Advances on Injection Molding of Polymers II

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

Deadline for manuscript submissions: closed (1 December 2023) | Viewed by 5834

Special Issue Editors

Department of Industrial Engineering, University of Salerno, Fisciano (SA), Italy
Interests: molding; effect of thermomechanical history on final structure of polymeric materials; analysis and numerical simulation of the injection molding process of thermoplastic materials; polymeric materials characterization; atomic force microscopy
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Department of Industrial Engineering, University of Salerno, Fisciano (SA), Italy
Interests: polymer processing; flow-induced crystallization and effect of crystallinity on rheology; morphology evolution during polymer processing; injection molding simulation
Special Issues, Collections and Topics in MDPI journals
Department of Industrial Engineering, University of Salerno, Via Giovanni Paolo II, 132, 84084 Fiscian, SA, Italy
Interests: advanced Injection molding; polymer structure development during injection molding; advanced characterization of the mechanical properties within injection molding objects; tuning of surface topography and properties by injection molding; rheology of hydrogels; supercritical fluid based processes
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Further to the successful conclusion of the previous Special Issue “Advances in Injection Molding of Polymers”, we are delighted to revisit the topic for a 2nd edition entitled “Advances in Injection Molding of Polymers II”. This edition will continue to collect high-quality papers which are dedicated to injection molding of polymers.

The simplest description of the injection molding process is that molten materials are injected into a cool cavity where they solidify. In reality, however, the process is very complex. Nevertheless, it allows us to produce finished objects of any geometry by a single shot. For this reason, the injection molding process is very diffuse, and more than 30% of all plastics are processed by injection molding machines. New developments of the process occur continuously in order to favor the production of parts for a particular use and/or realized with special materials. For instance, in the last few decades, standard injection molding has been adapted to realize very small parts due to the rapidly growing and evolving demand for micro- and nanostructured devices with a high level of reproducibility at a small cost.

Among the parameters that identify the quality of a part, the dimensional tolerance and stability of moldings are very important and may well run out of control. Furthermore, moldings’ final properties are related to their bulk and surface morphology distributions, which in turn are determined by processing conditions.

Thus, this Special Issue will welcome contributions that clarify (by either modeling or correlations) the effects of processing conditions on the quality and, above all, the structure and properties of the moldings. Furthermore, contributions on advanced topics, such as micro-molding, or special techniques, such as gas injection molding, will be welcome. Another relevant topic is the production of highly valuable parts obtained by combining polymers with other materials, such as for powder injection molding.

Dr. Vito Speranza
Prof. Dr. Giuseppe Titomanlio
Dr. Sara Liparoti
Guest Editors

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

  • injection molding
  • injection molding modeling
  • morphology structuring and characterization of moldings
  • relationships between processing conditions and final properties of the moldings

Published Papers (3 papers)

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Research

17 pages, 6248 KiB  
Article
A Semi-Analytical Method for Designing a Runner System of a Multi-Cavity Mold for Injection Molding
by Chung-Chih Lin, Tian-Cheng Wu, Yu-Shiang Chen and Bo-Yu Yang
Polymers 2022, 14(24), 5442; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14245442 - 12 Dec 2022
Cited by 2 | Viewed by 2005
Abstract
Multi-cavity mold design is an efficient approach to achieving mass production and is frequently used in plastic injection applications. The runner system of a multi-cavity mold delivers molten plastic to each cavity evenly and makes the molded product from each individual cavity possess [...] Read more.
Multi-cavity mold design is an efficient approach to achieving mass production and is frequently used in plastic injection applications. The runner system of a multi-cavity mold delivers molten plastic to each cavity evenly and makes the molded product from each individual cavity possess an equivalent quality. Not only the dimensions, but also the invisible quality, e.g., the internal stress of the product is of great concern in regard to molding quality. Using commercial software to find an optimal solution for the runner system may be time-consuming in respect to iterations if the engineers lack empirical rules. The H-type runner system is often used due to an inherently balanced filling in multi-cavities. However, the shear heat inducing an imbalanced flow behavior requires the H-type runner system to be improved as the number of the cavities is increased. This work develops a methodology based on the rheological concept to determine the runner system of a multi-cavity mold semi-analytically. As the relation of the viscosity with respect to shear rate is known, the runner system can be constructed step-by-step via this method. The use of the proposed method helps to focus attention on the connection between the physical situation and its related mathematical model. The influences of the melt temperature and resin type can be easily investigated. Three design examples, a 16-cavity mold with a fishbone runner system, an 8-cavity mold with an arbitrary runner layout, and the influences of melt temperature and resin type on the runner design are demonstrated and validated by the commercial software. The proposed method shows its great benefit when a new runner design project is launched in the initial design stage and then cooperates with the commercial software for further modifications. Full article
(This article belongs to the Special Issue Advances on Injection Molding of Polymers II)
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16 pages, 5094 KiB  
Article
Modeling and Analysis of Morphology of Injection Molding Polypropylene Parts Induced by In-Mold Annealing
by Rita Salomone, Vito Speranza, Sara Liparoti, Giuseppe Titomanlio and Roberto Pantani
Polymers 2022, 14(23), 5245; https://doi.org/10.3390/polym14235245 - 01 Dec 2022
Cited by 2 | Viewed by 1052
Abstract
It is generally recognized that high-temperature treatments, namely annealing, influence the microstructure and the morphology, which, in turn, determine the mechanical properties of polymeric parts. Therefore, annealing can be adopted to control the mechanical performance of the molded parts. This work aims to [...] Read more.
It is generally recognized that high-temperature treatments, namely annealing, influence the microstructure and the morphology, which, in turn, determine the mechanical properties of polymeric parts. Therefore, annealing can be adopted to control the mechanical performance of the molded parts. This work aims to assess the effect of annealing on the morphology developed in isotactic polypropylene (iPP) injection-molded parts. In particular, a two-step annealing is adopted: the polymer is injected in a mold at a high temperature (413 or 433 K), which is kept for 5 min (first annealing step); afterward, the mold temperature is cooled down at 403 K and held at that temperature for a time compatible with the crystallization half-time at that temperature (second annealing step). The characterization of morphology is carried out by optical and electronic scanning microscopy. The temperature of the first annealing step does not influence the thickness of the fibrillar skin layer; however, such a layer is thinner than that found in the molded parts obtained without any annealing steps. The second annealing step does not influence the thickness of the fibrillar skin layer. The dimension of spherulites found in the core is strongly influenced by both annealing steps: the spherulite dimensions enlarge by the effect of annealing steps. A model that considers spherulite and fibril evolutions is adopted to describe the effect of molding conditions on the final morphology distribution along the part thickness. The model, which adopts as input the thermo-mechanical histories calculated by commercial software for injection molding simulation, consistently predicts the main effects of the molding conditions on the morphology distributions. Full article
(This article belongs to the Special Issue Advances on Injection Molding of Polymers II)
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13 pages, 2870 KiB  
Article
Evaluating the Injection Moulding of Plastic Parts Using In Situ Time-Resolved Small-Angle X-ray Scattering Techniques
by André A. Costa, Fábio Gameiro, Artur Potêncio, Daniel P. da Silva, Pedro Carreira, Juan Carlos Martinez, Paula Pascoal-Faria, Artur Mateus and Geoffrey R. Mitchell
Polymers 2022, 14(21), 4745; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14214745 - 05 Nov 2022
Cited by 4 | Viewed by 2230
Abstract
In this study, we describe the design and fabrication of an industrial injection moulding system that can be mounted and used on the NCD-SWEET small-angle X-ray scattering beamline at ALBA. We show how highly useful time-resolved data can be obtained using this system. [...] Read more.
In this study, we describe the design and fabrication of an industrial injection moulding system that can be mounted and used on the NCD-SWEET small-angle X-ray scattering beamline at ALBA. We show how highly useful time-resolved data can be obtained using this system. We are able to evaluate the fraction of the material in the mould cavity and identify the first material to solidify and how this varies with the injection temperature. The design follows current industrial practice and provides opportunities to collect time-resolved data at several points within the mould cavity so that we can build up a 4D perspective of the morphology and its temporal development. The quantitative data obtained will prove invaluable for the optimisation of the next generation of injection moulding techniques. This preliminary work used results from the injection moulding of a general-purpose isotactic polypropylene. Full article
(This article belongs to the Special Issue Advances on Injection Molding of Polymers II)
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