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Polymers
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Injection Molding Process in Polymer Processing
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Injection Molding Process 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: 5 February 2025 | Viewed by 11449

Special Issue Editors

Prof. Dr. Hans-Peter Heim

E-Mail Website
Guest Editor
Department Polymer Technology, Institute of Mechanical Engineering, University of Kassel, Mönchebergstr. 3, 34125 Kassel, Germany
Interests: injection molding; 2C-injection molding; 3D-printing; biopolymers; digitalization; functional integration
Dr. Ralf Urs Giesen

E-Mail Website
Guest Editor
Department Polymer Technology, Institute of Mechanical Engineering, University of Kassel, Mönchebergstr. 3, 34125 Kassel, Germany
Interests: silicone rubber; polymer processing; hard–soft components; injection molding; testing of elastomers

Special Issue Information

Dear Colleagues

Injection Molding of Silicone Rubber

In plastics manufacturing, the processing of high consistency rubber (HCR) and liquid silicone rubber (LSR) is becoming increasingly important. In medical technology, LSR is given preference over other elastomers because of its good processability and physiological compatibility. In automotive engineering, silicones are often used in the temperature range between −50 and +200 °C because of their ideal elastic properties. Consumer electronics is another market for which silicones are anticipated to experience strong growth, since they have excellent damping and haptic properties. Silicone rubbers are also popular in sanitary applications (e.g., showers) because they have ideal sealing properties and limescale can easily be removed. In addition, foamed silicone parts are also, or even especially, suitable for all the aforementioned fields of application and allow making components that are cheaper and lighter. Furthermore, it is becoming increasingly important to reduce assembly steps and integrate functions into components. Silicone rubbers are ideal for this purpose and can be processed into hard–soft components.

Injection molding of silicone rubber is very different from thermoplastic injection molding and also from injection molding of synthetic and natural rubbers. In the process, a 2-component liquid silicone rubber (LSR) mix is introduced into the injection molding unit, which is cooled. Solidification of the component takes place under a crosslinking process at approx. 180 °C. Special features of LSR processing are the special mold technology, the injection molding of hard–soft composites, and the foaming of LSR. 

Back Injection Molding of Functional Films

Back injection molding of films is particularly well established in the packaging sector. Here, buckets and cups are decorated with films in the injection molding process. However, the requirements here are not as high as for back molding of functional and visible parts. The challenges are to adapt melt temperatures and injection pressures to the corresponding foils so as not to damage them. Adhesion between the materials must also be ensured when two different thermoplastics are used. This often occurs when functional films are used that were not actually developed for back molding.

The back injection molding of multilayer composites such as electroactive polymers (EAPs) or electrochromic films requires a special mold technology and, in connection with this, a process technology adapted to the temperatures and pressures. Many materials in the multilayer composites are unstable due to the high pressures and temperatures. Here, it is important to determine the properties of the multilayer films as well as which injection molding and injection compression molding technology is suitable for their processing.

Prof. Dr. Hans-Peter Heim
Dr. Ralf Urs Giesen
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

  • silicone rubber
  • liquid injection molding
  • electrochromic films
  • functional films

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Published Papers (5 papers)

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Research

17 pages, 6974 KiB  
Article
A Global Approach to Modeling Injection Molding
by Przemysław Narowski and Krzysztof Wilczyński
Polymers 2024, 16(1), 147; https://doi.org/10.3390/polym16010147 - 3 Jan 2024
Viewed by 2561
Abstract
A problem of modeling plastic injection forming (molding) is presented, including both the plasticizing system of the injection-forming machine and the mold. When modeling the plastic flow in the mold, the input quantities are essentially unknown, e.g., the plastic melt temperature. Thus, a [...] Read more.
A problem of modeling plastic injection forming (molding) is presented, including both the plasticizing system of the injection-forming machine and the mold. When modeling the plastic flow in the mold, the input quantities are essentially unknown, e.g., the plastic melt temperature. Thus, a comprehensive (global) model of the injection-forming process is needed for the flow in the plasticizing system and in the mold. The process output quantities from the plasticizing system will be the input quantities for the mold. When modeling the plastic flow in the injection-forming machine, a comprehensive approach should be applied to consider the solid material conveying, material plasticizing, and the material melt flow. The model of material plasticizing is a basis for building such global models. In this research, the effect of the flow (including plasticizing) in the injection-forming machine on the flow in the mold is studied by simulation (using Moldex3D 2023R3OR 64-bit software) and experimentation. These studies are carried out for the injection forming of selected material using a specialized spiral mold. Simulations performed with the use of Moldex3D software for the plasticizing system significantly improved the accuracy of the simulation of the flow in the mold. However, the best results were obtained using experimental data (plastic melt temperature) as input quantities for mold filling simulations. The novel concepts of injection-forming process modeling based on our previous experimentations are also discussed. Full article
(This article belongs to the Special Issue Injection Molding Process in Polymer Processing)
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22 pages, 7235 KiB  
Article
Analysis of the Machine-Specific Behavior of Injection Molding Machines
by Julia Knoll and Hans-Peter Heim
Polymers 2024, 16(1), 54; https://doi.org/10.3390/polym16010054 - 22 Dec 2023
Cited by 1 | Viewed by 2411
Abstract
The performance of an injection molding machine (IMM) influences the process and the quality of the parts manufactured. Despite increasing data collection capabilities, their machine-specific behavior has not been extensively studied. To close corresponding research gaps, the machine-specific behavior of two hydraulic IMMs [...] Read more.
The performance of an injection molding machine (IMM) influences the process and the quality of the parts manufactured. Despite increasing data collection capabilities, their machine-specific behavior has not been extensively studied. To close corresponding research gaps, the machine-specific behavior of two hydraulic IMMs of different sizes and one electric IMM were compared with each other as part of the investigations. Both the start-up behavior from the cold state and the behavior of the machine at different operating points were considered. To complement this, the influence of various material properties on the machine-specific behavior was investigated by processing an unreinforced and glass-fiber-reinforced polyamide. The results obtained provide crucial insights into machine-specific behavior, which may, for instance, account for disparities between computer fluid dynamic (CFD) simulations and experimental results. Furthermore, it is expected that the description of the machine-specific behavior can contribute to transfer knowledge when applying transfer learning algorithms. Looking ahead to future research, it is advised to create what is referred to as a “machine fingerprint”, and this proposal is accompanied by some preliminary recommendations for its development. Full article
(This article belongs to the Special Issue Injection Molding Process in Polymer Processing)
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12 pages, 3496 KiB  
Article
MC-Injection Molding with Liquid Silicone Rubber (LSR) and Acrylonitrile Butadiene Styrene (ABS) for Medical Technology
by Mohammad Ali Nikousaleh, Ralf-Urs Giesen, Hans-Peter Heim and Michael Hartung
Polymers 2023, 15(19), 3972; https://doi.org/10.3390/polym15193972 - 2 Oct 2023
Cited by 3 | Viewed by 2246
Abstract
The multicomponent injection molding of liquid silicone rubbers (LSR) with thermoplastics, such as polybutylene terephthalate (PBT) or polyamide (PA), is a state-of-the-art technique and is used in the manufacturing process for many components in the automotive industry and in the field of sanitary [...] Read more.
The multicomponent injection molding of liquid silicone rubbers (LSR) with thermoplastics, such as polybutylene terephthalate (PBT) or polyamide (PA), is a state-of-the-art technique and is used in the manufacturing process for many components in the automotive industry and in the field of sanitary engineering. Standard thermoplastics, such as acrylonitrile butadiene styrene (ABS), cannot be bonded with silicone rubbers in injection molding because of their low heat deflection temperature. In this study, we investigated ABS grades approved for medical applications to show how dynamic mold heating and various pretreatment methods for thermoplastic surfaces can be used to produce ABS-LSR test specimens. In addition, such components’ sterilization effect on the adhesive bond will be shown. Full article
(This article belongs to the Special Issue Injection Molding Process in Polymer Processing)
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28 pages, 4357 KiB  
Article
Integration of Multivariate Statistical Control Chart and Machine Learning to Identify the Abnormal Process Parameters for Polylactide with Glass Fiber Composites in Injection Molding; Part I: The Processing Parameter Optimization for Multiple Qualities of Polylactide/Glass Fiber Composites in Injection Molding
by Chi-Hao Hsiao, Chang-Chiun Huang, Chung-Feng Jeffrey Kuo and Naveed Ahmad
Polymers 2023, 15(14), 3018; https://doi.org/10.3390/polym15143018 - 12 Jul 2023
Cited by 2 | Viewed by 1378
Abstract
This paper discusses the mixing of polylactide (PLA) and glass fiber which use injection molding to produce a functional composite material with glass fiber properties. The injection molding process explores the influence of glass fiber ratio, melt temperature, injection speed, packing pressure, packing [...] Read more.
This paper discusses the mixing of polylactide (PLA) and glass fiber which use injection molding to produce a functional composite material with glass fiber properties. The injection molding process explores the influence of glass fiber ratio, melt temperature, injection speed, packing pressure, packing time and cooling time on the mechanical properties of composite. Using the orthogonal table planning experiment of the Taguchi method, the optimal parameter level combination of a single quality process is obtained through main effect analysis (MEA) and Analysis of variance (ANOVA). Then, the optimal parameter level combination of multiple qualities is obtained through principal component analysis (PCA) and data envelopment analysis (DEA), respectively. It is observed that if all the quality characteristics of tensile strength, hardness, impact strength and bending strength are considered at the same time, the optimal process conditions are glass fiber addition 20 wt %, melt temperature 185 °C, injection speed 80 mm/s, holding pressure 60 MPa, holding time 1 s and cooling time 15 s, and the corresponding mechanical properties are tensile strength 95.04 MPa, hardness 86.52 Shore D, impact strength 4.4408 J/cm2, bending strength 119.89 MPa. This study effectively enhances multiple qualities of PLA/GF composite. Full article
(This article belongs to the Special Issue Injection Molding Process in Polymer Processing)
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16 pages, 19175 KiB  
Article
Development of an Injection Mold with High Energy Efficiency of Vulcanization for Liquid Silicone Rubber Injection Molding of the Fisheye Optical Lens
by Chil-Chyuan Kuo, Qing-Zhou Tasi, Song-Hua Hunag and Shih-Feng Tseng
Polymers 2023, 15(13), 2869; https://doi.org/10.3390/polym15132869 - 29 Jun 2023
Cited by 13 | Viewed by 2120
Abstract
Liquid silicone rubber (LSR) techniques are experiencing exponential growth, particularly in the field of high technology due to the low-temperature flexibility, superior heat stability, chemical resistance, and aging resistance of LSR components. Enhancing the curing rate of LSR parts in liquid silicone rubber [...] Read more.
Liquid silicone rubber (LSR) techniques are experiencing exponential growth, particularly in the field of high technology due to the low-temperature flexibility, superior heat stability, chemical resistance, and aging resistance of LSR components. Enhancing the curing rate of LSR parts in liquid silicone rubber injection molding is an important research topic. In this study, an injection mold with high energy efficiency of vulcanization for the liquid silicone rubber injection molding of a fisheye lens was developed and implemented. The LSR injection mold has a conformal heating channel (CHC) and conformal cooling channel (CCC) simultaneously. The function of CHC is to enhance the curing rate of a fisheye lens in the LSR injection molding to meet the requirements of sustainable manufacturing. The curing rates of a fisheye lens were numerically examined using the Moldex3D molding simulation software. It was found that the curing rate of the fisheye optical lens cured by injection mold with CHC was better than that of the injection mold with a conventional heating channel. The curing efficiency could be increased by about 19.12% when the heating oil temperature of 180 °C was used to cure the fisheye optical lens. The simulation results showed that the equation y = −0.0026x3 + 1.3483x2 − 232.11x + 13,770 was the most suitable equation for predicting the curing time (y) through the heating oil temperature (x). It was found that the trend of the experimental results was consistent with the simulation results. In addition, the equation y = −0.0656x2 + 1.5827x − 0.894 with the correlation coefficient of 0.9974 was the most suitable equation for predicting the volumetric shrinkage of the fisheye optical lens (y) through the heating oil temperature (x). The volume shrinkage of the fisheye optical lens cured by injection mold with CHC was very similar to that of the injection mold with a conventional heating channel. The maximum volume shrinkage of the fisheye optical lens cured at 180 °C was about 8.5%. Full article
(This article belongs to the Special Issue Injection Molding Process in Polymer Processing)
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