High-performance Epoxy Nanocomposites Research Articles

In Situ Processing to Achieve High-Performance Epoxy Nanocomposites with Low Graphene Oxide Loading

Modifying the polymer matrix by nanoparticles can be a promising approach to improve the performance of fiber-reinforced polymer (FRP) composites. Organic solvents are usually used for dispersing graphene oxide (GO) well in the polymer matrix. In this study, a green, facile, and efficient approach was developed to prepare epoxy/GO nanocomposites. In situ polymerization is used for synthesizing nanocomposites, eliminating the need for organic solvents and surfactants. By loading just 0.6 wt% of GO into the epoxy resin, Young’s modulus, tensile strength, and toughness improved by 38%, 46%, and 143%, respectively. Fractography analysis indicates smooth fracture surfaces of pure resin that changed to highly toughened fracture surfaces in this nanocomposite. Plastic deformation, crack pinning, and deflection contributed to improving the toughness of the nanocomposites. FTIR investigations show that amide bonding was created by the reaction of the carboxylic acid groups in GO with some amine groups in the curing agent during the dispersion processes.

High-performance epoxy nanocomposites via constructing a rigid-flexible interface with graphene oxide functionalized by polyetheramine and f-SiO2

Graphene oxide (GO) is an ideal reinforcement for improving mechanical properties of epoxy (EP) and reducing its coefficient of thermal expansion (CTE). However, the poor interfacial interaction between GO and polymer matrix seriously hinders the reinforcing effect of GO. To improve their interface, we first functionalized GO with flexible polyetheramine (PEA) and f-SiO2 rigid nanoparticles, obtaining PEA-GO and SiO2-PEA-GO hybrids, respectively. Then the PEA-GO and SiO2-PEA-GO were incorporated into EP to obtain nanocomposites with flexible interphases and rigid-flexible interphases, respectively. The interfaces were tuned by two PEA molecules (D230 and D2000) with different chain lengths. The effects of the different interface structures on the mechanical properties and CTE of the GO/EP nanocomposites with a 0.25 wt% filler loading were investigated. It was found that the effects of SiO2-PEA-GO on strengthening and toughening EP matrix and on reducing its CTE were much better than those of PEA-GO, because the rigid-flexible interfaces provided higher bonding strength and better energy dissipation mechanisms than the flexible interfaces. Moreover, the D230-GO/EP nanocomposite containing shorter PEA (D230) molecules exhibited higher strength but lower toughness and CTE than the D2000-GO/EP nanocomposite. However, the SiO2-D2000-GO/EP nanocomposite showed greater strength, toughness and CTE than the SiO2-D230-GO/EP nanocomposite. This indicated that the longer PEA molecules in rigid-flexible interphases produced higher improvement in strength and toughness but smaller decreases in CTE. This work provides a promising strategy of constructing an adjustable flexible-rigid interfacial structure and opens an avenue for developing GO/EP nanocomposites with high mechanical properties and low CTE.

Hierarchical MXene@PBA nanohybrids towards high-efficiency flame retardancy and smoke suppression of robust yet tough polymer nanocomposites at ultra-low additions

Developing efficient flame-retardant MXene-based polymeric materials with enhanced mechanical properties has been a huge challenge. Herein, Prussian blue analogues (PBAs) were used to modify the surface of MXene nanosheets via an electrostatic self-assembly method to construct hierarchical MXene-based nanohybrids (MXene@PBA). Then, MXene@PBA was incorporated into the epoxy matrix to fabricate high-performance epoxy nanocomposites (EP-MXene@PBA). The study indicates that hierarchical MXene@PBA exhibits excellent dispersion performance in the epoxy matrix. Notably, MXene@PBA results in high-efficiency flame retardancy and smoke suppression for epoxy nanocomposites at ultra-low additions. What is very surprising is that only 1.0 wt% MXene@PBA can easily enhance the UL-94 rating of EP-1.0%MXene@PBA to V0. Meanwhile, the peak heat release rate (pHRR), total smoke production (TSP), and peak CO production rate (pCO) are remarkably reduced by 36.70%, 34.28%, and 43.48%, compared to those of the pristine epoxy resin, respectively. Furthermore, the 1.0 wt% MXene@PBA nanohybrids can enhance the flexural and impact strengths of EP-1.0%MXene@PBA. This work provides a feasible strategy for the creation of multifunctional MXene derivatives and their polymeric nanocomposites and holds great promise for many industrial applications.

Tough and Conductive Nacre-inspired MXene/Epoxy Layered Bulk Nanocomposites.

A long-standing quest in materials science has been the development of tough epoxy resin nanocomposites for use in numerous applications. Inspired by nacre, here we report tough and conductive MXene/epoxy layered bulk nanocomposites. The orientation of MXene lamellar scaffolds is enhanced by annealing treatment. The improved interfacial interactions between MXene lamellar scaffold and epoxy through surface chemical modification resulted in a synergistic effect. Tailoring the interlayer spacing of MXene nanosheets to a critical distance resulted in a fracture toughness about eight times higher than that of pure epoxy, surpassing other epoxy nanocomposites. Our nacre-inspired MXene/epoxy layered bulk nanocomposites also show high electrical conductivity that provides self-monitoring capability for structural integrity and exhibits an excellent electromagnetic interference shielding efficiency. Our proposed strategy provides an avenue for fabricating high-performance epoxy nanocomposites.

One-Pot Synthesis of UPy-Functionalized Nanocellulose under Mechanochemical Synergy for High-Performance Epoxy Nanocomposites.

The high strength, high specific surface area, excellent biocompatibility, and degradability of nanocellulose (NCC) make it a potential reinforcing phase for composite materials. However, the polyhydroxyl property of NCC renders it prone to self-aggregation and it has weak interfacial compatibility with non-polar substrates, limiting its enhancement performance for composite materials. Therefore, based on the high reactivity of NCC, the chemical modification of NCC to introduce functional groups is the basis for effectively reducing its self-aggregation, improving its interfacial compatibility with the polymer matrix, and creating nanocellulose-based functional materials. The existing functional modifications of NCC have limitations; they require cumbersome steps, generate low yields, and are environmentally unfriendly. Herein, ureido-pyrimidinone (UPy) was introduced to NCC through a sustainable and high-efficiency avenue formed by the mechanochemical synergy of microwaves and ultrasonication. The obtained UPy-modified nanocellulose (NCC-UPy) exhibited a rod-like shape, with a length of 200–300 nm and a width of 20–30 nm, which presented oriented and stable dispersion in an aqueous medium, and the zeta potential reached −40 mV. Moreover, NCC-UPy had good thermostability (>350 °C) and high crystallinity (82.5%) within the crystal type of cellulose I. Using the as-prepared NCC-UPy as a molecular bridge, it was organically combined with epoxy resin through multiple hydrogen bonds to construct a nanocomposite membrane with superior mechanical strength and thermal stability. The results revealed that NCC-UPy dispersed uniformly in the epoxy matrix without aggregating and that the interfacial compatibility was good, leading to an 87% increase in the tensile strength of the formed nanocomposite membrane when 0.5 wt.% NCC-UPy was loaded. It was proved that NCC-UPy had remarkable reinforcing potential and effective stress transfer capacity for composites. Consequently, this study may open the door to the development of a one-pot green approach for undertaking the functional modification of NCC, and it is of great significance for the development of NCC-based nanocomposites.

Molecular Dynamics Simulation for the Effect of Fluorinated Graphene Oxide Layer Spacing on the Thermal and Mechanical Properties of Fluorinated Epoxy Resin.

Traditional epoxy resin (EP) materials have difficulty to meet the performance requirements in the increasingly complex operating environment of the electrical and electronic industry. Therefore, it is necessary to study the design and development of new epoxy composites. At present, fluorinated epoxy resin (F-EP) is widely used, but its thermal and mechanical properties cannot meet the demand. In this paper, fluorinated epoxy resin was modified by ordered filling of fluorinated graphene oxide (FGO). The effect of FGO interlayer spacing on the thermal and mechanical properties of the composite was studied by molecular dynamics (MD) simulation. It is found that FGO with ordered filling can significantly improve the thermal and mechanical properties of F-EP, and the modification effect is better than that of FGO with disordered filling. When the interlayer spacing of FGO is about 9 Å, the elastic modulus, glass transition temperature, thermal expansion coefficient, and thermal conductivity of FGO are improved with best effect. Furthermore, we calculated the micro parameters of different systems, and analyzed the influencing mechanism of ordered filling and FGO layer spacing on the properties of F-EP. It is considered that FGO can bind the F-EP molecules on both sides of the nanosheets, reducing the movement ability of the molecular segments of the materials, so as to achieve the enhancement effect. The results can provide new ideas for the development of high-performance epoxy nanocomposites.

One-pot synthesis of aminated cellulose nanofibers by “biological grinding” for enhanced thermal conductivity nanocomposites

Aminated cellulose nanofibers (A-CNF) with high thermostability (>350 ℃), high crystallinity (81.25 %), and high dispersion stability were extracted from “biological grinding” biomass through one-pot microwave-hydrothermal synthesis. Worm-eaten wood powder (WWP) as the product of “biological grinding” by borers is a desirable lignocellulose for fabricating A-CNF in a green and cost-effective way since it is a well-milled fine powder with dimension of dozens of microns, which can be used directly, saving energy and labor. Generated A-CNF proved to be an excellent reinforcing and curing agent for constructing high performance epoxy nanocomposites. The nanocomposites exhibited a thermal conductivity enhancement of about 120 %, coefficient of thermal expansion reduction of 78 %, and Young’s modulus increase of 108 % at a low A-CNF loading of 1 wt.%, demonstrating their remarkable reinforcing potential and effective stress transfer behavior. The process proposed herein might help to bridge a closed-loop carbon cycle in the whole production-utilization of biomass.

Imidazole-functionalized nitrogen-rich Mg-Al-CO3 layered double hydroxide for developing highly crosslinkable epoxy with high thermal and mechanical properties

Ionic liquid-based N-octadecyl-N'-octadecyl imidazolium iodide functionalized layered double hydroxide (LDH-IM) was synthesized for manufacturing high-performance epoxy nanocomposites. Nonisothermal differential scanning calorimetry (DSC) was performed to study cure kinetics of epoxy reinforced قث with LDH and LDH-IM. Incorporation of Mg-Al-CO3 LDH into epoxy hindered the curing reaction, as detected by dimensionless Cure Index (CI). By contrast, epoxy/LDH-IM cured Good and Excellent due to imidazolium ionic liquid. Higher activation energy for completely cured epoxy/LDH-IM nanocomposite was obtained compared to epoxy and epoxy/LDH nanocomposites. The curing reaction rate was obtained by calculation of the orders of instantaneous autocatalytic and non-catalytic reactions, and optimal kinetic parameters based on isoconversional methods were in good agreement with experimental cure reaction rates. Lower value of Tg for epoxy/LDH nanocomposite compared to the neat epoxy signified weak interactions between Mg-Al-CO3-LDH and epoxy matrix, while a higher Tg was obtained for epoxy/LDH-IM. Network degradation kinetics of the samples was also investigated. The higher decomposition activation energy for epoxy/LDH-IM approved strong interfacial adhesion in the assigned system. The highly reactive nature of the developed LDH-IM gives reason for its usage for developing highly curable epoxy with high thermal and mechanical properties.

High performance epoxy nanocomposites based on dual epoxide modified α-Zirconium phosphate nanoplatelets

Epoxy nanocomposites with exfoliated α-zirconium phosphate (ZrP) using proton exchanged polyetheramines as surfactants have previously been demonstrated to show significant improvements anti-corrosion, barrier, and mechanical properties. However, these nanocomposites have a significant reduction in glass transition temperature (Tg). The low Tg of the nanocomposites is caused by detachment of the polyetheramine from ZrP which interferes with the epoxy curing process. Here, ZrP surfaces with covalently bound molecules containing epoxide functional groups were used to achieve ZrP exfoliation in epoxy without sacrificing Tg. By introducing dual epoxide functionalized ZrP, it is possible to achieve exfoliation and self-assembly of ZrP at high loadings in epoxy with greatly increased Young's modulus and significantly reduced thermal expansion coefficient, while maintaining a high Tg. Implication of the present study for preparation of high-performance polymer nanocomposites is discussed.

High performance epoxy nanocomposites with enhanced thermal and mechanical properties by incorporating amine-terminated oligoimide-grafted graphene oxide

In this work, thermal conductivity and mechanical strength of a commercial epoxy resin were improved by incorporating an amine-terminated oligoimide modified graphene oxide (ATO-GO). For this purpose, the surface of GO was modified with flexible/stable imide backbone and amine terminals. The ATO-GO was incorporated in epoxy proportion to prepare series of nanocomposites. The terminal amino group of ATO-GO also acted as curing moiety for epoxy resin leading to good interfacial compatibility and dispersion in the epoxy matrix resulting in improved properties. The epoxy resin was cured with hardener Aradur-22962 and ATO-GO separately and the results of curing behavior were compared with each other, which clearly showed the curing action of ATO-GO. In the prepared ATO-GO-epoxy nanocomposites, the filler enhanced the thermal conductivity, hardness and elastic modulus without decrease in thermal stability even at higher filler loading. In previous studies, it is reported that at higher GO, filler-loading properties like elastic modulus, hardness values, and glass transition temperature ( T g) were decreased. An enhancement of 59.5% in thermal conductivity was achieved for 5 wt% loading of ATO-GO filler as compared to neat epoxy. Along with this, thermal analysis revealed that the nanocomposites with 5 wt% filler loading have high T g and thermal strength. Nanoindentation results revealed that elastic modulus and hardness values enhanced by 104% and 147%, respectively, for the same nanocomposites. The enhanced thermal conductivity and good elastic behavior of the ATO-GO-epoxy nanocomposites demonstrated that these can be used as high-performance materials in electronic packing and electronic devices.

Natural bauxite nanosheets: A multifunctional and sustainable 2D nano-reinforcement for high performance polymer nanocomposites

Synthesis of two dimensional (2D) nanomaterials from natural resources for the fabrication of high performance multifunctional polymer nanocomposites has gained great interest. Herein, we report on a facile method for synthesizing 2D bauxite nanosheets (BNS) directly from its ore using a combination of ball-milling and hydrothermal processes. Successful preparation of the BNS was confirmed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) specific surface area, and particle size distribution. The changes in phases monitored by X-ray diffraction (XRD), before and after ball-milling and hydrothermal treatment, indicated the presence of γ-Al2O3 in the BNS structure. As a promising application, the BNS was introduced into a thermosetting epoxy resin. Thermal analysis and rheological analyses were performed to understand the influence of BNS on the curing and processing of the epoxy matrix. Higher mechanical performance of the epoxy resin reinforced with BNS was achieved and characterized using tensile, flexural, and dynamic thermo-mechanical (DMT) analyses. Thermal stability of the epoxy nanocomposites containing BNS were also evaluated using thermogravimetry analyses (TGA). The overall results indicate that BNS can effectively serve as a cost-effective multifunctional reinforcing agent in fabrication of high performance epoxy nanocomposites.

Ultra-Tough Inverse Artificial Nacre Based on Epoxy-Graphene by Freeze-Casting.

Epoxy nanocomposites combining high toughness with advantageous functional properties are needed in many fields. However, fabricating high-performance homogeneous epoxy nanocomposites with traditional methods remains a great challenge. Nacre with outstanding fracture toughness presents an ideal blueprint for the development of future epoxy nanocomposites. Now, high-performance epoxy-graphene layered nanocomposites were demonstrated with ultrahigh toughness and temperature-sensing properties. These nanocomposites are composed of ca. 99 wt % organic epoxy, which is in contrast to the composition of natural nacre (ca. 96 wt % inorganic aragonite). These nanocomposites are named an inverse artificial nacre. The fracture toughness reaches about 4.2 times higher than that of pure epoxy. The electrical resistance is temperature-sensitive and stable under various humidity conditions. This strategy opens an avenue for fabricating high-performance epoxy nanocomposites with functional properties.

Achieving high-performance epoxy nanocomposites with trifunctional poly(oxypropylene)amines functionalized graphene oxide

In this article, two types of functional graphene oxide (GO) with amine-rich surface were synthesized through chemically grafting two different molecular chain length trifunctional poly(oxypropylene)amines T5000 and T403, which were named as T5000-GO and T403-GO, respectively. The functionalized GO was then added to epoxy (EP) resin. Fourier transform infrared spectra analysis confirmed successful chemical functionalization on GO. Both T403-GO and T5000-GO were tightly embedded in the EP, because the amine-rich surface of functionalized-GO could form covalent bonds with the EP matrix, thereby contributing to the enhancement of mechanical properties. Particularly, T5000-GO, which has longer grafting molecule chains, achieved better compatibility and dispersibility in the EP matrix, resulting in a better reinforcing efficiency in mechanical properties. For example, the T5000-GO/EP composites showed an incremental enhancement in tensile strength with increasing filler concentrations, whereas their T403-GO/EP counterparts failed to follow the same trend. Meanwhile, the T5000-GO/EP composites with only 0.1-wt% T5000-GO achieved a prominent increase in flexural strength (approximately 50%) and flexural modulus (approximately 26.8%), which were higher than those of T403-GO-filled counterparts. This work indicated that the compatibility and interphase between GO and EP could be designed by manipulating the length of grafting molecule chains, thereby providing a better understanding of the relationship between the structure and mechanical properties of the graphene/EP nanocomposites.

High-performance nanocomposites synergistically reinforced by two-dimensional montmorillonite and zero-dimensional nanoTiO2

Comprehensive high-performance epoxy nanocomposites were successfully prepared by co-incorporating two-dimensional montmorillonite (MMT) and zero-dimensional nanoTiO2 into epoxy. Mechanical tests and thermal analyses showed that the resulting epoxy/MMT/nanoTiO2 nanocomposites obtained great improvements over pure epoxy, epoxy/MMT nanocomposites, and epoxy/nanoTiO2 nanocomposites in tensile modulus, tensile strength, flexural modulus, flexural strength, notch impact strength, glass transition temperature, and thermal decomposition temperature. The best performance occurred with the nanocomposite containing 5 phr MMT/nanoTiO2. At this loading, the tensile modulus increased by 154.75, 35.69, and 89.56%, the tensile strength by 81.53, 143.46, and 22.01%, the flexural modulus by 21.12, 6.04, and 3.31%, the flexural strength by 25.25, 16.98, and 9.73%, the notch impact strength by 65.57, 37.23, and 25.94%, the glass transition temperature by 11.3, 12.2, and 11.4 °C, and the thermal decomposition temperature by 15.3, 3.0, and 3.2 °C as compared with those of pure epoxy, 5 phr epoxy/MMT nanocomposite and 5 phr epoxy/nanoTiO2 nanocomposite, respectively. X-ray diffraction and transmission electron microscopy inspection revealed that in the epoxy/MMT/nanoTiO2 nanocomposites, the MMT was completely exfoliated into two-dimensional nanoscale mono-platelets, which formed special intermingled structure with the zero-dimensional nanoTiO2 spheres. This study suggests that co-incorporating two proper, dimensionally different nanomaterials into polymer matrices could be a pathway to success in preparing comprehensive high-performance polymer nanocomposites.

In situ preparation of reduced graphene oxide/DOPO-based phosphonamidate hybrids towards high-performance epoxy nanocomposites

Abstract The work reports a strategy based on piperazine-reduced graphene oxide (rGO)/piperazine-based DOPO-phosphonamidate (PiP-DOPO) to overcome the challenge of the dispersion of graphene and mechanical deterioration of epoxy resin (EP) matrix with additive-type flame retardants. Graphene oxide (GO) was functionalized and reduced by piperazine simultaneously, and then incorporated into PiP-DOPO through in situ reaction, resulting in the formation of the hybrids (PD-rGO). Subsequently, the PD-rGO was incorporated into epoxy resin (EP) to fabricate nanocomposite. The structure and thermal properties of PD-rGO were well characterized. The presence of PD-rGO in EP improved the char yields at 700 °C and reduced the maximum mass loss rate under nitrogen, indicating the improved thermal stability at elevated temperature. The evaluation of combustion behavior demonstrated that the PHRR and THR values were decreased significantly by 43.0% and 30.2% by the addition of 4 wt% PD-rGO10 (10 wt% rGO in hybrid) in EP respectively, in comparison to neat EP. The epoxy composite with 4 wt% PD-rGO5 (5 wt% rGO in hybrid) could pass UL-94 V0 rating and the LOI was 28.0%. The flame retardant mechanism could be attributed to the synergism between two compositions in PD-rGO hybrid: the PiP-DOPO was favorable to flame spread inhibition in UL-94 burning test, while the barrier effect of graphene was dominant in terms of heat release rate suppression. Moreover, the addition of PD-rGO hybrid led to slightly improved storage modulus and tensile strength, due to the high stiffness of graphene in hybrids. The PD-rGO hybrid combines the outstanding mechanical behavior of graphene with the good flame retardant effect of DOPO-based compounds, which provides a promising solution to high performance epoxy nanocomposites with improved flame retardant and mechanical properties simultaneously.

Preparation and physical properties of an epoxy nanocomposite with amine-functionalized graphenes

Graphene, consisted of a single layer of carbon atom in a two-dimensional lattice, has superior electrical and physical properties that promise many exciting applications. In this study, graphenes were prepared from graphite powder by chemical method and their images were investigated by TEM and SEM. To develop high performance epoxy nanocomposites with good dispersion of graphenes and strong epoxy-graphene interfacial bonding, graphenes were amine-functionalized and the effects of the amine-functionalization on the curing behavior and physical properties of epoxy/graphene nanocomposites were studied. FTIR spectra confirmed the amine-functionalization. The physical properties of the nanocomposites were investigated by DSC, DMA, TMA, and impact tester. Fracture surfaces were investigated by SEM. The physical properties of the nanocomposites could be improved considerably by the amine-functionalization of graphenes. POLYM. ENG. SCI., 54:985–991, 2014. © 2012 Society of Plastics Engineers

Epoxy nanocomposites co-reinforced by two dimensionally different nanoscale particles

Comprehensive high-performance epoxy nanocomposites were prepared by simultaneous incorporating montmorillonite (MMT) and nanoSiO2 into epoxy. Mechanical tests and thermal analyses showed that the epoxy/MMT/nanoSiO2 nanocomposites obtained considerable improvement over basic epoxy in tensile modulus, tensile strength, flexural modulus, flexural strength, notch impact strength, glass transition temperature, and thermal decomposition temperature. X-ray diffraction measurements and transmission electronic microscopy observations revealed that the layered structure of MMT was completely exfoliated into two-dimensional nanoscale mono-platelets. These 2D mono-platelets formed intermingled structure with the zero-dimensional nanoSiO2 spheres in the nanocomposites. This study suggests that employing the synergistic reinforcement effect of two dimensionally different nanoscale particles is one pathway to success in developing comprehensive high-performance polymer nanocomposites.

New high-performance epoxy nanocomposites co-reinforced by two- and zero-dimensional nanoscale particles

New epoxy nanocomposites co-reinforced by two-dimensional montmorillonite and zero-dimensional nanoSiO 2 were prepared. Mechanical tests and thermal analyses showed that the nanocomposites obtained considerable improvements over neat epoxy in tensile modulus, tensile strength, flexural modulus, flexural strength, notch impact strength, glass transition temperature, and thermal decomposition temperature.

Organoclay-modified high performance epoxy nanocomposites

Organoclay-modified high performance epoxy nanocomposites were synthesized with a direct-mixing method (DMM) or a high-pressure mixing method (HPMM). X-ray diffraction (XRD) results showed that the basal spacing of organoclay particles in the nanocomposites fabricated with the DMM is increased, but that the organoclay is aggregated on the micro-scale in the epoxy resin. These agglomerates of organoclay mainly came from poor dispersion and could be broken down by the HPMM. The mechanical behavior of materials formed by these mixing methods was investigated. The organoclay was found to simultaneously improve both fracture toughness and elastic modulus of the TGDDM-DDS epoxy system without decreasing strength. The nanocomposites formed by the HPMM showed a dramatic improvement in fracture toughness at very low clay loading; that is, K 1C and G 1C were increased by 1.7 and 3.2 times respectively, at 1.5 phr (about 1 wt%) organoclay loading. Dynamic mechanical analysis results showed that the glass transition temperature ( T g) of all the nanocomposites decreases slightly as the content of clay increases.