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Polymers
Special Issues
In-Situ Polymer Characterization in Polymer Processing
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In-Situ Polymer Characterization in Polymer Processing

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Processing and Engineering".

Deadline for manuscript submissions: closed (15 February 2022) | Viewed by 8234

Special Issue Editor

Dr. Bernhard Praher

E-Mail Website
Guest Editor
1. Institute of Polymer Injection Moulding and Process Automation, Johannes Kepler University Linz, Linz, Austria
2. MoldSonics GmbH, Hafenstraße 47-51, 4020 Linz, Austria
Interests: polymers characterization; polymer processing; process measurement in polymer processing

Special Issue Information

Dear Colleagues,

In polymer processing applications (e.g., extrusion or injection molding), the determination of state variables or morphological parameters is limited by the high process pressures and temperatures required. Nevertheless, there is an increasing demand for generating more information about processed polymers in industrial and scientific applications. In industrial environments, mainly pressure and temperature measurements are available, however promising on-line methods for the measurement of melt homogeneity, filler dispersion, temperature distributions, melt density, melting behaviour, colour, molecule orientation, rheology, and other properties have been developed by different scientific groups. This Special Issue will cover the latest developments in the field of in-situ polymer characterization in polymer processing using methods like ultrasound; terahertz; microwaves; and NIR-, UV-, VIS-, and dielectric-spectroscopy. Both original contributions and reviews (from academia and industry) are welcome.

Dr. Bernhard Praher
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Polymer processing 
  • Melt processing 
  • Inline-monitoring 
  • Injection molding 
  • Extrusion 
  • Ultrasound 
  • Spectroscopy 
  • Rheology

Published Papers (3 papers)

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Research

28 pages, 18210 KiB  
Article
A Comparison of Numerical and Actual Measurements of Large-Scale Rib-Structured Pallet Flatness Using Recycled Polypropylene in Injection Molding
by Yi-Ling Liao and Hsi-Hsun Tsai
Polymers 2022, 14(8), 1631; https://doi.org/10.3390/polym14081631 - 18 Apr 2022
Cited by 2 | Viewed by 1661
Abstract
Many challenges are associated with the injection molding process for forming a rib-structured pallet (1100 mm × 1100 mm × 140 mm, length × width × height) because greater flowing resistance through the rib channels within the pallet can induce insufficient filling. Essentially, [...] Read more.
Many challenges are associated with the injection molding process for forming a rib-structured pallet (1100 mm × 1100 mm × 140 mm, length × width × height) because greater flowing resistance through the rib channels within the pallet can induce insufficient filling. Essentially, multi-gate filling involves a sequential valve gate system, which helps to spread the filling front with fewer weld lines. Based on the presetting of the sequential scheme of the valve gates, actual measurements of pallet flatness using the ATOS scan system were compared to numerical warpage measurements of a pallet derived by Moldex3D 2020. In this study, we propose a sequential scheme by actuating the valve gates to open once the flow front spreads towards them; then, actual warpage measurements of a pallet are compared with numerical measurements. The results show that the warpage of the top surface of the pallet is 5.144 mm in actual measurements and 5.729 mm in simulation. The results all indicated small warpage with respect to the pallet size. The simulation and actual measurements of flatness are in excellent agreement; the difference in top flatness between the simulated and actual pallet is 0.59 mm, while the bottom flatness difference is 0.035 mm. By adjusting the cooling water temperature, increasing the mold temperature, and decreasing the material temperature, overall flatness and warpage displacement can be reduced. Full article
(This article belongs to the Special Issue In-Situ Polymer Characterization in Polymer Processing)
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10 pages, 1318 KiB  
Article
Towards Real-Time In-Situ Mid-Infrared Spectroscopic Ellipsometry in Polymer Processing
by Alexander Ebner, Robert Zimmerleiter, Kurt Hingerl and Markus Brandstetter
Polymers 2022, 14(1), 7; https://doi.org/10.3390/polym14010007 - 21 Dec 2021
Cited by 8 | Viewed by 3218
Abstract
Recent developments in mid-infrared (MIR) spectroscopic ellipsometry enabled by quantum cascade lasers (QCLs) have resulted in a drastic improvement in signal-to-noise ratio compared to conventional thermal emitter based instrumentation. Thus, it was possible to reduce the acquisition time for high-resolution broadband ellipsometric spectra [...] Read more.
Recent developments in mid-infrared (MIR) spectroscopic ellipsometry enabled by quantum cascade lasers (QCLs) have resulted in a drastic improvement in signal-to-noise ratio compared to conventional thermal emitter based instrumentation. Thus, it was possible to reduce the acquisition time for high-resolution broadband ellipsometric spectra from multiple hours to less than 1 s. This opens up new possibilities for real-time in-situ ellipsometry in polymer processing. To highlight these evolving capabilities, we demonstrate the benefits of a QCL based MIR ellipsometer by investigating single and multilayered polymer films. The molecular structure and reorientation of a 2.5 µm thin biaxially oriented polyethylene terephthalate film is monitored during a stretching process lasting 24.5 s to illustrate the perspective of ellipsometric measurements in dynamic processes. In addition, a polyethylene/ethylene vinyl alcohol/polyethylene multilayer film is investigated at a continuously varying angle of incidence (0∘– 50∘) in 17.2 s, highlighting an unprecedented sample throughput for the technique of varying angle spectroscopic ellipsometry in the MIR spectral range. The obtained results underline the superior spectral and temporal resolution of QCL ellipsometry and qualify this technique as a suitable method for advanced in-situ monitoring in polymer processing. Full article
(This article belongs to the Special Issue In-Situ Polymer Characterization in Polymer Processing)
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26 pages, 9403 KiB  
Article
In Situ Detection of Interfacial Flow Instabilities in Polymer Co-Extrusion Using Optical Coherence Tomography and Ultrasonic Techniques
by Alexander Hammer, Wolfgang Roland, Maximilian Zacher, Bernhard Praher, Günther Hannesschläger, Bernhard Löw-Baselli and Georg Steinbichler
Polymers 2021, 13(17), 2880; https://doi.org/10.3390/polym13172880 - 27 Aug 2021
Cited by 8 | Viewed by 2630
Abstract
Co-extrusion is a widely used processing technique for combining various polymers with different properties into a tailored multilayer product. Individual melt streams are combined in a die to form the desired shape. Under certain conditions, interfacial flow instabilities are observed; however, fundamental knowledge [...] Read more.
Co-extrusion is a widely used processing technique for combining various polymers with different properties into a tailored multilayer product. Individual melt streams are combined in a die to form the desired shape. Under certain conditions, interfacial flow instabilities are observed; however, fundamental knowledge about their onset and about critical conditions in science and industry is scarce. Since reliable identification of interfacial co-extrusion flow instabilities is essential for successful operation, this work presents in situ measurement approaches using a novel co-extrusion demonstrator die, which is fed by two separate melt streams that form a well-controlled two-layer co-extrusion polymer melt flow. An interchangeable cover allows installation of an optical coherence tomography (OCT) sensor and of an ultrasonic (US) measurement system, where the former requires an optical window and the latter good direct coupling with the cover for assessment of the flow situation. The feasibility of both approaches was proven for a material combination that is typically found in multilayer packaging applications. Based on the measurement signals, various parameters are proposed for distinguishing reliably between stable and unstable flow conditions in both measurement systems. The approaches presented are well suited to monitoring for and systematically investigating co-extrusion flow instabilities and, thus, contribute to improving the fundamental knowledge about instability onset and critical conditions. Full article
(This article belongs to the Special Issue In-Situ Polymer Characterization in Polymer Processing)
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