In this work, a series of cellulose acetate (CA)/poly(vinylpyrrolidone) (PVP) membranes composed ... more In this work, a series of cellulose acetate (CA)/poly(vinylpyrrolidone) (PVP) membranes composed of different CA/PVP ratios were synthesized using 2-stage phase inversion protocol. The ions dialysis separation performance of the membranes was investigated using dialysis process with mix solution containing K + , Na + , Ni 2+ and Zn 2+ ions for separation of following pair of ions:
Cellulose acetate/Polyethylene glycol-600 composite membranes were fabricated by two step phase i... more Cellulose acetate/Polyethylene glycol-600 composite membranes were fabricated by two step phase inversion procedure and modified by in-situ reduction of silver nitrate. FTIR spectra demonstrated the existence of functional groups for bonding of silver with oxygen at 370 cm −1 , 535 cm −1. The XRD diffractogram indicates characteristic peaks at 2 values of 38.10 • , 44.30 • , 64.40 • , and 77.30 • which confirm the successful incorporation of silver within matrix of composite membranes. The morphology of composite membranes with appearances of spongy voids was exemplified from the scanning electron microscope. The atomic force microscopy was used to determine the increase in the surface roughness of the membranes. The increase in hydrophilicity, measured through contact angle, is rendered to the embedment of silver. The modification of membranes increased the flux from 0.80 to 0.95 L/hr.m 2. The resulting membranes have outstanding ability to fight against gram negative Escherichia Coli and Bacillus Sabtilus. The novel cellulose acetate/polyethylene glycol membranes customized with silver have paved the path for evolution of axenic membranes.
In this work, a series of cellulose acetate (CA)/poly(vinylpyrrolidone) (PVP) membranes composed ... more In this work, a series of cellulose acetate (CA)/poly(vinylpyrrolidone) (PVP) membranes composed of different CA/PVP ratios were synthesized using 2-stage phase inversion protocol. The ions dialysis separation performance of the membranes was investigated using dialysis process with mix solution containing K + , Na + , Ni 2+ and Zn 2+ ions for separation of following pair of ions:
In this study, glass fiber/epoxy composites were interfacially tailored by introducing polyamidoa... more In this study, glass fiber/epoxy composites were interfacially tailored by introducing polyamidoamine (PAM) dendrimer functionalized graphene oxide (GO) into epoxy matrix. Two different composites each containing varying loading fraction (0.5, 1.0, and 1.5 wt%) of GO and GO-PAM were fabricated via hot press processing. Composites were evaluated for interlaminar shear strength (ILSS), dynamic mechanical properties and thermal conductivity. The inclusion of 1.5 wt% GO-PAM resulted~57.3%,~42.7%, and~54% enhancement in ILSS, storage modulus and thermal conductivity, respectively. Almost, 71% reduction in coefficient of thermal expansion was also observed at same GO-PAM loading. Moreover, higher glass transition temperature was observed with GO-PAM addition. GO-PAM substantially improved fiber/matrix interfacial adhesion, which was witnessed through scanning electron microscopy. The enhanced thermo-mechanical performance was attributed to interfacial covalent interactions engendered by ring opening reaction between epoxy and amine moieties of PAM dendrimers. These multiscale composites with extraordinary functional properties can outperform conventional counterparts with improved reliability and performance.
Surface tuned GO sheets are considered the opportune pothunter for the reinforcement of conventio... more Surface tuned GO sheets are considered the opportune pothunter for the reinforcement of conventional glass fiber reinforced composites (GFRCs). Herein, we have tried to disseminate the effects of N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane functionalized GO (GO-AEAPTS) and pristine GO sheets on thermo-mechanical properties of epoxy/glass fiber composites. Fourier Transform-infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic light scattering (DLS) and transmission electron microscope (TEM) were used to characterize the GO sheets. Multiscale composites integrated with GO-AEAPTS (1.5 wt%) provided maximum gain in all the studied properties i.e., interlaminar shear strength (ILSS), impact strength and thermal conductivity were improved by ~ 55, ~ 24 and ~ 70%, respectively. Storage modulus and glass transition temperature increased by ~ 44% and 14 °C, over the neat GFRC. In addition, GO-AEAPTS composites exhibited higher coefficient of effectiveness and crosslink density than those of GO counterparts. These property enhancements were credited to the homogeneous distribution of GO sheets, strong interfacial interactions (interfacial covalent interactions and hydrogen bonding) between GO-AEAPTS and epoxy resin as well as good fiber/matrix compatibility. Such multiscale composites with functional properties can outperform conventional counterparts with improved safety and reliability of structures and reduce maintenance costs.
Novel Polyurethane/Polyvinyl chloride-co-vinyl acetate (PU/PVCA) blend RO membranes were synthesi... more Novel Polyurethane/Polyvinyl chloride-co-vinyl acetate (PU/PVCA) blend RO membranes were synthesized in four different ratios 90/10, 80/20, 70/30, 60/40. On the basis of appreciable salt rejection, PU/PVCA-4 (60/40) was selected for chemical crosslinking with 1 to 4 wt% of Epichlorohydrin (ECH). The confirmation of physical and chemical crosslinking between PU and PVCA was validated by Fourier transform infrared spectroscopy (FTIR). The SEM micrographs confirmed the dense film structure for all crosslinked and un-crosslinked membranes. Tensile testing, thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) evaluated the performance of ECH crosslinked membranes. In addition, DMA revealed the existence of single glass transition temperature (T g) in case of crosslinked membranes advocating the compatibility of PU and PVCA. In terms of flux and salt rejection, PU/PVCA-4 membrane crosslinked with 3 wt% ECH demonstrated the optimum results. The permeation data was collected at two different temperatures i.e. 25°C and 70°C for crosslinked membranes and the results indicated~67.6% higher flux at 70°C over the flux obtained at 25°C. This amelioration in flux shows the thermo-sensitive behavior of crosslinked membranes. These results demonstrate that ECH crosslinked PU/PVCA membranes can outstand the conventional PU membranes in terms of mechanical, thermal and permeation properties.
This review aims at reporting on very recent developments in syntheses, properties and (future) a... more This review aims at reporting on very recent developments in syntheses, properties and (future) applications of polymer-layered silicate nanocomposites. This new type of materials, based on smectite clays usually rendered hydrophobic through ionic exchange of the sodium interlayer cation with an onium cation, may be prepared via various synthetic routes comprising exfoliation adsorption, in situ intercalative polymerization and melt intercalation. The whole range of polymer matrices is covered, i.e. thermoplastics, thermosets and elastomers. Two types of structure may be obtained, namely intercalated nanocomposites where the polymer chains are sandwiched in between silicate layers and exfoliated nanocomposites where the separated, individual silicate layers are more or less uniformly dispersed in the polymer matrix. This new family of materials exhibits enhanced properties at very low filler level, usually inferior to 5 wt.%, such as increased Young's modulus and storage modulus, increase in thermal stability and gas barrier properties and good flame retardancy.
A review is given of the academic and industrial aspects of the preparation, characterization, ma... more A review is given of the academic and industrial aspects of the preparation, characterization, materials properties, crystallization behavior, melt rheology, and processing of polymer/layered silicate nanocomposites. These materials are attracting considerable interest in polymer science research. Hectorite and montmorillonite are among the most commonly used smectite-type layered silicates for the preparation of nanocomposites. Smectites are a valuable mineral class for industrial applications because of their high cation exchange capacities, surface area, surface reactivity, adsorptive properties, and, in the case of hectorite, high viscosity and transparency in solution. In their pristine form they are hydrophilic in nature, and this property makes them very difficult to disperse into a polymer matrix. The most common way to remove this difficulty is to replace interlayer cations with quarternized ammonium or phosphonium cations, preferably with long alkyl chains.
Especially in the course of modern automotive coatings comprising a reduced number of layers the ... more Especially in the course of modern automotive coatings comprising a reduced number of layers the resistance towards the stone chipping is becoming an issue. Layered double hydroxide (LDH)-based polymer composites are readily accessible materials and suitable to impart impact resistance to coatings, provided that an accurate understanding of the structure property relations both of the platelets and the composites is achieved.
In the present investigation, effect of nano layered silicates on the properties of an automotive... more In the present investigation, effect of nano layered silicates on the properties of an automotive refinish clear coat based on polyurethane has been studied. Observation by means of X-ray diffraction (XRD) technique indicates the presence of a partially intercalated structure due to dispersion of nano layers in the polymer matrix. Some levels of hazing have been established by increasing the amount of nano-filler. The effect of nano-filled clear coat on the reflectance spectra of a metallic coated substrate has been studied under three different light sources using a goniospectrophotometer and compared with a blank clear coat to determine if it can be identified by human eye. Scratch and mar resistance tests showed significant improvement even 48 h after application, when there was no gloss reduction due to usage of nano-filler. Gloss retention was increased by about 10% in presence of only 3 wt% of nano-filler. In addition to some scratch and mar resistance tests, other standard tests like adhesion, impact and bending were performed to find out optimum nano-filler/polymer ratio.
This review reports recent advances in the field of polymer-layered silicate nanocomposites. Thes... more This review reports recent advances in the field of polymer-layered silicate nanocomposites. These materials have attracted both academic and industrial attention because they exhibit dramatic improvement in properties at very low filler contents. Herein, the structure, preparation and properties of polymer-layered silicate nanocomposites are discussed in general, and detailed examples are also drawn from the scientific literature.
A condensed review of mechanical properties of carbon nanotubes is given. Theory as well as exper... more A condensed review of mechanical properties of carbon nanotubes is given. Theory as well as experiments is examined with a view to extracting the fundamental elements that should allow the reader to build his own perspective of the subject.
Carbon nanotubes (CNTs) were integrated in glass fibres epoxy composites by either including CNTs... more Carbon nanotubes (CNTs) were integrated in glass fibres epoxy composites by either including CNTs in the fibre sizing formulation, in the matrix, or both. The effects of such controlled placement of CNTs on the thermophysical properties (glass transition temperature and coefficient of thermal expansion) and the Mode I interlaminar fracture toughness of the composites were studied. The present method of CNT-sizing of the glass fibres produces an increase of almost +10% in the glass transition temperature and a significant reduction of À31% in the coefficient of thermal expansion of the composites. Additionally, the presence of CNTs in the sizing resulted in an increased resistance of crack initiation fracture toughness by +10%, but a lowered crack propagation toughness of À53%. Similar trends were observed for both instances when CNTs were introduced only in the matrix and in combination of both matrix and sizing.
Various percentages of coiled carbon nanotubes (CCNTs) and single-walled carbon nanotubes (SWNTs)... more Various percentages of coiled carbon nanotubes (CCNTs) and single-walled carbon nanotubes (SWNTs) added into the epoxy resin were mixed by mechanical stirring and then mould forming to a dog-bone shape samples. The mechanical properties of the composites were characterized in terms of nanoindentation tests and tensile tests. Hardness and elastic modulus were measured using a nanoindenter. In situ scanning electron microscopy studies were employed to investigate the deformation mechanisms and interlocking of the coiled nanotubes in matrix.
A polyurethane/multi-walled carbon nanotube elastomer composite was synthesized. The microstructu... more A polyurethane/multi-walled carbon nanotube elastomer composite was synthesized. The microstructure of the composite was examined by field-emission scanning electron microscopy and transmission electron microscopy. The thermal and mechanical properties of the composite were characterized by dynamic mechanical thermal analysis, thermogravimetric analysis and tensile testing. The chemical linkage of carbon nanotubes with polyurethane matrix was confirmed by Fourier transform infrared spectra. The study on the structure of the composite showed that carbon nanotubes could be dispersed in the polymer matrix well apart from a few of clusters. The results from thermal analysis indicated that the glass transition temperature of the composite was increased by about 10°C and its thermal stability was obviously improved, in comparison with pure polyurethane. The investigation on the mechanical properties showed that the modulus and tensile strength could be obviously increased by adding 2 wt% (by weight) CNT to the matrix.
The superlative mechanical properties of carbon nanotubes make them the filler material of choice... more The superlative mechanical properties of carbon nanotubes make them the filler material of choice for composite reinforcement. In this paper we review the progress to date in the field of mechanical reinforcement of polymers using nanotubes. Initially, the basics of fibre reinforced composites are introduced and the prerequisites for successful reinforcement discussed. The effectiveness of different processing methods is compared and the state of the art demonstrated. In addition we discuss the levels of reinforcement that have actually been achieved. While the focus will be on enhancement of Young's modulus we will also discuss enhancement of strength and toughness. Finally we compare and tabulate these results. This leads to a discussion of the most promising processing methods for mechanical reinforcement and the outlook for the future.
Single-wall carbon nanotubes (SWNTs) have exceptional strength and stiffness and high thermal and... more Single-wall carbon nanotubes (SWNTs) have exceptional strength and stiffness and high thermal and electrical conductivity, making them excellent candidates for aerospace structural materials. However, one of the most fundamental challenges is purifying the SWNTs. The purpose of this study was to develop a simple purification process for SWNTs, along with an understanding of the purification process. In addition, uncomplicated analytical methods were sought to screen and compare various purification methods. In this study, we demonstrate an easy method of cleaning SWNTs and evaluating their purity. The cleaning method, which employed oxidative heat treatment followed by acid reflux, was straightforward, inexpensive, and fairly effective. The purification mechanism was determined to be, first, that much of the non-nanotube carbon and iron catalyst was oxidized and, second, that the acid washing removed the iron oxide, leaving relatively pure SWNTs. Also, it was shown that a combination of thermal gravimetric analysis and Raman spectroscopy, both of which take only a few minutes and require little sample preparation, are sufficient as qualitative screening tools to determine the relative purity of SWNTs. Other analytical techniques were used to verify the validity of the screening techniques. Published by Elsevier Science Ltd.
Carbon fiber reinforced epoxy composite laminates, with strategically incorporated fluorine funct... more Carbon fiber reinforced epoxy composite laminates, with strategically incorporated fluorine functionalized carbon nanotubes (f-CNTs) at 0.2, 0.3 and 0.5 weight percent (wt.%), are studied for improvements in tensile strength and stiffness and durability under both tension-tension (R = +0.1) and tension-compression (R = À0.1) cyclic loadings, and then compared to the neat (0.0 wt.% CNTs) composite laminate material. To develop the nanocomposite laminates, a spraying technology was used to deposit nanotubes on both sides of each four-harness satin weave carbon fiber fabric piece for the 12 ply laminate lay up. For these experimental studies the carbon fiber reinforced epoxy laminates were fabricated using a heated vacuum assisted resin transfer molding (H-VARTM Ò ) method followed by a 2 soak curing cycle. The f-CNTs toughened the epoxy resin-fiber interfaces to mitigate the evolution of fiber/fabric-matrix interfacial cracking and delamination under both static and cyclic loadings. As a consequence, significant improvements in the mechanical properties of tensile strength, stiffness and resistance to failure due to cyclic loadings resulted for this carbon fiber reinforced epoxy composite laminate.
Composites have set the standard for high strength materials for several decades. With the discov... more Composites have set the standard for high strength materials for several decades. With the discovery of nanotubes, new possibilities for reinforced composites have arisen, with potential mechanical properties superior to those of currently available materials. This paper reports the properties of epoxy matrix reinforced with fibres of carbon nanotubes (CNTs) which, in many ways, are similar to standard composites reinforced with commercial fibres. The composites were formed by the back diffusion of the uncured epoxy into an array of aligned fibres of CNTs. The fibre density and volume fraction were measured from thermogravimetric analysis (TGA). Properties in tension and compression were measured, and the level of fibre-matrix interaction analysed fractographically. The results show the significant potential for this route to CNT reinforcement.
Multiwalled carbon nanotubes (MWCNTs)/epoxy nanocomposites were fabricated by using ultrasonicati... more Multiwalled carbon nanotubes (MWCNTs)/epoxy nanocomposites were fabricated by using ultrasonication and the cast molding method. In this process, MWCNTs modified by mixed acids were well dispersed and highly loaded in an epoxy matrix. The effects of MWCNTs addition and surface modification on the mechanical performances and fracture morphologies of composites were investigated. It was found that the tensile strength improved with the increase of MWCNTs addition, and when the content of MWCNTs loading reached 8 wt.%, the tensile strength reached the highest value of 69.7 MPa. In addition, the fracture strain also enhanced distinctly, implying that MWCNTs loading not only elevated the tensile strength of the epoxy matrix, but also increased the fracture toughness. Nevertheless, the elastic modulus reduced with the increase of MWCNTs loading. The reasons for the mechanical property changes are discussed.
In this work, a series of cellulose acetate (CA)/poly(vinylpyrrolidone) (PVP) membranes composed ... more In this work, a series of cellulose acetate (CA)/poly(vinylpyrrolidone) (PVP) membranes composed of different CA/PVP ratios were synthesized using 2-stage phase inversion protocol. The ions dialysis separation performance of the membranes was investigated using dialysis process with mix solution containing K + , Na + , Ni 2+ and Zn 2+ ions for separation of following pair of ions:
Cellulose acetate/Polyethylene glycol-600 composite membranes were fabricated by two step phase i... more Cellulose acetate/Polyethylene glycol-600 composite membranes were fabricated by two step phase inversion procedure and modified by in-situ reduction of silver nitrate. FTIR spectra demonstrated the existence of functional groups for bonding of silver with oxygen at 370 cm −1 , 535 cm −1. The XRD diffractogram indicates characteristic peaks at 2 values of 38.10 • , 44.30 • , 64.40 • , and 77.30 • which confirm the successful incorporation of silver within matrix of composite membranes. The morphology of composite membranes with appearances of spongy voids was exemplified from the scanning electron microscope. The atomic force microscopy was used to determine the increase in the surface roughness of the membranes. The increase in hydrophilicity, measured through contact angle, is rendered to the embedment of silver. The modification of membranes increased the flux from 0.80 to 0.95 L/hr.m 2. The resulting membranes have outstanding ability to fight against gram negative Escherichia Coli and Bacillus Sabtilus. The novel cellulose acetate/polyethylene glycol membranes customized with silver have paved the path for evolution of axenic membranes.
In this work, a series of cellulose acetate (CA)/poly(vinylpyrrolidone) (PVP) membranes composed ... more In this work, a series of cellulose acetate (CA)/poly(vinylpyrrolidone) (PVP) membranes composed of different CA/PVP ratios were synthesized using 2-stage phase inversion protocol. The ions dialysis separation performance of the membranes was investigated using dialysis process with mix solution containing K + , Na + , Ni 2+ and Zn 2+ ions for separation of following pair of ions:
In this study, glass fiber/epoxy composites were interfacially tailored by introducing polyamidoa... more In this study, glass fiber/epoxy composites were interfacially tailored by introducing polyamidoamine (PAM) dendrimer functionalized graphene oxide (GO) into epoxy matrix. Two different composites each containing varying loading fraction (0.5, 1.0, and 1.5 wt%) of GO and GO-PAM were fabricated via hot press processing. Composites were evaluated for interlaminar shear strength (ILSS), dynamic mechanical properties and thermal conductivity. The inclusion of 1.5 wt% GO-PAM resulted~57.3%,~42.7%, and~54% enhancement in ILSS, storage modulus and thermal conductivity, respectively. Almost, 71% reduction in coefficient of thermal expansion was also observed at same GO-PAM loading. Moreover, higher glass transition temperature was observed with GO-PAM addition. GO-PAM substantially improved fiber/matrix interfacial adhesion, which was witnessed through scanning electron microscopy. The enhanced thermo-mechanical performance was attributed to interfacial covalent interactions engendered by ring opening reaction between epoxy and amine moieties of PAM dendrimers. These multiscale composites with extraordinary functional properties can outperform conventional counterparts with improved reliability and performance.
Surface tuned GO sheets are considered the opportune pothunter for the reinforcement of conventio... more Surface tuned GO sheets are considered the opportune pothunter for the reinforcement of conventional glass fiber reinforced composites (GFRCs). Herein, we have tried to disseminate the effects of N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane functionalized GO (GO-AEAPTS) and pristine GO sheets on thermo-mechanical properties of epoxy/glass fiber composites. Fourier Transform-infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic light scattering (DLS) and transmission electron microscope (TEM) were used to characterize the GO sheets. Multiscale composites integrated with GO-AEAPTS (1.5 wt%) provided maximum gain in all the studied properties i.e., interlaminar shear strength (ILSS), impact strength and thermal conductivity were improved by ~ 55, ~ 24 and ~ 70%, respectively. Storage modulus and glass transition temperature increased by ~ 44% and 14 °C, over the neat GFRC. In addition, GO-AEAPTS composites exhibited higher coefficient of effectiveness and crosslink density than those of GO counterparts. These property enhancements were credited to the homogeneous distribution of GO sheets, strong interfacial interactions (interfacial covalent interactions and hydrogen bonding) between GO-AEAPTS and epoxy resin as well as good fiber/matrix compatibility. Such multiscale composites with functional properties can outperform conventional counterparts with improved safety and reliability of structures and reduce maintenance costs.
Novel Polyurethane/Polyvinyl chloride-co-vinyl acetate (PU/PVCA) blend RO membranes were synthesi... more Novel Polyurethane/Polyvinyl chloride-co-vinyl acetate (PU/PVCA) blend RO membranes were synthesized in four different ratios 90/10, 80/20, 70/30, 60/40. On the basis of appreciable salt rejection, PU/PVCA-4 (60/40) was selected for chemical crosslinking with 1 to 4 wt% of Epichlorohydrin (ECH). The confirmation of physical and chemical crosslinking between PU and PVCA was validated by Fourier transform infrared spectroscopy (FTIR). The SEM micrographs confirmed the dense film structure for all crosslinked and un-crosslinked membranes. Tensile testing, thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) evaluated the performance of ECH crosslinked membranes. In addition, DMA revealed the existence of single glass transition temperature (T g) in case of crosslinked membranes advocating the compatibility of PU and PVCA. In terms of flux and salt rejection, PU/PVCA-4 membrane crosslinked with 3 wt% ECH demonstrated the optimum results. The permeation data was collected at two different temperatures i.e. 25°C and 70°C for crosslinked membranes and the results indicated~67.6% higher flux at 70°C over the flux obtained at 25°C. This amelioration in flux shows the thermo-sensitive behavior of crosslinked membranes. These results demonstrate that ECH crosslinked PU/PVCA membranes can outstand the conventional PU membranes in terms of mechanical, thermal and permeation properties.
This review aims at reporting on very recent developments in syntheses, properties and (future) a... more This review aims at reporting on very recent developments in syntheses, properties and (future) applications of polymer-layered silicate nanocomposites. This new type of materials, based on smectite clays usually rendered hydrophobic through ionic exchange of the sodium interlayer cation with an onium cation, may be prepared via various synthetic routes comprising exfoliation adsorption, in situ intercalative polymerization and melt intercalation. The whole range of polymer matrices is covered, i.e. thermoplastics, thermosets and elastomers. Two types of structure may be obtained, namely intercalated nanocomposites where the polymer chains are sandwiched in between silicate layers and exfoliated nanocomposites where the separated, individual silicate layers are more or less uniformly dispersed in the polymer matrix. This new family of materials exhibits enhanced properties at very low filler level, usually inferior to 5 wt.%, such as increased Young's modulus and storage modulus, increase in thermal stability and gas barrier properties and good flame retardancy.
A review is given of the academic and industrial aspects of the preparation, characterization, ma... more A review is given of the academic and industrial aspects of the preparation, characterization, materials properties, crystallization behavior, melt rheology, and processing of polymer/layered silicate nanocomposites. These materials are attracting considerable interest in polymer science research. Hectorite and montmorillonite are among the most commonly used smectite-type layered silicates for the preparation of nanocomposites. Smectites are a valuable mineral class for industrial applications because of their high cation exchange capacities, surface area, surface reactivity, adsorptive properties, and, in the case of hectorite, high viscosity and transparency in solution. In their pristine form they are hydrophilic in nature, and this property makes them very difficult to disperse into a polymer matrix. The most common way to remove this difficulty is to replace interlayer cations with quarternized ammonium or phosphonium cations, preferably with long alkyl chains.
Especially in the course of modern automotive coatings comprising a reduced number of layers the ... more Especially in the course of modern automotive coatings comprising a reduced number of layers the resistance towards the stone chipping is becoming an issue. Layered double hydroxide (LDH)-based polymer composites are readily accessible materials and suitable to impart impact resistance to coatings, provided that an accurate understanding of the structure property relations both of the platelets and the composites is achieved.
In the present investigation, effect of nano layered silicates on the properties of an automotive... more In the present investigation, effect of nano layered silicates on the properties of an automotive refinish clear coat based on polyurethane has been studied. Observation by means of X-ray diffraction (XRD) technique indicates the presence of a partially intercalated structure due to dispersion of nano layers in the polymer matrix. Some levels of hazing have been established by increasing the amount of nano-filler. The effect of nano-filled clear coat on the reflectance spectra of a metallic coated substrate has been studied under three different light sources using a goniospectrophotometer and compared with a blank clear coat to determine if it can be identified by human eye. Scratch and mar resistance tests showed significant improvement even 48 h after application, when there was no gloss reduction due to usage of nano-filler. Gloss retention was increased by about 10% in presence of only 3 wt% of nano-filler. In addition to some scratch and mar resistance tests, other standard tests like adhesion, impact and bending were performed to find out optimum nano-filler/polymer ratio.
This review reports recent advances in the field of polymer-layered silicate nanocomposites. Thes... more This review reports recent advances in the field of polymer-layered silicate nanocomposites. These materials have attracted both academic and industrial attention because they exhibit dramatic improvement in properties at very low filler contents. Herein, the structure, preparation and properties of polymer-layered silicate nanocomposites are discussed in general, and detailed examples are also drawn from the scientific literature.
A condensed review of mechanical properties of carbon nanotubes is given. Theory as well as exper... more A condensed review of mechanical properties of carbon nanotubes is given. Theory as well as experiments is examined with a view to extracting the fundamental elements that should allow the reader to build his own perspective of the subject.
Carbon nanotubes (CNTs) were integrated in glass fibres epoxy composites by either including CNTs... more Carbon nanotubes (CNTs) were integrated in glass fibres epoxy composites by either including CNTs in the fibre sizing formulation, in the matrix, or both. The effects of such controlled placement of CNTs on the thermophysical properties (glass transition temperature and coefficient of thermal expansion) and the Mode I interlaminar fracture toughness of the composites were studied. The present method of CNT-sizing of the glass fibres produces an increase of almost +10% in the glass transition temperature and a significant reduction of À31% in the coefficient of thermal expansion of the composites. Additionally, the presence of CNTs in the sizing resulted in an increased resistance of crack initiation fracture toughness by +10%, but a lowered crack propagation toughness of À53%. Similar trends were observed for both instances when CNTs were introduced only in the matrix and in combination of both matrix and sizing.
Various percentages of coiled carbon nanotubes (CCNTs) and single-walled carbon nanotubes (SWNTs)... more Various percentages of coiled carbon nanotubes (CCNTs) and single-walled carbon nanotubes (SWNTs) added into the epoxy resin were mixed by mechanical stirring and then mould forming to a dog-bone shape samples. The mechanical properties of the composites were characterized in terms of nanoindentation tests and tensile tests. Hardness and elastic modulus were measured using a nanoindenter. In situ scanning electron microscopy studies were employed to investigate the deformation mechanisms and interlocking of the coiled nanotubes in matrix.
A polyurethane/multi-walled carbon nanotube elastomer composite was synthesized. The microstructu... more A polyurethane/multi-walled carbon nanotube elastomer composite was synthesized. The microstructure of the composite was examined by field-emission scanning electron microscopy and transmission electron microscopy. The thermal and mechanical properties of the composite were characterized by dynamic mechanical thermal analysis, thermogravimetric analysis and tensile testing. The chemical linkage of carbon nanotubes with polyurethane matrix was confirmed by Fourier transform infrared spectra. The study on the structure of the composite showed that carbon nanotubes could be dispersed in the polymer matrix well apart from a few of clusters. The results from thermal analysis indicated that the glass transition temperature of the composite was increased by about 10°C and its thermal stability was obviously improved, in comparison with pure polyurethane. The investigation on the mechanical properties showed that the modulus and tensile strength could be obviously increased by adding 2 wt% (by weight) CNT to the matrix.
The superlative mechanical properties of carbon nanotubes make them the filler material of choice... more The superlative mechanical properties of carbon nanotubes make them the filler material of choice for composite reinforcement. In this paper we review the progress to date in the field of mechanical reinforcement of polymers using nanotubes. Initially, the basics of fibre reinforced composites are introduced and the prerequisites for successful reinforcement discussed. The effectiveness of different processing methods is compared and the state of the art demonstrated. In addition we discuss the levels of reinforcement that have actually been achieved. While the focus will be on enhancement of Young's modulus we will also discuss enhancement of strength and toughness. Finally we compare and tabulate these results. This leads to a discussion of the most promising processing methods for mechanical reinforcement and the outlook for the future.
Single-wall carbon nanotubes (SWNTs) have exceptional strength and stiffness and high thermal and... more Single-wall carbon nanotubes (SWNTs) have exceptional strength and stiffness and high thermal and electrical conductivity, making them excellent candidates for aerospace structural materials. However, one of the most fundamental challenges is purifying the SWNTs. The purpose of this study was to develop a simple purification process for SWNTs, along with an understanding of the purification process. In addition, uncomplicated analytical methods were sought to screen and compare various purification methods. In this study, we demonstrate an easy method of cleaning SWNTs and evaluating their purity. The cleaning method, which employed oxidative heat treatment followed by acid reflux, was straightforward, inexpensive, and fairly effective. The purification mechanism was determined to be, first, that much of the non-nanotube carbon and iron catalyst was oxidized and, second, that the acid washing removed the iron oxide, leaving relatively pure SWNTs. Also, it was shown that a combination of thermal gravimetric analysis and Raman spectroscopy, both of which take only a few minutes and require little sample preparation, are sufficient as qualitative screening tools to determine the relative purity of SWNTs. Other analytical techniques were used to verify the validity of the screening techniques. Published by Elsevier Science Ltd.
Carbon fiber reinforced epoxy composite laminates, with strategically incorporated fluorine funct... more Carbon fiber reinforced epoxy composite laminates, with strategically incorporated fluorine functionalized carbon nanotubes (f-CNTs) at 0.2, 0.3 and 0.5 weight percent (wt.%), are studied for improvements in tensile strength and stiffness and durability under both tension-tension (R = +0.1) and tension-compression (R = À0.1) cyclic loadings, and then compared to the neat (0.0 wt.% CNTs) composite laminate material. To develop the nanocomposite laminates, a spraying technology was used to deposit nanotubes on both sides of each four-harness satin weave carbon fiber fabric piece for the 12 ply laminate lay up. For these experimental studies the carbon fiber reinforced epoxy laminates were fabricated using a heated vacuum assisted resin transfer molding (H-VARTM Ò ) method followed by a 2 soak curing cycle. The f-CNTs toughened the epoxy resin-fiber interfaces to mitigate the evolution of fiber/fabric-matrix interfacial cracking and delamination under both static and cyclic loadings. As a consequence, significant improvements in the mechanical properties of tensile strength, stiffness and resistance to failure due to cyclic loadings resulted for this carbon fiber reinforced epoxy composite laminate.
Composites have set the standard for high strength materials for several decades. With the discov... more Composites have set the standard for high strength materials for several decades. With the discovery of nanotubes, new possibilities for reinforced composites have arisen, with potential mechanical properties superior to those of currently available materials. This paper reports the properties of epoxy matrix reinforced with fibres of carbon nanotubes (CNTs) which, in many ways, are similar to standard composites reinforced with commercial fibres. The composites were formed by the back diffusion of the uncured epoxy into an array of aligned fibres of CNTs. The fibre density and volume fraction were measured from thermogravimetric analysis (TGA). Properties in tension and compression were measured, and the level of fibre-matrix interaction analysed fractographically. The results show the significant potential for this route to CNT reinforcement.
Multiwalled carbon nanotubes (MWCNTs)/epoxy nanocomposites were fabricated by using ultrasonicati... more Multiwalled carbon nanotubes (MWCNTs)/epoxy nanocomposites were fabricated by using ultrasonication and the cast molding method. In this process, MWCNTs modified by mixed acids were well dispersed and highly loaded in an epoxy matrix. The effects of MWCNTs addition and surface modification on the mechanical performances and fracture morphologies of composites were investigated. It was found that the tensile strength improved with the increase of MWCNTs addition, and when the content of MWCNTs loading reached 8 wt.%, the tensile strength reached the highest value of 69.7 MPa. In addition, the fracture strain also enhanced distinctly, implying that MWCNTs loading not only elevated the tensile strength of the epoxy matrix, but also increased the fracture toughness. Nevertheless, the elastic modulus reduced with the increase of MWCNTs loading. The reasons for the mechanical property changes are discussed.
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Papers by Fahd Jamshaid