Developments in the Thermal, Electrical and Mechanical Properties of Polymer-Based Composites

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

Deadline for manuscript submissions: closed (25 January 2024) | Viewed by 4244

Special Issue Editors

School of Civil Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China
Interests: mechanics of materials; computational mechanics; engineering thermodynamics; heat and mass trasnfer; nanomechanics
School of Civil Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China
Interests: micro-plasticity behavior; physically based strain-hardening of alloys; crystal plasticity; computational plasticity; crystal plastic finite element method; dislocation mechanics, multi-field coupling
School of Civil Engineering, Southeast University, Nanjing 211189, China
Interests: construction materials; structural dynamics; solid mechanics; construction engineering; earthquake engineering; bridge engineering; structural vibration; nonlinear analysis; mechanics of materials
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Special Issue Information

Dear Colleagues,

One of the main challenges in modern product development is weight reduction while simultaneously maximizing load-bearing capability. Polymer-based composites (PBC) have several excellent properties: high thermal conductivity, excellent electrical conductivity, outstanding mechanical properties at low density, and strength characteristics that can be tailored to a given load. These properties, combined with decreasing material prices and manufacturing costs, have contributed to the spread of this type of composite. They are now widely used and even mass-produced. The growth of the PBC market has had an impact on different industries where energy efficiency can be increased (e.g., the transportation industry) or low-density high-strength materials can be used for large structures (e.g. wind turbine blades). Firstly, thermal management is critical to the performance, lifetime, and reliability of PBCs, which have been significantly enhanced through the miniaturization, integration, and functionalization of electronics and the emergence of new applications such as light-emitting diodes and thermal dissipation. In recent decades, the fundamental design principles of highly thermally conductive PBCs have been investigated, for example the modelling of thermal conductivity (e.g., constitutive or micromechanical modeling, finite element modeling, and interfacial thermal resistance modeling) and thermal conductivity measurement techniques (the axial flow method, the heat flow meter method, or the transient hot wire method). The key factors influencing the thermal conductivity of PBCs and thermally conductive fillers (e.g., carbon nanotubes, metal particles, and ceramic particles such as boron nitride or aluminum oxide), such as chain structure, crystallinity, crystal form, and the orientation of polymer chains and ordered domains in both thermoplastics and thermosets, are addressed. Recently, special attention has also been paid to controlling the microstructure of PBCs to achieve high thermal conductivity (novel approaches to control filler orientation, the special design of filler agglomerates, the formation of a continuous filler network by a self-assembly process, the double percolation approach, etc.). Secondly, the excellent electric properties of PBCs allow the production of multifunctional structural parts which are capable of de-icing or protecting aircraft wings from thunder strike or storing energy, and PBCs have been extensively used in electromagnetic interference shielding and structural health monitoring sensors. With the development of information technology and the intense automation of industry, a new industrial revolution, Industry 4.0, is spreading on production lines. In order to satisfy the growing data and information requirements of Industry 4.0, PBCs, besides their structural role, can be used as sensors (e.g., for temperature, humidity, or deformation failure), and products can be designed that are able to collect data about the environment and structural state of a product throughout its lifetime, based on its electrical properties. For example, they can be used for crosslinking, welding, as sensors, and to facilitate self-healing. Thirdly, PBCs possess better strength-to-weight ratios than most conventional alloys and composites in use today for structural applications. Researchers are also designing with novel hybrid PBCs to achieve desired mechanical properties. In recent years, investigations have contributed to enhancing the mechanical properties and behavior of PBCs, such as their impact, flexural, and tensile strengths, which are influenced by critical factors like the type, orientation, and arrangement of reinforcements in polymer matrix composites. As previously discussed, although many studies have been carried out on this topic, some limitations and deficiencies remain for PBCs with engineering matrices (e.g., bamboo, frozen soil, and concrete) in extreme typical service conditions (e.g., low/high temperature and transient loading). For one, the thermal, electrical, and mechanical properties of polymer-based composites have been measured, yet there is no precise mechanism that accounts for the deviation of experimental and theoretical values. Moreover, the interplay between thermal transport properties and polymer composites is still not fully understood. And there are still some other important issues, such as modeling (e.g., constitutive modeling), measuring (e.g., steady-state methods and transient methods), and determining the influence of the morphology and properties of fillers on the thermal, electrical, and mechanical properties of PBCs (e.g., the effect of filler loading level, filler shape, size, and hybrid fillers).

Submissions are not limited in scope to the above topics, and research related to polymers or polymer-based composites will also be covered in the current Special Issue.

Dr. Chenlin Li
Dr. Huili Guo
Dr. Yeshou Xu
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

  • modeling, mechanisms, and measurement of thermal, electrical, mechanical properties of polymer-based composites in various engineering fields
  • investigation of the role of interface in thermal, electrical, mechanical properties of polymer-based composites
  • transport mechanism and characterization analysis in polymer-based composites
  • influence of the microstructure evolution on thermal, electrical, mechanical properties of polymer-based composites
  • multi-field coupling behavior of polymer-based composites
  • fabrication, exploitation, optimal design, 3D printing, and machine learning
  • design and application of smart and intelligent thermal, electric, and mechanical sensors driven by polymer-based composites

Published Papers (3 papers)

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Research

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15 pages, 4422 KiB  
Article
Influence of Dilution on the Mechanical Properties and Microstructure of Polyurethane-Cement Based Composite Surface Coating
by Chao Xie, Yufeng Shi, Ping Wu, Binqiang Sun and Yaqiang Yue
Polymers 2024, 16(1), 146; https://doi.org/10.3390/polym16010146 - 03 Jan 2024
Viewed by 585
Abstract
Polyurethane-cement composite are widely used in modern civil engineering, and the method of adding diluent is often used to adjust the construction process to adapt to the engineering environment. Studies have shown that the addition of diluent impacts the performance of polyurethane-cement based [...] Read more.
Polyurethane-cement composite are widely used in modern civil engineering, and the method of adding diluent is often used to adjust the construction process to adapt to the engineering environment. Studies have shown that the addition of diluent impacts the performance of polyurethane-cement based composite surface coatings, but there have been few reports on the influence of diluent content on the mechanical properties and microstructure of the coatings. To address this, polyurethane coatings with different diluent contents were prepared, and positron annihilation lifetime spectroscopy was used to test the microstructure of the coatings. The tensile strength and elongation at rupture were tested using a universal material testing machine, and the fracture interface morphology of each coating was observed by scanning electron microscopy. Finally, the correlation between the microstructure parameters and the mechanical properties of the coating was analyzed using grey relation theory. The results demonstrated that with the increase in diluent content, (i) the average radius of the free volume hole (R) and the free volume fraction (FV) of the coating both showed a trend of first decreasing and then increasing. The value of R was between 3.04 and 3.24 Å, and the value of FV was between 2.08 and 2.84%. (ii) The tensile strength of the coating increased first and then decreased, while the elongation at rupture decreased first and then increased. Among them, the value of tensile strength was between 3.23 and 4.02 MPa, and the value of elongation at fracture was between 49.34 and 63.04%. In addition, the free volume in polymers plays a crucial role in facilitating the migration of molecular chain segments and is closely related to the macroscopic mechanical properties of polymers. A correlation analysis showed that the R value of the coating had the greatest influence on its tensile strength, while FV showed a higher correlation with the elongation at rupture. Full article
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14 pages, 8666 KiB  
Article
Fabrication of Graphitized Carbon Fibers from Fusible Lignin and Their Application in Supercapacitors
by Linfei Zhou, Xiangyu You, Lingjie Wang, Shijie Qi, Ruichen Wang, Yasumitsu Uraki and Huijie Zhang
Polymers 2023, 15(8), 1947; https://doi.org/10.3390/polym15081947 - 19 Apr 2023
Cited by 3 | Viewed by 1354
Abstract
Lignin-based carbon fibers (LCFs) with graphitized structures decorated on their surfaces were successfully prepared using the simultaneous catalyst loading and chemical stabilization of melt-spun lignin fibers, followed by quick carbonization functionalized as catalytic graphitization. This technique not only enables surficial graphitized LCF preparation [...] Read more.
Lignin-based carbon fibers (LCFs) with graphitized structures decorated on their surfaces were successfully prepared using the simultaneous catalyst loading and chemical stabilization of melt-spun lignin fibers, followed by quick carbonization functionalized as catalytic graphitization. This technique not only enables surficial graphitized LCF preparation at a relatively low temperature of 1200 °C but also avoids additional treatments used in conventional carbon fiber production. The LCFs were then used as electrode materials in a supercapacitor assembly. Electrochemical measurements confirmed that LCF-0.4, a sample with a relatively low specific surface area of 89.9 m2 g−1, exhibited the best electrochemical properties. The supercapacitor with LCF-0.4 had a specific capacitance of 10.7 F g−1 at 0.5 A g−1, a power density of 869.5 W kg−1, an energy density of 15.7 Wh kg−1, and a capacitance retention of 100% after 1500 cycles, even without activation. Full article
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Review

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34 pages, 5898 KiB  
Review
The Preparation, Structural Design, and Application of Electroactive Poly(vinylidene fluoride)-Based Materials for Wearable Sensors and Human Energy Harvesters
by Weiran Zhang, Guohua Wu, Hailan Zeng, Ziyu Li, Wei Wu, Haiyun Jiang, Weili Zhang, Ruomei Wu, Yiyang Huang and Zhiyong Lei
Polymers 2023, 15(13), 2766; https://doi.org/10.3390/polym15132766 - 21 Jun 2023
Cited by 4 | Viewed by 1796
Abstract
Owing to their biocompatibility, chemical stability, film-forming ability, cost-effectiveness, and excellent electroactive properties, poly(vinylidene fluoride) (PVDF) and PVDF-based polymers are widely used in sensors, actuators, energy harvesters, etc. In this review, the recent research progress on the PVDF phase structures and identification of [...] Read more.
Owing to their biocompatibility, chemical stability, film-forming ability, cost-effectiveness, and excellent electroactive properties, poly(vinylidene fluoride) (PVDF) and PVDF-based polymers are widely used in sensors, actuators, energy harvesters, etc. In this review, the recent research progress on the PVDF phase structures and identification of different phases is outlined. Several approaches for obtaining the electroactive phase of PVDF and preparing PVDF-based nanocomposites are described. Furthermore, the potential applications of these materials in wearable sensors and human energy harvesters are discussed. Finally, some challenges and perspectives for improving the properties and boosting the applications of these materials are presented. Full article
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