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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 March 2023) | Viewed by 16326

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Dr. Adam Gnatowski

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Faculty of Mechanical Engineering and Computer Science, Czestochowa University of Technology, Dabrowskiego 69, 42-201 Czestochowa, Poland
Interests: mechanical properties; thermomechanical properties; polymer materials; composites; thermal analysis TG/DTG; DTA; DSC; QMS; computer simulation of processes
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Dr. Paweł Palutkiewicz

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Faculty of Mechanical Engineering and Computer Science, Czestochowa University of Technology, 42-200 Czestochowa, Poland
Interests: polymers; composites; modeling; processing of polymers; physical and processing properties; structure
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Prof. Dr. Jana Petru

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Faculty of Mechanical Engineering, Department of Machining, Assembly and Engineering Metrology, VSB - Technical University of Ostrava, 70800 Ostrava, Czech Republic
Interests: progressive machining; technology; materials; engineering metrology; additive technology; 3D printing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The Special Issue “Multifunctional Polymer Molding Processing of Polymers" aims to discuss the preparation and characterization of new ecologically friendly polymer materials, also containing recycled materials or waste that should find use in specific engineering applications. The development of polymer engineering, the search for new, innovative materials with often specific properties has resulted in the expansion of the area of their application, especially in the construction, machines and devices, packaging and medical industries and also expanded the scope of their processing methods, such as 3D printing. The practical application of new polymeric materials requires knowledge of their processing, mechanical, electrical and thermal properties, as well as recognition of changes in these properties during the operation and destruction of polymers.

For this reason, this Special Issue is an excellent opportunity to present and publish the latest research results in the field of processing of polymers and polymer-based composites, particularly their applications and physicochemical and mechanical properties.

Dr. Adam Gnatowski
Dr. Paweł Palutkiewicz
Prof. Dr. Jana Petru
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 applications
processing of polymers
3D printing of polymers
modification methods
structure analysis
properties analysis
composites
biomaterials
recycling
process simulations

Published Papers (10 papers)

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Research

18 pages, 5245 KiB

Open AccessArticle

Correlation between Processing Parameters, Morphology, and Properties of Injection-Molded Polylactid Acid (PLA) Specimens at Different Length Scales

by Laura Meinig, Regine Boldt, Yvonne Spoerer, Ines Kuehnert and Markus Stommel

Polymers 2023, 15(3), 721; https://doi.org/10.3390/polym15030721 - 31 Jan 2023

Cited by 4 | Viewed by 1498

Abstract

Polylactic acid (PLA) is one of the most promising bioplastic representatives that finds application in many different areas, e.g., as single-use products in the packaging industry, in the form of mulch film for agriculture, or in medical devices. For the development of new areas, especially in terms of long-term applications and the production of recyclable products, the material properties controlled by processing must be known. The state of the art is investigations at the global scale (integral values) without consideration of local structure inhomogeneities and their influence on the material properties. In this work, morphological, thermal, and mechanical properties of injection-molded PLA tensile bars are investigated at different length scales (global and local) as a function of processing parameters. In addition to the processing parameters, such as melt temperature, mold temperature, and cooling time in the mold, the influence of the D-isomer content on the crystallization behavior and the resulting material properties are investigated. The material was found to form crystalline structures only when cooled in a mold tempered above T_g. In addition, PLA with a lower content of D-isomer was found to have a higher degree of crystallinity. Since the mechanical properties obtained by tensile tests could not be correlated with the degree of crystallinity, detailed analysis were performed showing a characteristic inhomogeneous morphology within the tensile bars. By means of micromechanical investigations on samples with different microstructure ranges, the relationship between local morphology and failure behavior could be explained. Full article

(This article belongs to the Special Issue Multifunctional Polymer Molding Processing of Polymers)

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12 pages, 6251 KiB

Open AccessArticle

Research on the Penetration Characteristics of PELE Projectile with Reactive Inner Core

by Jingyuan Zhou, Xianwen Ran, Wenhui Tang, Kun Zhang, Haifu Wang, Pengwan Chen and Liangliang Ding

Polymers 2023, 15(3), 617; https://doi.org/10.3390/polym15030617 - 25 Jan 2023

Cited by 1 | Viewed by 1165

Abstract

With the improvement of protection technology, the damage power of conventional penetrators has become increasingly inferior. Reactive material is a new type of energetic material, which has strong energy release capabilities under high-velocity-impact conditions. In this paper, the reactive materials were put into the penetrator, and its penetration characteristics were studied. First, the penetrator with enhanced lateral effect (PELE) projectile structure with better penetration capability was obtained by numerical simulation. Then, based on the established polytetrafluoroethylene (PTFE)/Al reactive material reaction model, the numerical simulation and experimental research of the PELE projectile with a reactive inner core penetrating the target were carried out. The results show that the simulation results are in good agreement with the experimental results, which verifies the confidence of the numerical simulation. The PELE projectile had a significant increase in power with the use of a truncated conical head and reactive materials. The residual velocity of the truncated cone PELE projectile increases by 8.41–21% over conventional PELE projectiles. Its damage range is 43% higher than that of conventional penetrators. The simulation method and the conclusions obtained in this paper can provide support and reference for further research on reactive materials and on effectively improving the damage power of the penetrator. Full article

(This article belongs to the Special Issue Multifunctional Polymer Molding Processing of Polymers)

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18 pages, 3932 KiB

Open AccessArticle

Multi-Objective Optimization of Liquid Silica Array Lenses Based on Latin Hypercube Sampling and Constrained Generative Inverse Design Networks

by Hanjui Chang, Shuzhou Lu, Yue Sun, Guangyi Zhang and Longshi Rao

Polymers 2023, 15(3), 499; https://doi.org/10.3390/polym15030499 - 18 Jan 2023

Cited by 3 | Viewed by 1540

Abstract

Injection molding process parameters have a great impact on plastic production quality, manufacturing cost, and molding efficiency. This study proposes to apply the method of Latin hypercube sampling, and to combine the response surface model and “Constraint Generation Inverse Design Network (CGIDN)” to achieve multi-objective optimization of the injection process, shorten the time to find the optimal process parameters, and improve the production efficiency of plastic parts. Taking the LSR lens array of automotive LED lights as the research object, the residual stress and volume shrinkage were taken as the optimization objectives, and the filling time, melt temperature, maturation time, and maturation pressure were taken as the influencing factors to obtain the optimization target values, and the response surface models between the volume shrinkage rate and the influencing factors were established. Based on the “Constraint-Generated Inverse Design Network”, the optimization was independently sought within the set parameters to obtain the optimal combination of process parameters to meet the injection molding quality of plastic parts. The results showed that the optimal residual stress value and volume shrinkage rate were 11.96 MPa and 4.88%, respectively, in the data set of 20 Latin test samples obtained based on Latin hypercube sampling, and the optimal residual stress value and volume shrinkage rate were 8.47 MPa and 2.83%, respectively, after optimization by the CGIDN method. The optimal process parameters obtained by CGIDN optimization were a melt temperature of 30 °C, filling time of 2.5 s, maturation pressure of 40 MPa, and maturation time of 15 s. The optimization results were obvious and showed the feasibility of the data-driven injection molding process optimization method based on the combination of Latin hypercube sampling and CGIDN. Full article

(This article belongs to the Special Issue Multifunctional Polymer Molding Processing of Polymers)

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14 pages, 7074 KiB

Open AccessArticle

Optimization of Vibration Pretreatment Microwave Curing in Composite Laminate Molding Process

by Dechao Zhang, Lihua Zhan, Chenglong Guan, Jinzhan Guo, Bolin Ma, Guangming Dai and Shunming Yao

Polymers 2023, 15(2), 296; https://doi.org/10.3390/polym15020296 - 06 Jan 2023

Cited by 2 | Viewed by 1396

Abstract

Vibration pretreatment microwave curing is a high-quality and efficient composite out-of-autoclave molding process. Focusing on interlaminar shear strength, the effects of pretreatment temperature, pretreatment time and vibration acceleration on the molding performance of composite components were analyzed sequentially using the orthogonal test design method; a scanning electron microscope (SEM) and optical digital microscope (ODM) were used to analyze the void content and fiber-resin bonding state of the specimens under different curing and molding processes. The results show that the influence order of the different vibration process parameters on the molding quality of the components was: vibration acceleration > pretreatment temperature > pretreatment time. Within the parameters analyzed in this study, the optimal vibration pretreatment process parameters were: pretreatment temperature of 90 °C, pretreatment time of 30 min, and vibration acceleration of 10 g. Using these parameters, the interlaminar shear strength of the component was 82.12 MPa and the void content was 0.37%. Compared with the microwave curing process, the void content decreased by 71.8%, and the interlaminar shear strength increased by 31.6%. The microscopic morphology and mechanical properties basically reached the same level as the standard autoclave process, which achieved a high-quality out-of-autoclave curing and molding manufacturing of aerospace composite components. Full article

(This article belongs to the Special Issue Multifunctional Polymer Molding Processing of Polymers)

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17 pages, 4444 KiB

Open AccessArticle

Effect of Single-Walled Carbon Nanotubes on the Cross-Linking Process in Natural Rubber Vulcanization

by Yoliria Vázquez-Martínez, Claudia A. Ramírez-Herrera, Margarita Mondragón, Alex Elías-Zúñiga and Luis E. Elizalde

Polymers 2023, 15(1), 126; https://doi.org/10.3390/polym15010126 - 28 Dec 2022

Cited by 2 | Viewed by 1488

Abstract

In this study, the effect of single-walled carbon nanotubes (SWCNTs) on the cross-linking of natural rubber (NR) using organic peroxides was investigated. NR-SWCNTs nanocomposites were prepared in an open two-roller mill followed by vulcanization with the compression molding process. Three different organic peroxides, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane (T29), dicumyl peroxide (DCP), and 2,5-bis(tert-butylperoxy)-2,5-dimethyl-3-hexyne (T145), were used as vulcanizing agents. SWCNTs promote a remarkable reduction in the vulcanization time and increase the degree of cross-linking of vulcanized rubber when compared with neat or natural rubber–carbon-black composites; the same tendency was obtained in the NR-SWCNTs vulcanized with sulfur. Additionally, the mechanical performance of the NR-SWCNTs composites was significantly improved up to 75, 83, 27, and 10% for tensile strength, moduli, tear strength, and hardness. Raman spectroscopy studies evidence the occurrence of reaction between nanotube walls and free radicals generated from using organic peroxides during the vulcanization process. These results demonstrate that the incorporation of SWCNTs in combination with the use of organic peroxides for the NR vulcanization represents a potential alternative for the improvement of the physicochemical properties of NR composites. Full article

(This article belongs to the Special Issue Multifunctional Polymer Molding Processing of Polymers)

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16 pages, 7433 KiB

Open AccessArticle

Analysis of Thermomechanical Properties and the Influence of Machining Process on the Surface Structure of Composites Manufactured from Metal Chips with a Polymer Matrix

by Adam Gnatowski, Rafał Gołębski, Jana Petru and Marek Pagac

Polymers 2022, 14(17), 3501; https://doi.org/10.3390/polym14173501 - 26 Aug 2022

Cited by 2 | Viewed by 1246

Abstract

Nowadays, the dynamic development of the entire market of composite materials is noticeable, which is very often associated with the need to use waste or recycled materials in their production. In the process of producing composites themselves, the easy possibility of shaping their mechanical and thermomechanical properties becomes apparent, which can be a big problem for materials with a homogeneous structure. For the tests, samples made of a combination of acrylic–phenolic resin with fine aluminum and brass chips were used. The tests were performed for composite samples produced by pressing. This paper presents the results of the DMTA method of the conservative modulus and the tangent of mechanical loss angle of the composite, a detailed stereometric analysis of the surface after machining, roughness parameters and volumetric functional parameters were performed. For the tested samples, changes in the values of the conservative modulus and the mechanical loss coefficient were recorded, which indicated significant differences for the composite with brass chips in relation to composites with aluminum chips. In the case of the composite with aluminum chips, slight changes in the conservative modulus were recorded in the glass transition phase and the elastic deformation phase at different frequencies. In contrast, for composites with brass, slight changes were recorded in the entire range of the course of the conservative module as a function of temperature when different excitation frequencies were applied. In relation to the polymer matrix, a significant increase in the value of the conservative modulus of composites was recorded in the entire temperature range of the test. Significant differences were recorded in the study of the surface of composites in the case of using different materials obtained after machining as fillers. The dependences of the amplitude parameters of the surface after machining the sample made of phenolic–acrylic resin prove the poor performance properties of the surface. The use of chips in the composite significantly changed the surface geometry. Full article

(This article belongs to the Special Issue Multifunctional Polymer Molding Processing of Polymers)

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13 pages, 4164 KiB

Open AccessArticle

Experimental Validation of Numerical Model for Thermomechanical Performance of Material Extrusion Additive Manufacturing Process: Effect of Process Parameters

by Ans Al Rashid and Muammer Koç

Polymers 2022, 14(17), 3482; https://doi.org/10.3390/polym14173482 - 26 Aug 2022

Cited by 13 | Viewed by 1498

Abstract

The material extrusion additive manufacturing (MEAM) process for polymers seems straightforward. However, several controlled and uncontrolled factors affect the 3D printed product quality, e.g., MEAM process parameters, thermomechanical properties of the material, and part design. Therefore, it is crucial to understand these interlinked factors of part geometry, material properties, and 3D printing (3DP) process parameters to optimize 3D printed product quality. The numerical models and simulation tools can predict the thermomechanical performance of the MEAM process under given input parameters (material, design, and process variables) and reduce the research and development costs significantly. However, the numerical models and tools need further exploration and validation of simulation predictions for their adaptability and reliability. Therefore, in this study, numerical simulations were performed to observe the impact of process parameters on the part quality of MEAM 3D printed components. The two crucial process parameters (i.e., extrusion temperature and layer resolution) were varied while keeping the other process parameters, part geometry (tensile testing coupon), and material properties (acrylonitrile butadiene styrene (ABS)) constant. These two process parameters were sequentially optimized for optimum part quality, first by varying the extrusion temperature and secondly by changing the printing resolution using the optimum printing temperature. The 3DP process quality was evaluated in terms of dimensional accuracy, distortions, and residual stresses. Finally, the specimens were 3D printed under similar process conditions to validate the numerical model predictions. Full article

(This article belongs to the Special Issue Multifunctional Polymer Molding Processing of Polymers)

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19 pages, 4991 KiB

Open AccessArticle

Compression and Bending Properties of Short Carbon Fiber Reinforced Polymers Sandwich Structures Produced via Fused Filament Fabrication Process

by Sebastian Marian Zaharia, Mihai Alin Pop, Lucia-Antoneta Chicos, George Razvan Buican, Camil Lancea, Ionut Stelian Pascariu and Valentin-Marian Stamate

Polymers 2022, 14(14), 2923; https://doi.org/10.3390/polym14142923 - 19 Jul 2022

Cited by 8 | Viewed by 2494

Abstract

Additive manufacturing, through the process of thermoplastic extrusion of filament, allows the manufacture of complex composite sandwich structures in a short time with low costs. This paper presents the design and fabrication by Fused Filament Fabrication (FFF) of composite sandwich structures with short fibers, having three core types C, Z, and H, followed by mechanical performance testing of the structures for compression and bending in three points. Flatwise compression tests and three-point bending have clearly indicated the superior performance of H-core sandwich structures due to dense core structures. The main modes of failure of composite sandwich structures were analyzed microscopically, highlighting core shear buckling in compression tests and face indentation in three-point bending tests. The strength–mass ratio allowed the identification of the structures with the best performances considering the desire to reduce the mass, so: the H-core sandwich structures showed the best results in compression tests and the C-core sandwich structures in three-point bending tests. The feasibility of the FFF process and the three-point bending test of composite wing sections, which will be used on an unmanned aircraft, have also been demonstrated. The finite element analysis showed the distribution of equivalent stresses and reaction forces for the composite wing sections tested for bending, proving to validate the experimental results. Full article

(This article belongs to the Special Issue Multifunctional Polymer Molding Processing of Polymers)

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16 pages, 9136 KiB

Open AccessArticle

Weld Strength of Friction Welding of Dissimilar Polymer Rods Fabricated by Fused Deposition Modeling

by Chil-Chyuan Kuo, Jing-Yan Xu and Chong-Hao Lee

Polymers 2022, 14(13), 2582; https://doi.org/10.3390/polym14132582 - 25 Jun 2022

Cited by 5 | Viewed by 1863

Abstract

Friction welding (FRW) is a promising method for joining cylindrical components of dissimilar and similar polymers or metals. In particular, FRW is capable of generating defect-free welds. Fused deposition modeling (FDM) has been widely employed in the automotive industry, ranging from lightweight tools, testing models, and functional parts. Conventionally, dissimilar parts fabricated by FDM are joined by glue. However, distinct disadvantages of this approach include both low joining strength and low joining efficiency. Hitherto, little has been reported on the characterizations of weld strength of FRW of dissimilar parts fabricated by FDM. In addition, FRW of dissimilar polymeric materials is a difficult task because different polymers have different physical, rheological, and mechanical properties. In this study, the effects of welding revolution on the weld strength of friction welding dissimilar parts fabricated by FDM are investigated experimentally. It was found that the average flexural strength of dissimilar polymer rods fabricated by FRW is about 1.52 times that of dissimilar polymer rods fabricated by gluing. The highest flexure strength can be obtained by FRW using polylactic acid (PLA) and PC (polycarbonate) rods. The average impact strength of dissimilar polymer rods fabricated by FRW is about 1.04 times that of dissimilar polymer rods joined by gluing. The highest impact strength can be obtained by FRW using PLA to PLA rods. Full article

(This article belongs to the Special Issue Multifunctional Polymer Molding Processing of Polymers)

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20 pages, 7050 KiB

Open AccessArticle

Research on the Constitutive Model of PTFE/Al/Si Reactive Material

by Liangliang Ding, Xiaoxiao Cui, Wenhui Tang, Xue Zhong, Yuli Zhao, Yongzheng Huang, Peng Shi and Xiaoguang Xue

Polymers 2022, 14(7), 1358; https://doi.org/10.3390/polym14071358 - 27 Mar 2022

Cited by 1 | Viewed by 1393

Abstract

As a new type of energetic material, reactive materials are widely used at present; in particular, the metal/polymer mixtures type reactive materials show great advantages in engineering applications. This type of reactive material has good mechanical properties, and its overall performance is insensitive and high-energy under external impact loading. After a large number of previous studies, our team found that the energy release characteristics of PTFE/Al/Si reactive material are prominent. In order to master the mechanical properties of PTFE/Al/Si reactive materials, the quasi-static mechanical properties and dynamic mechanical properties were obtained by carrying out a quasi-static compression test and a dynamic SHPB test in this paper. Based on the experimental data, a Johnson-Cook constitutive model of PTFE/Al/Si reactive material considering strain hardening effect, strain rate hardening effect and thermal softening effect was constructed. The relevant research results will be used to guide future research on the reaction mechanism of PTFE/Al/Si reactive materials, in order to promote the engineering application of PTFE/Al/Si reactive materials. Full article

(This article belongs to the Special Issue Multifunctional Polymer Molding Processing of Polymers)

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