An Innovative Approach to the Synthesis of PMMA/PEG/Nanobifiller Filled Nanocomposites with Enhanced Mechanical and Thermal Properties

A facile route was adopted to blend the matrix. The PMMA/PEG blend was reinforced with three types of nanofillers, i.e., pristine MWCNT (P-CNT), amine functionalized MWCNT (PDA-EA-CNT) and nanobifiller i.e. nanodiamond functional MWCNT (PDA-EA-CNT-ND) to yield three different types of nanocomposites i.e. PMMA/PEG/P-CNT, PMMA/PEG/PDA-EA-CNT and PMMA/PEG/PDA-EA-CNT-ND. These nanocomposites were reinforced with nanofiller loading (1 wt. %, 3 wt. %, 5 wt. %, 10 wt. %, 30 wt. % and 50 wt. %) by solution casting method. Structure of composite and nanofillers was confirmed by FTIR. FESEM imaging revealed that nanocomposites have micro porous morphology. At high magnification, distribution of functionalized CNT/ND appears to be protruding out of the polymeric matrix. The TGA result suggests that the thermal stability of the nanocomposites was enhanced in comparison to PMMA due to grafting of filler molecules with PMMA/PEG macromolecules. The DTG results showed that the bifiller nanocomposites (PMMA/PEG/PDA-EA-CNT-ND) exhibited improved thermal stability with T_max (431^°C) as compared to P-CNT and amine functionalized CNT (PMMA/PEG/PDA-EA-CNT) with T_max of 395^°C and 418^°C respectively. XRD results showed fine interaction between filler and the polymeric matrix. As the filler loading was increased the composites showed pronounced XRD peak at 25.9^°, corresponding to (002) reflection of nanotubes. Significant improvement in the mechanical properties of composites was recorded with the reinforcement of fillers as compared to the neat matrix. The most significant improvement in tensile strength and elastic modulus was observed for the bifiller nanocomposites with 5 wt. % PDA-EA-CNT-ND. They showed a tensile strength and elastic modulus of 29.9 MPa and 1474.31 MPa respectively as compared to amine functionalized CNT with tensile strength (25.7) and elastic modulus (1466.99 MPa)and P-CNT with tensile strength(25 MPa) and elastic modulus (1155.75 MPa).     

Hybridizing MWCNT with nano metal oxides and TiO2 in epoxy composites: Influence on mechanical and thermal performances

In this study, the effects of multi‐walled carbon nanotubes (MWCNT), and its hybrids with iron oxide (Fe₂O₃) and copper oxide (CuO) nanoparticles on mechanical characteristics and thermal properties of epoxy binder was evaluated. Furthermore, simultaneous effects of using MWCNT with TiO₂ as pigment and CaCO₃ as filler for epoxy composites were determined. To investigate effects of nano‐ and micro‐particles on epoxy matrix, the samples were evaluated by TGA and DTA. It was found that the hybrid of MWCNT with nano metal oxides caused considerable increment in the tensile and flexural properties of epoxy samples in comparison to the single MWCNT containing samples at the same filler contents. Significant improvement in the thermal conductivity of epoxy samples was obtained by using TiO₂ pigment along with MWCNT. The TiO₂ pigment also caused considerable improvement in mechanical properties of the epoxy matrix and the MWCNT containing nanocomposite. The best mechanical and thermal properties of epoxy nanocomposites were obtained at 1.5 wt % of MWCNT and 7 wt % of TiO₂ that it should be attributed to particle network forming of the particles which cause better nano/micro dispersion and properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43834.     

Characterization and Properties of Layered Silicate Reinforced Spent DuraForm EX Nanocomposites

During the last decade, the nanocomposites based on layered silicate are widely studied and attracted the industrial and academic research. The effect of various loading levels of layered silicate reinforcement on the mechanical and thermal properties was studied by nano-indentation, flexural testing, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The maximum hardness (H), increased from 67 MPa for neat Spent DuraForm EX up to 170 MPa with 7 wt.% layered silicate-reinforced sample. The measured modulus (E), of unreinforced Spent DuraForm increased from 631 MPa to 2100 MPa with 7 wt.% layered silicate reinforcement. The thermal property of the EX nanocomposites revealed by DSC was improved by about 6?C up to 7 wt.% of layered silicate loading. Different levels of layered silicates dispersion as characterized using TEM and SEM correlated strongly with improvements in nanohardness and thermal properties. The improved hardness, modulus, crystalline and melting temperatures of Spent DuraForm EX nanocomposites are attributed mainly to the intercalated structures.     

Enhanced properties of phthalonitrile‐terminated polyarylene ether nitriles embedded with hybrid MWCNT–boehmite nanocomposites

The main motivation of the present work was to fabricate novel multifunctional polymer‐based nanocomposites. The nanocomposites embedded with multi‐walled carbon nanotube‐boehmite (MWCNT‐boehmite) were prepared via hot pressure casting technique. The MWCNT coated with boehmite were synthesized by hydrothermal synthesis. Subsequently, as‐prepared MWCNT‐boehmite was added into the phthalonitrile‐terminated polyarylene ether nitriles (PEN‐t‐CN) matrix in order to benefit from the synergetic effect of MWCNT and boehmite. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) X‐ray diffraction (XRD), and Fourier transform infrared (FTIR) were employed to confirm the existence of MWCNT‐boehmite in our article. Furthermore, the structures, fracture morphologies, thermal, mechanical and dielectric properties of the nanocomposites were investigated, respectively. SEM images indicated that the MWCNT‐boehmite was homogeneously dispersed in the polymer, which acted as an essential factor to ensure good physical properties. The TGA analysis showed that the incorporation of MWCNT‐boehmite enhanced the thermal stability of the nanocomposites with initial degradation temperature (T_id) increasing from 458 to 492°C, while that of the pure PEN‐t‐CN was 439°C. The mechanical testing proved that significant enhancement of mechanical properties has been achieved. The tensile strength of PEN‐t‐CN/MWCNT‐boehmite composites with 3 wt% MWCNT‐boehmite reached the maximum (78.33 MPa), with a 41.7 % increase compared to the pure polymer. More importantly, the unique dielectric properties were systematically discussed and the results demonstrated that dielectric properties exhibited little dependency on frequency. For the incorporation of hybrid filler, the positive impact of MWCNT‐boehmite hybrid material resulted in polymer‐based nanocomposites with enhanced physical properties. POLYM. COMPOS., 36:2193–2202, 2015. © 2014 Society of Plastics Engineers     

Improved impact strength of epoxy by the addition of functionalized multiwalled carbon nanotubes and reactive diluent

Multiwalled carbon nanotubes (MWCNTs), both oxidized and amine functionalized (triethylenetetramine—TETA), have been used to improve the mechanical properties of nanocomposites based on epoxy resin. The TGA and XPS analysis allowed the evaluation of the degree of chemical modification on MWCNTs. Nanocomposites were manufactured by a three‐roll milling process with 0.1, 0.5, and 1.0 wt % of MWCNT–COOH and MWCNT–COTETA. A series of nanocomposites with 5.0 wt % of reactive diluent was also prepared. Tensile and impact tests were conducted to evaluate the effects of the nanofillers and diluent on the mechanical properties of the nanocomposites. The results showed higher gains (258% increase) in the impact strength for nanocomposites manufactured with aminated MWCNTs. Optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to investigate the overall filler distribution, the dispersion of individual nanotubes, and the interface adhesion on the nanocomposites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42587.     

Nanoindentation analysis of 3D printed poly(lactic acid)-based composites reinforced with graphene and multiwall carbon nanotubes

Influences of different nanocomposite loadings in poly(lactic acid) (PLA) matrix on resulting hardness and elasticity were examined in nanoindentation experiments. The following study was focused on the nanomechanical properties of PLA reinforced with graphene nanoplatelets (GNPs) and multiwall carbon nanotubes (MWCNTs) by using Berkovich type pyramidal nanoindenter. A masterbatch strategy was developed to disperse GNP and MWCNT into PLA by melt blending. Young's modulus and nanohardness of as-prepared nanocomposites were characterized as a function of the graphene and carbon nanotubes loading. The nanoindentation analysis reveals that these carbon nanofillers improve the mechanical stability of the nanocomposites GNP/PLA, MWCNT/PLA, and GNP/MWCNT/PLA. That improvement of mechanical properties strongly depends on the fillers content. It was found that the best mechanical performance was achieved for the compound having 6 wt % graphene and 6 wt % MWCNTs in the PLA matrix. The received values for nanohardness and Young's modulus are among the highest reported for PLA-based nanocomposites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47260.     

Influence of processing condition and carbon nanotube on mechanical properties of injection molded multi‐walled carbon nanotube/poly(methyl methacrylate) nanocomposites

In this work, multi‐walled carbon nanotubes (MWCNT) and poly(methyl methacrylate) (PMMA) pellets were compounded via corotating twin‐screw extruder. The produced MWCNT/PMMA nanocomposite pellets were injection molded. The effect of MWCNT concentration, injection melt temperature and holding pressure on mechanical properties of the nanocomposites were investigated. To examine the mechanical properties of the MWCNT/PMMA nanocomposites, tensile test, charpy impact test, and Rockwell hardness are considered as the outputs. Design of experiments (DoE) is done by full factorial method. The morphology of the nanocomposites was performed using scanning electron microscopy (SEM). The results revealed when MWCNT concentration are increased from 0 to 1.5 wt %, tensile strength and elongation at break were reduced about 30 and 40%, respectively, but a slight increase in hardness was observed. In addition, highest impact strength belongs to the nanocomposite with 1 wt % MWCNT. This study also shows that processing condition significantly influence on mechanical behavior of the injection molded nanocomposite. In maximum holding pressure (100 bar), the nanocomposites show highest tensile strength, elongation, impact strength and hardness. According to findings, melt temperature has a trifle effect on elongation, but it has a remarkable influence on tensile strength. In the case of impact strength, higher melt temperature is favorable. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43738.     

Development and characterization of surface-modified mullite reinforced BMI-toughened epoxy nanocomposites

High-performance diglycidyl ether of bisphenol-A (DGEBA) epoxy-based composite systems with improved thermal stability for advanced structural applications were developed, using bismaleimide (BMI) as toughening agent and surface-modified mullite as reinforcing agent. The nanocomposites developed in the present study are referred to as M/DGEBA–BMI. 95 % by wt. of DGEBA was toughened with 5 % by wt. of BMI and further reinforced with varying weight percentages of (0.5, 1.0 and 1.5 wt%) glycidyl-functionalized mullite to obtain M/DGEBA–BMI nanocomposites. The formation of nanocomposites was ascertained using Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The mechanical and dielectric properties of nanocomposites were investigated by analytical techniques. The thermal behaviour of nanocomposites was characterized using thermogravimetric analyzer and differential scanning calorimeter. Contact angle, surface free energy and percentage water absorption were also studied and reported. Studies suggest that the properties of M/DGEBA–BMI nanocomposites viz; mechanical, dielectric, surface energy and thermal properties improved to an appreciable extent, when compared to those of neat epoxy matrix.     

Preparation and characterization of extruded nanocomposite based on polycarbonate/butadiene‐acrylonitrile‐styrene blend filled with multiwalled carbon nanotubes

Nanocomposites of polycarbonate/acrylonitrile‐butadiene‐styrene (PC/ABS) with multiwall carbon nanotubes (MWCNT) prepared by masterbatch dilution are investigated in this work. Melt compounding with twin screw extruder is followed by complete characterization of morphology, rheological‐, mechanical‐, and thermal‐properties of the nanocomposites. Light‐transmission‐ and scanning electron microscopy shows the preferential location of MWCNT in the PC. Nevertheless, relatively good dispersion in the whole matrix is achieved, what is corroborated with the specific mechanical energy. The study of viscoelastic properties of PC/ABS‐MWCNT shows the fluid–solid transition below 0.5 wt % MWCNT. Beyond this point the continuous nanofiller network is formed in the matrix promoting the reinforcement. Addition of 0.5 wt % MWCNT reduces ductility of PC/ABS and enhances Young's modulus by about 30% and yield stress by about 20%. Moreover, theoretical values of stiffness calculated within this work agree with the experimental data. Electrical conductivity, showing percolation at 2.0 wt % MWCNT, are influenced by processing temperature. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40271.     

Synthesis of New PI/MWCNT Containing Sulfone Groups via In Situ Polymerization: Study on Thermal,Electrical, and Optical Properties

New series of polyimide (PI) nanocomposites reinforced with three different amounts of multiwalled carbon nanotubes (MWCNT; 0.5, 1, and 3 wt%) were prepared by casting, evaporation and thermal imidization. Homogeneous dispersion of MWCNT in PI matrix was investigated by transmission electron microscopy. The effects of MWCNT on the thermal properties of the PI were investigated by thermogravimetric analysis. The results showed that the thermal stability of the nanocomposites enhanced with the increasing MWCNTs content. The resultant PI/MWCNT nanocomposites were electrically conductive with significant conductivity enhancement at 3 wt% MWCNT, which is favorable for many practical uses.     

Multiwalled Carbon Nanotubes/Hectorite Hybrid Reinforced Styrene Butadiene Rubber Nanocomposite: Preparation and Properties

Clay-assisted dispersion of MWCNT has emerged as a novel alternative to its conventional modification. The report deals with preparation of MWCNT/hectorite hybrid (HMH) by dry grinding method and its utilization for the reinforcement of styrene butadiene rubber (SBR). Significant improvement in tensile strength (210%) and elongation at break (42%) of SBR/HMH nanocomposite at 0.7 wt.% HMH shows its superior reinforcing efficiency. Comparison with individual fillers confirms significant synergy. Best thermal stability and dielectric response are achieved at 0.3 and 0.7 wt.% filler contents respectively. Improved properties of the nanocomposites are ascribed to enhanced level of filler dispersion and polymer-filler interaction.     

Oxidized multiwalled carbon nanotubes as effective reinforcement and thermal stability agents of poly(lactic acid) ligaments

In this study, nanocomposites of poly(lactic acid) (PLA) containing 0.5, 1, and 2.5 wt % oxidized multiwalled carbon nanotubes (MWCNT–COOHs) were prepared by the solved evaporation method. From transmission electron microscopy and scanning electron microscopy micrographs, we observed that the MWCNT–COOHs were well dispersed in the PLA matrix and, additionally, there was increased adhesion between PLA and the nanotubes. As a result, all of the studied nanocomposites exhibited higher mechanical properties than neat PLA; this indicated that the MWCNT–COOHs acted as efficient reinforcing agents, whereas in the nonoxidized multiwalled carbon nanotubes, the mechanical properties were reduced. Nanotubes can act as nucleating agents and, thereby, affect the thermal properties of PLA and, especially, the crystallization rate, which is faster than that of neat PLA. From the thermogravimetric data, we observed that the PLA/MWCNT–COOH nanocomposites presented relatively better thermostability than PLA; this was also verified from the calculation of activation energy. On the contrary, the addition of MWCNT–COOH had a negative effect on the enzymatic hydrolysis rate of PLA. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermosetting polyurethane‐multiwalled carbon nanotube composites: Thermomechanical properties and nanoindentation

In this study, composites based on a thermoset polyurethane elastomer (PU) and multiwalled carbon nanotubes (MWCNT) in the case of a PU of high elastic modulus (>200 MPa) are analyzed for the first time. As‐grown and modified nanotubes with 4 wt % of oxygenated functions (MWCNT‐ox) were employed to compare their effect on composite properties and maxima mechanical properties (elastic modulus and tensile strength) were reached at 0.5 wt % of MWCNT‐ox. Furthermore, by examining the morphology using optical and electron microscopies better dispersion and interaction of the nanotube‐matrix was observed for this material. DMTA data supports the observation of an increase in the glass transition temperature of ～20°C in the nanocomposites compared with the thermoset PU, which is an important result because it shows extended reliability in extreme environments. Finally, nanoindentation tests allowed a comparison with the conventional mechanical tests by measuring the elastic modulus and hardness at the subsurface of PU and the nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41207.     

Pressure-sensitive polymer nanocomposites: Carbon nanofiber-reinforced MWCNT-coated PMMA microbeads

ABSTRACT

A unique, thermoplastic polyurethane (TPU)-based, pressure-sensitive nanocomposites were prepared by the solution mixing method. Poly (methyl methacrylate) (PMMA) microbeads (10µm) were coated with multiwall carbon nanotubes (MWCNT) and dispersed in TPU matrix dissolved in tetrahydrofuran. 1, 2, and 5 wt. % of carbon nanofiber (CNF) were also added to the TPU matrix. The influence of MWCNT coated PMMA-microbeads along with different CNF contents on the pressure sensing properties were studied. Electrical and thermal conductivities were measured at different external loads. The prepared nanocomposites showed repeatable and reliable electric response with increasing external load and are suitable as pressure sensors.     

Effects of amino‐functionalized carbon nanotubes on the properties of amine‐terminated butadiene–acrylonitrile rubber‐toughened epoxy resins

Amino‐functionalized multiwalled carbon nanotubes (MWCNT‐NH₂s) as nanofillers were incorporated into diglycidyl ether of bisphenol A (DGEBA) toughened with amine‐terminated butadiene–acrylonitrile (ATBN). The curing kinetics, glass‐transition temperature (T_g), thermal stability, mechanical properties, and morphology of DGEBA/ATBN/MWCNT‐NH₂ nanocomposites were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis, a universal test machine, and scanning electron microscopy. DSC dynamic kinetic studies showed that the addition of MWCNT‐NH₂s accelerated the curing reaction of the ATBN‐toughened epoxy resin. DSC results revealed that the T_g of the rubber‐toughened epoxy nanocomposites decreased nearly 10°C with 2 wt % MWCNT‐NH₂s. The thermogravimetric results show that the addition of MWCNT‐NH₂s enhanced the thermal stability of the ATBN‐toughened epoxy resin. The tensile strength, flexural strength, and flexural modulus of the DGEBA/ATBN/MWCNT‐NH₂ nanocomposites increased increasing MWCNT‐NH₂ contents, whereas the addition of the MWCNT‐NH₂s slightly decreased the elongation at break of the rubber‐toughened epoxy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40472.     

Synthesis of Methylacryloypropyl-POSS/Poly(fluorine-acrylate) Core-Shell Nanocomposites and Effect on Thermal Properties of Materials

Core-shell nanocomposites were prepared from acrylates, fluorine- containing methacrylate monomers and methylacryloypropyl polyhedral oligomeric silsesquioxanes (MAP-POSS) by emulsion polymerization. The properties of latex and nanocomposites were characterized by FTIR, NMR, TEM, laser particle diameter analyzer, DMA and TGA. The results showed that the particle diameter of composite latexes was about 33.5 nm, dynamic mechanical loss peak temperature T_p of the nanocomposites had the best high value at 99.6°C when 7 wt.% MAP-POSS was added, which is 7.8°C higher than the pure polyacrylates. MAP-POSS could increase the thermal stability of materials, the initial thermal decomposition temperature increases about 34°C.     

Thermo mechanical behaviour of unsaturated polyester toughened epoxy–clay hybrid nanocomposites

The intercrosslinked networks of unsaturated polyester (UP) toughened epoxy–clay hybrid nanocomposites have been developed. Epoxy resin (DGEBA) was toughened with 5, 10 and 15% (by wt) of unsaturated polyester using benzoyl peroxide as radical initiator and 4,4′-diaminodiphenylmethane as a curing agent at appropriate conditions. The chemical reaction of unsaturated polyester with the epoxy resin was carried out thermally in presence of benzoyl peroxide-radical initiator and the resulting product was analyzed by FT-IR spectra. Epoxy and unsaturated polyester toughened epoxy systems were further modified with 1, 3 and 5% (by wt) of organophilic montmorillonite (MMT) clay. Clay filled hybrid UP-epoxy matrices, developed in the form of castings were characterized for their thermal and mechanical properties. Thermal behaviour of the matrices was characterized by differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Mechanical properties were studied as per ASTM standards. Data resulted from mechanical and thermal studies indicated that the introduction of unsaturated polyester into epoxy resin improved the thermal stability and impact strength to an appreciable extent. The impact strength of 3% clay filled epoxy system was increased by 19.2% compared to that of unmodified epoxy resin system. However, the introduction of both UP and organophilic MMT clay into epoxy resin enhanced the values of mechanical properties and thermal stability according to their percentage content. The impact strength of 3% clay filled 10% UP toughened epoxy system was increased by 26.3% compared to that of unmodified epoxy system. The intercalated nanocomposites exhibited higher dynamic modulus (from 3,072 to 3,820 MPa) than unmodified epoxy resin. From the X-ray diffraction (XRD) analysis, it was observed that the presence of d ₀₀₁ reflections of the organophilic MMT clay in the cured product indicated the development of intercalated clay structure which in turn confirmed the formation of intercalated nanocomposites. The homogeneous morphologies of the UP toughened epoxy and UP toughened epoxy–clay hybrid systems were ascertained from scanning electron microscope (SEM).     

Functionalization of carbon nanotubes with (3‐glycidyloxypropyl)‐trimethoxysilane: Effect of wrapping on epoxy matrix nanocomposites

In this work, multiwalled carbon nanotubes (MWCNT), after previous oxidation, are functionalized with excess (3‐glycidyloxypropyl)trimethoxysilane (GLYMO) and used as reinforcement in epoxy matrix nanocomposites. Infrared, Raman, and energy‐dispersive X‐ray spectroscopies confirm the silanization of the MWCNT, while transmission electron microscopy images show that oxidized nanotubes presented less entanglement than pristine and silanized MWCNT. Thickening of the nanotubes is also observed after silanization, suggesting that the MWCNT are wrapped by siloxane chains. Field‐emission scanning electron microscopy reveals that oxidized nanotubes are better dispersed in the matrix, providing nanocomposites with better mechanical properties than those reinforced with pristine and silanized MWCNT. On the other hand, the glass transition temperature of the nanocomposite with 0.05 wt % MWCNT‐GLYMO increased by 14 °C compared to the neat epoxy resin, suggesting a strong matrix–nanotube adhesion. The functionalization of nanotubes using an excess amount of silane can thus favor the formation of an organosiloxane coating on the MWCNT, preventing its dispersion and contributing to poor mechanical properties of epoxy nanocomposites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44245.     

Investigation of cure kinetics in epoxy/multiwalled carbon nanotube nanocomposites

With the increased interest in thermoset resin nanocomposites, it is important to understand the effects of the material on nanoscale characteristics. In this study, a curing reaction of an epoxy resin, which contained 0.25, 0.50, or 1.00 wt % of multiwalled carbon nanotubes (MWCNTs), at different heating rates was monitored by differential scanning calorimetry; cure kinetics were also evaluated to establish a relationship between crosslinking (network formation) and mechanical properties. MWCNT concentrations above 0.25 wt % favored crosslinking formation and decreased the activation energy (E_a) in the curing reaction. Examination of the kinetic mechanism suggests that the MWCNT locally restricted the spatial volume and favored the formation of nodular morphology in the resin, especially for high MWCNT concentrations. The MWCNT exhibited some entanglement in the matrix, which hindered a more pronounced effect on the mechanical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39857.     

Synthesis and characterization of epoxy based nanocomposites

Epoxy‐clay nanocomposites were synthesized to examine the effects of the content and type of different clays on the structure and mechanical properties of the nanocomposites. Diglycidyl ether of bisphenol‐A (epoxy) was reinforced by 0.5–11 wt % natural (Cloisite Na⁺) and organically modified (Cloisite 30B) types of montmorillonite. SEM results showed that as the clay content increased, larger agglomerates of clay were present. Nanocomposites with Cloisite 30B exhibited better dispersion and a lower degree of agglomeration than nanocomposites with Cloisite Na⁺. X‐ray results indicated that in nanocomposites with 3 wt % Cloisite 30B, d‐spacing expanded from 18.4 Å (the initial value of the pure clay) to 38.2 Å. The glass transition temperature increased from 73°C, in the unfilled epoxy resin, to 83.5°C in the nanocomposite with 9 wt % Cloisite 30B. The tensile strength exhibited a maximum at 1 wt % modified clay loading. Addition of 0.5 wt % organically modified clay improved the impact strength of the epoxy resin by 137%; in contrast, addition of 0.5 wt % unmodified clay improved the impact strength by 72%. Tensile modulus increased with increasing clay loading in both types of nanocomposites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1081–1086, 2005