models widely used for processing thermoplastic composites. This study resulted in a novel analytical model that can be applied to calculate the anisotropic thermal conductivity of thermoplastic composites depending on the deconsolidation temperature and the fiber orientation. The model was validated by running hot disk tests on polypropylene reinforced with glass fibers (PP/GF) and applying X‐ray computed tomography to the composite samples. The samples are first consolidated in a hot‐plate press and consecutively deconsolidated in a pressure‐free process. The study findings show that the model is highly accurate within the temperature range relevant to composite processing and will be a useful asset in process modeling.
    Materialart: Online-Ressource
    ISSN: 0272-8397 , 1548-0569
    URL: Issue
    URL: Article
    DOI: 10.1002/pc.v43.4
    DOI: 10.1002/pc.26538
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2022
    ZDB Id: 1475935-4
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  • 5
    Online-Ressource
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    Modeling of the anisotropic thermal conductivity of fabrics embedded in a thermoplastic matrix system
    Wiley ; 2021
    In:  Polymer Composites Vol. 42, No. 4 ( 2021-04), p. 2050-2060
    Details
    In: Polymer Composites, Wiley, Vol. 42, No. 4 ( 2021-04), p. 2050-2060
    Kurzfassung: Processing of thermoplastic composites is increasingly gaining importance due to their excellent mechanical properties combined with their recycling‐feasibility. However, distinguishing anisotropic thermal properties of these materials make process simulation challenging. This work deals with an alternative way of analytical modeling of the anisotropic thermal conductivity of fabrics embedded in a thermoplastic matrix, as in the case of sheets for thermoforming applications, in which heating times are often process limiting. By creation of a unit cell and applying heat flux balances, the thermal conductivity in the fiber direction and in the transversal direction can be calculated. The transversal direction is the most important factor for the addressed thermoforming applications. The proposed model is then successfully validated through Hot Disk measurements of glass fiber reinforced polyamide sheets. Furthermore, authentication is reached by the comparison to measured thermal conductivity values from another study. Hence, it can be shown that the model proves to be more accurate than existing analytical models.
    Materialart: Online-Ressource
    ISSN: 0272-8397 , 1548-0569
    URL: Issue
    URL: Article
    DOI: 10.1002/pc.v42.4
    DOI: 10.1002/pc.25958
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2021
    ZDB Id: 1475935-4
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  • 6
    Online-Ressource
    Online-Ressource
    Experimental study of the influences of the pellet shape on the bulk density and the frictional behavior of polypropylene
    Wiley ; 2015
    In:  Journal of Applied Polymer Science Vol. 132, No. 27 ( 2015-07-15)
    Details
    In: Journal of Applied Polymer Science, Wiley, Vol. 132, No. 27 ( 2015-07-15)
    Kurzfassung: Bulk solids are the raw material for almost every polymeric thermoplastic product. Their properties determine the quality of solids conveying and also influence the melting behavior of the material in processing units. This study investigates the influence of pressure and temperature on the bulk density of two thermoplastic polypropylene pellets of different shapes. Furthermore, the external friction dependent on temperature and pressure of those materials is examined at conditions usually occurring in the solids conveying zone of smooth barrel plasticating units. The experiments are carried out using a tribometer for polymer pellets which was adapted for these tests by making the sample chamber, the piston, and the cylindrical roll heatable. The tests show that long cylindrical pellets exhibit low bulk densities at low pressure and temperature, which can be increased dramatically—even above the values of spheroidal pellets—as those parameters increase. Moreover, the external coefficient of friction is always higher for the long cylinders and strongly dependent on the temperature. Those facts add up and can cause a higher output of single‐screw extruders. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132 , 42197.
    Materialart: Online-Ressource
    ISSN: 0021-8995 , 1097-4628
    URL: Issue
    URL: Article
    DOI: 10.1002/app.v132.27
    DOI: 10.1002/app.42197
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2015
    ZDB Id: 1491105-X
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  • 7
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    Online-Ressource
    Enhanced Simulation of Infrared Heating of Thermoplastic Composites Prior to Forming under Consideration of Anisotropic Thermal Conductivity and Deconsolidation by Means of Novel Physical Material Models
    MDPI AG ; 2022
    In:  Polymers Vol. 14, No. 16 ( 2022-08-16), p. 3331-
    Details
    In: Polymers, MDPI AG, Vol. 14, No. 16 ( 2022-08-16), p. 3331-
    Kurzfassung: In recent years, thermoplastic composites have found their place in large business sectors and are in direct rivalry to thermoset matrix composites. In order to ensure efficient and lean processes, process modeling gains ever-growing attention. This work shows the computational fluid dynamics (CFD)-modeling of a typical heating step in a thermoforming process of a thermoplastic composite sheet. When heating thermoplastic composites, the heat conduction proceeds anisotropic, and the sheets are subject to thermal deconsolidation when heated above the melting temperature of the polymer matrix adding to the anisotropic effect. These effects are neglected in known process models and this study shows the first successful attempt at introducing them into CFD-modeling of the heating of thermoplastic composite sheets. Thus, the simulation requires temperature dependent values for the anisotropic thermal conductivity and the coefficient of linear thermal expansion, which are calculated with novel physical models which were developed solely for this cause. This alters the behavior of an isotropic CFD-model and allows the successful validation via laboratory experiments using glass fiber reinforced polypropylene (PP/GF) sheets with embedded thermocouples to check the internal temperature distribution when the sheet is heated to the designated forming temperature in a composite thermoforming press. The incorporation of this newly developed process model reduces the error in the core temperature prediction from close to 70 °C to 3 °C at the forming temperature.
    Materialart: Online-Ressource
    ISSN: 2073-4360
    URL: Article
    DOI: 10.3390/polym14163331
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2022
    ZDB Id: 2527146-5
    Standort Signatur Einschränkungen Verfügbarkeit
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