In the presented study, the structural, thermal, and mechanical properties of the nanocomposites were investigated by doping silanized hexagonal boron carbide (h-B4C) nanoparticles in varying proportions (0.5%, 1%, 2%, 3%, 4%, and 5%) into the epoxy resin by weight. For this purpose, the surfaces of h-B4C nanoparticles were silanized by using 3-(glycidyloxypropyl) trimethoxysilane (GPS) to improve adhesion between h-B4C nanoparticles and epoxy matrix. Then, the silanized nanoparticles were added to the resin by ultrasonication and mechanical stirring techniques to produce nanocomposites. The bond structure differences of silanized B4C nanoparticles (s-B4C) and nanoparticle doped composites were investigated by using Fourier transform infrared spectroscopy. Scanning electron microscopy and energy dispersion X-ray spectroscopy (SEM-EDS) technique was used to examine the distribution of nanoparticles in the modified nanocomposites. Differential scanning calorimetry and thermogravimetric analysis techniques were used to determine the thermal properties of the neat and s-B4C doped nanocomposites. The tensile test and dynamic mechanical analysis were performed to determine the mechanical properties. When the experimental results were examined, changes in the bonding structure of the s-B4C nanoparticles doped nanocomposites and significant improvements in the mechanical and thermal properties were observed. The optimum doping ratio was determined as 2% by weight. At this doping ratio, the Tg, tensile strength and storage modulus increased approximately 18%, 35%, and 44% compared to the neat composite, respectively. 相似文献
The intercrosslinked networks of unsaturated polyester (UP) toughened epoxy–clay hybrid nanocomposites have been developed.
Epoxy resin (DGEBA) was toughened with 5, 10 and 15% (by wt) of unsaturated polyester using benzoyl peroxide as radical initiator
and 4,4′-diaminodiphenylmethane as a curing agent at appropriate conditions. The chemical reaction of unsaturated polyester
with the epoxy resin was carried out thermally in presence of benzoyl peroxide-radical initiator and the resulting product
was analyzed by FT-IR spectra. Epoxy and unsaturated polyester toughened epoxy systems were further modified with 1, 3 and
5% (by wt) of organophilic montmorillonite (MMT) clay. Clay filled hybrid UP-epoxy matrices, developed in the form of castings
were characterized for their thermal and mechanical properties. Thermal behaviour of the matrices was characterized by differential
scanning calorimetry (DSC), thermo gravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Mechanical properties
were studied as per ASTM standards. Data resulted from mechanical and thermal studies indicated that the introduction of unsaturated
polyester into epoxy resin improved the thermal stability and impact strength to an appreciable extent. The impact strength
of 3% clay filled epoxy system was increased by 19.2% compared to that of unmodified epoxy resin system. However, the introduction
of both UP and organophilic MMT clay into epoxy resin enhanced the values of mechanical properties and thermal stability according
to their percentage content. The impact strength of 3% clay filled 10% UP toughened epoxy system was increased by 26.3% compared
to that of unmodified epoxy system. The intercalated nanocomposites exhibited higher dynamic modulus (from 3,072 to 3,820 MPa)
than unmodified epoxy resin. From the X-ray diffraction (XRD) analysis, it was observed that the presence of d001 reflections of the organophilic MMT clay in the cured product indicated the development of intercalated clay structure which
in turn confirmed the formation of intercalated nanocomposites. The homogeneous morphologies of the UP toughened epoxy and
UP toughened epoxy–clay hybrid systems were ascertained from scanning electron microscope (SEM). 相似文献
Summary: In this work, epoxy resin/CaCO3 nanocomposites were prepared by in situ and inclusion polymerization. Nanoparticles with a size of 30–40 nm were dispersed efficiently in bisphenol‐A alkaline solution before polymerization and the dispersion could be kept in the resultant composite by a reaction that took place at the nanoparticle surface and among the nanoparticles when epichlorohydrin was added. Furthermore, the slightly conglomerated nanoparticles could even be separated by epoxy resin growing among them. This method showed a better dispersion of nanoparticles compared with solution‐blending as observed with TEM. Owing to better combination of epoxy resin and nanoparticles, the resultant nanocomposite showed a 12 °C increase in Tg compared to the nanocomposite prepared by solution‐blending. Tensile test revealed that the tensile strain of nanocomposites rises as the nano‐CaCO3 content increases.
The dispersion mechanism of nanoparticles through in situ and inclusion polymerization. 相似文献
In this paper, we synthesized epoxy resin/CaCO3 nanocomposites through in-situ and inclusion polymerization, and the nanoparticles were well dispersed in the resin matrix observed by SEM. The effects of the nanoparticles on the properties of epoxy resin are discussed. 相似文献
An experimental attempt was made to characterize the fracture behaviour of epoxies modified by halloysite nanotubes and to investigate toughening mechanisms with nanoparticles other than carbon nanotubes (CNTs) and montmorillonite particles (MMTs). Halloysite-epoxy nanocomposites were prepared by mixing epoxy resin with halloysite particles (5 wt% and 10 wt%, respectively). It was found that halloysite nanoparticles, mainly nanotubes, are effective additives in increasing the fracture toughness of epoxy resins without sacrificing other properties such as strength, modulus and glass transition temperature. Indeed, there were also noticeable enhancements in strength and modulus for halloysite-epoxy nanocomposites because of the reinforcing effect of the halloysite nanotubes due to their large aspect ratios. Fracture toughness of the halloysite particle modified epoxies was markedly increased with the greatest improvement up to 50% in KIC and 127% in GIC. Increases in fracture toughness are mainly due to mechanisms such as crack bridging, crack deflection and plastic deformation of the epoxy around the halloysite particle clusters. Halloysite particle clusters can interact with cracks at the crack front, resisting the advance of the crack and resulting in an increase in fracture toughness. 相似文献
Herein the kinetics of network formation (cross-linking) and network degradation (thermal decomposition) in a complex system based on epoxy resin reinforced with hyperbranched amino polymer-functionalized nanoparticles (HAPF) were discussed. Five classes of nanoparticles, that is, nano-SiO2, halloysite nanotubes (HNTs), HNTs@nano-SiO2 core/shell, HAPF/nano-SiO2, HAPF/HNTs@nano-SiO2 core/shell were loaded at 0.5, 1.0, 2.0 (optimal loading among prepared samples), and 5 wt% were examined. Parameters of the cure kinetics and degradation were correlated, and the mechanical properties were interpreted in terms of microstructure and rheological analyses. The isothermal chemorheological cure kinetics study (60, 70, and 80°C) revealed a low activation energy for epoxy/HAPF/HNTs@nano-SiO2 core/shell nanocomposite (72.21 kJ/mol), compared with the blank epoxy (79.99 kJ/mol). Correspondingly, gel time of the system decreased from 1040 to 515 to 237 s upon isotherms of 60, 70, and 80°C, respectively. Tensile strength was also increased vividly (ca. 32%), possibly due to the strong interfacial adhesion, which reflected in an induced shear yielding. Nitrogen-mediated thermal decomposition kinetics suggested an average degradation activation energies of ca. 150 and 210 kJ/mol for the assigned nanocomposites and the blank epoxy, respectively. Overall, there was a complete agreement between the kinetics of network formation and network degradation in the studied epoxy nanocomposite. This work enables understanding of structure-properties-performance in complex epoxy nanocomposites. 相似文献
In this work the effect of inorganic fullerene-like (closed cages) nanoparticles of tungsten disulfide (IF-WS2) on the mechanical properties and especially on the toughness of epoxy resins, was studied. The epoxy resin used was the well-known DGEBA (di-glycidyl ether of bis-phenol A) cured with polyamidoamine. The epoxy/IF-WS2 nanocomposites were prepared by applying a high shear mixing to obtain a uniform dispersion and homogeneous distribution of the IF nanoparticles in the epoxy matrix. Two mixing procedures were used — a low shear of short duration and high shear with a long mixing time. The resulting epoxy nanocomposites were first characterized for their shear and peel strength using appropriate bonded joints. The experimental results demonstrate that enhanced shear strengths and shear moduli were achieved, together with a significant increase in the peel strengths at low concentrations of the IF-WS2 nanoparticles (more than 100% increase at 0.5 wt% IF-WS2). Above the threshold value of 0.5% IF-WS2 the peel strength decreased sharply. The fractured surfaces of the bonded joints were examined by transmission and scanning electron microscopy in order to characterize the fracture mechanisms and analyze the dispersion level of the nanoparticles within the polymer. The electron micrographs indicated that the presence of the nanoparticles in the epoxy matrix induced fracture mechanisms which were different from those observed in the pristine epoxy phase. These mechanisms included: crack deflection; crack bowing; and crack pinning. Evidence for a chemical interaction between the nanoparticles and the epoxy were obtained by infrared measurements in the attenuated total transmittance mode. The data suggests the formation of new carbon–oxygen–sulfur bonds, which are most likely due to the reaction of the outermost sulfur layer of the IF nanoparticles with the reactive epoxy groups. The observed simultaneous increase in both shear and peel strengths at very low IF-WS2 concentrations, found in this work, could lead to the development of high performance adhesives and to new types of structural and ballistic fiber nanocomposites. 相似文献