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Polymers
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Polymer Processing and Molding
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Polymer Processing and Molding

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

Deadline for manuscript submissions: closed (28 February 2021) | Viewed by 33993

Special Issue Editors

Dr. Rossella Surace

E-Mail Website
Guest Editor
Institute of Intelligent Industrial Technologies and Systems for Advanced Manufacturing, National Research Council (STIIMA-CNR), 70124 Bari, Italy
Interests: injection molding; micro manufacturing; polymer properties and processing; composites; polymeric foams; additive manufacturing
Special Issues, Collections and Topics in MDPI journals
Dr. Irene Fassi

E-Mail Website
Co-Guest Editor
Institute of Intelligent Industrial Technologies and Systems for Advanced Manufacturing, National Research Council (STIIMA-CNR), 13900 Bari, Italy
Interests: micro manufacturing; micro robotics; micro assembly; micro EDM; micro injection molding
Special Issues, Collections and Topics in MDPI journals
Dr. Claudia Pagano

E-Mail Website
Co-Guest Editor
Institute of Intelligent Industrial Technologies and Systems for Advanced Manufacturing, National Research Council of Italy, Milano, Italy
Interests: micro manufacturing; polymers processing; compounding; micro assembly; mechanics of materials; nanoindentation; atomic force microscopy

Special Issue Information

Dear Colleagues,

As polymers and composite research is rapidly growing around the world and gaining increasing interest, at the same time, the aim of this Special Issue is to highlight the novel aspects of polymer processing and manufacturing. Polymer processing has effects on the material structure and crystallinity and, hence, defines the mechanical and functional performance of polymers in all possible products in different and emerging sectors.

Polymer processing covers a wide range of techniques including extrusion-based processes and molding-based processes, such as injection, compression, rotational, blow, plastic foam, precision and micro molding. Indeed, there is an ever-increasing need to understand these processes and specifically the influence of process parameters, optimization of product properties, and characterization of results.  This Special Issue will provide insights into the recent advances in material, process and product interactions, with a special focus on sustainable and climate neutral approaches.

Dr. Rossella Surace
Dr. Irene Fassi
Dr. Claudia Pagano
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

  • Polymers processing
  • Polymers manufacturing
  • Composite processing
  • Molding
  • Micro-injection molding
  • Polymers/process interactions
  • Structure/properties relationship
  • Functionalized polymers

Published Papers (10 papers)

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Research

18 pages, 5750 KiB  
Article
Micro Injection Molding of Thin Cavities Using Stereolithography for Mold Fabrication
by Rossella Surace, Vito Basile, Vincenzo Bellantone, Francesco Modica and Irene Fassi
Polymers 2021, 13(11), 1848; https://doi.org/10.3390/polym13111848 - 02 Jun 2021
Cited by 17 | Viewed by 4987
Abstract
At the present time, there is a growing interest in additive manufacturing (AM) technologies and their integration into current process chains. In particular, the implementation of AM for tool production in micro injection molding (µ-IM), a well-established process, could introduce many advantages. First [...] Read more.
At the present time, there is a growing interest in additive manufacturing (AM) technologies and their integration into current process chains. In particular, the implementation of AM for tool production in micro injection molding (µ-IM), a well-established process, could introduce many advantages. First of all, AM could avoid the need for the time-consuming and expensive fabrication of molds for small series of customized products. In this work, the feasibility, quality, and reliability of an AM/µ-IM process chain were evaluated by designing and fabricating mold inserts for µ-IM by stereolithography (SLA) technology; the mold inserts were characterized and tested experimentally. The selected geometry is composed of four thin cavities: This particular feature represents an actual challenge for both the SLA and µ-IM perspective due to the large surface-to-volume ratio of the cavity. Two different materials were used for the mold fabrication, showing sharply different performance in terms of endurance limit and cavity degradation. The obtained results confirm that the µ-IM process, exploiting an SLA fabricated mold insert, is feasible but requires great accuracy in material choice, mold design, fabrication, and assembly. Full article
(This article belongs to the Special Issue Polymer Processing and Molding)
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11 pages, 2719 KiB  
Article
Back Injection Molding of Sub-Micron Scale Structures on Roll-to-Roll Extrusion Coated Films
by Sijia Xie, Jerome Werder and Helmut Schift
Polymers 2021, 13(9), 1410; https://doi.org/10.3390/polym13091410 - 27 Apr 2021
Cited by 1 | Viewed by 3269
Abstract
Roll-to-roll extrusion coated films were bonded onto polymer parts by back injection molding (BIM). The polypropylene (PP) coated polyethylene terephthalate (PET) films were pre-patterned with microstructured V-shaped grooves with 3.2 µm and 53 µm width, and other geometries. Bonding on PET and poly(methyl [...] Read more.
Roll-to-roll extrusion coated films were bonded onto polymer parts by back injection molding (BIM). The polypropylene (PP) coated polyethylene terephthalate (PET) films were pre-patterned with microstructured V-shaped grooves with 3.2 µm and 53 µm width, and other geometries. Bonding on PET and poly(methyl methacrylate) (PMMA) parts was facilitated by either higher tool or melt temperatures but was particularly enhanced by applying a mild oxygen plasma to the backside of the PET film prior to injection of the polymer melt. Silver wires from conductive nanoparticle ink were embedded into the PP coating during the BIM process by controlled collapse of the V-grooves. Thus, the feasibility of combining standard carrier film materials for printed flexible electronics and packaging into a non-flat polymer part was demonstrated, which could be a helpful step towards the fabrication of polymer parts with surface functionality. Full article
(This article belongs to the Special Issue Polymer Processing and Molding)
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14 pages, 3688 KiB  
Article
Development of a Subpath Extrusion Tip and Die for Peripheral Inserted Central Catheter Shaft with Multi Lumen
by Han Chang Lee, Jinhyuk Jeong, Seunggi Jo, Dong Yun Choi, Gyu Man Kim and Woojin Kim
Polymers 2021, 13(8), 1308; https://doi.org/10.3390/polym13081308 - 16 Apr 2021
Cited by 4 | Viewed by 2984
Abstract
The tip and die for manufacturing multi-lumen catheter tubes should be designed considering the flow velocity of the molten polymer and the deformation of the final extruded tube. In this study, to manufacture non-circular double-lumen tubes for peripherally inserted central catheters (PICCs), three [...] Read more.
The tip and die for manufacturing multi-lumen catheter tubes should be designed considering the flow velocity of the molten polymer and the deformation of the final extruded tube. In this study, to manufacture non-circular double-lumen tubes for peripherally inserted central catheters (PICCs), three types of tip and die structures are proposed. The velocity field and swelling effect when the circular tip and die (CTD) are applied, which is the commonly used tip and die structure, are analyzed through numerical calculation. To resolve the wall and rib thickness and ovality issues, the ellipse tip and die (ETD) and sub-path tip and die (STD) were proposed. In addition, based on the results of numerical analysis, the tip and die structures were manufactured and used to perform extrusion. Finally, we manufactured tubes that satisfied the target diameter, ovality, wall, and rib thickness using the newly proposed STD. Full article
(This article belongs to the Special Issue Polymer Processing and Molding)
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20 pages, 9226 KiB  
Article
Hybrid Taguchi–Gray Relation Analysis Method for Design of Metal Powder Injection-Molded Artificial Knee Joints with Optimal Powder Concentration and Volume Shrinkage
by Chao-Ming Lin, Yu-Tung Hung and Chung-Ming Tan
Polymers 2021, 13(6), 865; https://doi.org/10.3390/polym13060865 - 11 Mar 2021
Cited by 12 | Viewed by 2336
Abstract
Artificial knee joints play a critical role in improving the quality of life of the elderly and those with knee injuries. Such knee joints are fabricated using a composite material consisting of metal alloy particles and polymer resin and are generally produced using [...] Read more.
Artificial knee joints play a critical role in improving the quality of life of the elderly and those with knee injuries. Such knee joints are fabricated using a composite material consisting of metal alloy particles and polymer resin and are generally produced using the metal powder injection molding (MIM) process. However, if the local powder concentration of the molded product is too low, the mechanical properties and aesthetic appearance of the joint are severely degraded. Similarly, if the product undergoes excessive shrinkage following removal from the mold, the dimensional accuracy will fail to meet the design specifications. Accordingly, the present study applies a hybrid approach based on the Taguchi robust design methodology and gray relation analysis (GRA) theory to determine the optimal MIM processing conditions that simultaneously maximize the powder concentration uniformity while minimizing the volume shrinkage. The feasibility of the proposed approach is demonstrated by means of CAE (Computer Aided Engineering) mold flow simulations. The results show that while the robust Taguchi design method enables the optimal processing parameters that maximize the powder concentration uniformity and minimize the volume shrinkage to be individually determined, the hybrid Taguchi–GRA method enables both quality measures to be optimized simultaneously. Full article
(This article belongs to the Special Issue Polymer Processing and Molding)
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18 pages, 4630 KiB  
Article
An Analysis of the Casting Polymer Mold Wear Manufactured Using PolyJet Method Based on the Measurement of the Surface Topography
by Paweł Turek, Grzegorz Budzik, Jarosław Sęp, Mariusz Oleksy, Jerzy Józwik, Łukasz Przeszłowski, Andrzej Paszkiewicz, Łukasz Kochmański and Damian Żelechowski
Polymers 2020, 12(12), 3029; https://doi.org/10.3390/polym12123029 - 17 Dec 2020
Cited by 26 | Viewed by 2916
Abstract
An important factor having an impact on the condition of machine parts is their surface topography. For instance, in the production of a molded element in casting or injection molding processes, the surface topography of the molding cavity has a significant impact on [...] Read more.
An important factor having an impact on the condition of machine parts is their surface topography. For instance, in the production of a molded element in casting or injection molding processes, the surface topography of the molding cavity has a significant impact on the surface condition of the product. An analysis of the wear of a mold made with the PolyJet technique was performed in this work, and we examined the surface topography using the stylus method after casting a wax model of the turbine blade. The surface topographies showed a gradual degradation of the mold cavity surface. After the manufacture of 40 castings, there was a significant deformation of the microstructure of the mold cavity. The maximum height value (Sz) parameter had the most dynamic change from 18.980 to 27.920 μm. Its growth dynamics are mainly influenced by maximum peak height (Sp) rather than the maximum pit height (Sv) parameter. In the case of the root mean square height (Sq) and arithmetic mean height (Sa), their gradual increases can be seen from 2.578 to 3.599 μm and from 2.038 to 2.746 μm. In the case of the value of the skewness (Ssk) parameter, a small positive skew was observed. As for the kurtosis (Sku) values, the distributions are clearly leptokurtic. Full article
(This article belongs to the Special Issue Polymer Processing and Molding)
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17 pages, 25217 KiB  
Article
Modeling the Adhesion Bonding Strength in Injection Overmolding of Polypropylene Parts
by Ruggero Giusti and Giovanni Lucchetta
Polymers 2020, 12(9), 2063; https://doi.org/10.3390/polym12092063 - 10 Sep 2020
Cited by 13 | Viewed by 4007
Abstract
In this work, the bonding strength of overmolded polypropylene is investigated and modeled. A T-joint specimen was designed to replicate the bonding between a base and an overmolded stem made of the same polymer: a previously molded plaque was used for the base, [...] Read more.
In this work, the bonding strength of overmolded polypropylene is investigated and modeled. A T-joint specimen was designed to replicate the bonding between a base and an overmolded stem made of the same polymer: a previously molded plaque was used for the base, and the stem was directly overmolded. The effect of melt temperature, holding pressure, and localized heating was investigated following the design of experiments approach. Both the melt and base temperature positively affect the welding strength. On the contrary, the holding pressure negatively contributed, as the crystallization temperature significantly increases with pressure. Then, the bonding strength of the specimens was predicted using a non-isothermal healing model. Moreover, the quadratic distance of diffusion (based on the self-diffusion model) was calculated and correlated with the bonding strength prediction. The non-isothermal healing model well predicts the bonding strength when the reptation time is calculated within the first 0.09 s of the interface temperature evolution. The prediction error ranges from 1% to 35% for the specimens overmolded at high and low melt and base temperatures, respectively. Full article
(This article belongs to the Special Issue Polymer Processing and Molding)
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29 pages, 18950 KiB  
Article
New Procedure for BIM Characterization of Architectural Models Manufactured Using Fused Deposition Modeling and Plastic Materials in 4.0 Advanced Construction Environments
by Daniel Diaz-Perete, Jorge Manuel Mercado-Colmenero, Jose Manuel Valderrama-Zafra and Cristina Martin-Doñate
Polymers 2020, 12(7), 1498; https://doi.org/10.3390/polym12071498 - 04 Jul 2020
Cited by 12 | Viewed by 2972
Abstract
This paper presents a new procedure for the building information modeling (BIM) characterization of structural topologies manufactured with plastic materials and fused deposition modeling (FDM) additive technology. The procedure presented here transforms the architectural geometry into an expanded three-dimensional model, capable of directly [...] Read more.
This paper presents a new procedure for the building information modeling (BIM) characterization of structural topologies manufactured with plastic materials and fused deposition modeling (FDM) additive technology. The procedure presented here transforms the architectural geometry into an expanded three-dimensional model, capable of directly linking the topology of the plastic structure with the technological, functional and economic requirements for working in advanced construction 4.0 environments. The model incorporates a new algorithm whose objective is to recognize the topological surface of the plastic structural part obtaining in a fully automated way the FDM manufacturing time as well as the manufacturing cost. The new algorithm starts from the voxelized geometrical surface of the architectural model, calculating the manufacturing time from the full geometric path traveled by the extruder in a voxel, the extruder’s speed, the print pattern and the layer height. In this way it is possible to obtain a complete digital model capable of managing and analyzing the plastic architectural object in an advanced BIM 4.0 environment. The model presented in this paper was applied to two architectural structures designed for a real urban environment. The final structural geometries have been obtained through topological processes in order to reduce the raw plastic manufacturing material and to improve the plastic structure strength. The architectural elements have been validated structurally by the means of numerical simulations, following the scenario of loads and boundary conditions required for the real project. The displacement maps point to a maximum value of 0.5 mm according to the project requirements. The Von Mises stress fields indicate maximum values of 0.423 and 0.650 MPa, not exceeding in any case the tensile yield strength of the thermoplastic material. Full article
(This article belongs to the Special Issue Polymer Processing and Molding)
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15 pages, 5359 KiB  
Article
Fabrication of Self-Lubricating Porous UHMWPE with Excellent Mechanical Properties and Friction Performance via Rotary Sintering
by Xianwu Cao, Yuping Li and Guangjian He
Polymers 2020, 12(6), 1335; https://doi.org/10.3390/polym12061335 - 12 Jun 2020
Cited by 14 | Viewed by 3003
Abstract
Porous ultra-high-molecular-weight polyethylene (UHMWPE) self-lubricating materials were designed and fabricated by a rotary sintering method, and the microstructure and properties were evaluated. Results showed that the rotary molding could not only significantly improve the molding efficiency but also formed uniform internal microstructures with [...] Read more.
Porous ultra-high-molecular-weight polyethylene (UHMWPE) self-lubricating materials were designed and fabricated by a rotary sintering method, and the microstructure and properties were evaluated. Results showed that the rotary molding could not only significantly improve the molding efficiency but also formed uniform internal microstructures with high porosity, excellent mechanical properties, and low friction coefficient. Under oil lubricating conditions, the friction curve of samples quickly reached a steady state, the friction coefficient was reduced by 50%, and the repeat utilization was up to 99%. The following optimum sintering conditions were shown: Sintering temperature of 180 °C or 190 °C, sintering time determined as 10 min, and loading capacity of between 3.6 g and 3.8 g. Therefore, it is expected that this work will open a convenient and compatible strategy for fabricating porous materials with good self-lubricating performance. Full article
(This article belongs to the Special Issue Polymer Processing and Molding)
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19 pages, 3474 KiB  
Article
Correlation between Processing Parameters and Degradation of Different Polylactide Grades during Twin-Screw Extrusion
by Olga Mysiukiewicz, Mateusz Barczewski, Katarzyna Skórczewska and Danuta Matykiewicz
Polymers 2020, 12(6), 1333; https://doi.org/10.3390/polym12061333 - 11 Jun 2020
Cited by 41 | Viewed by 3569
Abstract
This article presents the effect of twin-screw extrusion processing parameters, including temperature and rotational speed of screws, on the structure and properties of four grades of polylactide (PLA). To evaluate the critical processing parameters for PLA and the possibilities for oxidative and thermomechanical [...] Read more.
This article presents the effect of twin-screw extrusion processing parameters, including temperature and rotational speed of screws, on the structure and properties of four grades of polylactide (PLA). To evaluate the critical processing parameters for PLA and the possibilities for oxidative and thermomechanical degradation, Fourier-transform infrared spectroscopy (FT-IR), oscillatory rheological analysis, and differential scanning calorimetry (DSC) measurements were used. The influence of degradation induced by processing temperature and high shearing conditions on the quality of the biodegradable polyesters with different melt flow indexes (MFIs)was investigated by color analysis within the CIELab scale. The presented results indicate that considering the high-temperature processing of PLA, the high mass flow index and low viscosity of the polymer reduce its time of residence in the plastifying unit and therefore limit discoloration and reduction of molecular weight due to the degradation process during melt mixing, whereas the initial molecular weight of the polymer is not an essential factor. Full article
(This article belongs to the Special Issue Polymer Processing and Molding)
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17 pages, 6547 KiB  
Article
Research on Inner Gas Inflation Improvements in Double-layer Gas-assisted Extrusion of Micro-tubes
by Cheng Luo, Xingyuan Huang, Tongke Liu and Hesheng Liu
Polymers 2020, 12(4), 899; https://doi.org/10.3390/polym12040899 - 13 Apr 2020
Cited by 11 | Viewed by 2301
Abstract
Micro-tubes have small diameters and thin wall thicknesses. When using double-layer gas-assisted extrusion (DGAE) technology to process micro-tubes, due to the influence of flow resistance, airflow from the inner gas-assisted layer cannot flow into the atmosphere through the lumen. Over time, it will [...] Read more.
Micro-tubes have small diameters and thin wall thicknesses. When using double-layer gas-assisted extrusion (DGAE) technology to process micro-tubes, due to the influence of flow resistance, airflow from the inner gas-assisted layer cannot flow into the atmosphere through the lumen. Over time, it will inflate or even fracture the micro-tubes intermittently and periodically. To solve this problem, a new double-layer micro-tube gas-assisted extrusion die was designed in this study. Its mandrel has an independent airway leading to the lumen of the extrudate, with which the gas flow into the lumen of the extrudate can be regulated by employing forced exhaust. Using the new die, we carried out extrusion experiments and numerical calculations. The results show a significant positive correlation between micro-tube deformation and gas flow rate in the lumen of a micro-tube. Without considering the refrigerant distortion of the microtube, the flow rate of forced exhaust should be set equal to that of the gas from the inner gas-assisted layer flow into the micro-tube lumen. By doing this, the problem of the micro-tube being inflated can be eliminated without causing other problems. Full article
(This article belongs to the Special Issue Polymer Processing and Molding)
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