Polymers

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14 pages, 2302 KiB

Open AccessArticle

Effect of Immersion in Water or Alkali Solution on the Structures and Properties of Epoxy Resin

by Bin Wang, Dihui Li, Guijun Xian and Chenggao Li

Polymers 2021, 13(12), 1902; https://doi.org/10.3390/polym13121902 - 08 Jun 2021

Cited by 26 | Viewed by 3264

The durability of fiber-reinforced polymer (FRP) composites is significantly dependent on the structures and properties of the resin matrix. In the present paper, the effects of physical or chemical interactions between the molecular chain of the epoxy resin matrix and water molecules or [...] Read more.

The durability of fiber-reinforced polymer (FRP) composites is significantly dependent on the structures and properties of the resin matrix. In the present paper, the effects of physical or chemical interactions between the molecular chain of the epoxy resin matrix and water molecules or alkaline groups on the water absorption, mechanical structures, and microstructures of epoxy resin samples were studied experimentally. The results showed that the water uptake curves of the epoxy resin immersed in water and an alkali solution over time presented a three-stage variation. At different immersion stages, the water uptake behavior of the resin showed unique characteristics owing to the coupling effects of the solution concentration gradient diffusion, molecular hydrolysis reaction, and molecular segment movement. In comparison with the water immersion, the alkali solution environment promoted the hydrolysis reaction of the epoxy resin molecular chain. After the immersion in water or the alkali solution for one month, the water uptake of the resin was close to saturate, and the viscoelasticity was observed to decrease significantly. The micropore and free volume space on the surface and in the interior of the resin gradually increased, while the original large-scale free volume space decreased. The tensile strength decreased to the lowest point after the immersion in water and the alkali solution for one month, and the decrease percentages at 20 °C and 60 °C water or 60 °C alkali solution were 24%, 28%, and 22%, respectively. Afterward, the tensile strength recovered with the further extension of immersion time. In addition, it can be found that the effect of the alkali solution and water on the tensile strength of the epoxy resin was basically the same. Full article

(This article belongs to the Special Issue Epoxy Composites: Processes and Applications II)

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15 pages, 2352 KiB

Open AccessArticle

Kinetic Analysis of the Curing Process of Biobased Epoxy Resin from Epoxidized Linseed Oil by Dynamic Differential Scanning Calorimetry

by Diego Lascano, Alejandro Lerma-Canto, Vicent Fombuena, Rafael Balart, Nestor Montanes and Luis Quiles-Carrillo

Polymers 2021, 13(8), 1279; https://doi.org/10.3390/polym13081279 - 14 Apr 2021

Cited by 14 | Viewed by 2548

Abstract

The curing process of epoxy resin based on epoxidized linseed oil (ELO) is studied using dynamic differential scanning calorimetry (DSC) in order to determine the kinetic triplet (E_a,

f (α)

and A) at different heating rates. The [...] Read more.

The curing process of epoxy resin based on epoxidized linseed oil (ELO) is studied using dynamic differential scanning calorimetry (DSC) in order to determine the kinetic triplet (E_a,

f (α)

and A) at different heating rates. The apparent activation energy, E_a, has been calculated by several differential and integral isoconversional methods, namely Kissinger, Friedman, Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS) and Starink. All methods provide similar values of E_a (between 66 and 69 kJ/mol), and this shows independence versus the heating rate used. The epoxy resins crosslinking is characterized by a multi-step process. However, for the sake of the simplicity and to facilitate the understanding of the influence of the oxirane location on the curing kinetic, this can be assimilated to a single-step process. The reaction model has a high proportion of autocatalytic process, fulfilling that α_M is between 0 and α_p and α_M <

α_{p}^{\infty}

. Using as reference the model proposed by Šesták–Berggren, by obtaining two parameters (n and m) it is possible to obtain, on the one hand, the kinetic parameters and, on the other hand, a graphical comparison of the degree of conversion, α, versus temperature (T) at different heating rates with the average n and m values of this model. The good accuracy of the proposed model with regard to the actual values obtained by DSC gives consistency to the obtained parameters, thus suggesting the crosslinking of the ELO-based epoxy has apparent activation energies similar to other petroleum-derived epoxy resins. Full article

(This article belongs to the Special Issue Epoxy Composites: Processes and Applications II)

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13 pages, 2303 KiB

Open AccessArticle

Characterization of Hybrid Oil Palm Empty Fruit Bunch/Woven Kenaf Fabric-Reinforced Epoxy Composites

by Farah Hanan, Mohammad Jawaid, Md Tahir Paridah and Jesuarockiam Naveen

Polymers 2020, 12(9), 2052; https://doi.org/10.3390/polym12092052 - 09 Sep 2020

Cited by 16 | Viewed by 2951

Abstract

In this research, the physical, mechanical and morphological properties of oil palm empty fruit bunch (EFB) mat/woven kenaf fabric-reinforced epoxy composites have been investigated. The oil palm EFB/woven kenaf fabrics were varied, with weight ratios of 50/0 (T1), 35/15 (T2), 25/25 (T3), 15/35 [...] Read more.

In this research, the physical, mechanical and morphological properties of oil palm empty fruit bunch (EFB) mat/woven kenaf fabric-reinforced epoxy composites have been investigated. The oil palm EFB/woven kenaf fabrics were varied, with weight ratios of 50/0 (T1), 35/15 (T2), 25/25 (T3), 15/35 (T4) and 0/50 (T5). The composites were fabricated using a simple hand lay-up technique followed by hot pressing. The result obtained shows that an increase in kenaf fiber content exhibited higher tensile and flexural properties. On the other hand, the opposite trend was observed in the impact strength of hybrid composites, where an increase in kenaf fiber content reduced the impact strength. This can be corroborated with the physical properties analysis, where a higher void content, water absorption and thickness swelling were observed for pure oil palm EFB (T1) composites compared to other samples. The scanning electron microscopy analysis results clearly show the different failure modes of the tensile fractured samples. Statistical analysis was performed using one-way ANOVA and shows significant differences between the obtained results. Full article

(This article belongs to the Special Issue Epoxy Composites: Processes and Applications)

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23 pages, 7317 KiB

Open AccessArticle

Synergistic Effect of Multi-Walled Carbon Nanotubes and Graphene Nanoplatelets on the Monotonic and Fatigue Properties of Uncracked and Cracked Epoxy Composites

by Yi-Ming Jen, Jui-Cheng Huang and Kun-Yang Zheng

Polymers 2020, 12(9), 1895; https://doi.org/10.3390/polym12091895 - 23 Aug 2020

Cited by 27 | Viewed by 3171

Abstract

The fatigue properties of the polymer nanocomposites reinforced with a hybrid nano-filler system have seldom studied before. Accordingly, epoxy nanocomposites with various multi-walled carbon nanotube (MWCNT)/graphene nanoplatelet (GNP) filler ratios were prepared to study comprehensively the synergistic effect of the hybrid nano-fillers on [...] Read more.

The fatigue properties of the polymer nanocomposites reinforced with a hybrid nano-filler system have seldom studied before. Accordingly, epoxy nanocomposites with various multi-walled carbon nanotube (MWCNT)/graphene nanoplatelet (GNP) filler ratios were prepared to study comprehensively the synergistic effect of the hybrid nano-fillers on the monotonic and cyclic mechanical properties of the nanocomposites. The quasi-statically tensile properties and fatigue-life curves were experimentally determined using uncracked bulk specimens. Additionally, pre-cracked specimens were utilized to study the fracture toughness and fatigue crack growth rate of the nanocomposites. A synergistic index based on the properties of the nanocomposites with individual types of filler was proposed to evaluate the synergistic effect of two employed nano-fillers on the studied properties. The index was verified to be a highly discriminatory tool to evaluate the synergistic effect of hybrid nano-fillers on the studied mechanical properties. The experimental results show that the composites with a MWCNT:GNP ratio of 1:9 have the higher monotonic and fatigue properties than those with other filler ratios. Adding appropriate amount of CNTs can prevent the agglomeration of GNPs. The flexible CNTs bridge adjacent GNPs to constitute a favorable network for load transfer. Moreover, there is a linear relationship between the static and fatigue strengths of the studied nanocomposites. Integrated analysis of experimental data and a fracture surface study reveals that the dispersion of nano-fillers influences the mechanical properties significantly. The crack deflection effect due to the path bifurcation caused by encountering the filler cluster and the filler bridging effect are the main reinforcement mechanism of the studied properties. Full article

(This article belongs to the Special Issue Epoxy Composites: Processes and Applications)

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16 pages, 1355 KiB

Open AccessArticle

An Improved Physical-Stochastic Model for Simulating Electrical Tree Propagation in Solid Polymeric Dielectrics

by Johnatan M. Rodríguez-Serna, Ricardo Albarracín-Sánchez and Isabel Carrillo

Polymers 2020, 12(8), 1768; https://doi.org/10.3390/polym12081768 - 07 Aug 2020

Cited by 10 | Viewed by 2470

Abstract

The dielectric breakdown of solid polymeric materials is due to the inception and propagation of electrical trees inside them. The remaining useful life of the solid dielectrics could be determined using propagation simulations correlated with non-intrusive measurements such as partial discharges (PD). This [...] Read more.

The dielectric breakdown of solid polymeric materials is due to the inception and propagation of electrical trees inside them. The remaining useful life of the solid dielectrics could be determined using propagation simulations correlated with non-intrusive measurements such as partial discharges (PD). This paper presents a brief review of the different models for simulating electrical tree propagation in solid dielectrics. A novel improved physical-stochastic model is proposed, which allows quantitatively and qualitatively analyzing the electrical tree propagation process in polymeric dielectrics. Simulation results exhibit good agreement with measurements presented in the literature. It is concluded that the model allows adequately predicting the tree propagation behavior and additional experimental analyses are required in order to improve the model accuracy. Full article

(This article belongs to the Special Issue Epoxy Composites: Processes and Applications)

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14 pages, 6822 KiB

Open AccessArticle

Using 3-Isocyanatopropyltrimethoxysilane to Decorate Graphene Oxide with Nano-Titanium Dioxide for Enhancing the Anti-Corrosion Properties of Epoxy Coating

by Weihang Li, Bojun Song, Shirui Zhang, Fan Zhang, Chang Liu, Nan Zhang, Huiling Yao and Yuanchang Shi

Polymers 2020, 12(4), 837; https://doi.org/10.3390/polym12040837 - 06 Apr 2020

Cited by 35 | Viewed by 3628

Abstract

In this paper, the graphene oxide loaded with nano titanium dioxide (TiO₂–GO) was synthesized through 3-isocyanatopropyltrimethoxysilane (IPTMS) and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and [...] Read more.

In this paper, the graphene oxide loaded with nano titanium dioxide (TiO₂–GO) was synthesized through 3-isocyanatopropyltrimethoxysilane (IPTMS) and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and dispersion test. The results illustrated our modification was successful and TiO₂–GO was transferred from hydrophilic to hydrophobic. That greatly enhanced the dispersity of TiO₂–GO in epoxy through the observation of the coating morphology test. Moreover, the impact of TiO₂–GO on anti-corrosion property in epoxy was investigated by Electrochemical Impedance Spectroscopy (EIS). Comparing to pristine particles including GO and TiO₂, TiO₂–GO could more significantly improve the resistance of corrosion with the help of IPTMS. Furthermore, the anti-corrosion mechanism of TiO₂–GO in epoxy was tentatively proposed and discussed. Full article

(This article belongs to the Special Issue Epoxy Composites: Processes and Applications)

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14 pages, 1933 KiB

Open AccessArticle

The Effect of Ageing in Water Solution Containing Iron Sulfate on the Mechanical Properties of Epoxy Adhesives

by Anna Rudawska and Valentina Brunella

Polymers 2020, 12(1), 218; https://doi.org/10.3390/polym12010218 - 15 Jan 2020

Cited by 12 | Viewed by 2490

Abstract

This study investigates the effect of operating factors such as seasoning in water solution containing iron (II) sulfate—FeSO₄ (5 different water solution variants were tested) on the mechanical properties of an adhesive compound made of epoxy resin and amine curing agent, in [...] Read more.

This study investigates the effect of operating factors such as seasoning in water solution containing iron (II) sulfate—FeSO₄ (5 different water solution variants were tested) on the mechanical properties of an adhesive compound made of epoxy resin and amine curing agent, in a ratio of 100 g resin to 12 g curing agent. Strength tests of cured adhesive compound samples were performed on the Zwick/Roell Z150 testing machine in compliance with the EN ISO 604 standard. During the tests, compression modulus, compressive strength and compressive strain were measured. Obtained results served as a basis for analyzing the effect of a water environment containing iron sulfate on a given adhesive compound. It has been found that too high iron sulfate content in water has a negative effect on the mechanical properties of adhesive compound samples. Full article

(This article belongs to the Special Issue Epoxy Composites: Processes and Applications)

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16 pages, 4602 KiB

Open AccessArticle

Novel Phosphorus-Nitrogen-Containing Ionic Liquid Modified Metal-Organic Framework as an Effective Flame Retardant for Epoxy Resin

by Rong Huang, Xiuyan Guo, Shiyue Ma, Jixing Xie, Jianzhong Xu and Jing Ma

Polymers 2020, 12(1), 108; https://doi.org/10.3390/polym12010108 - 05 Jan 2020

Cited by 51 | Viewed by 5922

Abstract

Metal-organic frameworks (MOFs) have shown great potential in flame retardant applications; however, strategies for fully exploiting the advantages of MOFs in order to further enhance the flame retardant performance are still in high demand. Herein, a novel MOF composite was designed through the [...] Read more.

Metal-organic frameworks (MOFs) have shown great potential in flame retardant applications; however, strategies for fully exploiting the advantages of MOFs in order to further enhance the flame retardant performance are still in high demand. Herein, a novel MOF composite was designed through the generated cooperative role of MOF (NH₂-MIL-101(Al)) and a phosphorus-nitrogen-containing ionic liquid ([DPP-NC₃bim][PMO]). The ionic liquid (IL) was composed of imidazole cation modified with diphenylphosphinic group (DPP) and phosphomolybdic acid (PMoA) anions, which can trap the degrading polymer radicals and reduce the smoke emission. The MOF acts as a porous host and can avoid the agglomeration of ionic liquid. Meanwhile, the -NH₂ groups of NH₂-MIL-101(Al) can increase the compatibility with epoxy resin (EP). The framework is expected to act as an efficient insulating barrier to suppress the flame spread. It was demonstrated that the MOF composite (IL@NH₂-MIL-101(Al)) is able to effectively improve the fire safety of EP at low additions (3 wt. %). The LOI value of EP/IL@NH₂-MIL-101(Al) increased to 29.8%. The cone calorimeter results showed a decreased heat release rate (51.2%), smoke production rate (37.8%), and CO release rate (44.8%) of EP/IL@NH₂-MIL-101(Al) with respect to those of neat EP. This strategy can be extended to design other advanced materials for flame retardant. Full article

(This article belongs to the Special Issue Epoxy Composites: Processes and Applications)

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12 pages, 5991 KiB

Open AccessArticle

Preparation of Fly Ash/Epoxy Composites and Its Effects on Mechanical Properties

by Jeesoo Sim, Youngjeong Kang, Byung Joo Kim, Yong Ho Park and Young Cheol Lee

Polymers 2020, 12(1), 79; https://doi.org/10.3390/polym12010079 - 02 Jan 2020

Cited by 73 | Viewed by 4889

Abstract

In this research, a fly ash/epoxy composite was fabricated using fly ash filler classified as industrial waste. The behavior of its mechanical properties was investigated by changing the volume of fly ash to 10, 30 and 50 vol.%. To determine the influence of [...] Read more.

In this research, a fly ash/epoxy composite was fabricated using fly ash filler classified as industrial waste. The behavior of its mechanical properties was investigated by changing the volume of fly ash to 10, 30 and 50 vol.%. To determine the influence of particle size on the mechanical properties, we used two different sizes of the fly ash, which were separated by sieving to less than 90 μm and 53 μm. To optimize fabrication conditions, the viscosity of the fly ash/epoxy slurry was measured at various temperatures with different fly ash volume fractions. In terms of mechanical properties, tensile strength increased as the amount of fly ash increased, up to a critical point. On the other hand, the compression strength of the composite increased continuously as the amount of fly ash increased. Finally, the fracture surfaces were characterized and correlated with the mechanical properties. Full article

(This article belongs to the Special Issue Epoxy Composites: Processes and Applications)

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15 pages, 13359 KiB

Open AccessArticle

Insight into Hyper-Branched Aluminum Phosphonate in Combination with Multiple Phosphorus Synergies for Fire-Safe Epoxy Resin Composites

by Yao Yuan, Bin Yu, Yongqian Shi, Long Mao, Jianda Xie, Haifeng Pan, Yuejun Liu and Wei Wang

Polymers 2020, 12(1), 64; https://doi.org/10.3390/polym12010064 - 01 Jan 2020

Cited by 10 | Viewed by 2723

Abstract

Epoxy resin (EP) has widespread applications in thermosetting materials with great versatility and desirable properties such as high electrical resistivity and satisfactory mechanical properties. At present, 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) is widely applied to EP matrix for high flame resistance. Nevertheless, EP/DOPO composites acquire highly [...] Read more.

Epoxy resin (EP) has widespread applications in thermosetting materials with great versatility and desirable properties such as high electrical resistivity and satisfactory mechanical properties. At present, 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) is widely applied to EP matrix for high flame resistance. Nevertheless, EP/DOPO composites acquire highly toxic decomposition products and smoke particles produced during combustion due to the gaseous fire-inhibition mechanism, which will be a major problem. To address this concern, an effective hyper-branched aluminum phosphonate (AHPP) was rationally designed and then coupled with DOPO into EP matrix to fabricate the fire-safe epoxy resin composites. On the basis of the results, significant increment in limiting oxygen index value (an achievement of 32% from 23.5% for pristine EP) and reduction in peak heat release rate and total heat release (59.4% and 45.6%) with the DOPO/AHPP ratio of 2:1 were recorded. During the cone calorimeter test, both the smoke production and total CO yield of EP-4 composite with the DOPO/AHPP ratio of 1:2 were dramatically decreased by 42.7% and 53.6%, which was mainly associated with the excellent catalytic carbonization of AHPP submicro-particles for EP composite. Future applications of submicro-scaled flame-retardant with various phosphorus oxidation states will have good prospects for development. Full article

(This article belongs to the Special Issue Epoxy Composites: Processes and Applications)

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18 pages, 7357 KiB

Open AccessArticle

The Effect of Bi-Functionalized MMT on Morphology, Thermal Stability, Dynamic Mechanical, and Tensile Properties of Epoxy/Organoclay Nanocomposites

by Siew Sand Chee and Mohammad Jawaid

Polymers 2019, 11(12), 2012; https://doi.org/10.3390/polym11122012 - 04 Dec 2019

Cited by 39 | Viewed by 4302

Abstract

In this work, the optimum filler loading to prepare epoxy/organoclay nanocomposites by the in-situ polymerization method was studied. Bi-functionalized montmorillonite at different filler loading (0.5, 1.0, 2.0, 4.0 wt %) was dispersed in epoxy resin by using a high shear speed homogenizer. The [...] Read more.

In this work, the optimum filler loading to prepare epoxy/organoclay nanocomposites by the in-situ polymerization method was studied. Bi-functionalized montmorillonite at different filler loading (0.5, 1.0, 2.0, 4.0 wt %) was dispersed in epoxy resin by using a high shear speed homogenizer. The effect on morphology, thermal, dynamic mechanical, and tensile properties of the epoxy/organoclay nanocomposites were studied in this work. Wide-angle X-ray scattering (WAXS) and field emission scanning electron microscope (FESEM) studies revealed that possible intercalated structures were obtained in epoxy/organoclay nanocomposites. Thermogravimetric analysis (TGA) shows that epoxy/organoclay nanocomposites exhibit higher thermal stability at the maximum and final decomposition temperature, as well as higher char content, compared to pristine epoxy. The dynamic mechanical analysis (DMA) indicate that storage modulus (E′), loss modulus (E″), cross-link density and glass transition temperature (T_g) of the nanocomposites were improved with organoclay loading up to 1 wt %. Beyond this loading limit, the deterioration of properties was observed. A similar trend was also observed on tensile strength and modulus. We concluded from this study that organoclay loading up to 1 wt % is suitable for further study to fabricate hybrid nanocomposites for various applications. Full article

(This article belongs to the Special Issue Epoxy Composites: Processes and Applications)

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