Polymers

Research

13 pages, 3962 KiB

Open AccessArticle

The Synergistic Effects of Hybrid Micro and Nano Silica in Influencing the Mechanical Properties of Epoxy Composites—A New Model

by Raja Nor Raja Othman, Dinesh Kumar Subramaniam, Nursa’adah Ezani, Mohamad Faizal Abdullah and Ku Zarina Ku Ahmad

Polymers 2022, 14(19), 3969; https://doi.org/10.3390/polym14193969 - 22 Sep 2022

Cited by 5 | Viewed by 1511

Abstract

Epoxy nano composites containing micro and nano silica were prepared by varying the filler’s weight loading as an attempt to investigate the effects of incorporating these fillers in influencing its mechanical properties. Mechanical properties characterizations include the evaluation of tensile. The mechanical properties [...] Read more.

Epoxy nano composites containing micro and nano silica were prepared by varying the filler’s weight loading as an attempt to investigate the effects of incorporating these fillers in influencing its mechanical properties. Mechanical properties characterizations include the evaluation of tensile. The mechanical properties of the epoxy composites were found to tremendously increase as both micro and nano silica were added together at a 1:1 wt.% ratio. For example, the highest values of Young’s modulus were recorded to be 5.39 GPa for 25 wt.% loading (12.5 wt.% Micro + 12.5 wt.% nano), while Young’s modulus values of 5.22 MPa and 5.32 MPa were recorded for micro and nano silica, respectively, at the same weight loading. The most outstanding results were observed at 25 wt.% hybrids (12.5 wt.% micro silica + 12.5 wt.% nano silica), where the values of Young’s modulus were increased by 228% compared to the neat epoxy. This study successfully demonstrated synergistic effects demonstrated by combining micro and nano silica fillers, which created an interaction that significantly enhanced the Young’s modulus of epoxy composites. Full article

(This article belongs to the Special Issue Epoxy Resin and Epoxy Resin Based Polymer Materials)

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12 pages, 4458 KiB

Open AccessArticle

Study on the Mechanical and Toughness Behavior of Epoxy Nano-Composites with Zero-Dimensional and Two-Dimensional Nano-Fillers

by Xiaodong Li, Qi Wang, Xu Cui, Xinwen Feng, Fei Teng, Mingyao Xu, Weiguo Su and Jun He

Polymers 2022, 14(17), 3618; https://doi.org/10.3390/polym14173618 - 1 Sep 2022

Cited by 13 | Viewed by 1782

Abstract

The mechanical properties of epoxy resin can be enhanced by adding nanofillers into its matrix. This study researches and compares the impacts of adding nanofillers with different dimensions, including two-dimensional boron nitride and zero-dimensional silica, on the mechanical and toughness properties of epoxy [...] Read more.

The mechanical properties of epoxy resin can be enhanced by adding nanofillers into its matrix. This study researches and compares the impacts of adding nanofillers with different dimensions, including two-dimensional boron nitride and zero-dimensional silica, on the mechanical and toughness properties of epoxy resin. At low fractions (0–2.0 wt%), 2DBN/epoxy composites have a higher Young’s modulus, fracture toughness and critical strain energy release rate compared to SiO₂/epoxy composites. However, the workability deteriorated drastically for BN/epoxy composites above a specific nanofiller concentration (2.0–3.0 wt%). BN prevents crack growth by drawing and bridging. SiO₂ enhances performance by deflecting the crack direction and forming voids. Additionally, the dimension and content of nanofiller also influence glass transition temperature and storage modulus significantly. Full article

(This article belongs to the Special Issue Epoxy Resin and Epoxy Resin Based Polymer Materials)

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12 pages, 6309 KiB

Open AccessArticle

Thermal Stability, Mechanical Properties and Ceramization Mechanism of Epoxy Resin/Kaolin/Quartz Fiber Ceramifiable Composites

by Chenyi Xue, Yan Qin, Huadong Fu and Jiamin Fan

Polymers 2022, 14(16), 3372; https://doi.org/10.3390/polym14163372 - 18 Aug 2022

Cited by 6 | Viewed by 2269

Abstract

The application of epoxy resins in high temperature and thermal protection fields is limited due to their low decomposition temperature and low carbon residual rate. In this paper, epoxy resin (EP)/quartz fiber (QF) ceramifiable composites were prepared using a prepreg-molding process. The thermal [...] Read more.

The application of epoxy resins in high temperature and thermal protection fields is limited due to their low decomposition temperature and low carbon residual rate. In this paper, epoxy resin (EP)/quartz fiber (QF) ceramifiable composites were prepared using a prepreg-molding process. The thermal stability, phase change and mechanical properties after high-temperature static ablation and ceramization mechanism of EP/QF ceramifiable composites were investigated. The addition of glass frits and kaolinite ceramic filler dramatically increases the thermal stability of the composites, according to thermogravimetric (TG) studies. The composite has a maximum residual weight of 61.08%. The X-ray diffraction (XRD) results show that the mullite ceramic phase is generated, and a strong quartz diffraction peak appears at 1000 °C. The scanning electron microscope (SEM) and element distribution analyses reveal that the ceramic phase generated inside the material, when the temperature reaches 1000 °C, effectively fills the voids in composites. The composites have a bending strength of 175.37 MPa at room temperature and retain a maximum bending strength of 12.89 MPa after 1000 °C treatment. Full article

(This article belongs to the Special Issue Epoxy Resin and Epoxy Resin Based Polymer Materials)

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14 pages, 5261 KiB

Open AccessArticle

Ionic Liquid-Cured Epoxy/PCL Blends with Improved Toughness and Adhesive Properties

by Lidia Orduna, Iker Razquin, Itziar Otaegi, Nora Aranburu and Gonzalo Guerrica-Echevarría

Polymers 2022, 14(13), 2679; https://doi.org/10.3390/polym14132679 - 30 Jun 2022

Cited by 4 | Viewed by 1790

Abstract

In this work, ionic liquid (IL)-cured epoxy resins were modified by adding poly(ε-caprolactone) (PCL). Three different ILs were used in order to study how (a) the chemical structure of the ILs and (b) the PCL content affect the phase behaviour, microstructure, mechanical and [...] Read more.

In this work, ionic liquid (IL)-cured epoxy resins were modified by adding poly(ε-caprolactone) (PCL). Three different ILs were used in order to study how (a) the chemical structure of the ILs and (b) the PCL content affect the phase behaviour, microstructure, mechanical and adhesive properties. Regardless of the IL used or the PCL content, the obtained materials showed a single phase. The addition of PCL to the epoxy resin resulted in plasticizing of the network blends, lower glass transition temperatures (T_g), and crosslinking densities (ν_e). Low PCL contents did not have a significant impact on the mechanical properties. However, the adhesive properties improved significantly at low PCL contents. Higher PCL contents led to a significant increase in toughness, especially in the case of the imidazolium-based IL. The balance achieved between the mechanical and adhesive properties of these IL-cured epoxy/PCL blends constitutes an important step towards sustainability. This is because a biodegradable polymer (PCL) was used to substitute part of the epoxy resin, and the ILs—which are non-volatile and cure effectively at much lower contents—were used instead of conventional curing agents. Given the wide use of this kind of materials in the adhesive industry, the practical significance of these results must be emphasised. Full article

(This article belongs to the Special Issue Epoxy Resin and Epoxy Resin Based Polymer Materials)

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12 pages, 4149 KiB

Open AccessArticle

The Interaction of Waterborne Epoxy/Dicyandiamide Varnishes with Metal Oxides

by Gary Säckl, Jiri Duchoslav, Robert Pugstaller, Cornelia Marchfelder, Klaus Haselgrübler, Maëlenn Aufray, David Stifter and Gernot M. Wallner

Polymers 2022, 14(11), 2226; https://doi.org/10.3390/polym14112226 - 30 May 2022

Cited by 6 | Viewed by 2369

Abstract

For delayed crosslinking of waterborne epoxy varnishes, dicyandiamide (DICY) is often used as a latent curing agent. While, for amine-based curing agents such as diaminoethane (DAE), chemical interactions with metal oxides are well described, so far, no studies have been performed for DICY [...] Read more.

For delayed crosslinking of waterborne epoxy varnishes, dicyandiamide (DICY) is often used as a latent curing agent. While, for amine-based curing agents such as diaminoethane (DAE), chemical interactions with metal oxides are well described, so far, no studies have been performed for DICY and waterborne epoxy varnishes. Hence, in this work X-ray photoelectron spectroscopy (XPS) was used to investigate reactions of DICY and varnishes with technical surfaces of Al, Zn, and Sn. To directly study the reaction of DICY with metal oxides, immersion tests in a boiling solution of DICY in pure water were performed. A clear indication of the formation of metal–organic complexes was deduced from the change in the N1s peak of DICY. To understand the interfacial interaction and consequently the interphase formation during coating of waterborne epoxy varnishes, advanced cryo ultra-low-angle microtomy (cryo-ULAM) was implemented. Interestingly, a comparable reaction mechanism and the formation of metal complexes were confirmed for varnishes. The coatings exhibited a pronounced enrichment of the DICY hardener at the metal oxide–polymer interface. Full article

(This article belongs to the Special Issue Epoxy Resin and Epoxy Resin Based Polymer Materials)

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22 pages, 64169 KiB

Open AccessArticle

Physical, Thermal Transport, and Compressive Properties of Epoxy Composite Filled with Graphitic- and Ceramic-Based Thermally Conductive Nanofillers

by Siti Salmi Samsudin, Mohd Shukry Abdul Majid, Mohd Ridzuan Mohd Jamir, Azlin Fazlina Osman, Mariatti Jaafar and Hassan A. Alshahrani

Polymers 2022, 14(5), 1014; https://doi.org/10.3390/polym14051014 - 3 Mar 2022

Cited by 10 | Viewed by 2678

Abstract

Epoxy polymer composites embedded with thermally conductive nanofillers play an important role in the thermal management of polymer microelectronic packages, since they can provide thermal conduction properties with electrically insulating properties. An epoxy composite system filled with graphitic-based fillers; multi-walled carbon nanotubes (MWCNTs), [...] Read more.

Epoxy polymer composites embedded with thermally conductive nanofillers play an important role in the thermal management of polymer microelectronic packages, since they can provide thermal conduction properties with electrically insulating properties. An epoxy composite system filled with graphitic-based fillers; multi-walled carbon nanotubes (MWCNTs), graphene nanoplatelets (GNPs) and ceramic-based filler; silicon carbide nanoparticles (SiCs) was investigated as a form of thermal-effective reinforcement for epoxy matrices. The epoxy composites were fabricated using a simple fabrication method, which included ultrasonication and planetary centrifugal mixing. The effect of graphite-based and ceramic-based fillers on the thermal conductivity was measured by the transient plane source method, while the glass transition temperature of the fully cured samples was studied by differential scanning calorimetry. Thermal gravimetric analysis was adopted to study the thermal stability of the samples, and the compressive properties of different filler loadings (1–5 vol.%) were also discussed. The glass temperatures and thermal stabilities of the epoxy system were increased when incorporated with the graphite- and ceramic-based fillers. These results can be correlated with the thermal conductivity of the samples, which was found to increase with the increase in the filler loadings, except for the epoxy/SiCs composites. The thermal conductivity of the composites increased to 0.4 W/mK with 5 vol.% of MWCNTs, which is a 100% improvement over pure epoxy. The GNPs, SiCs, and MWCNTs showed uniform dispersion in the epoxy matrix and well-established thermally conductive pathways. Full article

(This article belongs to the Special Issue Epoxy Resin and Epoxy Resin Based Polymer Materials)

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17 pages, 3122 KiB

Open AccessArticle

Study on Curing Kinetics and the Mechanism of Ultrasonic Curing of an Epoxy Adhesive

by Zhaoyi Liu, Hui Wang, Yizhe Chen, Guodong Kang, Lin Hua and Jindong Feng

Polymers 2022, 14(3), 512; https://doi.org/10.3390/polym14030512 - 27 Jan 2022

Cited by 5 | Viewed by 1962

Abstract

Ultrasonic curing is an effective way to enhance the curing extent of composite material bonding in the aerospace industry. The non-thermal effect of ultrasonic has been revealed to improve curing efficiency. However, the mechanism of the ultrasonic non-thermal effect is still not clear. [...] Read more.

Ultrasonic curing is an effective way to enhance the curing extent of composite material bonding in the aerospace industry. The non-thermal effect of ultrasonic has been revealed to improve curing efficiency. However, the mechanism of the ultrasonic non-thermal effect is still not clear. In this work, a variable activation energy model of ultrasonic curing was established by utilizing the iso-conversional method, including the activation energy of the thermal effect and activation energy of the non-thermal effect. The thermal effect caused by ultrasonic was accurately peeled off. An obvious decrease in activation energy was found from 54 kJ/mol in thermal curing to 38 kJ/mol in ultrasonic curing. The activation energy of the reaction system in ultrasonic curing was substituted into the modified Kamal autocatalytic equation, and the parameters of the ultrasonic curing kinetic model were estimated by means of an ALO algorithm. Further discussion based on in situ FTIR showed that the non-thermal effect of ultrasonic can affect the vibration strength, stability, and chemical bond energy of internal groups, but cannot cause the fracture of chemical bonds. Moreover, frontier molecular orbital analysis showed that the chemical reactivity of epoxy/amine molecules increased and the HOMO–LUMO energy gap decreased from 6.511 eV to 5.617 eV under the effect of ultrasonic. Full article

(This article belongs to the Special Issue Epoxy Resin and Epoxy Resin Based Polymer Materials)

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15 pages, 3337 KiB

Open AccessArticle

D-GQDs Modified Epoxy Resin Enhances the Thermal Conductivity of AlN/Epoxy Resin Thermally Conductive Composites

by Duanwei Zhang, Fusheng Liu, Sheng Wang, Mengxi Yan, Xin Hu and Mengying Xu

Polymers 2021, 13(23), 4074; https://doi.org/10.3390/polym13234074 - 24 Nov 2021

Cited by 12 | Viewed by 2244

Abstract

This article proposes a method of increasing thermal conductivity (λ) by improving the λ value of a matrix and reducing the interfacial thermal resistance between such matrix and its thermally conductive fillers. D-GQDs (graphene quantum dots modified by polyetheramine D400) with a π–π-conjugated [...] Read more.

This article proposes a method of increasing thermal conductivity (λ) by improving the λ value of a matrix and reducing the interfacial thermal resistance between such matrix and its thermally conductive fillers. D-GQDs (graphene quantum dots modified by polyetheramine D400) with a π–π-conjugated system in the center of their molecules, and polyether branched chains that are rich in amino groups at their edges, are designed and synthesized. AlN/DG-ER (AlN/D-GQDs-Epoxy resin) thermally conductive composites are obtained using AlN as a thermally conductive and insulating filler, using D-GQDs-modified epoxy resin as a matrix. All of the thermal conductivity, electrically insulating and physical–mechanical properties of AlN/DG-ER are investigated in detail. The results show that D-GQDs linked to an epoxy resin by chemical bonds can increase the value of λ of the epoxy–resin matrix and reduce the interfacial thermal resistance between AlN and DG-ER (D-GQDs–epoxy resin). The prepared AlN/DG-ER is shown to be a good thermally conductive and insulating packaging material. Full article

(This article belongs to the Special Issue Epoxy Resin and Epoxy Resin Based Polymer Materials)

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14 pages, 3134 KiB

Open AccessArticle

Structural Adhesives Tapes Based on a Solid Epoxy Resin and Multifunctional Acrylic Telomers

by Mateusz Weisbrodt, Agnieszka Kowalczyk and Krzysztof Kowalczyk

Polymers 2021, 13(20), 3561; https://doi.org/10.3390/polym13203561 - 15 Oct 2021

Cited by 8 | Viewed by 1638

Abstract

Thermally curable pressure-sensitive structural adhesives tapes (SATs) were compounded using a solid epoxy resin and multifunctional acrylic telomer solutions (MATs) prepared by a thermally initiated telomerization process in an epoxy diluent containing two kinds of telogens (CBr₄ or CBrCl₃). Dynamic [...] Read more.

Thermally curable pressure-sensitive structural adhesives tapes (SATs) were compounded using a solid epoxy resin and multifunctional acrylic telomer solutions (MATs) prepared by a thermally initiated telomerization process in an epoxy diluent containing two kinds of telogens (CBr₄ or CBrCl₃). Dynamic viscosity, K-value, and volatile mater content in MATs (i.e., MAT-T with CBr₄, MAT-B with CBrCl₃) were investigated in relation to telogen type and content. The influence of MATs on the self-adhesive features and curing behavior of UV-crosslinked tapes as well as on the shear strength of thermally cured aluminum–SAT–aluminum joints was investigated as well. Increasing the telogen dose (from 5 to 15 wt. parts) caused significant improvement in the adhesion (+315% and +184%), tack (+147% and +298%), and cohesion (+414% and +1716%) of SATs based on MAT-T and MAT-B, respectively. Additionally, MATs with high telogen content (especially the MAT-T-type) improved the resistance of cured joints to aviation fuel, humidity, and elevated temperature. The highest overlap shear strength values were registered for SATs based on MATs containing 7.5 wt. parts of CBr₄ (16.7 MPa) or 10 wt. parts of CBrCl₃ (15.3 MPa). Full article

(This article belongs to the Special Issue Epoxy Resin and Epoxy Resin Based Polymer Materials)

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13 pages, 2934 KiB

Open AccessArticle

Influence of Ramped Compression on the Dielectric Behavior of the High-Voltage Epoxy Composites

by Muhammad Bilal Iqbal, Abraiz Khattak, Asghar Ali, M. Hassan Raza, Nasim Ullah, Ahmad Aziz Alahmadi and Adam Khan

Polymers 2021, 13(18), 3150; https://doi.org/10.3390/polym13183150 - 17 Sep 2021

Cited by 2 | Viewed by 1532

Abstract

The emergence of micro and nano-based inorganic oxide fillers with optimal filler-loadings further enhances the required insulation characteristics of neat epoxy. During manufacturing and service application, insulators and dielectrics face mechanical stresses which may alter their basic characteristics. Keeping this in mind, the [...] Read more.

The emergence of micro and nano-based inorganic oxide fillers with optimal filler-loadings further enhances the required insulation characteristics of neat epoxy. During manufacturing and service application, insulators and dielectrics face mechanical stresses which may alter their basic characteristics. Keeping this in mind, the facts’ influence of mechanical stresses and fillers on dielectric properties of polymeric insulators of two epoxy/silica composites were fabricated and thoroughly analyzed for dielectric characteristics under ramped mechanical compressions relative to the unfilled sample. Before compression, epoxy nanocomposites exhibited responses having an average dielectric constant of 7.68 with an average dissipation factor of 0.18. After each compression, dielectric properties of all samples were analyzed. The dissipation factor and the dielectric constant trends of each sample are plotted against a suitable frequency range. It was observed that after the successive compressions up to 25 MPa, the dielectric properties of epoxy micro-silica composites were highly affected, having an average final dielectric constant of 9.65 times that of the uncompressed sample and a dissipation factor of 2.2 times that of the uncompressed sample, and these were recorded. Full article

(This article belongs to the Special Issue Epoxy Resin and Epoxy Resin Based Polymer Materials)

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