Epoxy Resins and Composites

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

Deadline for manuscript submissions: closed (20 June 2022) | Viewed by 102032

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Department of Polymer Technology, Faculty of Chemistry, G. Narutowicza Str. 11/12, Gdańsk University of Technology, 80-233 Gdańsk, Poland
Interests: plastics and rubber recycling; reactive processing; composites; polymer blends and composites compatibilization; bitumen modification
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Guest Editor
Department of Polymer Technology, Faculty of Chemistry, G. Narutowicza Str. 11/12, Gdańsk University of Technology, 80-233 Gdańsk, Poland
Interests: thermoset polymers; cure kinetics analysis; organic coatings; flame retardancy analysis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Epoxy resins are thermosetting polymers known for their versatility and acceptable properties that have taken credit for a wide variety of applications. To make epoxy resins cross-linked, one needs the use of a proper curing agent. Depending on the functionality of epoxy resins and curing agents, the curability of systems may vary from a partially cured to an intensely cured 3D network. In correspondence to the degree of curing/cross-linking, materials with different properties can be achieved. Despite promising features of epoxy, some drawbacks necessitate the use of particular fillers/additives in developing epoxy-based systems. Correspondingly, further complexities are associated with cross-linking of epoxy, such as incomplete curing caused by constrained interaction between epoxy and hardener, inadequate dispersion of additive in the epoxy resin, and early-stage gelation. Thus, designing advanced thermosetting systems based on epoxy resin necessitates deep understanding of the structure–property relationship. On the other hand, a low potential of hard epoxy-based thermosets brings about serious concerns about environmental issues.

In the light of above, the following can reflect the importance of epoxy resins:

  • Epoxy resin;
  • Synthesis of bio-based epoxy resins;
  • Curing analysis of epoxy composites;
  • Epoxy resins in coatings;
  • Epoxy resins as construction and building materials;
  • Flame retardancy of epoxy-based composites;
  • Medical applications of epoxy resins;
  • Recycling of epoxy-based composites.

Dr. Krzysztof Formela
Dr. Mohammad Reza Saeb
Guest Editors

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Keywords

  • epoxy resin
  • cross-linking
  • thermosetting materials
  • bio-epoxy
  • epoxy and medicine
  • epoxy coatings
  • epoxy composites

Published Papers (27 papers)

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12 pages, 10717 KiB  
Article
Sound Insulation Properties of Hollow Polystyrene Spheres/Polyethylene Glycol/Epoxy Composites
by Xuejun Shi, Guangling Shi, Songtian Li, Xiangxiang Du and Yongjun Han
Polymers 2022, 14(7), 1388; https://doi.org/10.3390/polym14071388 - 29 Mar 2022
Cited by 8 | Viewed by 2318
Abstract
The generation of noise requires a noise source, transmission path, and passive acceptance target of noise, all of which are indispensable. Blocking the propagation path of noise is one of the available means when the existence of the noise source and passive receiving [...] Read more.
The generation of noise requires a noise source, transmission path, and passive acceptance target of noise, all of which are indispensable. Blocking the propagation path of noise is one of the available means when the existence of the noise source and passive receiving target cannot be addressed. This is an effective way to prevent noise pollution, often using sound insulation materials to block the path of noise transmission. In this work, composites with excellent sound insulation properties were designed and prepared. These composites, using epoxy resin (EP) as the matrix, polyethylene glycol (PEG), and hollow polystyrene spheres (HPS), were added to epoxy resin as a toughening agent and functional filler to prepare the ternary HPS/PEG/EP composites. The soundproofing results showed that when the thickness of the sample was 3 mm, the average sound transmission loss (STL) value of the neat EP and the HPS/PEG/EP composites with an HPS 32 vol% was up to 19.0 dB and 42.1 dB, and the STL values of the composites were increased by approximately 120% compared to the pure epoxy. When the sample was 10 mm thick, the average STL value of the HPS/PEG/EP composites with HPS 32 vol% contents was enhanced to 55.7 dB. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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23 pages, 6284 KiB  
Article
Determination of Mechanical Properties of Epoxy Composite Materials Reinforced with Silicate Nanofillers Using Digital Image Correlation (DIC)
by Aleksandra Jelić, Milica Sekulić, Milan Travica, Jelena Gržetić, Vukašin Ugrinović, Aleksandar D. Marinković, Aleksandra Božić, Marina Stamenović and Slaviša Putić
Polymers 2022, 14(6), 1255; https://doi.org/10.3390/polym14061255 - 21 Mar 2022
Cited by 8 | Viewed by 2989
Abstract
In this study, silicate nanofillers; dicalcium silicate, magnesium silicate, tricalcium silicate, and wollastonite; were synthesized using four different methods and incorporated into the epoxy resin to improve its mechanical properties. Characterization of the newly synthesized nanofillers was performed using Fourier-transformation infrared (FTIR) spectroscopy, [...] Read more.
In this study, silicate nanofillers; dicalcium silicate, magnesium silicate, tricalcium silicate, and wollastonite; were synthesized using four different methods and incorporated into the epoxy resin to improve its mechanical properties. Characterization of the newly synthesized nanofillers was performed using Fourier-transformation infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The purpose of this study was to analyze newly developed composite materials reinforced with silicate nanoparticles utilizing tensile testing and a full-field non-contact 3D Digital Image Correlation (DIC) method. Analysis of deformation and displacement fields gives precise material behavior during testing. Testing results allowed a more reliable assessment of the structural integrity of epoxy composite materials reinforced using different silicate nanofillers. It was concluded that the addition of 3% of dicalcium silicate, magnesium silicate, tricalcium silicate, and wollastonite lead to the increasement of tensile strength up to 31.5%, 29.0%, 27.5%, and 23.5% in comparison with neat epoxy, respectively. In order to offer more trustworthy information about the viscoelastic behavior of neat epoxy and composites, a dynamic mechanical analysis (DMA) was also performed and rheological measurements of uncured epoxy matrix and epoxy suspensions were obtained. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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17 pages, 7381 KiB  
Article
Investigating the Effects of Cement and Polymer Grouting on the Shear Behavior of Rock Joints
by Milad Abolfazli, Milad Bazli, Hossein Heydari and Ahmad Fahimifar
Polymers 2022, 14(6), 1229; https://doi.org/10.3390/polym14061229 - 18 Mar 2022
Cited by 8 | Viewed by 2045
Abstract
This study carried out a comparison between cement grouting and chemical grouting, using epoxy and polyurethane, with respect to their effects on the shear behavior of joints. Joint replicas, with three different grades of surface roughness, were molded and grouted by means of [...] Read more.
This study carried out a comparison between cement grouting and chemical grouting, using epoxy and polyurethane, with respect to their effects on the shear behavior of joints. Joint replicas, with three different grades of surface roughness, were molded and grouted by means of cement and epoxy grouts of various mixtures. To investigate their shear behavior, samples were subjected to direct shear tests under constant normal load (CNL) condition. According to the results obtained, grouting improves the overall shear strength of the rock joints. All the grouted samples yielded higher maximum and residual shear strength in comparison with the non-grouted joint. Grouting resulted in an improvement in the cohesion of all the samples. However, a fall in friction angle by 5.26° in the sample with JRC of nine was observed, yet it was reduced by 2.36° and 3.26° for joints with JRC of 14 and 19, respectively. Cement grouts were found to have a more brittle behavior, whereas the chemical grouts were more ductile. Higher amounts of cement used in the grout mixture do not provide as much cohesion and only increase the brittleness of the grout. As a result of being more brittle, cement grout breaks into small pieces and joint planes are in better contact during shearing; consequently, there would be less of a fall in friction angle as opposed to epoxy grout whose ductile characteristic prevents grout chipping; therefore, joint planes are not in contact and a greater fall in the friction angle occurs. There was no noticeable change in the cohesion of the larger grouted joints. However, the friction angle of both natural and grouted joints increased in the larger joint. This can be related to the distribution of random peaks and valleys on the joint surface, which increases with the joint size. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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12 pages, 10529 KiB  
Article
Investigation on the Correlation between Dispersion Characteristics at Terahertz Range and Dielectric Permittivity at Low Frequency of Epoxy Resin Nanocomposites
by Ze Lian, Danyang Chen and Shengtao Li
Polymers 2022, 14(4), 827; https://doi.org/10.3390/polym14040827 - 21 Feb 2022
Cited by 4 | Viewed by 1670
Abstract
Despite the extensive research on nanocomposites, a fundamental theory on the interface region is still difficult to achieve. In the present paper, we chose epoxy resin and nano-SiO2, nano-SiC, nano-ZnO to prepare three kinds of nanocomposites. The dispersion characteristics at the [...] Read more.
Despite the extensive research on nanocomposites, a fundamental theory on the interface region is still difficult to achieve. In the present paper, we chose epoxy resin and nano-SiO2, nano-SiC, nano-ZnO to prepare three kinds of nanocomposites. The dispersion characteristics at the terahertz range and dielectric permittivity at 1 Hz of epoxy resin-based nanocomposites were investigated. The reduction of the permittivity of nanocomposites at a slight filler concentration was absent at the terahertz range. The measurement results at 1 Hz show that the interaction between nano-SiO2, nano-SiC particles and epoxy resin was strong with the modification of the silane coupling agent. However, the modification of nano-ZnO particles was invalid. The Lorentz harmonic oscillator model was employed to fit the dispersion characteristics. The relevance between the damping constant and the dielectric permittivity at low frequency was established, indicating that the increase in the damping coefficient results from the restriction of the molecular chain motion by the interfacial region. The present results in this paper reveal a bright prospect of terahertz time-domain spectroscopy in establishing the theory of nanocomposite dielectric. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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15 pages, 4230 KiB  
Article
Preparation, Structure and Properties of Urethane-Containing Elastomers Based on Epoxy Terminal Oligomers
by Alexey Slobodinyuk, Vladimir Strelnikov, Valeriy Yu Senichev and Daria Slobodinyuk
Polymers 2022, 14(3), 524; https://doi.org/10.3390/polym14030524 - 27 Jan 2022
Cited by 7 | Viewed by 2177
Abstract
The effect of polyester oligoethylene adipate molecular weight, diisocyanate structure, and chain extender on the properties of epoxyurethane-based oligomer elastomers was studied in this research. Oligoethylene adipates were obtained via polycondensation of adipic acid and ethylene glycol. Epoxyurethane oligomers were synthesized according to [...] Read more.
The effect of polyester oligoethylene adipate molecular weight, diisocyanate structure, and chain extender on the properties of epoxyurethane-based oligomer elastomers was studied in this research. Oligoethylene adipates were obtained via polycondensation of adipic acid and ethylene glycol. Epoxyurethane oligomers were synthesized according to a two-step route with an oligodiisocyanate as an intermediate product. The elastomers with hard urethane hydroxyl blocks were synthesized from oligodiisocyanates. The deformation and strength properties of the elastomers were studied. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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10 pages, 2148 KiB  
Article
Evaluation of the Validity of Digital Optical Microscopy in the Assessment of Marginal Adaptation of Dental Adhesive Interfaces
by René Daher, Ivo Krejci, Enrico di Bella and Laurine Marger
Polymers 2022, 14(1), 83; https://doi.org/10.3390/polym14010083 - 27 Dec 2021
Viewed by 2453
Abstract
Analysis of marginal adaptation of dental adhesive interfaces using scanning electron microscopy has proven to be a powerful nondestructive method to evaluate the quality of adhesion. This methodology is, however, time-consuming and needs expensive equipment. The purpose of this study was to evaluate [...] Read more.
Analysis of marginal adaptation of dental adhesive interfaces using scanning electron microscopy has proven to be a powerful nondestructive method to evaluate the quality of adhesion. This methodology is, however, time-consuming and needs expensive equipment. The purpose of this study was to evaluate the possibility and efficiency of using a digital optical microscope (DOM) to perform marginal analysis and to compare it with the scanning electron microscope (SEM) analysis. Fifteen defect-free molars were selected for this study. Class V cavities were prepared and restored with resin composite, and epoxy replicas were obtained from silicone impressions of the restored teeth. Custom-made image analysis software was then used to measure the percentage of the noncontinuous margins (NCM) of each sample. To compare the DOM to the gold standard, SEM, each sample was analyzed 10 times using the DOM and three times using the SEM, by the same experienced operator. The repeatability coefficient and concordance were evaluated, and a Bland and Altman analysis was used for comparison of the two methods of measurements. To validate the DOM analysis method, an ANOVA approach (Gage R R) was used. Repeatability and reproducibility, which are two components of precision to validate the DOM analysis system, were calculated. For this, the same restorations were analyzed by two additional operators three times with the DOM. The duration of each step of the analysis using both methods was also recorded as a secondary outcome. Regarding the repeatability of each method, the Friedman test showed no statistically significant difference within the repetitions of measurements by SEM and DOM (p = 0.523 and p = 0.123, respectively). Moreover, the Bland-Altman analysis revealed a bias of 0.86 and concluded no statistically significant difference between the two methods, DOM and SEM. ANOVA evaluated DOM measurement system variation including the variances of repeatability and reproducibility that represented, respectively, 0.3% and 4% of the variance components. Reproducibility or inter-operator variability represented the principal source of variability with a statistically significant difference (p = 0.024). The time required for analysis with SEM was almost double that of DOM. The use of digital optical microscopy appears to be a valid alternative to the SEM for the analysis of marginal adaptation of dental adhesive interfaces. Further studies to evaluate the effect of training of operators in digital optical microscopy could reveal higher accuracy for this method and inter-operator agreement when experience is gained. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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14 pages, 4159 KiB  
Article
Polymers under Load and Heating Deformability: Modelling and Predicting
by Alexander Korolev, Maxim Mishnev, Dmitry Zherebtsov, Nikolai Ivanovich Vatin and Maria Karelina
Polymers 2021, 13(3), 428; https://doi.org/10.3390/polym13030428 - 29 Jan 2021
Cited by 6 | Viewed by 2102
Abstract
The polymer deformability under load and heating is the determining factor in calculating reinforced polymer structures used under heating. Deformability–load/temperature relations make it possible to calculate temperature stresses and deformations in bearing cross-sections of polymer structures such as chimneys, smokestacks, etc. The present [...] Read more.
The polymer deformability under load and heating is the determining factor in calculating reinforced polymer structures used under heating. Deformability–load/temperature relations make it possible to calculate temperature stresses and deformations in bearing cross-sections of polymer structures such as chimneys, smokestacks, etc. The present study suggests a method of calculating deformability of polymers subjected to the temperature loads. The method is based on the structure model of pack or layer bonded polymer domains where the elasticity of rigid bonds decreases with heating according to entropy principles. The method has been successfully tested on various polymers and compounds with due account for the effect of mineral additives on the deformation modulus increase. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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23 pages, 5105 KiB  
Article
A Study on the Life Estimation and Cavity Surface Degradation Due to Partial Discharges in Spherical Cavities within Solid Polymeric Dielectrics Using a Simulation Based Approach
by Johnatan M. Rodríguez-Serna and Ricardo Albarracín-Sánchez
Polymers 2021, 13(3), 324; https://doi.org/10.3390/polym13030324 - 20 Jan 2021
Cited by 7 | Viewed by 2993
Abstract
Partial Discharges (PD) in cavities are responsible for the greatest ageing rate in polymeric solid dielectrics due to chemical and physical deterioration mechanisms activated by the charge carriers, Ultra Violet (UV) radiation and local temperature rising during PDs activity. From the above, it [...] Read more.
Partial Discharges (PD) in cavities are responsible for the greatest ageing rate in polymeric solid dielectrics due to chemical and physical deterioration mechanisms activated by the charge carriers, Ultra Violet (UV) radiation and local temperature rising during PDs activity. From the above, it is necessary to develop prognosis tools based on PDs measurements as diagnostic quantities in order to infer the time-to-breakdown, life, of solid dielectrics for improving the reliability of electrical assets, especially in current applications where they are subject to great electrical stresses in voltage frequency and magnitude. In this paper, the degradation in polymeric materials induced by PDs in cavities is briefly discussed from a phenomenological point of view, and then it is quantitatively evaluated using a simulation-based approach and a new proposed damage function. The time-to-breakdown calculated from simulations exhibits good agreement when compared with experimental measurements. Additionally, an analysis on the effect of the magnitude and frequency of the applied voltage on the degradation rate is also presented and the effectiveness of a degradation indicator, proposed by other authors, is evaluated under different stress conditions. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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14 pages, 5629 KiB  
Article
In-Situ Observations of Microscale Ductility in a Quasi-Brittle Bulk Scale Epoxy
by Olivier Verschatse, Lode Daelemans, Wim Van Paepegem and Karen De Clerck
Polymers 2020, 12(11), 2581; https://doi.org/10.3390/polym12112581 - 3 Nov 2020
Cited by 10 | Viewed by 2522
Abstract
Fiber reinforced composite materials are typically comprised of two phases, i.e., the reinforcing fibers and a surrounding matrix. At a high volume fraction of reinforcing fibers, the matrix is confined to a microscale region in between the fibers (1–200 µm). Although these regions [...] Read more.
Fiber reinforced composite materials are typically comprised of two phases, i.e., the reinforcing fibers and a surrounding matrix. At a high volume fraction of reinforcing fibers, the matrix is confined to a microscale region in between the fibers (1–200 µm). Although these regions are interconnected, their behavior is likely dominated by their micro-scale. Nevertheless, the characterization of the matrix material (without reinforcing fibers) is usually performed on macroscopic bulk specimens and little is known about the micro-mechanical behavior of polymer matrix materials. Here, we show that the microscale behavior of an epoxy resin typically used in composite production is clearly different from its macroscale behavior. Microscale polymer specimens were produced by drawing microfibers from vitrifying epoxy resin. After curing, tensile tests were performed on a large set of pure epoxy microfiber specimens with diameters ranging from 30 to 400 µm. An extreme ductility was observed for microscale epoxy specimens, while bulk scale epoxy specimens showed brittle behavior. The microsized epoxy specimens had a plastic deformation behavior resulting in a substantially higher ultimate tensile strength (up to 380 MPa) and strain at break (up to 130 %) compared to their bulk counterpart (68 MPa and 8%). Polarized light microscopy confirmed a rearrangement of the internal epoxy network structure during loading, resulting in the plastic deformation of the microscale epoxy. This was further accompanied by in-situ electron microscopy to further determine the deformation behavior of the micro-specimens during tensile loading and make accurate strain measurements using video-extensometry. This work thus provides novel insights on the epoxy material behavior at the confined microscale as present in fiber reinforced composite materials. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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14 pages, 2455 KiB  
Article
Hydrogenation of High Molecular Weight Bisphenol A Type Epoxy Resin BE503 in a Functional and Greener Solvent Mixture Using a Rh Catalyst Supported on Carbon Black
by Bo-Xin Lai, Saurav Bhattacharjee, Yi-Hao Huang, An-Bang Duh, Ping-Chieh Wang and Chung-Sung Tan
Polymers 2020, 12(11), 2513; https://doi.org/10.3390/polym12112513 - 28 Oct 2020
Cited by 4 | Viewed by 3439
Abstract
A functional greener solvent mixture containing water, isopropyl alcohol (IPA) and ethyl acetate with the ratio 10:20:70 (wt%) was found to accelerate hydrogenation of bisphenol A type epoxy resin BE503 with a molecular weight of 1500 through an on-water mechanism, and led to [...] Read more.
A functional greener solvent mixture containing water, isopropyl alcohol (IPA) and ethyl acetate with the ratio 10:20:70 (wt%) was found to accelerate hydrogenation of bisphenol A type epoxy resin BE503 with a molecular weight of 1500 through an on-water mechanism, and led to an increased H2 availability, due to high solubility of H2 in IPA. Different carbon-based supports were tested and VulcanXC72 was found as the best support among the tested carbon-based ones as it possessed the highest amount of electron deficient promoter, RhOx. The catalyst, Rh5/VulcanXC72-polyol, synthesized by the microwave assisted polyol method, yielded a 100% hydrogenation of aromatic rings with an epoxy ring opening below 20.0% at 50 °C and a H2 pressure of 1000 psi in 2.25 h. Intrinsic activation energies for the hydrogenation of aromatic rings and epoxy ring opening were experimentally estimated and a mechanism for the hydrogenation of BE503 was proposed, wherein the hydrogenation of aromatic rings and epoxy ring opening in BE503 proceeded simultaneously in parallel and in-series with parallel being the major pathway. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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13 pages, 1680 KiB  
Article
Electrospun Multiple-Chamber Nanostructure and Its Potential Self-Healing Applications
by Yubo Liu, Xinkuan Liu, Ping Liu, Xiaohong Chen and Deng-Guang Yu
Polymers 2020, 12(10), 2413; https://doi.org/10.3390/polym12102413 - 20 Oct 2020
Cited by 24 | Viewed by 3065
Abstract
To address the life span of materials in the process of daily use, new types of structural nanofibers, fabricated by multifluid electrospinning to encapsulate both epoxy resin and amine curing agent, were embedded into an epoxy matrix to provide it with self-healing ability. [...] Read more.
To address the life span of materials in the process of daily use, new types of structural nanofibers, fabricated by multifluid electrospinning to encapsulate both epoxy resin and amine curing agent, were embedded into an epoxy matrix to provide it with self-healing ability. The nanofibers, which have a polyacrylonitrile sheath holding two separate cores, had an average diameter of 300 ± 140 nm with a uniform size distribution. The prepared fibers had a linear morphology with a clear three-chamber inner structure, as verified by scanning electron microscope and transmission electron microscope images. The two core sections were composed of epoxy and amine curing agents, respectively, as demonstrated under the synergistic characterization of Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry. The TGA results disclosed that the core-shell nanofibers contained 9.06% triethylenetetramine and 20.71% cured epoxy. In the electrochemical corrosion experiment, self-healing coatings exhibited an effective anti-corrosion effect, unlike the composite without nanofibers. This complex nanostructure was proven to be an effective nanoreactor, which is useful to encapsulate reactive fluids. This engineering process by multiple-fluid electrospinning is the first time to prove that this special multiple-chamber structure has great potential in the field of self-healing. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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14 pages, 4157 KiB  
Article
Influence of Accelerated Weathering on the Mechanical, Fracture Morphology, Thermal Stability, Contact Angle, and Water Absorption Properties of Natural Fiber Fabric-Based Epoxy Hybrid Composites
by Krittirash Yorseng, Sanjay Mavinkere Rangappa, Jyotishkumar Parameswaranpillai and Suchart Siengchin
Polymers 2020, 12(10), 2254; https://doi.org/10.3390/polym12102254 - 30 Sep 2020
Cited by 40 | Viewed by 3520
Abstract
Epoxy-based biocomposites are a good alternative for metals in lightweight applications. This research has been focused on the effect of accelerated weathering on the mechanical, thermal, contact angle, and water absorption behavior of neat epoxy, individual kenaf and sisal, and kenaf/sisal hybrid epoxy [...] Read more.
Epoxy-based biocomposites are a good alternative for metals in lightweight applications. This research has been focused on the effect of accelerated weathering on the mechanical, thermal, contact angle, and water absorption behavior of neat epoxy, individual kenaf and sisal, and kenaf/sisal hybrid epoxy composites. The composite was fabricated by hand layup method. Among the various composites studied, sisal/kenaf/sisal hybrid epoxy composites showed the best properties and retained the thermo-mechanical properties with the lowest water absorption properties even after the weathering test. Thus, composites with hybridized kenaf and sisal with sisal outer layer are encouraging semistructural materials in outdoor applications. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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12 pages, 8529 KiB  
Article
Dielectric and Thermal Conductivity Characteristics of Epoxy Resin-Impregnated H-BN/CNF-Modified Insulating Paper
by Hongda Yang, Qingguo Chen, Xinyu Wang, Minghe Chi and Jinfeng Zhang
Polymers 2020, 12(9), 2080; https://doi.org/10.3390/polym12092080 - 13 Sep 2020
Cited by 10 | Viewed by 2999
Abstract
High-voltage direct-current (HVDC) dry bushing capacitor-core insulation is composed of epoxy resin-impregnated insulating paper (RIP). To improve the thermal conductivity, breakdown strength, and space charge characteristics of RIP, 0.1 wt % nano-cellulose fiber (CNF)-modified RIP (CNF/RIP), 2.5–30 wt % hexagonal boron nitride (h-BN)-modified [...] Read more.
High-voltage direct-current (HVDC) dry bushing capacitor-core insulation is composed of epoxy resin-impregnated insulating paper (RIP). To improve the thermal conductivity, breakdown strength, and space charge characteristics of RIP, 0.1 wt % nano-cellulose fiber (CNF)-modified RIP (CNF/RIP), 2.5–30 wt % hexagonal boron nitride (h-BN)-modified RIP (h-BN/RIP), and 2.5–30 wt % h-BN + 0.1 wt % CNF-modified RIP (h-BN + 0.1 wt % CNF/RIP) were prepared. Scanning electron microscopy (SEM) was implemented; the thermal conductivity, DC conductivity, DC breakdown strength, and space charge characteristics were tested. The maximum thermal conductivity of h-BN + 0.1 wt % CNF/RIP was 0.376 W/m.K with a h-BN content of 30 wt %. The thermal conductivity was 85.2% higher than that of unmodified RIP. The breakdown strength and charge suppression were the best in the case of 10 wt % h-BN + 0.1 wt % CNF/RIP. The maximum breakdown strength was 11.2% higher than that of unmodified RIP. These results can play a significant role in the research and development of insulation materials for HVDC dry bushing. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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15 pages, 5555 KiB  
Article
Halloysite Nanotubes as an Additive to Ensure Enhanced Characteristics of Cold-Curing Epoxy Resins under Fire Conditions
by Jaroslav Hornak, Petr Kadlec and Radek Polanský
Polymers 2020, 12(9), 1881; https://doi.org/10.3390/polym12091881 - 20 Aug 2020
Cited by 4 | Viewed by 2515
Abstract
At present, the most commonly used electrical insulating materials, including cold-curing epoxy resins, are well designed for normal operating conditions. However, new generations of materials should also be capable of withstanding extreme emergency conditions, e.g., in case of fire. For this reason, this [...] Read more.
At present, the most commonly used electrical insulating materials, including cold-curing epoxy resins, are well designed for normal operating conditions. However, new generations of materials should also be capable of withstanding extreme emergency conditions, e.g., in case of fire. For this reason, this study presents the possibilities of an improved cold-curing epoxy resin using halloysite nanotubes (HNTs) to increase its operational safety. The positive effect of HNT addition is indicated mainly in terms of the suppression of thermo-oxidation processes, which has been demonstrated by the decreases in the maximum heat flow peaks as well as the specific enthalpy values during the thermal decomposition of the epoxy resin. The observed dielectric parameters of the HNT-added materials differ only slightly from those without a filler, whereas their mechanical properties strongly depend on the amount of dispersed HNTs. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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14 pages, 4329 KiB  
Article
Epoxy Nanocomposites Reinforced with Functionalized Carbon Nanotubes
by Anton Mostovoy, Andrey Yakovlev, Vitaly Tseluikin and Marina Lopukhova
Polymers 2020, 12(8), 1816; https://doi.org/10.3390/polym12081816 - 13 Aug 2020
Cited by 35 | Viewed by 3703
Abstract
In this article, amino functionalized multiwalled carbon nanotubes (MWCNTs) were prepared by chemical modification of the surface of a MWCNTs using γ-aminopropyltriethoxysilane (APTES) and dispersed into the epoxy composition. The modifying agent (APTES) was directly deposited on the MWCNTs surfaces. For the functionalization [...] Read more.
In this article, amino functionalized multiwalled carbon nanotubes (MWCNTs) were prepared by chemical modification of the surface of a MWCNTs using γ-aminopropyltriethoxysilane (APTES) and dispersed into the epoxy composition. The modifying agent (APTES) was directly deposited on the MWCNTs surfaces. For the functionalization of MWCNTs, was used not the APTES concentrate, as it had been described in previous works, but its freshly prepared aqueous solution. Properties of APTES-treated MWCNTs were characterized by transmission electron microscope (TEM), Raman spectroscopy and FT-IR. The results showed that the functionalization and chemical compatibility of APTES-treated MWCNTs with epoxy composition provides their best dispersion in the epoxy composition, had important influence on curing behavior, structure and physicochemical properties of the epoxy composites plasticized with trichloroethyl phosphate. The results showed that the functionalization and chemical compatibility of APTES-treated MWCNTs with epoxy composition provides increased of physicomechanical properties of epoxy composites: bending stress increases by 194% and bending modulus increases by 137%, the tensile strength increases by 108% and the tensile elastic modulus increases by 52%, impact strength increases by 300%, in comparison with plasticized epoxy composite that does not contain MWCNTs. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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15 pages, 3804 KiB  
Article
Reinforcement of Epoxy Composites with Application of Finely-ground Ochre and Electrophysical Method of the Composition Modification
by Amirbek Bekeshev, Anton Mostovoy, Lyazzat Tastanova, Yulia Kadykova, Svetlana Kalganova and Marina Lopukhova
Polymers 2020, 12(7), 1437; https://doi.org/10.3390/polym12071437 - 27 Jun 2020
Cited by 30 | Viewed by 3522
Abstract
The conducted studies have proven the possibility of the directed control of operational properties of epoxy composites, due to the addition of finely-ground ocher into their composition, and the use of microwave modification of the epoxy composition. The rational content of ocher as [...] Read more.
The conducted studies have proven the possibility of the directed control of operational properties of epoxy composites, due to the addition of finely-ground ocher into their composition, and the use of microwave modification of the epoxy composition. The rational content of ocher as a modifying additive (0.5 parts by mass) and a filler (75 parts by mass) of the epoxy composition has been selected, which ensures the improvement of the studied complex of physical-mechanical properties. It has been proven that ocher affects the structure formation processes and the structure of the epoxy composite, thus increasing its thermal, heat and fire resistance. During the research, the application efficiency has been proven, and the optimal parameters of the microwave modification (power—350 W; duration—30 s) of epoxy compositions filled with ocher, which increase physical-mechanical characteristics of composites, have been selected. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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21 pages, 3860 KiB  
Article
Kinetics of Cross-Linking Reaction of Epoxy Resin with Hydroxyapatite-Functionalized Layered Double Hydroxides
by Zohre Karami, Mohammad Reza Ganjali, Maryam Zarghami Dehaghani, Mustafa Aghazadeh, Maryam Jouyandeh, Amin Esmaeili, Sajjad Habibzadeh, Ahmad Mohaddespour, Inamuddin, Krzysztof Formela, Józef T. Haponiuk and Mohammad Reza Saeb
Polymers 2020, 12(5), 1157; https://doi.org/10.3390/polym12051157 - 18 May 2020
Cited by 23 | Viewed by 4471
Abstract
The cure kinetics analysis of thermoset polymer composites gives useful information about their properties. In this work, two types of layered double hydroxide (LDH) consisting of Mg2+ and Zn2+ as divalent metal ions and CO32− as an anion intercalating [...] Read more.
The cure kinetics analysis of thermoset polymer composites gives useful information about their properties. In this work, two types of layered double hydroxide (LDH) consisting of Mg2+ and Zn2+ as divalent metal ions and CO32− as an anion intercalating agent were synthesized and functionalized with hydroxyapatite (HA) to make a potential thermal resistant nanocomposite. The curing potential of the synthesized nanoplatelets in the epoxy resin was then studied, both qualitatively and quantitatively, in terms of the Cure Index as well as using isoconversional methods, working on the basis of nonisothermal differential scanning calorimetry (DSC) data. Fourier transform infrared spectroscopy (FTIR) was used along with X-ray diffraction (XRD) and thermogravimetric analysis (TGA) to characterize the obtained LDH structures. The FTIR band at 3542 cm−1 corresponded to the O–H stretching vibration of the interlayer water molecules, while the weak band observed at 1640 cm−1 was attributed to the bending vibration of the H–O of the interlayer water. The characteristic band of carbonated hydroxyapatite was observed at 1456 cm−1. In the XRD patterns, the well-defined (00l) reflections, i.e., (003), (006), and (110), supported LDH basal reflections. Nanocomposites prepared at 0.1 wt % were examined for curing potential by the Cure Index as a qualitative criterion that elucidated a Poor cure state for epoxy/LDH nanocomposites. Moreover, the curing kinetics parameters including the activation energy (Eα), reaction order, and the frequency factor were computed using the Friedman and Kissinger–Akahira–Sunose (KAS) isoconversional methods. The evolution of Eα confirmed the inhibitory role of the LDH in the crosslinking reactions. The average value of Eα for the neat epoxy was 54.37 kJ/mol based on the KAS method, whereas the average values were 59.94 and 59.05 kJ/mol for the epoxy containing Zn-Al-CO3-HA and Mg Zn-Al-CO3-HA, respectively. Overall, it was concluded that the developed LDH structures hindered the epoxy curing reactions. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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19 pages, 5528 KiB  
Article
Effect of Surface Treatment of Halloysite Nanotubes (HNTs) on the Kinetics of Epoxy Resin Cure with Amines
by Vahideh Akbari, Maryam Jouyandeh, Seyed Mohammad Reza Paran, Mohammad Reza Ganjali, Hossein Abdollahi, Henri Vahabi, Zahed Ahmadi, Krzysztof Formela, Amin Esmaeili, Ahmad Mohaddespour, Sajjad Habibzadeh and Mohammad Reza Saeb
Polymers 2020, 12(4), 930; https://doi.org/10.3390/polym12040930 - 17 Apr 2020
Cited by 33 | Viewed by 4116
Abstract
The epoxy/clay nanocomposites have been extensively considered over years because of their low cost and excellent performance. Halloysite nanotubes (HNTs) are unique 1D natural nanofillers with a hollow tubular shape and high aspect ratio. To tackle poor dispersion of the pristine halloysite (P-HNT) [...] Read more.
The epoxy/clay nanocomposites have been extensively considered over years because of their low cost and excellent performance. Halloysite nanotubes (HNTs) are unique 1D natural nanofillers with a hollow tubular shape and high aspect ratio. To tackle poor dispersion of the pristine halloysite (P-HNT) in the epoxy matrix, alkali surface-treated HNT (A-HNT) and epoxy silane functionalized HNT (F-HNT) were developed and cured with epoxy resin. Nonisothermal differential scanning calorimetry (DSC) analyses were performed on epoxy nanocomposites containing 0.1 wt.% of P-HNT, A-HNT, and F-HNT. Quantitative analysis of the cure kinetics of epoxy/amine system made by isoconversional Kissinger–Akahira–Sunose (KAS) and Friedman methods made possible calculation of the activation energy (Eα) as a function of conversion (α). The activation energy gradually increased by increasing α due to the diffusion-control mechanism. However, the average value of Eα for nanocomposites was lower comparably, suggesting autocatalytic curing mechanism. Detailed assessment revealed that autocatalytic reaction degree, m increased at low heating rate from 0.107 for neat epoxy/amine system to 0.908 and 0.24 for epoxy/P-HNT and epoxy/A-HNT nanocomposites, respectively, whereas epoxy/F-HNT system had m value of 0.072 as a signature of dominance of non-catalytic reactions. At high heating rates, a similar behavior but not that significant was observed due to the accelerated gelation in the system. In fact, by the introduction of nanotubes the mobility of curing moieties decreased resulting in some deviation of experimental cure rate values from the predicted values obtained using KAS and Friedman methods. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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9 pages, 2968 KiB  
Article
Rheological and Electrical Study of a Composite Material Based on an Epoxy Polymer Containing Cyclotriphosphazene
by O. Dagdag, M. El Gouri, A. El Mansouri, A. Outzourhit, A. El Harfi, O. Cherkaoui, A. El Bachiri, O. Hamed, S. Jodeh, G. Hanbali and B. Khalaf
Polymers 2020, 12(4), 921; https://doi.org/10.3390/polym12040921 - 16 Apr 2020
Cited by 21 | Viewed by 3134
Abstract
In this work, we have studied, formulated, prepared, and characterized the rheological and electrical behavior of a composite material based on an epoxy resin Diglycidyl Ether of Bisphenol A (DGEBA) reinforced with hexaglycidyl cyclotriphosphazene (HGCP). The epoxy system was cured with 4,4’-methylene dianiline [...] Read more.
In this work, we have studied, formulated, prepared, and characterized the rheological and electrical behavior of a composite material based on an epoxy resin Diglycidyl Ether of Bisphenol A (DGEBA) reinforced with hexaglycidyl cyclotriphosphazene (HGCP). The epoxy system was cured with 4,4’-methylene dianiline (MDA). DGEBA-HGCP-MDA epoxy composite materials with reinforced HGCP which varied from 5% to 10% by weight were prepared by mixing in the molten state. The morphology was evaluated by SEM. The rheological behavior was studied using small deformation rheology. The electrical characterization was carried out with a frequency variation range from 1 Hz to 100 KHz at room temperature. These measurements revealed that the rheological and electrical behaviors strongly depend on the quantity of HGCP in the DGEBA matrix. The linear viscoelastic properties study reveals that the modulus of elasticity G’ is dependent on the amount of HGCP present in the epoxy resin DGEBA. The capacitance-frequency measurements suggest a distribution of localized states in the band gap of the blends. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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13 pages, 4651 KiB  
Article
Dielectric Relaxation in the Hybrid Epoxy/MWCNT/MnFe2O4 Composites
by Darya Meisak, Jan Macutkevic, Artyom Plyushch, Polina Kuzhir, Algirdas Selskis and Juras Banys
Polymers 2020, 12(3), 697; https://doi.org/10.3390/polym12030697 - 21 Mar 2020
Cited by 16 | Viewed by 2491
Abstract
The electrical properties of epoxy/MWCNT (multi-walled carbon nanotubes)/MnFe2O4 hybrid composites loaded with MWCNTs (below, 0.09 vol.%, and above, 0.58 vol.%, percolation threshold) and varying concentrations of MnFe2O4 up to 10 vol.% were studied in a wide frequency [...] Read more.
The electrical properties of epoxy/MWCNT (multi-walled carbon nanotubes)/MnFe2O4 hybrid composites loaded with MWCNTs (below, 0.09 vol.%, and above, 0.58 vol.%, percolation threshold) and varying concentrations of MnFe2O4 up to 10 vol.% were studied in a wide frequency range (20 Hz–40 GHz) at different temperatures (20 K–500 K). At low frequencies, the dielectric permittivity and the electrical conductivity of composites with fixed amounts of MWCNT are strongly dependent on MnFe2O4 content. For MWCNT concentrations above the percolation threshold (i.e., 0.58 vol.%), the electrical conductivity highly decreases with the increase of the MnFe2O4 fraction. In contrast, for the epoxy/MWCNT just below the onset of electrical conductivity (0.09 vol.% of MWCNTs), there exists an optimal concentration of MnFe2O4 inclusions (i.e., 0.025 vol.%), leading to a dramatic increase of the electrical conductivity by three orders of magnitude. The electrical transport in composites is mainly governed by electron tunneling at lower temperatures (below 200 K), and it is highly impacted by the matrix conductivity at higher temperatures (above 400 K). The electrical properties were discussed in terms of the Maxwell–Wagner relaxation and distributions of relaxation times. A non-invasive platform based on dielectric relaxation spectroscopy was proposed for enhancing the synergetic effect coursed by using multiple nanoinclusions in polymer composites just below the percolation threshold. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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22 pages, 5490 KiB  
Article
Curing Kinetics and Thermal Stability of Epoxy Composites Containing Newly Obtained Nano-Scale Aluminum Hypophosphite (AlPO2)
by Farimah Tikhani, Shahab Moghari, Maryam Jouyandeh, Fouad Laoutid, Henri Vahabi, Mohammad Reza Saeb and Philippe Dubois
Polymers 2020, 12(3), 644; https://doi.org/10.3390/polym12030644 - 12 Mar 2020
Cited by 48 | Viewed by 5283
Abstract
For the first time, nano-scale aluminum hypophosphite (AlPO2) was simply obtained in a two-step milling process and applied in preparation of epoxy nanocomposites varying concentration (0.1, 0.3, and 0.5 wt.% based on resin weight). Studying the cure kinetics and thermal stability [...] Read more.
For the first time, nano-scale aluminum hypophosphite (AlPO2) was simply obtained in a two-step milling process and applied in preparation of epoxy nanocomposites varying concentration (0.1, 0.3, and 0.5 wt.% based on resin weight). Studying the cure kinetics and thermal stability of these nanocomposites would pave the way toward the design of high-performance nanocomposites for special applications. Scanning electron microscopy (SEM) and transmittance electron microscopy (TEM) revealed AlPO2 particles having domains less than 60 nm with high potential for agglomeration. Excellent (at heating rate of 5 °C/min) and Good (at heating rates of 10, 15 and 20 °C/min) cure states were detected for nanocomposites under nonisothermal differential scanning calorimetry (DSC). While the dimensionless curing temperature interval (ΔT*) was almost equal for epoxy/AlPO2 nanocomposites, dimensionless heat release (ΔH*) changed by densification of polymeric network. Quantitative cure analysis based on isoconversional Friedman and Kissinger methods gave rise to the kinetic parameters such as activation energy and the order of reaction as well as frequency factor. Variation of glass transition temperature (Tg) was monitored to explain the molecular interaction in the system, where Tg increased from 73.2 °C for neat epoxy to just 79.5 °C for the system containing 0.1 wt.% AlPO2. Moreover, thermogravimetric analysis (TGA) showed that nanocomposites were thermally stable. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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23 pages, 3956 KiB  
Article
Durability of an Epoxy Resin and Its Carbon Fiber- Reinforced Polymer Composite upon Immersion in Water, Acidic, and Alkaline Solutions
by Arya Uthaman, Guijun Xian, Sabu Thomas, Yunjia Wang, Qiang Zheng and Xiaoling Liu
Polymers 2020, 12(3), 614; https://doi.org/10.3390/polym12030614 - 7 Mar 2020
Cited by 94 | Viewed by 9933
Abstract
The usage of polymer composites in various engineering fields has increased. However, the long-term service performance of such materials under aggressive conditions is still poorly understood, which limits the development of safe and economically effective designs. In this study, the aging of an [...] Read more.
The usage of polymer composites in various engineering fields has increased. However, the long-term service performance of such materials under aggressive conditions is still poorly understood, which limits the development of safe and economically effective designs. In this study, the aging of an epoxy resin and its carbon fiber-reinforced polymer (CFRP) composites upon immersion in water, acidic, and alkaline solutions was evaluated at different temperatures. The service life of the CFRP composites under various conditions could be predicted by the Arrhenius theory. The thermal and mechanical analysis results indicated that the CFRP composites were more vulnerable to HCl owing to the higher moisture absorption and diffusion of HCl into their cracks. The scanning electron microscopy results showed that the polymer matrix was damaged and degraded. Therefore, to allow long-term application, CFRP composites must be protected from acidic environments. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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13 pages, 3627 KiB  
Article
Study of UHMWPE Fiber Surface Modification and the Properties of UHMWPE/Epoxy Composite
by Lei Han, Haifeng Cai, Xu Chen, Cheng Zheng and Weihong Guo
Polymers 2020, 12(3), 521; https://doi.org/10.3390/polym12030521 - 1 Mar 2020
Cited by 34 | Viewed by 6240
Abstract
Ultra-high molecular weight polyethylene (UHMWPE)/epoxy composites with excellent adhesive properties were prepared by forming an interface membrane on the UHMWPE fiber surface. The interface membrane of the UHMWPE fiber and epoxy resin was polymerized by an aldol condensation between polyvinyl alcohol (PVA) and [...] Read more.
Ultra-high molecular weight polyethylene (UHMWPE)/epoxy composites with excellent adhesive properties were prepared by forming an interface membrane on the UHMWPE fiber surface. The interface membrane of the UHMWPE fiber and epoxy resin was polymerized by an aldol condensation between polyvinyl alcohol (PVA) and glutaraldehyde. Different surface treatment methods of UHMWPE fibers were optimized and the two-step PVA-glutaraldehyde condensation (Corona-PG-2S) method is the best. The interfacial adhesion between UHMWPE fiber and epoxy resin was enhanced, and the adhesive properties of the composite were improved. X-ray photoelectron spectroscopy (XPS) and energy dispersive spectrum (EDS) results of the fiber treated by Corona-PG-2S shows that the surface oxygen content was up to 25.0 wt %, with an increase of 17.3 wt % compared with the surface oxygen content of unmodified UHMWPE fiber, which indicated that the surface polarity was greatly enhanced. The adhesive properties were improved by improving the polarity of the surface. The peel strength, ultimate cohesive force, tensile strength and flexural strength of the composite treated by Corona-PG-2S were greatly increased to 262.8%, 166.9%, 139.7%, 200.6% compared with those of unmodified samples. The composite prepared by Corona-PG-2S had excellent adhesive properties, demonstrating that the Corona-PG-2S method plays a major role in significantly improving the composite adhesive properties. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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15 pages, 2328 KiB  
Article
Investigation of the Thermal Conductivity of Resin-Based Lightweight Composites Filled with Hollow Glass Microspheres
by Zhipeng Xing, Hongjun Ke, Xiaodong Wang, Ting Zheng, Yingjie Qiao, Kaixuan Chen, Xiaohong Zhang, Lili Zhang, Chengying Bai and Zhuoran Li
Polymers 2020, 12(3), 518; https://doi.org/10.3390/polym12030518 - 29 Feb 2020
Cited by 33 | Viewed by 4726
Abstract
The design and development of thermal insulation materials is very important for the treatment of offshore oil pipelines. Understanding thermal energy transport in thermal insulation materials and predicting their thermal conductivities have important theoretical and practical value for the design of thermal insulation [...] Read more.
The design and development of thermal insulation materials is very important for the treatment of offshore oil pipelines. Understanding thermal energy transport in thermal insulation materials and predicting their thermal conductivities have important theoretical and practical value for the design of thermal insulation materials. In this work, lightweight and thermally insulated (LWTI) composites with the desired mechanical strength for offshore oil pipelines applications were prepared using epoxy resin (EP) as the matrix and hollow glass microspheres (HGMs) as the filler. The morphology, density, and mechanical properties of HGM/EP LWTI composites were studied first. The flexural strength and the flexural modulus of HGM/EP LWTI composites could still be as high as 22.34 ± 2.75 Mpa and 1.34 ± 0.03 GPa, respectively, while the density was only 0.591 g/cm3. The relationship between the effective thermal conductivity of HGM/EP LWTI composites and material parameters (sizes and contents together) has been studied systematically. A three-phase prediction model was built using the self-consistent approximation method to predict the effective thermal conductivity of HGM/EP LWTI composites, and the resin matrix, the wall thickness, the HGM particle size, and other parameters (such as air) were fully considered during the derivation of this three-phase thermal conductivity model. Finally, the insulation mechanism of HGM/EP LWTI composites was systematically analyzed. The thermal conductivities of HGM/EP LWTI composites with different diameters and HGM contents calculated by the three-phase prediction model agreed well with the experimental test results, with a minimum error of only 0.69%. Thus, this three-phase thermal conductivity model can be used to theoretically simulate the thermal conductivity of epoxy resin-based LWTI composites and can be the theoretical basis for the design and prediction of the thermal conductivity of other similar hollow spheres filled materials. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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12 pages, 3371 KiB  
Article
Core-Shell Graphitic Carbon Nitride/Zinc Phytate as a Novel Efficient Flame Retardant for Fire Safety and Smoke Suppression in Epoxy Resin
by Weiwei Zhang, Weihong Wu, Weihua Meng, Weiya Xie, Yumeng Cui, Jianzhong Xu and Hongqiang Qu
Polymers 2020, 12(1), 212; https://doi.org/10.3390/polym12010212 - 15 Jan 2020
Cited by 26 | Viewed by 3852
Abstract
Novel core-shell graphitic carbon nitride/zinc phytate (g-C3N4/PAZn) flame retardant was simple synthetized using two-dimensional g-C3N4 and bio-based PAZn by self-assembly and incorporated into epoxy resin (EP) for improving the fire safety. The flame retardance and smoke [...] Read more.
Novel core-shell graphitic carbon nitride/zinc phytate (g-C3N4/PAZn) flame retardant was simple synthetized using two-dimensional g-C3N4 and bio-based PAZn by self-assembly and incorporated into epoxy resin (EP) for improving the fire safety. The flame retardance and smoke suppression were investigated by cone calorimetry. The results indicated that g-C3N4/PAZn-EP displayed outstanding flame retardancy and smoke suppression, for example, the peak heat release rate and peak smoke production rate decreased by 71.38% and 25%, respectively. Furthermore, the flame retardancy mechanism was further explored by char residue and thermal stability analysis. It can be predicted that g-C3N4/PAZn will provide valuable reference about bio-based flame retardant. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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16 pages, 4101 KiB  
Article
Surface Modification of Bamboo Fibers to Enhance the Interfacial Adhesion of Epoxy Resin-Based Composites Prepared by Resin Transfer Molding
by Dong Wang, Tian Bai, Wanli Cheng, Can Xu, Ge Wang, Haitao Cheng and Guangping Han
Polymers 2019, 11(12), 2107; https://doi.org/10.3390/polym11122107 - 15 Dec 2019
Cited by 39 | Viewed by 4957
Abstract
Bamboo fibers (BFs)-reinforced epoxy resin (EP) composites are prepared by resin transfer molding (RTM). The influence of BFs surface modification (NaOH solution or coupling agents, i.e., KH550 and KH560) on interfacial properties of BFs/EP composites is systematically investigated. The synergistic effect of hydrolysis, [...] Read more.
Bamboo fibers (BFs)-reinforced epoxy resin (EP) composites are prepared by resin transfer molding (RTM). The influence of BFs surface modification (NaOH solution or coupling agents, i.e., KH550 and KH560) on interfacial properties of BFs/EP composites is systematically investigated. The synergistic effect of hydrolysis, peeling reaction of BFs, and the condensation reaction of hydrolyzed coupling agents are confirmed by FTIR. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) reveal that the interfacial compatibility of NaOH- and silane-modified BFs/EP composites was significantly improved. KH550-modified BFs/EP composite renders optimal tensile, flexural, and impact strength values of 68 MPa, 86 MPa, and 226 J/m. The impact resistance mechanism at the interface of BFs/EP composites was proposed. Moreover, the dynamic mechanical properties, creep behavior, and differential scanning calorimetry of BFs/EP composites have also been carried out to understand thermal stabilities. Overall, the surface-modified BFs-reinforced EP composites exhibited superior interfacial bonding. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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17 pages, 3130 KiB  
Review
Natural Fillers as Potential Modifying Agents for Epoxy Composition: A Review
by Natalia Sienkiewicz, Midhun Dominic and Jyotishkumar Parameswaranpillai
Polymers 2022, 14(2), 265; https://doi.org/10.3390/polym14020265 - 10 Jan 2022
Cited by 35 | Viewed by 4931
Abstract
Epoxy resins as important organic matrices, thanks to their chemical structure and the possibility of modification, have unique properties, which contribute to the fact that these materials have been used in many composite industries for many years. Epoxy resins are repeatedly used in [...] Read more.
Epoxy resins as important organic matrices, thanks to their chemical structure and the possibility of modification, have unique properties, which contribute to the fact that these materials have been used in many composite industries for many years. Epoxy resins are repeatedly used in exacting applications due to their exquisite mechanical properties, thermal stability, scratch resistance, and chemical resistance. Moreover, epoxy materials also have really strong resistance to solvents, chemical attacks, and climatic aging. The presented features confirm the fact that there is a constant interest of scientists in the modification of resins and understanding its mechanisms, as well as in the development of these materials to obtain systems with the required properties. Most of the recent studies in the literature are focused on green fillers such as post-agricultural waste powder (cashew nuts powder, coconut shell powder, rice husks, date seed), grass fiber (bamboo fibers), bast/leaf fiber (hemp fibers, banana bark fibers, pineapple leaf), and other natural fibers (waste tea fibers, palm ash) as reinforcement for epoxy resins rather than traditional non-biodegradable fillers due to their sustainability, low cost, wide availability, and the use of waste, which is environmentally friendly. Furthermore, the advantages of natural fillers over traditional fillers are acceptable specific strength and modulus, lightweight, and good biodegradability, which is very desirable nowadays. Therefore, the development and progress of “green products” based on epoxy resin and natural fillers as reinforcements have been increasing. Many uses of natural plant-derived fillers include many plant wastes, such as banana bark, coconut shell, and waste peanut shell, can be found in the literature. Partially biodegradable polymers obtained by using natural fillers and epoxy polymers can successfully reduce the undesirable epoxy and synthetic fiber waste. Additionally, partially biopolymers based on epoxy resins, which will be presented in the paper, are more useful than commercial polymers due to the low cost and improved good thermomechanical properties. Full article
(This article belongs to the Special Issue Epoxy Resins and Composites)
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