Graphene nanoplate and multiwall carbon nanotube–embedded polycarbonate hybrid composites: High electromagnetic interference shielding with low percolation threshold

This study has reported the preparation of polycarbonate (PC)/graphene nanoplate (GNP)/multiwall carbon nanotube (MWCNT) hybrid composite by simple melt mixing method of PC with GNP and MWCNT at 330°C above the processing temperature of the PC (processing temperature is 280°C) followed by compression molding. Through optimizing the ratio of (GNP/MWCNT) in the composites, high electromagnetic interference shielding effectiveness (EMI SE) value (∼21.6 dB) was achieved at low (4 wt%) loading of (GNP/MWCNT) and electrical conductivity of ≈6.84 × 10⁻⁵ S.cm⁻¹ was achieved at 0.3 wt% (GNP/MWCNT) loading with low percolation threshold (≈0.072 wt%). The high temperature melt mixing of PC with nanofillers lowers the melt viscosity of the PC that has helped for better dispersion of the GNPs and MWCNTs in the PC matrix and plays a key factor for achieving high EMI shielding value and high electrical conductivity with low percolation threshold than ever reported in PC/MWCNT or PC/graphene composites. With this method, the formation of continuous conducting interconnected GNP‐CNT‐GNP or CNT‐GNP‐CNT network structure in the matrix polymer and strong π–π interaction between the electron rich phenyl rings and oxygen atom of PC chain, GNP, and MWCNT could be possible throughout the composites. POLYM. COMPOS., 37:2058–2069, 2016. © 2015 Society of Plastics Engineers     

Indentation and scratch behavior of functionalized MWCNT–PMMA composites at the micro/nanoscale

Polymethylmethacrylate (PMMA) and functionalized multiwalled carbon nanotube (F‐MWCNT) based composite films were prepared using solution casting method. Nanoindentation and scratch measurements were carried out to study the influence of F‐MWCNT as the reinforcement on the mechanical properties of the composite at the sub‐micron scale. The composites were prepared with varying weight percentages of F‐MWCNT in the PMMA matrix. The composites containing an adequate amount (0.25 wt%) of F‐MWCNT was found to demonstrate the maximum nanomechanical properties, viz. hardness, elastic modulus, recovery index. Scratch resistance measured in terms of coefficient of friction, also showed maximum value for the PMMA composite reinforced with 0.25 wt% of F‐MWCNT. POLYM. COMPOS., 35:948–955, 2014. © 2013 Society of Plastics Engineers     

Preparation and characterization of melt‐processed polycarbonate/multiwalled carbon nanotube composites

This study describes the preparation of polycarbonate (PC)/multiwalled carbon nanotube (MWCNT) composites by melt processing the PC and PC/MWCNT master batch at 260°C. The PC/MWCNT master batch was prepared using ultrasonic mixing the carboxylic acid containing MWCNT and PC in a tetrahydrofuran (THF) solution. The HRTEM images of PC/MWCNT master batch and PC/MWCNT nanocomposites show that the MWCNT is well separated and uniformly distributed in the PC matrices. Mechanical properties of the fabricated nanocomposites measured by dynamic mechanical analysis indicate significant improvements in the storage modulus when compared with that of pure PC matrix. The conductivities of 2 and 5 wt% PC/MWCNT nanocomposites are more than four and seven orders in magnitude higher than that of PC without MWCNT, respectively. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

The Preparation and Characterization of Silk/Gelatin Biocomposites

There is a growing interest in the use of composite materials. Silk fiber/gelatin biocomposites were fabricated using compression molding. The fiber content in the composite varied from 10–30 wt%. Composite containing 30 wt% silk showed the best mechanical properties. Tensile strength, tensile modulus, bending strength, bending modulus and impact strength, hardness of the 30% silk content composites were found 54 MPa, 0.95 GPa, 75 MPa and 0.43 GPa and 5.4 kJ/m², 95.5 Shore A, respectively. Water uptake properties at room temperature, accelerated weathering aging, irradiation, thermomechanical analysis, and degradation in soil were carried out in this experiment.     

Effect of phenol functionalized carbon nanotube on mechanical,dynamic mechanical,and thermal properties of isotactic polypropylene nanocomposites

In this work, multiwall carbon nanotubes (MWCNT) were functionalized with phenol and characterized by using Fourier transform infrared spectroscopy (FTIR). Isotactic polypropylene (iPP)/MWCNT composites of both the unfunctionalized and functionalized MWCNT were prepared by melt blending in a miniextruder at different loadings of nanotubes (i.e., 0.1, 0.25, 1.0, and 5.0 wt%). The tensile properties of the composites were found to increase with increase in nanotube loading with a maximum in Young's modulus being achieved at 1.0 wt% loading of phenol functionalized MWCNT. The differential scanning calorimetry (DSC) studies reveal the nucleating effect of MWCNT on the crystallization of iPP. Percentage crystallinity was found to increase on phenol functionalization of MWCNT. Results of X‐ray diffraction studies of the composites are in conformity with that of DSC studies. Dynamic mechanical studies reveal that the functionalized MWCNT causes many fold increase in the storage modulus, and the effect is pronounced in the case of functionalized MWCNT. POLYM. ENG. SCI. 2012. © 2011 Society of Plastics Engineers     

Carbon nanotube reinforced poly(trimethylene terephthalate) nanocomposites: Viscoelastic properties and chain confinement

Through a very facile route, a new class of nanocomposites involving poly(trimethylene terephthalate; PTT) and multiwalled carbon nanotubes (MWCNTs) was developed which was found to be high performance engineering material showing high modulus. Morphological, mechanical, viscoelastic, and thermal properties of the PTT nanocomposites with varying compositions of MWCNT were systematically studied and the results were analyzed. The dynamic mechanical and tensile properties of all the nanocomposites were seen to be enhanced with the addition of MWCNT and the sample containing 2 wt% MWCNT showing a storage modulus as much as 9.4 × 10⁸ GPa. The results were correlated with the morphological features obtained from scanning electron microscopy and transmission electron microscopy. Coefficient of effectiveness, degree of entanglement density, and reinforcement efficiency factor were estimated from the storage modulus values and, in addition, the degree of chain confinement also could be quantified. Furthermore, theoretical modelling was also done on the elastic properties of the composites. The crystallization temperature, glass transition temperature, and percentage crystallinity were estimated for all the nanocomposites and it was found that the sample with 3 wt% MWCNT content exhibited the highest glass transition temperature of 68.2°C. POLYM. ENG. SCI., 59:E435–E445, 2019. © 2018 Society of Plastics Engineers     

Synthesis and mechanical properties of polybenzimidazole nanocomposites reinforced by vapor grown carbon nanofibers

Polybenzimidazole (PBI) nanocomposites containing 0.5–5 wt% vapor grown carbon nanofibers (VGNFs) were successfully synthesized by solvent evaporation method. Fracture morphology examination confirmed the uniform dispersion of VGNFs in the matrix. The mechanical properties of neat PBI and the nanocomposites were systematically measured by tensile test, dynamic mechanical analysis (DMA), hardness measurement, and friction test. Tensile tests revealed that Young's modulus increased by about 43.7% at 2 wt% VGNFs loading, and further modulus growth was observed at higher filler loadings. DMA studies showed that the nanocomposites have higher storage modulus than neat PBI in the temperature range of 30–350°C, holding storage modulus larger than 1.54 GPa below 300°C. Outstanding improvement of hardness was achieved for PBI upon incorporating 2 wt% of VGNFs. The results of friction test showed that coefficient of friction of PBI nanocomposites decreased with VGNFs content compared with neat PBI. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Montmorillonite–multiwalled carbon nanotube nanoarchitecture reinforced thermoplastic polyurethane

Montmorillonite (MMT)–multiwalled carbon nanotube (MWCNT) hybrids were prepared in different weight ratios by simple dry grinding method and characterized. Subsequently, MMT–MWCNT (1:1) hybrid was used as reinforcing filler in developing thermoplastic polyurethane (TPU) nanocomposites by solution blending method. Thermogravimetric analysis showed that 0.25 wt% hybrid‐loaded TPU nanocomposite exhibited maximum enhancement of 31°C corresponding to 50 wt% loss in thermal stability when compared with neat TPU. Differential scanning calorimetry of this composite also indicated that its crystallization and melting temperatures are enhanced by 37 and 13°C, respectively. Mechanical data showed that tensile strength and Young's modulus of 0.50 wt% filled TPU were maximum improved by 57 and 87.5%, respectively. Dynamic mechanical analysis (DMA) measurements indicated 174% (50°C) improvement in storage modulus of 0.50 wt% hybrid‐loaded TPU. Such improvements in thermal and mechanical properties have been attributed to homogeneous dispersion, strong interfacial interaction, and synergistic effect. POLYM. COMPOS., 37:1775–1785, 2016. © 2014 Society of Plastics Engineers     

Effect of multiwall carbon nanotubes on thermomechanical and electrical properties of poly(trimethylene terephthalate)

Multiwalled carbon nanotubes (MWCNTs) were synthesized using chemical vapor deposition and poly(trimethylene terephthalate) (PTT)/MWCNT composites with varying amounts of MWCNTs were prepared by melt compounding using DSM micro‐compounder. Morphological characterization by SEM and TEM showed uniform dispersion of MWCNTs in PTT matrix upto 2% (w/w) MWCNT loading. Incorporation of MWCNTs showed no effect on percent crystallinity but affected the crystallite dimensions and increased the crystallization temperature. Dynamic mechanical characterization of composites showed an increase in storage modulus of PTT upon incorporation of MWCNTs above glass transition temperature. The electrical conductivity of PTT/MWCNT composites increased upon incorporation of MWCNTs and percolation threshold concentration was obtained at a loading of MWCNTs in the range of 1–1.5% (w/w). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Highly filled graphene‐benzoxazine composites as bipolar plates in fuel cell applications

This research emphasizes on the development of highly filled graphene‐polybenzoxazine composites and investigates thermal, electrical, and mechanical properties of the obtained composites for bipolar plate applications. The composition of graphene loading was achieved to be in the range of 10–60 wt%. The experimental results revealed that at the maximum graphene content of 60 wt% (44.8 vol%) in the polybenzoxazine, storage moduli at room temperature of the composites were considerably enhanced with the amount of the graphene, that is, from 5.9 GPa of the neat polybenzoxazine to about 25.1 GPa at 60 wt% of graphene. Glass transition temperatures (T_g) of the obtained composites were observed to be 174–188°C and the values substantially increased with increasing the filler contents. At 60 wt% of graphene content, thermal conductivity, as high as 8.0 W/mK, is achieved for the graphene‐filled polybenzoxazine. Furthermore, the flexural modulus and flexural strength of the composites were found to be as high as 18 GPa and 42 MPa, respectively. Water absorption of graphene filled‐composite is relatively low with the value of only about 0.06% at 24 h of water immersion. Additionally, electrical conductivity was measured to be 357 S/cm at maximum loading of the graphene. Therefore, the graphene‐filled composites based on polybenzoxazine are highly attractive as bipolar plates for polymer electrolyte membrane fuel cells applications. POLYM. COMPOS., 37:1715–1727, 2016. © 2014 Society of Plastics Engineers     

Thermal,Mechanical and Morphological Characterization of Jute/Gelatin Composites

Jute fabrics/gelatin biocomposites were fabricated using compression molding. The fiber content in the composite varied from 20–60 wt%. Composites were subjected to mechanical, thermal, water uptake and scanning electron microscopic (SEM) analysis. Composite contained 50 wt% jute showed the best mechanical properties. Tensile strength, tensile modulus, bending strength, bending modulus and impact strength of the 50% jute content composites were found to be 85 MPa, 1.25 GPa, 140 MPa and 9 GPa and 9.5 kJ/m², respectively. Water uptake properties at room temperature were evaluated and found that the composites had lower water uptake compared to virgin matrix.     

Dynamic mechanical properties of extruded nylon–wood composites

Dynamic mechanical properties determine the potential end use of a newly developed extruded nylon–wood composite in under‐the‐hood automobile applications. In this article, the dynamic mechanical properties of extruded nylon–wood composites were characterized using a dynamic mechanical thermal analyzer (DMTA) to determine storage modulus, glass transition temperature (T_g), physical aging effects, long‐term performance prediction, and comparisons to similar products. The storage modulus of the nylon–wood composite was found to be more temperature stable than pure nylon 66. The T_g range of the nylon–wood composite was found to be between 23 and 56°C, based on the decrease in storage modulus. A master curve was constructed based on the creep curves at various temperatures from 30 to 80°C. The results show that the relationship between shift factors and temperature follows Arrhenius behavior. Nylon–wood composites have good temperature‐dependent properties. Wood fillers reduced the physical aging effects on nylon in the wood composites. The comparison of the nylon–wood composite with other similar products shows that nylon–wood composites are a promising low cost material for industrial applications. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Experimental investigation and numerical simulation of granite powder filled polymer composites for wind turbine blade: A comparative analysis

This paper describes the mechanical, thermo‐mechanical, and thermal behavior of unfilled E‐glass fiber (10–50 wt%) reinforced polymer (GFRP) composites and granite powder filled (8–24 wt%) GFRP composite in different weight percentages, respectively. The void fraction of unfilled glass epoxy composite is decreased from 7.71% to 3.17% with the increase in fiber loading from 10 to 50 wt%. However, void fraction for granite powder filled GFRP composites show reverse in trend. The granite powder addition in glass‐epoxy composites show significant improvement in hardness (37–47 Hv), impact strength (31.56–37.2 kJ/m²), and stress intensity factor (by 14.29% for crack length of 5 mm) of the composites. The thermo‐mechanical analyses also show strong correlation with the mechanical performance of the composites. The minimum difference of 0.17 GPa in storage and flexural moduli are observed for unfilled 20 wt% glass epoxy composite; whereas, maximum difference of 0.71 GPa is recorded for unfilled 50 wt% glass epoxy composite. Moreover, the numerical and experimentally measured thermal conductivity of unfilled and granite powder filled epoxy composites are within the lower and upper bound values. Hence, a successful attempt is presented for mechanical analysis of full scale model by finite element analysis. The results show that finite element analysis predicted reasonably actual stress value and tip deflection of wind turbine blade. POLYM. COMPOS., 38:1335–1352, 2017. © 2015 Society of Plastics Engineers     

Positive temperature coefficient to resistively characteristics of polystyrene/nickel powder/multiwall carbon nanotubes composites

Positive temperature coefficient to resistivity (PTCR) characteristics of polystyrene (PS)/Ni‐powder (40 wt%) composites in the presence of multiwall carbon nanotubes (MWCNTs) has been investigated with reference to PS/carbon black (CB) composites. The PS/CB (10 wt%) composites showed a sudden rise in resistivity (PTC trip) at ≈110°C, above the glass transition temperature (T_g) of PS (T_g ≈95°C). Interestingly, the PTC trip temperature of PS/Ni‐powder (40 wt%)/MWCNT (0.75 phr) composites appeared at ≈90°C (below T_g of PS), indicating better dimensional stability of the composites at PTC trip temperature. The PTC trip temperature of the composites below the T_g of matrix polymer (PS) has been explained in terms of higher coefficient of thermal expansion (CTE) value of PS than Ni that led to a disruption in continuous network structure of Ni even below the T_g of PS. The dielectric study of PS/Ni‐powder (40 wt%)/MWCNT (0.75 phr) composites indicated possible use of the PTC composites as dielectric material. Dynamic mechanical analysis (DMA) and thermogravimetric analysis studies revealed higher storage modulus and improved thermal stability of PS/Ni‐powder (40 wt%)/MWCNT (0.75 phr) composites than the PS/CB (10 wt%) composites. POLYM. COMPOS., 33:1977–1986, 2012. © 2012 Society of Plastics Engineers     

Preparation,microstructure, mechanical,and thermal properties of in situ polymerized polyimide/organically modified sericite mica composites

In this work, sericite mica was initially modified with a multi‐step procedure and the novel composites of polyimide (PI) with the organophilic sericite mica were subsequently synthesized via in situ polymerization technique. XRD patterns revealed d₀₀₂‐spacing of clay was expanded from 0.99 to 2.77 nm. TEM photographs indicated majority of the organoclay exhibited an exfoliated morphology structure in composites with 5 wt% filler loading. Several critical properties of composites such as thermal stability, mechanical property, and storage modulus were tremendously enhanced with the increasing organoclay loading. Especially, the glass transition temperature of composites with 7 wt% organoclay addition revealed a 72°C increment compared with pristine PI, indicating greater improvement than the reported literature values. POLYM. COMPOS., 37:2243–2251, 2016. © 2015 Society of Plastics Engineers     

Evaluation of multiwalled carbon nanotubes as reinforcement for natural fiber‐based composites

This paper presents the effects of multi‐walled carbon nanotube (MWCNT) as reinforcing agent on some properties of natural fiber/polypropylene composites. In the sample preparation, MWCNT contents and fiber types (bagasse stalk and poplar) were used as variable parameters. The composites with different MWCNT contents were fabricated by melt compounding in a twin‐screw extruder and then by injection molding. The mass ratio of the wood flour to polymer was 40/60 (w/w). The mechanical properties of composites in terms of tensile, flexural, and Izod impact strength were evaluated. The morphology of the specimens was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. Based on the findings of this study, it appears that mechanical properties reached the maximum when 2.5 wt% MWCNT were used. However, addition of 3.5 wt% MWCNT could not enhance the mechanical properties considerably. TEM micrographs showed that at high level of MWCNT loading (3.5 wt%) increased population of MWCNT leads to agglomeration and stress transfer gets blocked. The mechanical properties of composites filled with poplar fibers were generally greater than bagasse stalk composites. POLYM. COMPOS., 37:3269–3274, 2016. © 2015 Society of Plastics Engineers     

Synthesis of glass fiber‐multiwall carbon nanotube hybrid structures for high‐performance conductive composites

The conductive polyamide 66 (PA66)/carbon nanotube (CNT) composites reinforced with glass fiber‐multiwall CNT (GF‐MWCNT) hybrids were prepared by melt mixing. Electrostactic adsorption was utilized for the deposition of MWCNTs on the surfaces of glass fibers (GFs) to construct hybrid reinforcement with high‐electrical conductivity. The fabricated PA66/CNT composites reinforced with GF‐MWCNT hybrids showed enhanced electrical conductivity and mechanical properties as compared to those of PA66/CNT or PA66/GF/CNT composites. A significant reduction in percolation threshold was found for PA66/GF‐MWCNT/CNT composite (only 0.70 vol%). The morphological investigation demonstrated that MWCNT coating on the surfaces of the GFs improved load transfer between the GFs and the matrix. The presence of MWCNTs in the matrix‐rich interfacial regions enhanced the tensile modulus of the composite by about 10% than that of PA66/GF/CNT composite at the same CNT loading, which shows a promising route to build up high‐performance conductive composites. POLYM. COMPOS. 34:1313–1320, 2013. © 2013 Society of Plastics Engineers     

Silver-filled epoxy composites: effect of hybrid and silane treatment on thermal properties

The combination effects of hybrid nano–micron fillers and filler treatment on the thermal properties of silver-filled epoxy composites are experimentally evaluated. These hybrid composites are fabricated using two different sizes and shapes of silver particles, namely 80 nm with spherical shape and 4–8 μm with flaky shape. In this study, the ratio of silver flakes to silver nanoparticles was varied from 100:0, 75:25, 50:50, 25:75, and 0:100 at a fixed silver loading of 6 vol.%. The silver fillers are treated with 3-aminopropyl triethoxysilane (3AMPTES) at different concentrations of 5, 10, and 30 wt%. The hybrid micro:nano at 50:50 shows the highest storage modulus and the lowest coefficient of thermal expansion (CTE) value compared with other ratios. The silver fillers with 10 wt% of 3AMPTES show improvement in storage modulus, CTE, and thermal stability compared with untreated and further increasing of 3AMPTES at 30 wt% did not show any significant improvement.     

Crosslinked carboxylated SBR composites reinforced with chitin nanocrystals

This study aims to develop and characterize the nanocomposites using sulfur cross-linked carboxylated styrene-butadiene rubbers (S-xSBR) as the matrix and chitin nanocrystals (CNCs) as nanofillers. The composites’ morphology and properties were examined by light transmittances, fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), dynamic mechanical analysis (DMA), thermo gravimetric analyzer (TGA), and tensile properties determination. The addition of CNCs has slight effect on transparency of the composite films. FTIR data confirm the interfacial interactions between CNCs and S-xSBR via hydrogen bonds. CNCs are uniformly dispersed in the matrix from SEM result. The addition of CNCs can significantly improve the tensile strength and modulus both in static and dynamic states. The tensile modulus and tensile strength of S-xSBR/CNCs composites with the 4 wt.% CNCs is 62.5 % and 97.6 % higher than that of pure S-xSBR. The storage modulus, glass transition temperature, and the thermal stability of the composites are higher than those of the neat S-xSBR. The mechanical properties of the composite films are water-responsive, as the swollen samples exhibit obviously decreased strength and modulus. The greatest mechanical contrast is shown in the S-xSBR/CNCs composites with 2 wt.% CNCs loading whose tensile modulus decrease from 60.4 to 6.1 MPa after swelling equilibrium. The significant reinforcement effect of CNCs on S-xSBR is attributed to the unique structure of CNCs and the interfacial interactions in the composite.     

Mechanical, rheological, and thermal behavior assessments in HDPE/PA-6/EVOH ternary blends with variable morphology

Visco-elastic and dielectric spectra of multiwalled carbon-nanotube reinforced silicon elastomer nanocomposites were used to study relaxation behavior. SEM photomicrographs shows well dispersion of MWCNT in elastomer matrix. In visco-elastic analysis primary relaxation was studied as a function of temperature (?100 to 100 °C) at frequency 1Hz and strain 1 %. The effect of MWCNT loadings on storage modulus, loss modulus, and loss tangent has been studied. The non-linearity in loss tangent, storage modulus and loss modulus was explained on the basis of MWCNT-elastomer interaction and the inter-aggregate attraction of MWCNT. The secondary β relaxation was studied using dielectric relaxation spectra in the frequency range of 0.1 Hz to 10⁶ Hz. The effect of MWCNT loadings on the complex and real parts of impedance was distinctly visible which has been explained on the basis of interfacial polarization of fillers in a heterogeneous medium and relaxation dynamics of polymer chains in the vicinity of fillers. The dielectric formalism has been utilized to further investigate the conductivity and relaxation phenomenon. The ‘percolation limit’ of the MWCNT in the silicon elastomer was found to be in the range of 4 phr loading.