Mechanical Properties Of Nanocomposites Research Articles

Diamond nanothreads as novel nanofillers for cross-linked epoxy nanocomposites

The recently synthesized novel 1D diamond nanothreads (DNTs) have been reported to possess excellent mechanical property and may act as extraordinary new reinforcements for polymer-matrix nanocomposites. By performing a series of molecular dynamics simulations of cross-linked epoxy nanocomposites, the presence of DNTs are found to provide a remarkable improvement in the mechanical property of DNTs/epoxy nanocomposites, yielding an increase of ∼33% in tensile modulus compared with neat epoxy resin. Interestingly, a moderate aggregation of DNTs enables better enhancement in the tensile modulus, which contradicts to common notion that aggregation of nanofillers usually causes a severe deterioration on the mechanical property of nanocomposites. This encouraging reinforcing mechanism mainly stems from two aspects: 1) aggregated DNTs cause a less deterioration to the tensile modulus of cross-linked epoxy network than uniformly dispersed DNTs, and 2) aggregated DNTs enable a higher reinforcing efficiency along the loading direction owing to their straight structure arising from their relatively high bending rigidity. Moreover, the mechanical property of DNTs/epoxy nanocomposites can be further enhanced through the DNTs' functionalization because of improved load transfer capability across DNT/matrix interface. Our results suggest that DNTs are truly attractive reinforcement and may provide valuable design guidelines for high performance nanocomposites applications.

PCL/POSS Nanocomposites: Effect of POSS Derivative and Preparation Method on Morphology and Properties.

The incorporation of polyhedral oligomeric silsesquioxanes (POSS) molecules as nanoparticles into polymers can provide improved physico-chemical properties. The enhancement depends on the extent of dispersion of the nanofiller, which is determined by the compatibility with the polymer that is by the POSS type, and the processing method. In this study, poly(ε-caprolactone)/POSS derivatives nanocomposites (PCL/POSS) were obtained via solution-casting and melt compounding. Two amino-derivatives containing different alkyl substituents, and ditelechelic POSS-containing hybrid PCL masterbatch were used as nanofillers. The effect of preparation method, POSS content and type on the morphology, thermal, mechanical, and surface properties of nanocomposites were studied. Morphological analysis evidenced the formation of POSS crystalline aggregates, self-assembled POSS molecules of submicrometer size dispersed in the polymer matrix. The best dispersion was achieved using the ditelechelic POSS-containing hybrid PCL masterbatch, and comparing the two amino-POSS derivatives, the one with longer alkyl chain of substituents exhibited better degree of dispersion independent of preparation method. DSC analysis showed the role of POSS derivatives as nucleating agents for PCL. The incorporation of POSS derivatives into the PCL matrix improved thermal stability. The preparation method, POSS type and content had influence on mechanical properties of nanocomposites. POSS nanoparticles enhanced the surface hydrophobicity of PCL.

The ultrasonic-assisted synthesis of tetrafunctional acrylated epoxy clay nanocomposite

The acrylation of a tetrafunctional epoxy resin was carried out through the reaction with acrylic acid in the presence of two different organoclays under ultrasonic irradiation. As reinforcing agents, two different kinds of commercial organoclays, namely Cloisite 15A and Cloisite 30B, were used individually in nanocomposite fabrication. The acrylation reaction of epoxy resin in addition to curing processes was monitored by Fourier transform infrared spectroscopy. The main advantage of the ultrasonic process was a significant reduction in reaction time as low as 8 min. Thermal and mechanical properties of the UV-cured samples were investigated by means of differential scanning calorimetry, dynamic mechanical thermal analysis and the film hardness. The clay dispersion was characterized through X-ray diffraction patterns coupling with the images of two microscopic techniques. The enhancements in nanocomposite glass transition temperature, thermal stability and mechanical properties may be attributed to proper dispersion of organoclay platelets as evidenced in transmission electron microscopy. However, the nanocomposite films reinforced with the Cloisite 30B exhibit more pronounced improvements in the final properties of the nanocomposite film.

Preparation of Multiwall Carbon Nanotubes/Cellulose Nanocomposites Stabilized By 1-Butyl-3-Methyl-Imidazolium (BMIM) - Surfactants

Multiwall carbon nanotubes (MWCNTs) ability to improve electrical, optical and mechanical properties of nanocomposites, have attracted great amount of interest for their huge potential in applying them as filler in polymer matrix. However, this application was hindered because of their low dispersion in polymer matrix and tendency to self-associate into macro-scale aggregates. Recently, diffusion of MWCNTs in cellulose polymer matrix was studied and prepared via latex technology approaches by the addition of 1-butyl-3-methyl-imidazolium (BMIM)-surfactant. The performance of BMIM-surfactants for dispersing MWCNTs in polymer was characterized using a range of techniques including field emission scanning electron microscopy (FESEM), and Thermogravimetric analysis (TGA). Meanwhile, the conductivities of the nanocomposites were also investigated using four-point probe measurements. In this study, MWCNTs were efficiently dispersed in cellulose utilizing 1-butyl-3-methyl imidazolium-dodecyl benzene sulfonate (BMIM-DBS). Interestingly, it was found that BMIM-DBS performs much better than that of the commercially available surfactant sodium dodecyl benzenesulfonate (SDBS), demonstrating the importance of the effect of surfactant counter-ion leading to improved dispersion of MWCNTs in cellulose. This finding will significantly contribute towards the improvement of properties of cellulose for nanocomposite industries.

The Effect of Walled Nano-Carbon on the Physical, Thermal and Mechanical Properties of Epoxy

The physical, the thermal and the mechanical properties of Nano-composites, that consisted of Polyprime EP epoxy that reinforced by multi-walled carbon nanotubes (MWCNTs), have been studied. Various loading ratios, 0.1, 0.5, and 1 wt. %of MWCNT shave been infused into epoxy by a magnetic stirrer and then the hardener mixed with the mthat supplied with the epoxy. All sample shave been cutting using CNC machine. Tensile test, three-point bending, hardness tests, lee's disk, differential scanning calorimetry, water absorption and dielectric and electrical conductivity test were utilized on unfilled, MWCNT-filled epoxy to identify the loading effect on the properties of materials. Scanning electron microscopy (SEM) was used to determine the dispersion case of nanotubes in the base matrix. The tensile test results showed an improvement in Young’s modulus with higher MWCNT addition percentages. The highest value of the tensile strength was obtained at 0.5 wt.% of MWCNT with increasing ratio 66.7%. The values of the Shore D hardness tests are slightly increases as the filler percentage increased, and the maximum value was observed at MWCNT weight percent of 4.4. Images of SEM showed that the specimen of 0.1 wt.% MWCNT has less voids as compared with other specimen. Thermal conductivity and glass transition temperature increase when the loading ratio increased the maximum increasing at 1wt% with 120% and 23% respectively. The true density and electrical conductivity increase when nano carbon infused but decreasing in the dielectric constant and water absorber.

Preparation Of Poly(Vinyl) Alcohol – Multiwalled Carbon Nanotubes Nanocomposite As Conductive And Transparent Film Using Casting Method

PVA nanocomposite was prepared with acid functionalized multiwalled carbon nanotubes as the reinforcing material. The presence of functional groups on MWCNT was revealed by FTIR techniques. Functionalization of MWCNT was conducted by oxidation using acid solution (HNO3 and H2SO4). The functionalized MWCNT induces hydrophilicity to the PVA nanocomposites. Dispersed MWCNT solution was mixed with 10.0% (w/v) PVA as nanocomposite solution (10-40% (v/v)), casted and dried at 60°C. The effect of MWCNT concentration on the electrical conductivities of the PVA nanocomposites was studied very well. The electrical conductivity of the nanocomposites was increased with the concentration of MWCNT, and PVA with 40% (v/v) nanotubes loaded nanocompsoite showed better electric properties. Analysis using spectrofotometry UV-VIS show that adding 10% MWCNT has maximum transmittance at 95.52% and minimum transmittance by 40% MWCNT at 38.95%. As the concentration of MWCNT increased to 40% (v/v), the PVA nanocomposites got transformed from a region of insulator to semiconductor was revealed by taue plot methode. Tensile test was finished to characterizing PVA/MWCNT nanocomposite mechanical properties that show the maximum tensile strength by 40% MWCNT at 45.2 MPa and minimum tensile strength by 10% MWCNT at 36.3 MPa. Change of physical properties describes the existence of important role of MWCNT on the nanocomposite film.

Effect of Carbon Nanotube and Surfactant on Processing, Mechanical, Electrical and EMI-Shielding of Epoxy Composites

Dispersing nanoparticles in a polymer matrix is intrinsically challenging due to unfavorable entropic interactions between the matrix and the nanoparticle. In this research dispersion of nanoparticles in polymer matrix was studied and the effect of dispersion on properties was investigated. The properties of polymer composite depend on the type, size, shape, concentration of nanoparticles, and interactions of polymer-nanaoparticle. The lack of compatibility between inorganic particles and polymer matrix limits the applications of produced nanocomposite. Due to incompatibility, the dispersion of nanoparticles in polymer matrix is very difficult. The epoxy/MWCNT composite was fabricated by solution mixing process. The effect of MWCNT and Amine-Functionalized surfactant, on curing process, EMI-shielding, mechanical and electrical properties of nanocomposite were investigated. Dispersion of MWCNT in solution was investigated using UV-vis spectroscopy. Curing behavior of nanocomposites at different MWCNT loadings was investigated. EMI-shielding of nanocomposite at different concentrations of MWCNT was studied and the results showed that MWCNT and ferric oxide improve absorption loss, reflection loss and shielding effectiveness. Effect of MWCNT inclusion on thermal and mechanical properties of nanocomposites was investigated. Finally, the electrical conductivity was measured using a two-point conductivity test method.

Influence of mixing protocol on the morphology and mechanical properties of PP/SEBS/MMT and PP/SEBS/PPgMA/MMT blends

PP/SEBS blends containing MMT and MMT/PPgMA were obtained by extrusion using different mixing protocols. Specimens were subjected to mechanical testing (tensile, flexural and impact tests) and blend morphologies were characterized by SEM, TEM and XRD. MMT and PPgMA incorporation and the mixing protocol were shown to affect morphology (droplet size), whereas MMT location resulted in variations in nanocomposite mechanical properties. The presence of PPgMA attracted the organoclay towards the matrix phase due to the interaction between the functional groups at the MMT surface layers and the maleic anhydride groups. Nanocomposites with or without PPgMA obtained in one step presented higher stiffness, while nanocomposites obtained in two steps presented higher impact strength.

Selective localization of cellulose nanocrystals in the biodegradable poly(vinyl alcohol)/poly(ε-caprolactone) blend composites prepared by Pickering emulsions

Cellulose nanocrystal (CNC) particles were used as the solid emulsifier to stabilize poly(ε-caprolactone) (PCL) solution-in-poly(vinyl alcohol) (PVA) solution emulsions (oil-in-water), with the objective to prepare ternary nanocomposites using as-obtained Pickering emulsions as the templates. The morphology of emulsions and mechanical properties of nanocomposites were studied, aiming at establishing a convenient route to regulate selective localization of CNCs and multiphase structures. The results show that emulsion stability depend strongly on CNC loadings and PVA concentrations in continuous phase. The evolution of multiphase morphology of emulsions from locally coalesced droplet structure to interfacial saturation one, and finally to droplet-particle interfacial flocculation, shows scaling characteristics with increasing CNC loadings, and can be detected through rheological way. The interfacial localization makes CNCs show excellent reinforcement to ternary nanocomposites because of their two-phase bridging effect. This work provides an interesting strategy of fabrication of the CNC reinforced polymer blend composites with controllable multiphase structures.

Modeling the interphase region in carbon nanotube‐reinforced polymer nanocomposites

Carbon nanotubes are regarded as ideal fillers for polymeric materials due to their excellent mechanical properties. Mechanical analysis without consideration of nanotube–matrix interphase, may not give precise predictions. In this work, the impacts of interphase on the behavior of polymer‐based nanocomposites are studied. For this purpose, a closed‐form micromechanical interphase model considering the diameter of nanotube, the thickness of interphase, and mechanical properties of nanotube and polymer is proposed to estimate the overall mechanical properties of nanotube‐reinforced polymer nanocomposites. Furthermore, the effective elastic constants of the nanocomposites for a wide range of diameters and volume fractions of nanotubes, evaluated via the suggested interphase model, are compared with the results of molecular dynamics simulations. Thereafter, the effects of diameter, length and volume fraction of nanotubes on the mechanical properties of nanocomposites are investigated using the suggested model. The results indicate that mechanical properties of nanocomposites are significantly influenced by the interphase. POLYM. COMPOS., 40:E1219–E1234, 2019. © 2018 Society of Plastics Engineers

Synthesis, structure and mechanical properties of nanocomposites based on exfoliated nano magnesium silicate crystal and poly(acrylamide)

In this study, hydrolyzed polyacrylamide based nanocomposite (HPAM-NC) hydrogels crosslinked by chromium (III) acetate, was synthesized using free radical polymerization. The introduction of magnesium silicate nanocrystals (MSNCs) into the hydrolyzed polyacrylamide (HPAM) network endows the system with enhanced mechanical properties. The successful formation and crystalline behavior of HPAM-NC hydrogels was verified by Fourier Transform Infrared (FTIR) spectroscopy and X-Ray Diffraction (XRD) analyses. Field-Emission Scanning Electron Microscopy (FESEM) and rheology tests showed that the morphology and mechanical properties of HPAM-NC hydrogels were strongly influenced by different content of parameters including concentration of copolymer, nanoparticle and cross-linker. The results showed that this nanocomposite hydrogel is a moldable material so it can expand its application as value-added product.

Spatial distribution and orientation of nanotubes for suppression of stress concentrations optimized using genetic algorithm and finite element analysis

The spatial distribution and orientation of carbon nanotubes (CNTs) have significant effects on the mechanical properties of nanocomposites. But what is the ideal CNT network morphology to achieve a desired mechanical performance? To help answer this question, we propose a novel computational approach to optimize position and orientation of CNTs in a nanocomposite to reduce stress concentrations. The presence of stress risers (either intrinsic or intentionally introduced) is known to control failure of materials and structures at different scales. The present methodology is based on the combined implementation of genetic algorithm and finite element method. The optimization problem is formulated as minimization of a global measure of stress field, found to be more efficient than minimization of the stress concentration factor directly. For the nanocomposites with 0.15% and 0.30% of CNTs, the nanostructure optimization is responsible for 39.5% and 54.4% of stress-concentration reduction compared to unfilled polymer, and 35.6% and 48.9% compared to the polymer filled with uniformly distributed CNTs, respectively. The predicted nanostructures redistribute stresses in the material and decrease the volume of high-stress region. The proposed optimization approach supports ongoing developments in the field of 3D printing that made the design and production of spatially resolved nanostructures possible.

Synthesis and evaluation of surfactants with functional derivatives as additives for improvement of the mechanical and thermal properties of drinking water pipes

In the present study, some thiol surfactants were prepared. Polyester / (nano bentonite) nano composite (A), polyester/(5% nano Bentonite) / thiol surfactant (I) nano composite (B), polyester / (5% nano Bentonite)/thiol surfactant (II) nano composite (C) and Polyester/(5% nano Bentonite)/thiol surfactant (III) nano composite D were fabricated. The mechanical, thermal properties and morphological structure of fabricated composites were studied. The results showed that nano Bentonite powder / polyester composite improve these properties at 5% weight and begins to weaken as the filling ratios increased. However using thiol surfactants as additives to polyester / (nano bentonite) nano composites improve the thermal and mechanical properties of nano composites. But nano composite (D) gave the optimum thermal and mechanical properties which can be used in manufacture of drinking water pipes.

Synthesis of Graphene Oxide and Functionalized CNT Nanocomposites Based on Epoxy Resin

Lately, nanomaterials have been largely studied as reinforcements for epoxy resin. Although their usage is highly promising, the literature has reported some drawbacks regarding the improvement of mechanical properties in nanocomposites. These difficulties are usually due to dispersion of nanomaterials and its adhesion to the polymeric matrix. One approach to this problem is the functionalization of nanomaterials such as carbon nanotubes (CNTs) and graphene. In this work, we have studied the synthesis and functionalization process of CNTs and graphene oxide (GO) to be used as reinforcements for epoxy resin nanocomposites. CNTs were synthesized at 850 °C in a quartz furnace, from hexane and ferrocene vapor, and functionalized by acids and ethylenediamine treatments. GO was obtained by graphite exfoliation through a modified Hummer’s method. The nanomaterials were characterized by Raman spectrum, FT-IR, XRD, and SEM images. Nanocomposites were prepared using these nanomaterials and evaluated by DMA. While both nanomaterials showed an improvement in mechanical properties, suggesting a chemical bond between nanomaterial and the epoxy matrix, it was clear that GO reinforced samples presented a higher storage modulus.

Prediction of mechanical properties of MWCNT-reinforced composites using the RVE model

Carbon nanotube (CNT) composites have mechanical, thermal, and electrical properties superior to those of conventional polymer resin materials. In particular, multi-walled carbon nanotube (MWCNT) composites have higher mechanical strength than single-walled carbon nanotube composites. This work investigates the methods for analytically evaluating and predicting the mechanical properties of MWCNT-reinforced nanocomposites to enable their effective mechanical design. First, the correlation between the thickness of the interphase region (between the carbon nanotubes and the polymer matrix) and the mechanical properties of the MWCNT-reinforced composite was studied. Next, the effect of the relative distribution of carbon nanotubes in the matrix on the mechanical properties of nanocomposites fabricated by injection molding was evaluated. Finally, the effect of agglomerate size on the mechanical properties of nanocomposites was investigated, and a critical size for carbon nanotube agglomerates was analytically proposed.

Synergistic effect of organic and inorganic nano fillers on the dielectric and mechanical properties of epoxy composites

Titanium oxide TiO2/epoxy and TiO2 with detonation nano-diamond (DND)/epoxy nanocomposites were prepared by using ultrasonication method. TiO2 and DND particles as reinforcement species and epoxy as matrix were used to produce nanocomposites. The addition of DND particles into TiO2/epoxy composite improved the dielectric and mechanical properties of nanocomposites in significant amount. The dielectric properties of TiO2-DND/epoxy nanocomposite demonstrated increase in permittivity and conductivity after addition of the DND particles. The maximum and minimum reflection losses of TiO2-DND/epoxy nanocomposite for 0.6 and 0.2wt% DND loading were detected at −14.5 and −1.3dB, respectively. The flexural and tensile strength of TiO2-DND/epoxy nanocomposites with the addition of 0.4wt% DNDs were enhanced to 220% and 223%, respectively. Additionally, the energy to break and percent break strain were 3.9J and 3.86, respectively for 0.4wt% DND loading in TiO2-DND/epoxy nanocomposite. Therefore, the present work findings claim that DND particles are well suitable to enrich the dispersion of TiO2 nanoparticles in epoxy matrix, which develops a strong load transfer interface between the nanoparticles and epoxy matrix and consequently leads to superior properties.

Green and facile surface modification of cellulose nanocrystal as the route to produce poly(lactic acid) nanocomposites with improved properties

In this study, lactic acid monomer or dimer is grafted onto CNC by a simple esterification reaction. The quantitative solid-state 13C NMR spectrum suggests that more than 87% of all the available OH groups on the surface of CNC are substituted by lactic acid. Such modified CNC (CNC-g-LA) exhibits excellent thermostability and nano-sized dispersion in chloroform. Benefit from this character, fully biobased PLLA/CNC-g-LA nanocomposite could be prepared simply by a solution-casting method. The crystallization behavior of obtained nanocomposites has been systematically investigated by differential scanning calorimetry (DSC). The results show that the crystallization rate of PLLA is distinctly enhanced. Moreover, the mechanical properties of nanocomposites are also improved remarkably by the addition of CNC-g-LA because of its excellent dispersion and compatibility with PLLA matrix. This study provides a green and facile way to modify CNC for fabricating bio-nanocomposites with fast crystallization rate and improved mechanical properties.

Analysis of the intragranular microstructure in ceramic nanocomposites and their effect on the mechanical properties

AbstractThe formation of intragranular microstructure in Al2O3/ZrO2 and Si2N2O/Si3N4 nanocomposites was analyzed, and the effect of intragranular microstructure on the mechanical properties of nanocomposites was investigated. Results suggest 3 requisite conditions for the formation of intragranular microstructure and the role of intracrystalline glass phase and scar microstructure. In case of Al2O3/ZrO2, the intragranular microstructure leads to the formation of transgranular fracture, which in turn improves the mechanical properties via strengthening and toughening. On the other hand, in case of Si3N4/Si2N2O nanocomposites, intragranular microstructure reduces the possibility of bridging, pulling out, and crack deflection, thereby leading to the deterioration of strength and toughness. Based on these results, we can conclude that the formation of intragranular microstructure does not necessarily improve the mechanical properties in all kinds of materials. Rather, the effect of intragranular microstructure on the mechanical properties of nanocomposites is related to the strengthening and toughing mechanism of matrix materials.

Micromechanical characterizing the effective elastic properties of general randomly distributed CNT–reinforced polymer nanocomposites

This work deals with a comprehensive study on the general off-axis mechanical properties of polymer nanocomposites reinforced by carbon nanotubes (CNTs) using a three-dimensional micromechanical model. The representative volume element (RVE) of the model consists of three phases including CNT, polymer matrix and interphase formed due to the non-bonded interaction between a CNT and the polymer. The CNTs are assumed to be transverse isotropic. Both random under several statistical distribution and regular arrangements of the CNTs within the matrix are considered in the analysis. The results are shown to be consistent with the results of other theoretical methods and experiment. Effects of various parameters, including the CNT aspect ratio, orientation, distribution, cross sectional shape and volume fraction, the interphase characteristics and the matrix material properties are examined on the effective elastic properties of CNT–reinforced polymer nanocomposites. The results reveal that the mechanical properties of the nanocomposite are extremely dependent on the CNTs off-axis angle. The interphase effect is more significant for the elastic modulus of 70°off-axis coupon. It is found that CNT volume fraction has the maximum effect for the longitudinal elastic modulus. For 90°coupons, elastic modulus of the nanocomposite is significantly affected by the matrix properties. The results obviously indicate that the elastic modulus, especially in the longitudinal direction increases up to a threshold value and then saturates as the CNT aspect ratio increases. Also, it is found that the CNT arrangement does not affect the longitudinal elastic modulus of CNT–polymer nanocomposites, whereas the transverse elastic modulus is significantly affected by the CNT arrangement.

Amine-modified graphene oxide as co-curing agent of epoxidized polysulfide prepolymer: Thermophysical and mechanical properties of nanocomposites

Amine-modified graphene oxide (GO) nanosheets were used to co-cure epoxy-terminated polysulfide pre-polymer and fabrication of polysulfide polymer/graphene nanocomposites. GO was modified with ethylenediamine (EDA) to obtain amine-functionalized reduced GO-EDA nanosheets. Besides, epichlorohydrin reacted with disodium tetrasulfide (Na2S4) to prepare epoxide-terminated polysulfide prepolymer. Different amounts of GO-EDA nanosheets were used to fabricate EDA-cured nanocomposites. Different properties of nanocomposites were investigated consisting of structural, thermophysical, thermal and mechanical properties. Also, in-plane tensile properties of samples were evaluated by a peel approach where a film of nanocomposites was exerted onto the surface of aluminum and adhesion was evaluated via ASTM D3039. Results showed that glass transition temperature (Tg), melting temperature (Tm) and enthalpy of melting (ΔHm) of nanocomposites increased by increasing the amount of GO-EDA nanosheets up to 0.7 wt% whereas they were not changed significantly by more increase of nanosheets. Also, using 0.7 wt% GO-EDA led to the highest thermal stability, hardness and in-plane tensile properties of nanocomposites. In this field, variation of crystallinity of samples played the most important role in determining thermophysical and mechanical properties.