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Polymers
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Injection Molding and Special Injection Molding Technologies of Polymer and...
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Injection Molding and Special Injection Molding Technologies of Polymer and Polymer Composites

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

Deadline for manuscript submissions: 25 March 2025 | Viewed by 17177

Special Issue Editor

Prof. Dr. Jian Wang

E-Mail Website
Guest Editor
State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, China
Interests: precision injection molding technology; advanced molding technology of polymer composites; advanced extrusion molding technology

Special Issue Information

Dear Colleagues,

Injection molding is the most commonly used manufacturing process for the batch preparation of polymer products. With the continuous updating of polymers and their composites, the requirements for injection molding technology are also increasing. Especially for the improvement of the product quality and production efficiency, it involves material characteristics and the determination of polymer properties, product design, mold design and tooling, injection molding machines, injection molding process, and control, etc. In addition, there are a variety of special injection molding techniques that cannot be realized by standard injection molding processes, such as insert injection molding or injection overmolding, injection compression molding, foam injection molding, gas- or water-assisted injection molding, micro injection molding, etc. These special injection molding technologies can transform polymer processing into a highly-efficient, integrated type of manufacturing. This Special Issue of the open-access journal Polymers will be focused on but not limited to the following topics:

  • Polymer testing techniques for injection molding;
  • Plastic part design for injection molding;
  • Mold design and tooling for injection molding;
  • Novel injection molding machines;
  • Intelligent/smart injection molding;
  • Precision injection molding;
  • Process/part monitoring for injection molding;
  • Insert injection molding / injection overmolding;
  • Injection compression molding;
  • Foam injection molding;
  • Fluid-assisted injection molding;
  • Micro injection molding.

Prof. Dr. Jian Wang
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.

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Published Papers (7 papers)

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Research

14 pages, 3759 KiB  
Article
Investigation of Dual Network Construction for Toughening in Bio-Based Polyamide Composites
by Chenxu Zhou, Chao Ding, Huaguang Yang and Xianbo Huang
Polymers 2024, 16(16), 2248; https://doi.org/10.3390/polym16162248 - 8 Aug 2024
Viewed by 1032
Abstract
This study investigated the role of constructing a dual network in toughening bio-based long-chain polyamide 610 (PA610) composites. Rheological studies were conducted to reveal the effects of toughening agent type and content on the material properties. According to the variation trend of mechanical [...] Read more.
This study investigated the role of constructing a dual network in toughening bio-based long-chain polyamide 610 (PA610) composites. Rheological studies were conducted to reveal the effects of toughening agent type and content on the material properties. According to the variation trend of mechanical properties and the appearance of a rheological low-frequency plateau of the materials, the percolation network concentration ϕc of the toughening agent in the PA610 matrix was determined to be 13.5 vol.%. The interfacial interaction of the composite was evaluated through the percolation theory, and the scaling value v = 1.36 for both indicated the good affinity between PA610 and the toughening agent. Rheology results found that the combination of ethylene terpolymer (PTW) and maleic anhydride-g-styrene-b-(ethylene-butylene)-b-styrene (MAH-SEBS) could achieve an optimal balance between the mechanical properties and fluidity of the composites. Furthermore, the addition of ultra-high-molecular-weight polytetrafluoroethylene (PTFE), in conjunction with the toughening agent, facilitated the construction of a dual semi-interpenetrating network. The strengthened intermolecular interactions restricted the relative slippage and mobility of the polymer chains and therefore enhanced the strength and toughness of the material. This study provides new possibilities and approaches for optimizing the comprehensive properties of bio-based polyamide materials. Full article
(This article belongs to the Special Issue Injection Molding and Special Injection Molding Technologies of Polymer and Polymer Composites)
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21 pages, 4756 KiB  
Article
An Enhanced Vacuum-Assisted Resin Transfer Molding Process and Its Pressure Effect on Resin Infusion Behavior and Composite Material Performance
by Rulin Shen, Taizhi Liu, Hehua Liu, Xiangfu Zou, Yanling Gong and Haibo Guo
Polymers 2024, 16(10), 1386; https://doi.org/10.3390/polym16101386 - 13 May 2024
Cited by 1 | Viewed by 3030
Abstract
In this paper, an enhanced VARTM process is proposed and its pressure effect on resin infusion behavior and composite material performance is studied to reveal the control mechanism of the fiber volume fraction and void content. The molding is vacuumized during the resin [...] Read more.
In this paper, an enhanced VARTM process is proposed and its pressure effect on resin infusion behavior and composite material performance is studied to reveal the control mechanism of the fiber volume fraction and void content. The molding is vacuumized during the resin injection stage while it is pressurized during the mold filling and curing stages via a VARTM pressure control system designed in this paper. Theoretical calculations and simulation methods are used to reveal the resin’s in-plane, transverse, and three-dimensional flow patterns in multi-layer media. For typical thin-walled components, the infiltration behavior of resin in isotropic porous media is studied, elucidating the control mechanisms of fiber volume fraction and void content. The experiments demonstrate that the enhanced VARTM process significantly improves mold filling efficiency and composite’s performance. Compared to the regular VARTM process, the panel thickness is reduced by 4% from 1.7 mm, the average tensile strength is increased by 7.3% to 760 MPa, the average flexural strength remains at approximately 720 MPa, porosity is decreased from 1.5% to below 1%, and the fiber volume fraction is increased from 55% to 62%. Full article
(This article belongs to the Special Issue Injection Molding and Special Injection Molding Technologies of Polymer and Polymer Composites)
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Graphical abstract

16 pages, 6000 KiB  
Article
Out-of-Mold Sensor-Based Process Parameter Optimization and Adaptive Process Quality Control for Hot Runner Thin-Walled Injection-Molded Parts
by Feng-Jung Cheng, Chen-Hsiang Chang, Chien-Hung Wen, Sheng-Jye Hwang, Hsin-Shu Peng and Hsiao-Yeh Chu
Polymers 2024, 16(8), 1057; https://doi.org/10.3390/polym16081057 - 11 Apr 2024
Viewed by 1336
Abstract
Injection molding is a highly nonlinear procedure that is easily influenced by various external factors, thereby affecting the stability of the product’s quality. High-speed injection molding is required for production due to the rapid cooling characteristics of thin-walled parts, leading to increased manufacturing [...] Read more.
Injection molding is a highly nonlinear procedure that is easily influenced by various external factors, thereby affecting the stability of the product’s quality. High-speed injection molding is required for production due to the rapid cooling characteristics of thin-walled parts, leading to increased manufacturing complexity. Consequently, establishing appropriate process parameters for maintaining quality stability in long-term production is challenging. This study selected a hot runner mold with a thin wall fitted with two external sensors, a nozzle pressure sensor and a tie-bar strain gauge, to collect data regarding the nozzle peak pressure, the timing of peak pressure, the viscosity index, and the clamping force difference value. The product weight was defined as the quality indicator, and a standardized parameter optimization process was constructed, including injection speed, V/P switchover point, packing, and clamping force. Finally, the optimized process parameters were applied to the adaptive process control experiments using the developed control system operated within the micro-controller unit (MCU). The results revealed that the control system effectively stabilized the product weight variation and standard deviation of 0.677% and 0.0178 g, respectively. Full article
(This article belongs to the Special Issue Injection Molding and Special Injection Molding Technologies of Polymer and Polymer Composites)
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Graphical abstract

18 pages, 6822 KiB  
Article
Weld Line Strength of Polyamide Fiberglass Composite at Different Processing Parameters in Injection Molding Technique
by Van-Thuc Nguyen, Tran Minh The Uyen, Pham Son Minh, Thanh Trung Do, Trung H. Huynh, Tronghieu Nguyen, Vinh Tien Nguyen and Van Thanh Tien Nguyen
Polymers 2023, 15(20), 4102; https://doi.org/10.3390/polym15204102 - 16 Oct 2023
Cited by 1 | Viewed by 1726
Abstract
This study examines the impact of injection parameters on the weld line strength of the polyamide 6 and 30% fiberglass (PA6 + 30% FG) composite samples. The effects of filling time, packing time, packing pressure, melt temperature, and mold temperature on the ultimate [...] Read more.
This study examines the impact of injection parameters on the weld line strength of the polyamide 6 and 30% fiberglass (PA6 + 30% FG) composite samples. The effects of filling time, packing time, packing pressure, melt temperature, and mold temperature on the ultimate tensile strength (UTS) and the elongation value of the weld line are investigated. The results reveal that the filling time factor has the lowest influence rate. On the contrary, the packing pressure has the most considerable value of UTS standard deviation, indicating that this factor has a high impact rate. The melt temperature factor has the highest elongation standard deviation, pointing out the strong impact of melt temperature on the elongation value. In reverse, the filling time factor has the lowest elongation standard deviation, showing the low impact of this factor on the elongation value. Increasing the mold temperature enhances the elongation value greatly because a higher temperature generates a better connection in the weld line area. Although the UTS value improves modestly when the mold temperature control system is used, the elongation result from the mold temperature parameter is better than expected. The UTS result from all parameters presents a minor deviation; therefore, it is lower than expected. The optimal strength result from artificial neural networks with genetic algorithm optimization is 85.1 MPa, which is higher than the best experiment result of 76.8 MPa. Scanning electron microscopy (SEM) results show that the interface between the fiberglass and the PA matrix has high adherence. The fracture surface is smooth, indicating that the PA6 + 30% FG composite sample has a high fragility level. The findings could help to increase the injection sample’s weld line strength by optimizing the injection molding conditions. Full article
(This article belongs to the Special Issue Injection Molding and Special Injection Molding Technologies of Polymer and Polymer Composites)
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24 pages, 19490 KiB  
Article
Conformal Cooling Channel Design for Improving Temperature Distribution on the Cavity Surface in the Injection Molding Process
by Van-Thuc Nguyen, Pham Son Minh, Tran Minh The Uyen, Thanh Trung Do, Nguyen Canh Ha and Van Thanh Tien Nguyen
Polymers 2023, 15(13), 2793; https://doi.org/10.3390/polym15132793 - 23 Jun 2023
Cited by 11 | Viewed by 2607
Abstract
Mold heating is an essential process in plastic injection molding. Raising the temperature of the mold before injecting liquefied plastic can ease the mold-filling process. A cooling channel can be used to transport high-temperature fluids for this purpose, such as hot water or [...] Read more.
Mold heating is an essential process in plastic injection molding. Raising the temperature of the mold before injecting liquefied plastic can ease the mold-filling process. A cooling channel can be used to transport high-temperature fluids for this purpose, such as hot water or oil. This dual purpose is a cost-effective solution for heating the mold because the target temperature is easily achieved using this method. In addition, a conformal cooling channel (CCC) can provide more efficient mold heating than a straight cooling channel. This study used the response surface methodology to determine the optimum CCC shape for heat distribution in a mold, and the simulation results confirmed its optimization. The average temperature of the mold using a CCC was better than that using a straight cooling channel, and the heat zone was uniform across the mold surface. Full article
(This article belongs to the Special Issue Injection Molding and Special Injection Molding Technologies of Polymer and Polymer Composites)
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19 pages, 8523 KiB  
Article
Direct In-Mold Impregnation of Glass Fiber Fabric by Polypropylene with Supercritical Nitrogen in Microcellular Injection Molding Process
by Qichao He, Weimin Yang, Jian Wang, Feng Ren, Da Wang, Fuhai Li and Zhonghe Shi
Polymers 2023, 15(4), 875; https://doi.org/10.3390/polym15040875 - 10 Feb 2023
Viewed by 2207
Abstract
Combining microcellular injection molding and insert injection molding, an injection molding technique for glass fiber fabric (GFF) reinforced polypropylene (PP) composite foams was proposed. The GFF was directly set in the mold cavity, and then the PP with supercritical nitrogen (SCN) was injected [...] Read more.
Combining microcellular injection molding and insert injection molding, an injection molding technique for glass fiber fabric (GFF) reinforced polypropylene (PP) composite foams was proposed. The GFF was directly set in the mold cavity, and then the PP with supercritical nitrogen (SCN) was injected into the cavity for in-mold impregnation. The impregnation effects of two types of GFFs (EWR300 and EWR600) by the PP/SCF solutions at different injection temperatures (230, 240, and 250 °C) were investigated. The results of the morphological and tensile properties of the samples showed that the interfacial bonding was not good, because of the heterogeneity between the GFF and PP. In comparison with solid PP, the unfoamed GFF/PP did not present a higher tensile strength and presented a lower specific tensile strength. However, the increased tensile strength of the GFF/PP composite foams indicated an improvement in the impregnation effect and interfacial bonding. The SCN decreased the viscosity, which benefited the direct in-mold impregnation of the GFF. Increasing the temperature can improve the interfacial bonding, but it also influenced the foaming and thus led to a decrease in the tensile strength. According to the temperature distribution, the samples from different positions in the mold cavity had different properties. Full article
(This article belongs to the Special Issue Injection Molding and Special Injection Molding Technologies of Polymer and Polymer Composites)
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17 pages, 4465 KiB  
Article
Fabric Insert Injection Molding for the Preparation of Ultra-High Molecular Weight Polyethylene/High-Density Polyethylene Two-Component Self-Reinforced Composites
by Jian Wang, Da Wang, Qianchao Mao and Jinnan Chen
Polymers 2022, 14(20), 4384; https://doi.org/10.3390/polym14204384 - 17 Oct 2022
Cited by 9 | Viewed by 3239
Abstract
The fabric insert injection molding approach can be applied to produce easily recyclable self-reinforced polymer composites (SrCs) whose reinforcement and matrix are from the same polymer. However, the mechanical properties of the SrCs are usually limited due to the poor impregnation of the [...] Read more.
The fabric insert injection molding approach can be applied to produce easily recyclable self-reinforced polymer composites (SrCs) whose reinforcement and matrix are from the same polymer. However, the mechanical properties of the SrCs are usually limited due to the poor impregnation of the inserted fabric. In this work, the ultra-high molecular weight polyethylene (UHMWPE) fabrics were used as the insert, and the high-density polyethylene (HDPE) melt was injected to fill the mold cavity and impregnate the fabrics. The UHMWPE/HDPE two-component SrCs were prepared. The large difference of melting temperatures between UHMWPE and HDPE can establish a wide processing temperature window, and thus the impregnation of the fabric can be improved by increasing temperature. The tensile strength and modulus of the UHMWPE/HDPE SrCs were up to 148 and 1132 MPa, respectively. The peel strength could be up to 35.2 N/cm. The influences of four main injection molding parameters, including the injection temperature, injection pressure/packing pressure, injection velocity, and packing time, were investigated. The temperature, pressure, viscosity, and density of the matrix in the mold cavity were calculated by the numerical simulation to indicate the impregnation process during the fabric insert injection molding process. Full article
(This article belongs to the Special Issue Injection Molding and Special Injection Molding Technologies of Polymer and Polymer Composites)
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