Ball milling: An effective technique for the preparation of exfoliated clay filled unsaturated polyester toughened epoxy nanocomposite

This paper investigates the possibility of improving the mechanical and thermal properties of epoxy and unsaturated polyester toughened epoxy resins through the dispersion of octadecyl ammonium ion-exchanged montmorillonite (organoclay) through exfoliated mechanism. The nanocomposites prepared are characterized for their structural change and studied for their crystallite size, mechanical, thermal and water absorption (hydrophilicity) properties. The mechanical data indicates significant improvement in the flexural and tensile properties over the neat epoxy and UP-epoxy matrix according to the percentage content of organoclay. The thermal behavior too shows noticeable enhancement in glass transition temperature T _g and high thermal stability. Hydrophilicity of all the composites decreases irrespective of the concentration of organoclay on the epoxy and UP-epoxy matrices. The homogeneous morphology of epoxy and UP toughened epoxy nanocomposite hybrid systems is ascertained using scanning electron microscope (SEM). X-ray results point out that the cetyl ammonium modified clay filled composites exhibited the exfoliated structure.     

Preparation and Characterization of DGEBA/EPN Epoxy Blends with Improved Fracture Toughness

The physical and mechanical properties of blends composed of two kinds of epoxy resins of different numbers of functional groups and chemical structure were studied.One of the resins was a bifunctional epoxy resin based on diglycidyl ether ofbisphenol A and the other resin was a multifunctional epoxy novolac resin.Attempt was made to establish a correlation between the structure and the final properties of cured epoxy samples.The blend samples containing high fraction of multifunctional epoxy resin showed higher solvent resistance and lower flexural modulus compared with the blends containing high fraction of bifunctional epoxy resin.The epoxy blends showed significantly higher ductility under bending test than the neat epoxy samples.The compressive modulus and strength increased with increasing of multifunctional epoxy in the samples,probably due to enhanced cross-link density and molecular weight.Morphological analysis revealed the presence of inhomogeneous sub-micrometer structures in all samples.The epoxy blends exhibited significantly higher fracture toughness (by 23％ at most) compared with the neat samples.The improvement of the fracture toughness was attributed to the stick-slip mechanism for crack growth and activation of shear yielding and plastic deformation around the crack growth trajectories for samples with higher content of bifunctional epoxy resin as evidenced by fractography study.     

Effect of maleic anhydride-grafted ethylene-propylene rubber on the mechanical, rheological and morphological properties of organoclay reinforced polyamide 6/polypropylene nanocomposites

Polyamide 6/polypropylene (PA6/PP = 70/30 parts) blends containing 4 phr (parts per hundred resin) of organophilic modified montmorillonite (organoclay) were compatibilized with maleic anhydride-grafted ethylene-propylene rubber (EPRgMA). The blends were melt compounded in twin screw extruder followed by injection molding. The mechanical properties of PA6/PP nanocomposites were studied by tensile and flexural tests. The microstructure of the nanocomposite were assessed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The dynamic mechanical properties of the PA6/PP blend-based nanocomposites were analyzed by using a dynamic mechanical thermal analyzer (DMTA). The rheological properties were conducted from plate/plate rheometry via dynamic frequency sweep scans. The melt viscosity in a high shear rate region was performed by using a capillary rheometer. The strength and stiffness of the PA6/PP-based nanocomposites were improved significantly with the incorporation of EPRgMA. Adding EPRgMA to the PA6/PP blends resulted in a finer dispersion of the PP phase. TEM and XRD results revealed that the organoclay was dispersed more homogeneously in the presence of EPRgMA, however, mostly in the PA6 phase of the blends. DMTA results showed that EPRgMA worked as an effective compatibilizer. The storage (G′) and loss moduli (G″) assessed by plate/plate rheometry of PA6/PP blends increased with the incorporation of EPRgMA and organoclay. Furthermore, the apparent shear viscosity of the PA6/PP blend increased significantly for the EPRgMA compatibilized PA6/PP/organoclay nanocomposite. This was traced to the formation of an interphase between PA6 and PP (via PA6-g-EPR) and effective intercalation/exfoliation of the organoclay.     

Influence of SEBS-g-MA on morphology, mechanical, and thermal properties of PA6/PP/organoclay nanocomposites

Polyamide 6/polypropylene (PA6/PP = 70/30 parts) blends containing 4 phr (parts per hundred resin) of organically modified clay (organoclay) toughened with maleated styrene-ethylene-butylene-styrene (SEBS-g-MA) were prepared by melt compounding using co-rotating twin-screw extruder followed by injection molding. X-ray diffraction (XRD) and transmission electron microscope (TEM) were used to characterize the structure of the nanocomposites. The mechanical properties of the nanocomposites were determined by tensile, flexural, and notched Izod impact tests. The single edge notch three point bending test was used to evaluate the fracture toughness of SEBS-g-MA toughened PA6/PP nanocomposites. Thermal properties were studied by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). XRD and TEM results indicated the formation of the exfoliated structure for the PA6/PP/organoclay nanocomposites with and without SEBS-g-MA. With the exception of stiffness and strength, the addition of SEBS-g-MA into the PA6/PP/organoclay nanocomposites increased ductility, impact strength and fracture toughness. The elongation at break and fracture toughness of PA6/PP blends and nanocomposites were increased with increasing the testing speed, whereas tensile strength was decreased. The increase in ductility and fracture toughness at high testing speed could be attributed to the thermal blunting mechanism in front of crack tip. DSC results revealed that the presence of SEBS-g-MA had negligible effect on the melting and crystallization behavior of the PA6/PP/organoclay nanocomposites. TGA results showed that the incorporation of SEBS-g-MA increased the thermal stability of the nanocomposite.     

Structure and properties of isobutylene-isoprene rubber/swollen organoclay nanocomposites prepared by shear mixing

A new approach was developed to prepare high-performance isobutylene-isoprene rubber/swollen organoclay nanocomposites by shear mixing.Compared with traditional melt compounding method,better dispersion of nanoclay layers in rubber matrix was verified through transmission electron microscopy(TEM) and X-ray diffraction(XRD).The nanocomposites also exhibit significantly improved mechanical properties and gas barrier property.As a mechanism,the molecules of organic swelling agent play a vital role in accelerating the diffusion and intercalation of the matrix molecules.     

SYNTHESIS, CHARACTERIZATION AND PROPERTIES OF ORGANOCLAY-MODIFIED POLYSULFONE/EPOXY INTERPENETRATING POLYMER NETWORK NANOCOMPOSITES

Organoclay-modified hydroxylterminated polysulfone (PSF)/epoxy interpenetrating network nanocomposites (oM-PSF/EP nanocomposites) were prepared by adding organophilic montmorillonite (oMMT) to interpenetrating polymer networks (IPNs) of polysulfone and epoxy resin (PSF/EP) using diaminodiphenylmethane (DDM) as curing agent.The mechanical properties like tensile strength,tensile modulus,flexural strength,flexural modulus and impact properties of the nanocomposites were studied as per ASTM standards.Differ...     

Nanocomposites by melt intercalation based on polycaprolactone and organoclay

Nanocomposites based on biodegradable polycaprolactone (PCL) and organically modified layered silicates (organoclay) were prepared by melt mixing. Their structures and properties were characterized by wide‐angle X‐ray diffraction, thermal analysis, and rheological measurements. The exfoliation of the organoclay was achieved via a melt mixing process in an internal mixer and showed a dependence on the type of organic modifier, the organoclay contents, and the processing temperature. The addition of the organoclay to PCL increased the crystallization temperature of PCL, but a high content of the organoclay could show an inverse effect. The PCL/organoclay nanocomposites showed a significant enhancement in their mechanical properties and thermal stability due to the exfoliation of the organoclay. The nanocomposites showed a much higher complex viscosity than the neat PCL and significant shear‐thinning behavior in the low frequency range. The shear storage modulus and loss modulus of the nanocomposites also exhibited less frequency dependence than the pure PCL in the low frequency range, and this was caused by the strong interactions between the organoclay layers and PCL molecules and by the good dispersion of exfoliated organoclay platelets in the PCL. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 670–678, 2003     

Influence of organoclay dispersed state of poly(ethylene glycol‐co‐1,3/1,4‐cyclohexanedimethanol terephthalate)/organoclay nanocomposites on their characteristics

This work prepared poly(ethylene glycol‐co‐1,3/1,4‐cyclohexanedimethanol terephthalate) (PETG)/organoclay nanocomposites via a melt intercalation process and investigated the influences of organoclay aspect ratio and organoclay content on the dispersed state, mechanical, thermal, gas barrier, and heat recovery properties of PETG/organoclay nanocomposites. X‐ray diffraction (XRD) and transmission electron microscopic analyses showed that the organoclay dispersed in the polymer matrix with intercalation in the nanometer scale range. Differential scanning calorimetry (DSC) analysis demonstrated that all of the obtained nanocomposites were amorphous, indicating that the addition of organoclay did not affect the amorphous nature of PETG. The gas barrier properties of the nanocomposites improved with organoclay content and the properties were also affected by the organoclay aspect ratio. Water vapor and oxygen transmission rates (OTRs) of PETG/organoclay nanocomposites containing 3 phr Cloisite 15A, and 3 phr modified polymer grade Na‐montmorillonites (MPGN) were the lowest among the samples tested, and were 41.7 and 44.3%, respectively, of those of neat PETG. Similar organoclay content‐ and aspect ratio‐related effects were observed in the mechanical and heat recovery properties of the tested nanocomposites. Copyright © 2010 John Wiley & Sons, Ltd.     

混合条件对环氧有机土纳米复合材料插层剥离行为及性能的影响

采用X 射线衍射仪、透射电镜 (TEM )研究了混合条件 ,即混合温度和时间 ,对环氧 /16 烷基胺有机蒙脱土体系在固化前的混合物以及加入固化剂、促进剂固化后有机土的插层与剥离行为的影响 .同时采用拉伸试验机、冲击试验机和热机械分析仪测定了插层与剥离型纳米复合材料的物理力学性能 .从X 射线衍射看出 ,有机土很容易在混合过程被环氧所插层 .混合物经固化后可以形成插层型或剥离型纳米复合材料 .存在一个混合温度 时间 插层剥离转变的 3 T图 .只有在一定的混合条件的区域内才能形成剥离型纳米复合材料 .剥离型比插层型纳米复合材料具有较高的力学性能     

Enhanced mechanical properties of unidirectional basalt fiber/epoxy composites using silane-modified Na+-montmorillonite nanoclay

This study explores the effects of 3-glycidoxypropyltrimethoxysilane (3-GPTS) modified Na-montmorillonite (Na-Mt) nanoclay addition on mechanical response of unidirectional basalt fiber (UD-BF)/epoxy composite laminates under tensile, flexural and compressive loadings. Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and simultaneous thermal analysis (STA) data confirmed the reaction mechanism between the silane compound and Mt. It was demonstrated that addition of 5 wt % 3-GPTS/Mt resulted in 28%, 11% and 35% increase in flexural, tensile and compressive strengths. Scanning electron microscopy (SEM) clarified the improvement in the adhesion between the basalt fibers and matrix in the case of Mt-enhanced epoxy specimens. Also, a theoretical route based on a Euler-Bernoulli beam-based approach was employed to estimate the compressive properties of the composites. The results demonstrated good agreement between theoretical and experimental approaches. Totally, the results of the study show that matrix modification is an effective strategy to improve the mechanical behavior of fibrous composites.     

Preparation of highly exfoliated epoxy/clay nanocomposites by clay grafted with liquid crystalline epoxy

Epoxy/clay nanocomposites with a high degree of exfoliation were achieved by intercalating liquid crystalline epoxy into clay intragallery as well as using a so-called ‘solution compounding’ process. In this process, clay modified was first treated with trichloromethane to form organoclay-trichloromethane suspension followed by liquid crystalline epoxy modification. The liquid crystalline epoxy grafted clay was then mixed extensively with epoxy to form epoxy/nanoclay composites. The mechanism of exfoliation was explored by monitoring the change of morphology of organoclay during each stage of processing with X-ray diffraction (XRD). The liquid crystalline epoxy grafted clay synthesised was characterised by fourier transform infrared spectroscopy (FT-IR) and polarising optical microscopy (POM). The clay platelets uniformly dispersed and highly exfoliated in the whole epoxy matrix were observed using transmission electron microscopy (TEM) and FT-IR imaging system. The epoxy nanocomposites were fabricated by incorporating different liquid crystalline epoxy grafted clay loading. The results revealed that the incorporation of liquid crystalline epoxy grafted clay resulted in a significant improvement in glass transition temperature (Tg) derived from dynamic mechanical analysis (DMA) and thermal stability measured by thermogravimetric analysis (TGA).     

Thermal stability and water uptake of high performance epoxy layered silicate nanocomposites

Intercalated and ordered exfoliated layered silicate nanocomposites based on three different epoxy resins of different structures and functionalities were synthesized using an octadecyl ammonium modified smectite clay. Water uptake properties of series of each nanocomposite system with different organoclay concentrations were determined by gravimetric measurements over a period of time. The diffusion coefficients were determined and the effect of the absorbed water on the thermal relaxations investigated. The equilibrium water uptake of all nanocomposites was reduced compared to the neat epoxy system but the rate of water diffusion remained unaffected. Further, the thermal stability of the different nanocomposites was determined using thermogravimetric analysis. The nanocomposites showed slightly reduced thermal stability, as indicated by a slight decrease in onset of degradation, whilst the final char concentration increased for greater organoclay concentrations.     

Clay dispersibility and mechanical property of the epoxy/clay nanocomposites prepared by different treatment methods

The bisphenol‐A type epoxy resin was combined with layered clays. Three types of epoxy/clay nanocomposites were prepared by different clay pretreatment methods, that is, the slurry (clay swelling with polar solvent), organo, and solubilization (organoclay swelling with polar solvent) methods. The organo and solubilization systems showed good dispersibility. The basal spacing of the layered clays in the obtained nanocomposites was evaluated by XRD and TEM observations. The basal spacing of the nanoclay in the solubilization system drastically increased. The mechanical properties were improved with the increase in the clay dispersion. A high modulus and fracture toughness were obtained by improvement of the clay dispersion into the matrix. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1753–1761, 2009     

Barrier and Mechanical Properties of Poly(caprolactone)/organoclay Nanocomposites

In this study, biodegradable poly(caprolactone) (PCL) hybrids with two types of organoclays: Cloisite 30B (30B) and Cloisite 93A (93A) have been prepared by melt mixing and their barrier performance to air permeation and mechanical properties were investigated. The hybrids of PCL/30B were found to be nanocomposites resulted from the strong interaction between organic modifier of 30B and PCL and those of PCL/93A were microcomposites. The barrier performance of PCL/30B nanocomposite film to air permeation was much more improved than pure PCL and PCL/93A microcomposites at low organoclay concentration. With the increase of organoclay content the permeability coefficient was also increased that could attributed to the extra tortuous pathway for gas permeation caused by organoclay exfoliation. The barrier behaviour of PCL/30B nanocomposites could be approximately described by a theoretical model developed for composites. The mechanical properties measurements showed that the reinforcement of organoclay 30B in nanocomposites is more significant than 93A in microcomposites. Both tensile modulus and tensile strength were increased in PCL/30B nanocomposites even at at low amount of organoclay without much loss of strain at break as compared to pure PCL. The significant improvements in both barrier and mechanical properties in PCL nanocomposites could be attributed to the fine dispersion state of organoclay 30B platelets in PCL matrix and the strong interaction between organic modifier of 30B and matrix molecules.     

Influence concentration of modifying agent on properties of natural rubber/organoclay nanocomposites

Sodium-montmorillonite (Na-MMT) nanoclay was modified with different concentrations of octadecylamine organic modifying agent at 0.5, 1.0 and 1.5 times the CEC of Na-MMT. Influence of concentration of modifying agent on properties of the organoclays and natural rubber/organoclay nanocomposites was investigated. It was found that the optimum concentration of modifying agent was 1.5 times the CEC of Na-MMT. That is, at this concentration, larger d-spacing of organoclay particles and higher degree of clay dispersion in natural rubber matrix were observed. Larger interlayer d-spacing also caused enhancement of the mechanical properties of the NR/organoclay nanocomposites. Additionally, the NR/organoclay nanocomposites with higher concentration of modifying agent exhibited faster curing reaction with higher crosslink density. Furthermore, the organoclays with larger d-spacing and higher degree of dispersion in the natural rubber matrix exhibited enhancement of the mechanical and dynamic properties and thermal stability of natural rubber/organoclay nanocomposites.     

Effect of internal mold release agent on flexural and inter laminar shear properties of carbon and glass fabric reinforced thermoset composites

The study is focused on thermoset composites reinforced with carbon and glass woven fabrics. Two types of thermoset resins, for example, epoxy and vinyl ester were used as the matrix. Varying concentrations of internal mold releasing (IMR) agent was used in the resin. The composites were cured both at room temperature and at 80°C. The flexural properties were studied using 3‐point bending test method. Further theinter‐laminar shear strength (ILSS) was investigated using the short beam shear strength test based on 3‐point bending. The flexural modulus of room temperature cured epoxy resin is higher than that of high temperature cured epoxy resin and cured vinyl ester resin. The flexural modulus is lowest for 1% IMR sample in epoxy system and the modulus for 0% and 2% epoxy are not significantly different. Lowest flexural strength and modulus can be observed for the combination of reinforcement and curing conditions for samples containing 1% IMR for the epoxy systems. Carbon fiber is found to be less compatible with the vinyl ester resin system and the addition of IMR to the resin degraded the properties further. Inter‐laminar shear strength for epoxy‐based composites is not much affected by presence of IMR, but in case of vinyl ester based composites there is a decrease in ILSS on addition of IMR agent. The study explains variation in flexural properties on addition of IMR and change of curing conditions. These results can be used for ascertaining variation in mechanical properties in real use.     

剥离型硅橡胶/黏土纳米复合材料研究

利用层状硅酸盐制备有机 无机纳米复合材料是当前人们研究的热点[1,2 ] ,这类材料具有较常规聚合物 无机填料复合材料无法比拟的优点 ,可以明显改善高分子材料的物理机械性能、热稳定性、气体阻隔性、阻燃性、导电性、光学性等 .一般来说 ,聚合物 层状硅酸盐 (Ｐｏｌｙｍｅｒｌａｙｅｒｅｄｓｉｌｉｃａｔｅ ,ＰＬＳ)纳米复合材料可分为插层型和剥离型两种类型 .插层型纳米复合材料即聚合物插入到硅酸盐层中 ,硅酸盐在近程仍保持原有的有序晶体结构 ,在远程则是无序的 .对弹性体而言 ,硅酸盐含量在插层型杂化材料中的含量比较高 ,力学性能…     

Nanomorphology and fire behavior of polystyrene/organoclay nanocomposites containing brominated epoxy and antimony oxide

Organoclay nanocomposites were prepared by ultrasound‐assisted solution intercalation technique based on polystyrene containing brominated epoxy and a combination of brominated epoxy and antimony oxide. Aspects of nanomorphology and nanodispersion were investigated by X‐ray diffraction and transmission electron microscopy whereas flammability and reaction to fire were evaluated using limiting oxygen index, UL‐94, and mass loss calorimeter tests. Polystyrene/brominated‐epoxy‐blend‐based nanocomposites showed mixed intercalated–exfoliated nanomorphology where polymer‐intercalated crystallites predominantly exist in polystyrene matrix and exfoliated silicate layers reside on polystyrene/brominated epoxy phase boundaries and within brominated epoxy domains. Organoclay was found to impart a compatibilization effect on polystyrene and dispersed brominated epoxy, which facilitates uniform distribution of a fine flame‐retarding phase within the matrix. With the reduction of the rate at which decomposition products evolve into the gas phase, organoclay nanocomposites showed notable reductions in peak heat release rate and increases in limiting oxygen index. The gas‐phase hot radical entrapment by halogenated flame‐retardant system was coupled with the condensed‐phase physical action of nanodispersed organoclay, which increased the overall fire‐retardant effectiveness. Fire‐retardant mechanisms of nanocomposites based on polystyrene/brominated epoxy blends were attributed to nanoconfinement and tortuous pathway effects of organoclay rather than to carbonaceous char formation proposed earlier for polystyrene/organoclay systems without conventional flame retardants. Copyright © 2011 John Wiley & Sons, Ltd.     

Layered silicate/epoxy nanocomposites: synthesis,characterization and properties

Novel epoxy‐clay nanocomposites have been prepared by epoxy and organoclays. Polyoxypropylene triamine (Jeffamine T‐403), primary polyethertriamine (Jeffamine T‐5000) and three types of polyoxypropylene diamine (Jeffamine D‐230, D‐400, D‐2000) with different molecular weight were used to treat Na‐montmorillonite (MMT) to form organoclays. The preparation involves the ion exchange of Na⁺ in MMT with the organic ammonium group in Jeffamine compounds. X‐ray diffraction (XRD) confirms the intercalation of these organic moieties to form Jeffamine‐MMT intercalates. Jeffamine D‐230 was used as a swelling agent for the organoclay and curing agent. It was established that the d₀₀₁ spacing of MMT in epoxy‐clay nanocomposites depends on the silicate modification. Although XRD data did not show any apparent order of the clay layers in the T5000‐MMT/epoxy nanocomposite, transmission electron microscopy (TEM) revealed the presence of multiplets with an average size of 5 nm and the average spacing between multiplets falls in the range of 100 Å. The multiplets clustered into mineral rich domains with an average size of 140 nm. Scanning electron microscopy (SEM) reveals the absence of mineral aggregate. Nanocomposites exhibit significant increase in thermal stability in comparison to the original epoxy. The effect of the organoclay on the hardness and toughness properties of crosslinked polymer matrix was studied. The hardness of all the resulting materials was enhanced with the inclusion of organoclay. A three‐fold increase in the energy required for breaking the test specimen was found for T5000‐MMT/epoxy containing 7 wt% of organoclay as compared to that of pure epoxy. Copyright © 2004 John Wiley & Sons, Ltd.     

The effect of different treatment methods of multiwalled carbon nanotubes on thermal and flexural properties of their epoxy nanocomposites

Multiwalled carbon nanotubes (MWCNTs) were oxidized using four different acid‐treatment methods followed by their functionalization with 3‐aminopropyltriethoxysilane (3‐APTES). Diglycidyl ether of bisphenol A (DGEBA) nanocomposites with unmodified and silanized MWCNTs (0.2 wt %) were prepared by a cast molding method. The effect of functionalization of MWCNTs on thermal, flexural, and morphological properties of the epoxy nanocomposites were studied. The epoxy/MWCNTs nanocomposites were characterized by thermogravimetric analysis, flexural testing, and field emission electron microscopic analysis. The results showed that the silanization of MWCNTs which were oxidized by a two‐step process using nitric acid and hydrochloric acid showed better thermal and flexural properties due to good interfacial adhesion between MWCNTs and the epoxy matrix. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1175–1184, 2010