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Article

Epoxy-Functionalized POSS and Glass Fiber for Improving Thermal and Mechanical Properties of Epoxy Resins

by
Jianliang Jiang
1,2,†,
Jingbo Shen
1,†,
Xiao Yang
1,
Dongqi Zhao
3 and
Yakai Feng
1,4,5,*
1
School of Chemical Engineering and Technology, Tianjin University, Tianjin 300350, China
2
China (Yangzhou) Material Handling Tech-Engineering Ltd., Yangzhou 225009, China
3
Tianjin Joaboa Technology Co., Ltd., No. 24 Road, Tianjin 301609, China
4
Frontiers Science Center for Synthetic Biology, Tianjin University, Weijin Road 92, Tianjin 300072, China
5
Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Appl. Sci. 2023, 13(4), 2461; https://doi.org/10.3390/app13042461
Submission received: 21 December 2022 / Revised: 3 February 2023 / Accepted: 11 February 2023 / Published: 14 February 2023
(This article belongs to the Section Materials Science and Engineering)
Browse Figures
Versions Notes

Abstract

:
To improve the thermal and mechanical properties of epoxy resins, epoxy-functionalized POSS (E-POSS) and glass fiber (GF) were used to reinforce epoxy resin (E51) composites. The tensile, thermo-mechanical, fractured, and thermal tests were carried out to characterize these hybrid materials. The results show that E-POSS and GF could significantly improve the mechanical and thermal properties of epoxy resins due to high crosslink density of resin matrix and synergistic interaction between the epoxy resin, E-POSS, and GF. Compared with the pure E51 resin, the tensile strength of the E51 + E-POSS (10%) + GF (16%) sample increased by 257.6%, and the thermal decomposition temperature (Td5%) of the E51 + E-POSS (10%) + GF (16%) sample increased by 32 °C to 378 °C.

1. Introduction

Epoxy resins play an important role as thermosetting materials because of their excellent mechanical properties, low price, good adhesion, and chemical stability. They have been widely used in many fields, such as aviation, aerospace, mechanics, electronics, transportation, and so on [1,2,3,4,5]. However, the epoxy resin is limited in many high-performance application fields, due to their fracture brittleness, poor fatigue resistance, and low thermal deformation temperature [6,7,8].
Many efforts have been made to improve the properties of epoxy resins. Generally, researchers focus on optimization of curing agents and fillers such as carbon fiber [9], glass fiber (GF) [10], nanoparticles [11], and organic–inorganic hybrid materials [12]. Braga et al. [13] investigated and compared mechanical and thermal properties of raw jute and glass-fiber-reinforced epoxy hybrid composites, and found that the addition of jute fiber and glass fiber in the epoxy resin increased the density, the impact energy, the tensile strength, and the flexural strength, but decreased the mass loss in the function of temperature and water absorption. Naresh et al. improved the tensile strength and modulus of the epoxy resin by adding glass fiber and carbon fiber [14]. Some researchers investigated the epoxy resin/silica hybrid materials and found that their mechanical properties and thermal stability were improved because of the high modulus and large surface areas of nanoparticles [15,16]. Especially, the organic–inorganic hybrid materials could take full advantage of both inorganic materials (rigidity and high stability) and organic polymers (flexibility, ductility, and processability) [17]. Therefore, it has become an important approach to preparing high-performance and functional materials [18].
Among organic–inorganic hybrid materials, polyhedral oligomeric silsesquioxane (POSS) is one of most widely studied materials for thermoplastic and thermoset composites [19]. The structure of epoxy-functionalized POSS (E-POSS) is shown in Figure 1. The functional POSS is a class of intramolecular organic–inorganic hybrid material with a three-dimensional cage-like network structure, which contains a thermally stable inorganic core composed of Si-O bond, while the outer side of the cage is surrounded by substituent R groups (R = hydrogen, alkyl, epoxy group, arylene group, or other organic functional derivatives) [20]. The diameter of the cubic cage core of POSS is about 0.53 nm. POSS possesses many excellent properties, such as nano-size effects, excellent thermal stability, and molecular designable ability, because of its special micro-hybrid structure. Thus, functional POSS offers opportunities to modify polymers on the molecular level and has potential applications in compatibilizing organic and inorganic materials. Many researchers studied POSS/epoxy resin composites and found that thermal and mechanical properties of epoxy resins could be improved by incorporating POSS into epoxy resins. Hou et al. [21] investigated the MAP-POSS/epoxy resins’ nanocomposites, and the dynamic mechanics showed that the glass transition temperature (Tg) had a slight increase when the MAP-POSS content was between 4 wt% and 8 wt%. The Tg of an 8 wt% MAP-POSS/epoxy resin sample was 175.6 °C, which was 6.1 °C higher than the pure epoxy resin. Xin et al. [22] introduced EP-POSS and SiO2 into epoxy resins; their results showed that the impact strength, flexural strength, and modulus of the SiO2/EP-POSS/epoxy composites increased by around 57.9, 14.1, and 44.0%, compared with the pure epoxy resin. POSS (which contains a partial T8 cage with one corner Si missing, leaving three Si-OH groups) with free Si-OH groups can be grafted on the epoxy resin’s chain to improve flame retardancy by forming a stable char layer to protect decomposition [23]. Dhanapal et al. [24] found that the amine-functionalized POSS could act as a coupling agent for epoxy resin/GF-reinforced nanocomposites. Han et al. [25] synthesized the biphenyl diol formaldehyde resin as a curing agent and found that POSS with glycidyloxypropyl groups can improve the mechanical and thermal properties of the composite.
It has been well established that the mixed species could exert a significant influence on the mechanical and thermal properties of epoxy resins. To the best of our knowledge, little attention has been focused on the ternary composite of E51, POSS, and GF (E51 + E-POSS + GF). In this work, both E-POSS and GF were used to improve the properties of polyethylenepolyamine (PEPA)-cured epoxy resins. The influence of E-POSS and GF on mechanical properties and thermal stability was investigated in detail.

2. Experiment

2.1. Materials

Octavinyl-substituted POSS (Ov-POSS), m-chloroperoxybenzoic acid (m-CPBA) and dichloromethane (CH2Cl2), glass fiber (the unsized short fiber with a length of about 1~2 mm), and bisphenol A epoxy resins (E51, epoxy value = 0.51) were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. Polyethylenepolyamine (PEPA) was purchased from Shanghai Macklin Biochemical Co., Ltd. (Shanghai, China). Other materials were purchased from Shanghai Energy Chemical Co., Ltd. (Shanghai, China).

2.2. Synthesis of E-POSS

E-POSS was synthesized with reference to literature methodology [26]. Typically, 1.0 g of Ov-POSS and 2.3 g of m-CPBA were dissolved in 15 mL of CH2Cl2 in a 25 mL flask equipped with a magnetic stirrer and a reflux condenser. The reaction was stopped after being refluxed for 40 h, and the flask was cooled by an ice water bath leading to further precipitation of side product (m-chlorobenzoic acid, m-CBA), which was filtered out with filter paper. The filtrate (CH2Cl2 solution of E-POSS) was washed with 0.2 M phosphate buffer (pH = 7.5), and then separated to obtain the filtrate using a separation funnel and dried over anhydrous Na2SO4. Finally, CH2Cl2 was removed by rotary evaporation. The E-POSS was recrystallized from methanol. The obtained E-POSS must be placed in a dryer for storage, because the epoxy group activity of E-POSS is highly reactive and side reactions easily occur.

2.3. E51 Curing

The synthesis route is shown in Figure 2A. Typically, 10 g of E51 and a certain amount of PEPA were added into a beaker, and then stirred at a speed of 600 rpm for 1 h with a mechanical mixer at room temperature (20~25 °C). Next, the blend was dumped into the preheated mold at 80 °C for 12 h. Finally, the cured E51 resin was obtained. The mixing ratios (mass ratios) of E51 and PEPA were 1:1, 2:1, 3:1, and 4:1, respectively.

2.4. Preparation of the E51 + E-POSS Composite

The synthesis route is shown in Figure 2B. In a typical synthesis of E51 + E-POSS composite, the blend, consisting of 10 g of E51 and a certain amount of E-POSS, was stirred at room temperature, and then 5 g of PEPA was added to the beaker. Next, the blend was stirred for 1 h at room temperature. The above blend was dumped into the preheated mold at 80 °C for 12 h. Finally, the cured E51 + E-POSS composite was obtained. The mass percentages of E-POSS in E51 + E-POSS composite were 5 wt%, 10 wt%, and 15 wt%, respectively.

2.5. Preparation of the E51 + GF Composite

Typically, the blend consisting of 10 g of E51 and a certain amount of GF was stirred in a beaker at room temperature, and then 5 g of PEPA was added to the beaker. Next, the blend was stirred for 1 h at room temperature. The above blend was dumped into the preheated mold at 80 °C for 12 h. Finally, the cured E51 + GF composite was obtained. The mass percentages of GF in the E51 + GF composite were 8 wt%, 16 wt% and 24 wt%, respectively.

2.6. Preparation of the E51 + E-POSS + GF Composite

In a typical synthesis of the E51 + E-POSS+GF composite, 10 g of E51, a certain amount of E-POSS, and GF were added into a beaker, and then 5 g of PEPA was added to the above beaker, and the blend was stirred for 1 h at room temperature. The above blend was dumped into a preheated dog-bone-shaped mold at 80 °C for 12 h. Finally, the cured E51 + E-POSS+GF composite was obtained. In this case, the corresponding contents of E-POSS and GF were 10 wt% and 16 wt%, respectively.

2.7. Measurements

ATR-FTIR spectra were recorded on a VERTEX70 spectrometer. Samples were characterized by signals averaging 32 scans at a resolution of 4 cm−1 in the wavenumber range of 500~4000 cm−1. Dynamic mechanical analyses (DMAs) were performed on a DMA-1 analyzer (Mettler Toledo Corp., Switzerland) using a controlled single cantilever 10 bending mode (1 Hz, 15 mm amplitude) at a heating rate of 3 °C/min from 25 °C to 200 °C. The loss factor (tanδ) represents the ratio of loss modulus and storage modulus of materials. The tensile properties of the samples were tested using a GT-AI-7000-S high-temperature stretching machine with a speed of 25 mm/min at room temperature. Ts denotes the tensile strength, and the tensile modulus was calculated from the slope at the initial stage of the tensile curve. The sample with a dog-bone shape had a length of 180 mm, a thickness of 3 mm, a maximum width of 25 mm, and a minimum width of 15 mm. The average value of five individual samples was recorded for each sample. The thermogravimetric analysis (TGA) curves were achieved on a TGA8000 instrument (PerkinElmer), and the 10 mg sample was placed in a platinum crucible and heated from 50 to 800 °C at a heating rate of 20 °C/min under a constant nitrogen flow rate. Td5% denotes the temperature at which the initial mass loss of the sample is 5%. Scanning electron microscopy (SEM) of different samples was carried out using a SU8010 (HITACHI). 1H NMR spectra were recorded at 27 °C using (JEOL) a JNM-ECA600 spectrometer (600 MHz for 1H). Chemical shifts of 1H NMR were referenced to tetramethylsilane (δ = 0 ppm), and deuterated chloroform was used as the solvent.

3. Results and Discussion

3.1. Characterization of E-POSS

The active carbon–carbon double bonds of Ov-POSS cannot participate in the curing reaction of E51, so they were converted into epoxy groups (E-POSS) by oxidation method with m-CPBA. E-POSS can act as a crosslinker to increase the crosslinking degree and mechanical properties, owing to their epoxy groups and the inorganic core of POSS. The FTIR spectrum of E-POSS is shown in Figure 3. The absorption band at around 910 cm−1 was assigned to the epoxy group stretching vibration, the absorption bands at around 2875 cm−1 and 2940 cm−1 were assigned to C-H stretching vibration, the absorption bands at around 1205 cm−1 were assigned to the antisymmetric bridge C-O-C stretching, and the absorption band centered at around 1120 cm−1 was assigned to the Si-O-Si stretching vibration [27,28]. The vibrational absorption band of the carbon–carbon double bond of Ov-POSS completely disappears in the FTIR spectrum of the obtained product, indicating that C=C groups had been oxidized to epoxy groups.
As shown in Figure 4, the 1H NMR spectrum of E-POSS also showed that the carbon–carbon double bonds of Ov-POSS converted into epoxy groups as the absorption peaks of three protons of the epoxy group appeared at 2.26 ppm, 2.76 ppm, and 2.98 ppm, respectively, while the protons of the carbon–carbon double bond disappeared (the absorption peaks of three protons of the ethylene group of Ov-POSS were located at 5.93 ppm, 6.05 ppm, and 6.12 ppm [29]). The results of 1H NMR and FTIR were consistent, indicating that all the C=C bonds of Ov-POSS had been converted to epoxy groups by the oxidation with m-CPBA. Therefore, E-POSS can be successfully synthesized by this method.

3.2. Tensile Strength

Figure 5A shows the tensile strengths of E51/PEPA resins with different mixing ratios of E51 and PEPA. The E51/PEPA (2:1) resin achieved the highest tensile strength compared with E51/PEPA (1:1), E51/PEPA (3:1), and E51/PEPA (4:1) resins. The result implies that the proper mixing ratio of E51/PEPA could bring forth the best curing effect. Although the E51/PEPA (2:1) resin achieved the highest tensile strength, it is still limited in many high-performance application fields. E-POSS and GF were employed to improve the tensile strength of epoxy resins [24,25]. The influence of E-POSS and GF on tensile strength of epoxy resins was tested and the result is shown in Figure 5B and Table 1. The tensile strength of E51 resin is illustrated as the black column in Figure 5B, and the tensile strength of E51 resin was 60.1 MPa. The tensile strength of E51 + E-POSS composite is presented as the green column in Figure 5B, showing that the tensile strength increased with the increasing E-POSS content from 5 wt% to 10 wt%. However, an excessive amount of E-POSS (15 wt%) resulted in a slightly reduced tensile strength. The tensile strength of E51 + E-POSS composite with 10 wt% E-POSS content achieved the maximum value (92.5 MPa). Compared with the E51 resin, the tensile strength of E51 + E-POSS composites with 5 wt%, 10 wt%, and 15 wt% E-POSS increased by 30.3, 53.9, and 45.8%, respectively. Epoxy groups of E-POSS and E51 can react with PEPA to form the cross-linking network; E-POSS contains multiple epoxy groups and a network with high cross-linking grid density is formed around inorganic nanofiller (POSS). These grids break preferentially and consume energy during the tensile process, which leads to the high tensile strength of the epoxy resin.
The blue column in Figure 5B shows the tensile strength of E51 + GF composite at different mixing ratios of E51/GF. With an increase in GF content (8 wt%~16 wt%), the tensile strength of E51 + GF composite became higher, while the tensile strength slightly decreased when the GF content was 24 wt%. The E51 + GF (16%) composite exhibited the highest tensile strength (186.7 MPa) compared with the E51 + GF (8%) and E51 + GF (24%) composites. The tensile strength of E51 + GF (16%) composite was increased by 210.6% compared with the E51 sample. The incorporation of GF could enhance the tensile strength due to the bridging mechanism. On the one hand, the addition of GF could scatter the extension of impact cracks and produce the fracture modes of multiple cracks. On the other hand, it could hinder the progress of the cracks in the direction of the cracks’ fracture modes. The ternary composite of E51 + E-POSS + GF was prepared by adding 10 wt% E-POSS and 16 wt% GF. The red column of Figure 5B shows the tensile strength of the ternary composite of E51 + E-POSS (10%) + GF (16%); it was obvious that the ternary composite exhibited the highest tensile strength among the E51, E51 + E-POSS, and E51 + GF composites. The tensile strength of the E51 + E-POSS (10%) + GF (16%) composite was 214.9 MPa (Table 1), increasing by around 257.6% compared with the E51 sample. The epoxy groups of E-POSS and E51 reacted with the amino groups of PEPA to form a three-dimensional cross-linking network, and a large number of polar groups such as hydroxyl and secondary amino groups (-NH) were formed around the cross-linking bonds. The hydroxyl polar groups were also produced on the surface of GF due to the hydrolysis of the chemical bonds of silica. These polar groups on the surface of the glass fiber and in the epoxy resin matrix could form strong hydrogen bonds, thus improving the compatibility of the epoxy resin matrix and glass fiber. It can be inferred that simultaneous introduction of E-POSS and GF into E51 resin may yield a synergistic effect on matrix modification for improving the tensile strength of the E51 + E-POSS (10%) + GF (16%) composite.

3.3. Thermo-Mechanical Properties

Dynamic mechanical analysis (DMA) was conducted to establish the influence of E-POSS and GF on the storage modulus (E) and glass transition temperature (Tg) of the cured epoxy resins. As shown in Figure 6A, the incorporation of E-POSS and GF led to the higher storage modulus of the obtained composites in comparison with the pure E51 sample, indicating that the crosslinking density of the E51 + E-POSS (10%), E51 + GF (16%), and E51 + E-POSS (10%)+GF (16%) samples may be higher. The E51 + E-POSS (10%) + GF (16%) sample showed the maximum storage modulus value. In other words, the E51 + E-POSS (10%) + GF (16%) sample exhibited a highest stiffness even in comparison with the E51 + E-POSS (10%), E51 + GF (16%), and E51 samples.
The curves of tanδ showed the viscoelastic transition of the cross-linked polymers, and further exhibited the structural information of the cured resins [29]. Generally, there is a one-to-one relationship between the glass transition temperature (Tg) and the tanδ peak temperature (Tp); Tp is often designated as Tg [30]. From the tanδ curves (Figure 6B), it can be found that the incorporation of E-POSS and GF led to a slight increase in Tg of the obtained samples in comparison with the pure E51 sample. It was illustrated that the Tg of E51 resin can be increased by adding a proper amount of E-POSS or GF. This is caused by the reactive epoxy group of E-POSS and the hydroxyl group of GF. The reactive group of E-POSS can directly participate in the curing reaction, forming a curing composite with the PEPA, and produce a higher cross-linking density structure. With the increase in the cross-linking density, the molecular chain segments between cross-linking bonds are bound more strongly, and the glass transition temperature of the epoxy resin composite will increase correspondingly. In addition, the test curve of all samples contained one simple tanδ peak, suggesting that the epoxy resin was homogeneous. According to DMA analysis, the higher the cross-linking density, the higher the Tg. These results were consistent with the results reported in the literature [31,32].

3.4. Thermal Stability

The thermal stability of the different composites was evaluated by TGA measurements. The TGA result of E-POSS-reinforced E51 is illustrated in Figure 7A, and the data are summarized in Table 2. It can be seen that the Td5% of E51 + E-POSS (10 wt%) was higher than that of the E51 sample, which indicates that the thermal stability of the E51 + E-POSS sample was improved by adding E-POSS into the epoxy resin, as the bond energy of the Si-O bond is high, and the high temperature stability of POSS is good. The dissociation energy of the Si-O bond (460 kJ/mol) was higher than that of the Si-C bond (318 kJ/mol), or the C-C bond (344 kJ/mol) or C-O bond (345 kJ/mol) [33,34]. A higher bond energy will lead to a higher thermal decomposition temperature. As the cube structure of E-POSS is mainly composed of Si-O bonds, the incorporation of E-POSS into E51 resin will increase the number of Si-O bonds in the composite. Only under higher temperature (higher energy) will an E51 + E-POSS (10%) sample be destroyed. It is worth noting that the residue of the E51 + E-POSS (10%) sample was higher than that of the E51 sample (Table 2). The results show that the incorporation of E-POSS into the E51 resin could reduce the rate of sample mass loss, leading to a higher residue at the same temperature. The TGA result of E-POSS reinforced with E51 is illustrated in Figure 7A. It can be seen that the Td5% value of E51 + E-POSS (E-POSS (10%)) was higher than that of the E51 sample, indicating that the incorporation of E-POSS into the epoxy resin could increase the thermostability of the obtained E51 + E-POSS hybrid because the E-POSS structure is mainly composed of Si-O bonds.
The TGA curves of the E51 + GF composite are presented in Figure 7B and the data are summarized in Table 2, which show that the initial decomposition temperature and residue were improved. The Td5% of the E51 + GF (16%) sample was higher than that of the E51 sample, and the residue of E51 + GF (16%) was also higher than that of the E51 sample. The incorporation of GF into E51 could improve the thermal decomposition temperature and reduce the rate of mass loss, resulting in a larger weight of residue under the same high-temperature conditions. The GF contributes to the increased thermostability and reduced mass loss rate, owing to its inorganic properties, because the softening point of common glass fiber is generally higher than 600 °C. The TGA curves of the ternary composite E51 + E-POSS (10%) + GF (16%) sample are shown in Figure 7C and the results are summarized in Table 2. The Td5% and residue of the E51 + E-POSS (10%) + GF (16%) sample were 378 °C and 21.2%, and increased remarkably by 42 °C and 18.8% compared with the E51 sample. In addition, the thermal stability of the ternary composite E51 + E-POSS (10%) + GF (16%) sample was better than that of the E51 + E-POSS (10%) and E51 + GF (16%) sample. Because the ternary composite of the E51 + E-POSS (10%) + GF (16%) sample contains a large number of stable Si-O bonds, inorganic GF can slow down the thermal decomposition temperature and increase the quality of residues. These results show that the synergistic effect between E-POS and GF was beneficial to improve the heat resistance of the epoxy resin. In other words, the thermal stability of E-POSS and GF improves the heat resistance of E51 composite [35,36].

3.5. Fracture Analysis

The fracture surface of different samples was investigated by SEM. As shown in Figure 8, the fracture surface of the E51 sample was relatively smooth and homogeneous, and the shearing deformation was low. The phenomena showed a brittle fracture under no uninterrupted crack propagation path which will lead to poor resistance to crack propagation. The fracture surface image of the E51 + E-POSS (10%) sample is shown in Figure 8B. It was found that the fracture surface morphology contained some wrinkles and a few toughening whorls. It can be inferred that when the E51 + E-POS (10%) sample is destroyed, more fracture energy is absorbed which will hinder the further destruction of E51 + E-OSS (10%). The fracture surface image of the E51 + GF (16%) sample is presented in Figure 8C. It can be clearly seen from the fracture surface image that the glass fiber at the fracture interface was partially pulled out of the resin matrix and partially fractured. It can be speculated that the strong interaction between the epoxy resin matrix and GF is the reason for the above phenomenon [37,38]. Figure 8D presents the fracture surface image of the E51 + E-POSS (10%) + GF (16%) sample, and shows that the glass fiber at the fracture interface was partially pulled out of the resin matrix, and the circular boundary of the generated voids was not perfect, indicating that the adhesion between the GF interface and resin matrix is good. The mechanical bonding between the epoxy resin matrix and GF was being further reinforced because the reactive epoxy group of E-POSS can directly participate in the curing reaction with PEPA. Therefore, the E51 + E-POSS (10%) + GF (16%) sample exhibited better mechanical and thermal properties.

4. Conclusions

In summary, E-POSS was successfully prepared by the epoxidation of C=C bonds. With the blending method, the E51 + E-POSS, E51 + GF, and E51 + E-POSS + GF composites were prepared. The results show that the tensile strengths of binary composites of E51 + E-POSS and E51 + GF were higher than that of pure E51. In addition, the ternary composite of the E51 + E-POSS + GF sample showed the optimum tensile strength with the addition of E-POSS (10 wt%) and GF (16 wt%), compared with E51 + E-POSS (10 wt%), E51 + GF (16 wt%), and pure E51 samples. Moreover, the DMA results show that the E51 + E-POSS (10%) + GF (16%) sample exhibited the highest stiffness in comparison with the E51 + E-POSS (10%), E51 + GF (16%), and pure E51 samples. The TGA results indicate that Td5% and residues of the E51 + E-POSS (10%) + GF (16%) sample were significantly improved compared with those of E51 + E-POSS (10%), E51 + GF (16%), and pure E51 samples, revealing that the thermal stability of ternary composite was better than that of binary and pure E51 samples. It can be concluded that the incorporation of an appropriate amount of E-POSS (10 wt%) and GF (16 wt%) into E51 could significantly improve the mechanical and thermal properties of E51 resin. The improvement was not only related to interaction between E51/POSS and E51/GF, but also related to the synergistic effect between E-POSS and GF.

Author Contributions

Conceptualization, project administration, supervision, writing—review & editing, Y.F.; investigation, J.S.; methodology, investigation, writing—original draft preparation, J.J.; writing—review and editing, X.Y. and D.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

There are no conflict to declare.

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Applsci 13 02461 g001 550
Figure 1. The chemical structures of (A) functional POSS, (B) polyethylenepolyamine (PEPA), (C) E51 resin, and (D) the preparation of E-POSS.
Figure 1. The chemical structures of (A) functional POSS, (B) polyethylenepolyamine (PEPA), (C) E51 resin, and (D) the preparation of E-POSS.
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Figure 2. Schematic of fabrication of epoxy resins: (A) E51/PEPA epoxy resin, (B) E51 + E-POSS/PEPA composite.
Figure 2. Schematic of fabrication of epoxy resins: (A) E51/PEPA epoxy resin, (B) E51 + E-POSS/PEPA composite.
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Figure 3. FTIR spectrum of E-POSS.
Figure 3. FTIR spectrum of E-POSS.
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Figure 4. 1H NMR spectrum of E-POSS.
Figure 4. 1H NMR spectrum of E-POSS.
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Figure 5. (A) Tensile strength of E51/PEPA with different mixing ratios, (B) tensile strength of different samples.
Figure 5. (A) Tensile strength of E51/PEPA with different mixing ratios, (B) tensile strength of different samples.
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Figure 6. DMA spectra of the different samples. (A) Storage modulus, (B) Tan δ.
Figure 6. DMA spectra of the different samples. (A) Storage modulus, (B) Tan δ.
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Figure 7. TGA curves of different samples. (A) E51 and E51 + E-POSS(10%), (B) E51 and E51 + GF(16%), (C) E51 and E51 + E-POSS(10%) + GF(16%).
Figure 7. TGA curves of different samples. (A) E51 and E51 + E-POSS(10%), (B) E51 and E51 + GF(16%), (C) E51 and E51 + E-POSS(10%) + GF(16%).
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Figure 8. SEM image of the fracture surface. (A) E51, (B) E51 + E-POSS (10%), (C) E51 + GF (16%), and (D) E51 + E-POSS (10%) + GF (16%).
Figure 8. SEM image of the fracture surface. (A) E51, (B) E51 + E-POSS (10%), (C) E51 + GF (16%), and (D) E51 + E-POSS (10%) + GF (16%).
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Table
Table 1. The data of tensile strength of different samples.
Table 1. The data of tensile strength of different samples.
Sample IDE-POSS (wt%)GF
(wt%)		Modulus
(GPa)		Tensile Strength (MPa) T s s a m p l e T s E 51 100 %
E51--3.7 ± 0.160.1 ± 6.5100%
E51 + E-POSS (5%)5-4.5 ± 0.278.3 ± 7.4130.3%
E51 + E-POSS (10%)10-4.9 ± 0292.5 ± 7.8153.9%
E51 + E-POSS (15%)15-4.7 ± 0.287.6 ± 8.3145.8%
E51 + GF (8%)-85.2 ± 0.2132.1 ± 10.4219.8%
E51 + GF (16%)-166.6 ± 0.2186.7 ± 11.5310.6%
E51 + GF (24%)-245.8 ± 0.2172.1 ± 15.3286.4%
E51 + E-POSS (10%) + GF (16%)10167.5 ± 0.2214.9 ± 18.8357.6%
NOTE: Ts denotes the tensile strength.
Table
Table 2. The thermal degradation data of TGA.
Table 2. The thermal degradation data of TGA.
Sample IDTd5% (°C)Residues (wt%)
E513362.4
E51 + E-POSS (10%)35411.5
E51 + GF (16%)36615.3
E51 + E-POSS (10%) + GF (16%)37821.2
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Jiang, J.; Shen, J.; Yang, X.; Zhao, D.; Feng, Y. Epoxy-Functionalized POSS and Glass Fiber for Improving Thermal and Mechanical Properties of Epoxy Resins. Appl. Sci. 2023, 13, 2461. https://doi.org/10.3390/app13042461

AMA Style

Jiang J, Shen J, Yang X, Zhao D, Feng Y. Epoxy-Functionalized POSS and Glass Fiber for Improving Thermal and Mechanical Properties of Epoxy Resins. Applied Sciences. 2023; 13(4):2461. https://doi.org/10.3390/app13042461

Chicago/Turabian Style

Jiang, Jianliang, Jingbo Shen, Xiao Yang, Dongqi Zhao, and Yakai Feng. 2023. "Epoxy-Functionalized POSS and Glass Fiber for Improving Thermal and Mechanical Properties of Epoxy Resins" Applied Sciences 13, no. 4: 2461. https://doi.org/10.3390/app13042461

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