The Effect of WS2 Nanotubes on the Properties of Epoxy-Based Nanocomposites

In this paper we evaluated the effect of embedding inorganic nanotubes (INT) of tungsten disulfide (WS₂) in an epoxy matrix, on the mechanical, thermal and adhesion properties of the resulting nanocomposites. The nanotube content spanned a range of values (0, 0.1, 0.3, 0.5 and 1.0 wt%), and the nanotube incorporation process consisted of a combination of both distributive (magnetic stirring) and dispersive (ultrasonic mixing) methods. The adhesion of the nanocomposites to an aluminum substrate was characterized by both a single lap shear and a T-peel test. The fracture toughness (K _IC) of the nanocomposites was characterized by a standard compact tension (CT) plane-strain fracture test. The thermal properties of the nanocomposites were determined by dynamic mechanical thermal analysis (DMTA). Overall, the addition of INT-WS₂ was found to improve the shear strength and peel properties of the nanocomposite, and to significantly improve its fracture toughness and glass transition temperature. The extent and character of the nanotube–epoxy interaction were examined by electron microscopy, as was the energy dissipation mechanisms during fracture.     

Simultaneous improvement in strength,toughness, and thermal stability of epoxy/halloysite nanotubes composites by interfacial modification

This work investigated the effect of silane modification of halloysite nanotubes (HNTs) on the mechanical properties of epoxy/HNTs nanocomposites. Three kinds of silane coupling agents, including 3‐(2‐aminoethyl)‐aminopropyltrimethoxysilane (AEAPS), (3‐glycidyloxypropyl)‐trimethoxysilane (GPTMS), and octyltriethoxysilane (OTES), were employed. It was shown that the modified HNTs exhibited a better dispersion in the epoxy matrix compared with pristine one. Because of strong interfacial interaction between AEAPS modified HNTs and the epoxy matrix, the nanocomposites exhibited the highest glass transition temperature and modulus among all the samples. On the other hand, AEAPS and GPTMS modified HNTs/epoxy nanocomposites showed enhanced tensile strength and toughness. The toughing mechanisms were identified by the SEM micrographs of the fracture surfaces of the different kinds of samples. In this study, simultaneous enhancement of strength, toughness, and thermal stability of epoxy by the modified HNTs provides a novel approach to produce high‐performance thermosets. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43249.     

Preparation and properties of TiO2‐filled poly(acrylonitrile‐butadiene‐styrene)/epoxy hybrid composites

Poly (acrylonitrile‐butadiene‐styrene) (ABS) was used to modify diglycidyl ether of bisphenol‐A type of epoxy resin, and the modified epoxy resin was used as the matrix for making TiO₂ reinforced nanocomposites and were cured with diaminodiphenyl sulfone for superior mechanical and thermal properties. The hybrid nanocomposites were characterized by using thermogravimetric analyzer (TGA), dynamic mechanical analyzer (DMA), universal testing machine (UTM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The bulk morphology was carefully analyzed by SEM and TEM and was supported by other techniques. DMA studies revealed that the DDS‐cured epoxy/ABS/TiO₂ hybrid composites systems have two T_gs corresponding to epoxy and ABS rich phases and have better load bearing capacity with the addition of TiO₂ particles. The addition of TiO₂ induces a significant increase in tensile properties, impact strength, and fracture toughness with respect to neat blend matrix. Tensile toughness reveals a twofold increase with the addition of 0.7 wt % TiO₂ filler in the blend matrix with respect to neat blend. SEM micrographs of fractured surfaces establish a synergetic effect of both ABS and TiO₂ components in the epoxy matrix. The phenomenon such us cavitation, crack path deflection, crack pinning, ductile tearing of the thermoplastic, and local plastic deformation of the matrix with some minor agglomerates of TiO₂ are observed. However, between these agglomerates, the particles are separated well and are distributed homogeneously within the polymer matrix. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Study of morphological and mechanical performance of amine‐cured glassy epoxy–clay nanocomposites

The effect of three different alkylammonium‐modified montmorillonite on morphological and mechanical properties of glassy epoxy‐amine nanocomposites is reported. Small amounts of clays <10 phr (part per hundred of resin) were used in each system of nanocomposite. The morphology of the prepared nanocomposites was performed by means of X‐ray diffraction and transmission electron microscopy. Differential scanning calorimetry (DSC) was used to investigate the glass transition temperatures (T_g). Mechanical properties were based on tensile characteristics (Young's modulus), impact strength, and fracture toughness. The measured moduli were compared to theoretical predictions. Scanning electron microscopy was used to study the morphological structure of the fracture surfaces of impacted specimens. It was found that at a low content of 2 phr (1.2 wt %) of nanoclays, the impact strength and the fracture toughness were improved by 77 and 90% respectively, comparatively to the neat epoxy, whereas DSC revealed a reduction of the T_g of nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of cloisite 30B clay and sisal fiber on dynamic mechanical and fracture behavior of unsaturated polyester toughened epoxy network

This study examined the dynamic mechanical properties of sisal fiber reinforced unsaturated polyester (UP) toughened epoxy nanocomposites. The chemical structures changes in Epoxy, UP and UP toughened epoxy (Epoxy/UP) systems were characterized by Proton Nuclear magnetic resonance (¹HNMR) spectroscopy. The morphological alterations of the nanocomposites were analyzed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The untreated, chemically treated fibers, nanoclays, and the fiber reinforced Epoxy/UP nanocomposites were confirmed by FTIR spectrometer. The obtained mechanical results showed that alkali‐silane treated fibers improve the tensile strength (96%) and flexural strength (60%) of the Epoxy/UP nanocomposite than that of Epoxy/UP blend due to the strong interfacial bonding between the sisal fiber and matrix. The fracture toughness (K_IC) and fracture energy (G_IC) of treated sisal fiber reinforced DGEBA/UP/C30B nanocomposites found to be higher than that of untreated sisal fiber nanocomposites. The dynamic mechanical analysis (DMA) reveals that the fiber reinforced Epoxy/UP nanocomposites contains 30 wt% treated fiber and 1 wt% nanoclays, exhibits the highest storage modulus and better glass transition temperature (T_g) among the other kind of systems. The surface morphology of the fibers, fractured surface of the resins and composites were confirmed by scanning electron microscope (SEM). POLYM. COMPOS., 37:2832–2846, 2016. © 2015 Society of Plastics Engineers     

Sequences of fracture toughness micromechanisms in PP/CaCO3 nanocomposites

Mechanical properties and fracture toughness micromechanisms of copolypropylene filled with different amount of nanometric CaCO₃ (5–15 wt %) were studied. J‐integral fracture toughness was incorporated to measure the effect of incorporation of nanoparticle into PP matrix. Crack‐tip damage zones and fracture surfaces were studied to investigate the effect of nanofiller content on fracture toughness micromechanisms. It was found that nanofiller acted as a nucleating agent and decreased the spherulite size of polypropylene significantly. J‐integral fracture toughness (J_c) of nanocomposites was improved dramatically. The J_c value increased up to approximately two times that of pure PP at 5 wt % of nano‐CaCO₃. The fracture micromechanisms varied from rubber particles cavitation and shear yielding in pure PP to simultaneous existence of rubber particles cavitation, shear yielding, filler particles debonding, and crazing in PP/CaCO₃ nanocomposites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Fabrication and characterization of in situ synthesized nano‐CaCo3‐reinforced polypropylene composite materials

To improve the impact toughness of polypropylene (PP), nano‐CaCO₃ was prepared by an in situ synthesis. The surface of the nano‐CaCO₃ was modified by KH‐550 silane coupling agent and NDZ‐401 titanium acid ester coupling agent. Nano‐CaCO₃/PP composite materials were fabricated through a melt‐blending method and characterized, and their mechanical properties were analyzed. The impact toughness and the tensile strength of the PP were improved significantly by the incorporation of nano‐CaCO₃. When the weight fraction of nano‐CaCO₃ was 2%, the maximum impact toughness and tensile strength of the PP nanocomposites were 293% and 259%, respectively, of the values for neat PP. Observation of the impact fracture surface of the nanocomposites indicated that the dispersion of nano‐CaCO₃ modified by NDZ‐401 coupling agent was more homogeneous than that of nano‐CaCO₃ modified by the KH‐550 silane coupling agent. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

Toughening of cycloaliphatic epoxy resin improved by reactive copolymers with flexible alkyl side chains

Reactive copolymers with flexible alkyl side chains were used as modifiers to improve the toughness of a cycloaliphatic epoxy resin. In this study, we used three types of copolymers with different alkyl chain length (C₄H₉, C₆H₁₃, and C₁₀H₂₁). As a result, the system with an added copolymer having the longest alkyl chain length (C₁₀H₂₁) formed a phase separation structure. The addition of this copolymer (C₁₀H₂₁) led to a 50% increase in the fracture toughness (K_IC) of the cured resin at the slight expense of its glass transition temperature. Scanning electron microscope observations in the vicinity of a crack tip after a compact tension test showed that cavitation of the dispersed phase occurred. The crack growth was inhibited and thus the toughness was improved due to the plastic deformation of the epoxy matrix followed by cavitation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Toughening of Epoxy Adhesives by Nanoparticles

With the emergence and commercialization of nanoparticles, new opportunities have emerged for toughening of epoxy adhesives using nanoparticles without sacrificing strength, rigidity and glass transition temperature, as is the case with conventional elastomeric tougheners. Inorganic Fullerene-like tungsten disulfide (IF-WS₂) nanoparticles and functionalized nano-POSS (Polyhedral-Oligomeric-Sil-Sesquioxane) were used to study the effects of nanoparticles on the toughening and mechanical properties of low and high temperature curing epoxy systems. Experimental results indicated that IF-WS₂ increased the fracture toughness by more than 10 fold in both epoxy systems at very low concentrations (0.3–0.5 wt%) while increasing its storage modulus and preserving its glass transition temperature. Epoxy functionalized POSS demonstrated an increase in toughness in addition to preserving rigidity and thermal properties at higher concentrations (3 wt%). It was postulated that chemical interaction of the sulfide and the epoxy matrix and the inherent properties of WS₂ were the decisive factors with respect to the outstanding nano-effect in the case IF-WS₂.     

High‐performance epoxy hybrid nanocomposites containing organophilic layered silicates and compatibilized liquid rubber

A mixture of two epoxy resins, tetraglycidyl 4,4′‐diaminodiphenyl methane and bisphenol‐A diglycidylether, cured with 4,4′‐diaminodiphenyl sulfone, was used as matrix material for high‐performance epoxy hybrid nanocomposites containing organophilicly modified synthetic fluorohectorite and compatibilized liquid six‐arm star poly(propylene oxide‐block‐ethylene oxide) (abbreviated as PPO). The hydroxy end groups of the poly(propylene oxide‐block‐ethylene oxide) were modified, yielding a six‐arm star PPO with an average of two pendant stearate chains, two phenol groups, and two hydroxy end groups. The alkyl chains of the stearate end groups played an important role in tailoring the polarity of the polymer. Its phenol end groups ensured covalent bonding between liquid polymer and epoxy resin. Two different organophilic fluorohectorites were used in combination with the functionalized PPO. The morphology of the materials was examined by transmission electron microscopy. The hybrid nanocomposites were composed of intercalated clay particles as well as separated PPO spheres in the epoxy matrix. As determined by dynamic mechanical analysis, the prepared composites possessed glass‐transition temperatures around 220°C. Although the tensile moduli remain unaltered, the tensile strengths of the hybrid materials were significantly improved. The relatively high fracture toughness of the neat resin, though, was not preserved for the hybrid resins. Scanning electron microscopy of the fracture surfaces revealed extensive matrix shear yielding for the neat resin, whereas the predominant fracture mode of the hybrid nanocomposites was crack bifurcation and branching. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3088–3096, 2004     

Nano‐AlN functionalization by silane modification for the preparation of covalent‐integrated epoxy/poly(ether imide) nanocomposites

Aluminum nitride nanoparticle (nano‐AlN) organically modified with the silane‐containing epoxide groups (3‐glycidoxypropyltrimethoxy silane, GPTMS) was incorporated into a mixture of poly(ether imide) (PEI), and methyl hexahydrophthalic anhydride‐cured bisphenol A diglycidyl ether grafted by GPTMS was prepared for nanocomposite. Scanning electron microscopy, transmission electron microscopy, and atomic force microscopy were used to investigate the microscopic structures of nanocomposites. According to experimental results, it was shown that addition of nano‐AlN and PEI into the modified epoxy could lead to the improvement of the impact and bend strengths. When the concentrations of nano‐AlN and PEI were 20 and 10 pbw, respectively, the toughness/stiffness balance could be achieved. Dynamic mechanical analysis (DMA) results displayed that two glass transition temperatures (T_g) found in the nanocomposites were assigned to the modified epoxy phase and PEI phase, respectively. As nano‐AlN concentration increased, T_g value of epoxy phase had gradually increased, and the storage modulus of the nanocomposite at the ambient temperature displayed an increasing tendency. Additionally, thermal stability of the nanocomposite was apparently improved. The macroscopic properties of nanocomposites were found to be strongly dependent on their components, concentrations, dispersion, and resulted morphological structures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Investigation on the mechanical performances of ternary nylon 6/SEBS elastomer/nano‐SiO2 hybrid composites with controlled morphology

The distribution of maleated styrene‐hydrogenated butadiene‐styrene (mSEBS) elastomer and nano‐SiO₂ in nylon 6 matrix was controlled by varying the blending procedure. Nano‐SiO₂ particles with different surface properties (hydrophilic versus hydrophobic) were adopted to adjust their interactions with other components. Two different structures, separate dispersion of nano‐SiO₂ and elastomer particles as well as encapsulation of nano‐SiO₂ fillers by the elastomer, were obtained. The structures were confirmed through scanning electron microscope (SEM) investigation. The mechanical measurement results showed that the microstructure and the interactions among the components had dramatic influences on the final mechanical properties, especially Izod fracture toughness, for the ternary nanocomposites. The nanocomposites containing hydrophilic nano‐SiO₂ had better mechanical performances compared with the composites filled with hydrophobic SiO₂ when they were in the same microstructure. The nanocomposites with separate dispersion structure showed higher stiffness compared with those of encapsulation type. However, the separately dispersed nano‐SiO₂ particles restricted the cavitation of elastomer phases that led to low toughening effectiveness. The difference of cavitation intensity for elastomer phase was revealed by SEM investigation on the facture surfaces for the nanocomposites with the two different microstructures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Toughening of epoxy systems by brominated epoxy

Blends of brominated epoxy (BE) and conventional epoxy resins were studied following curing with aliphatic triethylenetetramine (TETA), etheric (polyether diamine‐ PEA4), and aromatic (3,3′‐diamino diphenyl sulfone [DDS]) hardeners. The addition of BE resulted in an increase in T_g in all tested blends. Blends with 50 wt% BE cured with TETA demonstrated an increase in flexural modulus and flexural strength, while preserving the elongation. Blends with 40 wt% BE cured with PEA4 and 50 wt% BE cured with DDS resulted in a significant enhanced tensile elongation. The shear strength of all cured systems decreased moderately with the addition of BE exhibiting a mixed mode failure. Analysis of the fracture morphology using electron microscopy supported the increase of toughness levels as a result of incorporating BE to conventional epoxy. A unique nodular and rough fracture morphology was obtained, which is related to a toughening mechanism caused by the addition of BE. It was concluded that blends of BE and conventional epoxy could be used as structural adhesives having high T_g, enhanced mechanical properties and increased toughness. POLYM. ENG. SCI., 59:206–215, 2019. © 2018 Society of Plastics Engineers     

High‐performance flexible epoxy/ZnO nanocomposites with enhanced mechanical and thermal properties

Flexible epoxy/ZnO nanocomposites were prepared using different loadings of ZnO nanoparticles (NPs) and nanotubes (NTs) via in situ curing of epoxy with polyoxyethylene diamines (ED₆₀₀). ZnO precursor was synthesized via precipitation method and ZnO NPs with an average size of 25 nm were used in the preparation of the nanocomposites. ZnO NTs with an average outer diameter, length of 200 nm and 2.4 µm respectively, were prepared by the wet method (hydrothermal method). The morphology, structure, and composition of the nanocomposites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), and thermo‐gravimetric analysis (TGA). The effect of morphology and content of nano‐ZnO materials on the thermal and mechanical properties of flexible epoxy was studied. In addition, the hardness and indentation depth were calculated by means of nanoindentation. Results showed that the mechanical and thermal properties of flexible epoxy were enhanced by incorporation of ZnO nanostructure into the polymer matrix. POLYM. ENG. SCI., 57:932–946, 2017. © 2016 Society of Plastics Engineers     

Nanoindentation and Morphological Studies of Epoxy Nanocomposites

Summary: This paper investigates the mechanical properties of the epoxy–organoclay nanocomposites by the nanoindentation technique. The nanocomposites were prepared by in situ polymerization and a mixture of exfoliated and intercalated composites structure was obtained as evidenced by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The hardness, elastic modulus, and the creep behavior of the nanocomposites have been evaluated as a function of clay concentration. It has been found that incorporation of 7.5 wt.‐% of clay nanofiller enhances the elastic modulus and hardness of the epoxy matrix by about 20 and 6%, respectively. The elastic modulus data calculated from indentation experiments are comparable with those obtained from a tensile test. An optimum clay loading level was found to be 2.5 wt.‐% to maximum enhance the creep resistance of the epoxy matrix. The lowered creep resistance with higher clay loading could be due to the reduced crosslinking density near the clay surface caused by the plasticizing effect from the pending of alkyl ammonium chains on the clay surface. An attempt has been made to correlate the fracture toughness of the nanocomposites with the ratio of modulus to hardness obtained from nanoindentation experiments.

Ratio of modulus to hardness (E/H) and the fracture toughness (K_IC) versus clay loading for the epoxy nanocomposites.     

Role of core‐shell rubber particle cavitation resistance on toughenability of epoxy resins

The role of rubber particle cavitation resistance on toughening of epoxy resins is still unresolved. In this research, the role of rubber particle cavitation resistance was exclusively studied. Two types of core‐shell rubber (CSR) particles with different cavitation resistances were utilized for modifying epoxy resin. Matrix crosslink density (XLD) was varied by using nonstoichiometric amounts of hardener. Fracture toughness values of neat and CSR‐modified epoxy samples decreased with lowering of XLD via deviation from stoichiometric point. It was resulted by higher modulus and lower elongation at break of the nonstoichiometric samples, and also antiplasticization of epoxy networks resulted from suppression of β‐transition relaxation motions. In all XLDs, the CSR particles with higher core T_g and modulus yielded higher fracture energy. Results showed that core properties such as T_g and modulus of CSR particles had a significant effect on toughening of the epoxy networks. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Control of the functionality of graphene oxide for its application in epoxy nanocomposites

Amino- and epoxy-functionalized graphene oxide (GO) were synthesized separately through a wash-and-rebuild process utilizing two differently terminated silane coupling agents. The modified GO sheets were then incorporated into an epoxy resin to prepare nanocomposites. The addition of 0.2 wt% amino-functionalized GO (APTS-GO) yielded a 32% increase in Young's modulus (3.3 GPa) and 16% increase in tensile strength (81.2 MPa). Less reinforcement was observed with the epoxy-functionalized GO (GPTS-GO) but there was a more significant increase in ductility for GPTS-GO/epoxy, with the fracture toughness (critical intensity factor, K_IC) and fracture energy (critical strain energy release rate, G_IC) nearly doubling at 0.2 wt% loading (1.46 MPam^1/2 and 0.62 kJ/m² for K_IC and G_IC, respectively). Raman spectroscopy measurements revealed that the GPTS-GO was dispersed more uniformly than the APTS-GO in the epoxy matrix, and better interfacial stress transfer was found for the APTS-GO. Thus the wash-and-rebuild process affords a novel strategy for controlling the functionality of graphene in the quest to develop high-performance graphene-based nanocomposites.     

Transparent dispensible high‐refractive index ZrO2/epoxy nanocomposites for LED encapsulation

In this study, we report a facile ex situ approach to preparing transparent dispensible high‐refractive index ZrO₂/epoxy nanocomposites for LED encapsulation. Highly crystalline, near monodisperse ZrO₂ nanoparticles (NPs) were synthesized by a nonaqueous approach using benzyl alcohol as the coordinating solvent. The synthesized particles were then modified by (3‐glycidyloxypropyl)trimethoxysilane (GMS) ligand. It was found that, with tiny amount of surface‐treating ligand, the modified ZrO₂ NPs were able to be easily dispersed in a commercial epoxy matrix because of the epoxy compatible surface chemistry design as well as the small matrix molecular weight favoring mixing. Transparent thick (1 mm) ZrO₂/epoxy nanocomposites with a particle core content as high as 50 wt % and an optical transparency of 90% in the visible light range were successfully prepared. The refractive index of the prepared composites increased from 1.51 for neat epoxy to 1.65 for 50 wt % (20 vol %) ZrO₂ loading and maintained the same high‐Abbe number as the neat epoxy matrix. Compared with the neat epoxy encapsulant, an increase of 13.2% in light output power of red LEDs was achieved with the 50 wt % ZrO₂/epoxy nanocomposite as the novel encapsulant material. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3785–3793, 2013     

Effect of tungsten disulfide nanotubes on the thermomechanical properties of polypropylene‐graft‐maleic anhydride nanocomposites

In this work, the influence of tungsten disulfide nanotubes (INT‐WS₂) on the mechanical, thermal, structural, and morphological characteristics of Polypropylene‐graft‐maleic anhydride (PPGMA) nanocomposites is investigated. The addition of 5% INT‐WS₂ increases the Young's Modulus by 28.5% and the storage modulus by 196.5% (in the rubbery state). Furthermore, the nanocomposites' thermal stability increases (up to 10 °C) with the addition of INT‐WS₂. Transmission electron microscopy observations of the nanocomposites revealed that nanotubes' length is significantly reduced during processing and that nanotubes are well‐dispersed inside the PPGMA matrix. DSC results indicated that INT‐WS₂ serve as nucleating agents in PPGMA. Moreover, AFM observations (coupled with DSC results) suggested the formation of fibrillar crystallites in the nanocomposites. This interfacial crystalline structure seems to interpose between the PPGMA and INT‐WS₂. Thus, it plays a crucial role in the load transfer from the amorphous part of the polymer to the rather stiff INT‐WS₂. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43887.     

Preparation and mechanical properties of epoxy/diamond nanocomposites

Nanodiamond (ND) has recently attracted much attention for its outstanding mechanical and other interesting properties. Surface functionalization of ND is necessary for applications in polymers. In this study, ND particles were functionalized with amine by covalent linking of triethylene tetramine, and further grafted with epoxy which was cured with amine curing agent. The particle dispersion and mechanical properties of epoxy/ND nanocomposites were evaluated. Both fracture toughness and storage modulus of epoxy resin were significantly improved with a low loading of ND‐NH₂ particles. The morphological structure of the epoxy/ND nanocomposites was examined, and toughening mechanism was explored. POLYM. COMPOS., 35:2144–2149, 2014. © 2014 Society of Plastics Engineers