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Donald R Paul - One of the best experts on this subject based on the ideXlab platform.
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Morphology and properties of polypropylene nanocomposites based on a silanized Organoclay
Polymer, 2011Co-Authors: M.w. Spencer, D L Hunter, B. W. Knesek, Donald R PaulAbstract:A silanized Organoclay (s-M2(HT)2) was prepared by reaction of trimethoxyphenyl silane with an Organoclay with a M2(HT)2 surfactant structure. Nanocomposites were formed from polypropylene (PP) and a blend of PP and maleic anhydride-grafted polypropylene (PP-g-MA) and the M2(HT)2 and s-M2(HT)2 Organoclays by melt processing to explore the extent of exfoliation and the mechanical properties. Wide angle X-ray scattering (WAXS) and transmission electron microscopy (TEM) coupled with detailed particle analysis were used to determine the effect of the Organoclay used and the PP-g-MA compatibilizer on exfoliation and mechanical, rheological, and thermal expansion properties. The PP/s-M2(HT)2 nanocomposites have higher particle densities than the PP/M2(HT)2 nanocomposites though the aspect ratio remains the same. Platelet dispersion is significantly improved by using PP-g-MA compatibilizer for both Organoclays. The rheological properties and the relative modulus improve for the PP/s-M2(HT)2 nanocomposites but not to the same degree as either Organoclay in a PP-g-MA compatibilized matrix. The thermal expansion properties, however, are not improved by using the s-M2(HT)2 Organoclay. The s-M2(HT)2 Organoclay is less prone to agglomeration during extrusion than the M2(HT)2 Organoclay.
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effect of Organoclay purity and degradation on nanocomposite performance part 1 surfactant degradation
Polymer, 2008Co-Authors: Dimitri M Khramov, Christopher W Bielawski, D L Hunter, P J Yoon, Donald R PaulAbstract:Abstract The alkylammonium surfactants used to form commercial Organoclays are known to begin to degrade at temperatures below the typical melt processing temperatures of some polymers. In this study, the thermal stability and degradation of various surfactants and their corresponding Organoclays were investigated. Several factors, such as surfactant type and excess surfactant in the Organoclay, that affect the thermal stability of surfactants on Organoclays are explored. Nuclear magnetic resonance (NMR) spectroscopy was used to analyze the decomposition products. Thermogravimetric analysis (TGA) was used as the primary method to characterize the thermal stability of these surfactants and Organoclays; the neat surfactants lose mass more rapidly, at a given temperature, than the corresponding Organoclay. Washing the Organoclay with methanol proved to be an effective way to remove the excess surfactant from the clay galleries. Such purification generally improves the thermal stability of the as-received Organoclays. Depending on the availability of residual halide anions in the Organoclay, the Organoclays decompose via either SN2 nucleophilic substitution or Hoffmann elimination pathways.
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effect of Organoclay structure on morphology and properties of nanocomposites based on an amorphous polyamide
Polymer, 2008Co-Authors: Donald R PaulAbstract:Abstract An amorphous polyamide (a-PA) and three Organoclays, M 3 (HT) 1 , M 2 (HT) 2 and (HE) 2 M 1 T 1 , were melt processed to explore the effect of the Organoclay structure on the extent of exfoliation and properties of these nanocomposites. Wide angle X-ray scattering, transmission electron microscopy, and stress–strain behavior were used to determine the degree of exfoliation of the nanocomposites. For quantitative assessment of the structure of the nanocomposites, a detailed particle analysis was made to provide various averages of the clay dimensions and aspect ratio. The results evaluated from different methods were generally consistent with each other. Nanocomposites based on the Organoclays with one alkyl tail and hydroxyl ethyl groups gave well-exfoliated structures and high matrix reinforcement while nanocomposites from two-tailed Organoclay contain a considerable concentration of intercalated stacks. Nanocomposites from the Organoclays with one alkyl tail showed slightly better exfoliation and matrix reinforcement than those from the Organoclays with hydroxyl ethyl groups. The Organoclay structure trends for a-PA are analogous to what has been observed for nylon 6; this suggests that a-PA, like nylon 6, has good affinity for the pristine silicate surface of the clay leading to better exfoliation and enhanced mechanical properties with one-tailed Organoclay than multiple-tailed Organoclay. Furthermore, heat distortion temperatures were predicted from the dynamic mechanical properties of nanocomposites.
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Thermal degradation of commercially available Organoclays studied by TGA-FTIR
Thermochimica Acta, 2007Co-Authors: Jesús Medina Cervantes, Humberto Vázquez-torres, Juan V. Cauich-rodríguez, Luis F. Garfias-mesías, Donald R PaulAbstract:Thermogravimetry coupled to Fourier transform infrared spectroscopy (TGA/FTIR) has been used to study the thermal decomposition products evolved during the degradation of several commercially available Organoclays (Cloisites™ Na+, 10A, 15A, 20A, 25A, 93A and 30B). It was found that the decomposition pattern of the Organoclays was different for each sample: Cloisite™ 10A shows three well-defined degradation stages, Cloisite™ 30B only two stages and the Cloisite™ 93A only one weight loss; Cloisites™ 15A, 20A and 25A exhibited a more complex behavior showing one main stage and a shoulder. It was also observed that the onset of the decomposition was different for each type of Organoclay, being Cloisite™ 10A the lowest (160 °C) and Cloisite™ 93A the highest (212 °C). FTIR analysis of the evolved products from their non-oxidative thermal degradation showed the release of water, aldehydes, carboxylic acids, aliphatic compounds and, in some cases, aromatic compounds and CO2. It is suggested that the degradation of both tallow residue and unexchanged surfactant explain the presence of some products evolved during degradation of Organoclays. © 2007 Elsevier B.V. All rights reserved.
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morphology and properties of thermoplastic polyurethane nanocomposites effect of Organoclay structure
Polymer, 2006Co-Authors: F Chavarria, Donald R PaulAbstract:Abstract A series of alkyl ammonium/MMT Organoclays were carefully selected to explore structure–property relationships for thermoplastic polyurethane (TPU) nanocomposites prepared by melt processing. Each Organoclay was melt-blended with a medium-hardness, ester-based TPU, while a more limited number of Organoclays was blended with a high-hardness, ether-based TPU. Wide-angle X-ray scattering, transmission electron microscopy, particle analysis, and stress–strain behavior were used to examine the effects of Organoclay structure and TPU chemical structure on morphology and mechanical properties. Specifically, the following were observed: (a) one long alkyl tail on the ammonium ion rather than two, (b) hydroxy ethyl groups on the amine rather than methyl groups, and (c) a longer alkyl tail as opposed to a shorter one leads to higher clay dispersion and stiffness for medium-hardness TPU nanocomposites. Overall, the Organoclay containing hydroxy ethyl functional groups produces the best dispersion of Organoclay particles and the highest matrix reinforcement, while the one containing two alkyl tails produces the poorest. The two TPU's exhibit similar trends with regard to the effect of Organoclay structure. The high-hardness TPU nanocomposites showed a slightly higher number of particles and clay dispersion. The Organoclay structure trends are analogous to what has been observed for nylon 6-based nanocomposites; this suggests that polar polymers like polyamides, and apparently polyurethanes, have a relatively good affinity for the polar clay surface; and in the case of polyurethanes, the high affinity of the matrix for the hydroxy ethyl functional groups in the Organoclay aids clay dispersion and exfoliation.
D. R. Paul - One of the best experts on this subject based on the ideXlab platform.
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Morphology and properties of nanocomposites based on HDPE/HDPE-g-MA blends
Polymer, 2010Co-Authors: M.w. Spencer, Youngjae Yoo, Lili Cui, D. R. PaulAbstract:Nanocomposites formed from blends of high density polyethylene (HDPE) and maleic anhydride-grafted high density polyethylene (HDPE-g-MA) and M2(HT)2Organoclay were melt processed to explore the extent of exfoliation and the mechanical properties. Wide angle X-ray scattering (WAXS) and transmission electron microscopy (TEM) coupled with detailed particle analysis were used to determine the effect of HDPE-g-MA content and Organoclay content on exfoliation and mechanical properties. As the HDPE-g-MA content increases, the global average particle aspect ratio initially increases drastically, reaches a maximum, and slightly decreases. The fraction of single platelets, however, increases at a steady rate for nanocomposites with HDPE-g-MA contents ≥25%. Relative modulus initially improves with increased levels of HDPE-g-MA, and then levels off with greater HDPE-g-MA content. Izod impact strength reaches a maximum at low HDPE-g-MA levels, decreases below the value for the pure HDPE nanocomposite, and levels off at higher HDPE-g-MA content. A composite model based on the Mori-Tanaka theory was developed to treat Organoclay tactoids and single platelets as two separate types of fillers. This model gives rather good quantitative agreement between the predicted values of modulus calculated from the TEM results and that measured experimentally. © 2010 Elsevier Ltd. All rights reserved.
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Organoclay degradation in melt processed polyethylene nanocomposites
Polymer, 2006Co-Authors: Rhutesh K. Shah, D. R. PaulAbstract:Melt processed nanocomposites were formed from low-density polyethylene, LDPE, and Organoclays over a wide range of processing temperatures. These composites show limited exfoliation, and hence, their X-ray analysis reveals a distinct peak corresponding to the interplatelet distances in the unexfoliated clay galleries. The degradation of the quaternary ammonium surfactant of the Organoclay in these systems was characterized by examining the change in the position of these peaks as a function of the melt processing temperature. Upon degradation, the mass of the surfactant within the clay galleries decreases, which causes the platelets to collapse and shifts the WAXS peak to lower d-spacings. The results of the WAXS analysis suggest that a significant portion of the surfactant is lost from the Organoclays when the melt processing temperature is increased from 180 to 200 °C or higher. The extent of surfactant degradation in these composites was determined to be independent of the Organoclay content. Organoclay degradation appears to limit the extent of exfoliation or dispersion in LDPE as revealed by stress-strain analyses of nanocomposites processed at different temperatures. The amount of surfactant lost during thermogravimetric analysis of various Organoclays indicates that surfactants with multiple alkyl tails have greater thermal stability than those with a single alkyl tail. A comparison of the mass of surfactant lost during melt processing of nanocomposites and during thermogravimetric analysis of Organoclays (in the absence of polymer) indicated that at a given time, a larger surfactant loss from the clay galleries occurs during extrusion than during the TGA experiment. This is attributed to the greater ease with which the degradation products (predominantly α-olefins) are solubilized in polyethylene for the composites as opposed to evaporated from the Organoclay during TGA. © 2006 Elsevier Ltd. All rights reserved.
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Surfactant degradation in melt processed polyethylene-Organoclay nanocomposites
AIChE Annual Meeting Conference Proceedings, 2005Co-Authors: Rhutesh K. Shah, D. R. PaulAbstract:Polymer-clay nanocomposites continue to generate much interest, owing to their potential for exceptional improvements in properties at lower filler concentrations as compared to their micro- and macro-composite counterparts. The key to achieving these benefits is exfoliating the clay into the polymer matrix to generate high aspect ratio particles. The first step in this direction is to make the hydrophilic smectite clay more organophilic using an ion exchange reaction between the naturally occurring alkali metal cations residing between aluminosilicate layers and alkyl ammonium surfactants to produce an "Organoclay". Unfortunately, the currently used alkyl ammonium surfactants have low thermal stability and are known to breakdown at the high temperatures required for melt processing most polymers. This could possibly affect the level of platelet exfoliation and interfacial bonding, which influence the physical and mechanical properties of the final nanocomposite. Since melt processing seems to be one of the most convenient and attractive methods of producing nanocomposites, the subject of Organoclay degradation during melt mixing has been the subject of recent attention in several laboratories. The objective of this study is to examine surfactant degradation in polyethylene- Organoclay nanocomposites prepared by melt processing. Since polyethylene has a low melting point, it was possible to conduct this examination over a wide range of temperatures (150°C to 240°C). Organoclay degradation was characterized using WAXD analysis and its effect on nanocomposite mechanical properties was determined by stress-strain analysis. Finally, the thermal stability of the three Organoclays with different alkyl contents (number of alkyl tails) are compared with each other by measuring the amount of surfactant lost during their thermogravimetric analysis (TGA). The surfactant degradation observed during TGA is also correlated to that seen in melt processed nanocomposites and a suitable degradation mechanism is proposed.
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Nanocomposites formed from linear low density polyethylene and Organoclays
Polymer, 2004Co-Authors: Shuhei Hotta, D. R. PaulAbstract:Polyethylene-clay nanocomposites were prepared by melt compounding various combinations of a maleic anhydride grafted linear low density polyethylene (LLDPE-g-MA), a linear low density polyethylene (LLDPE), and two Organoclays. The two types of Organoclay were selected to show the effect of the number of alkyl groups attached to the nitrogen of the organic modifier on exfoliation and improvement of mechanical properties. Nanocomposites derived from the Organoclay having two alkyl tails, M2(HT)2, exhibited better dispersion and improvement of mechanical properties than nanocomposites based on the Organoclay having one alkyl tail M3(HT)1. This result is the opposite of what is observed for nylon-6 nanocomposites. In addition, the rheological properties and gas permeability of the nanocomposites derived from the Organoclay having two alkyl tails, M2(HT)2were investigated. Both melt viscosity and melt tension (melt strength) increased with increased content of clay (MMT) and LLDPE-g-MA. Gas permeability was decreased by the addition of MMT. © 2004 Published by Elsevier Ltd.
Rhutesh K. Shah - One of the best experts on this subject based on the ideXlab platform.
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Organoclay degradation in melt processed polyethylene nanocomposites
Polymer, 2006Co-Authors: Rhutesh K. Shah, Donald R PaulAbstract:Abstract Melt processed nanocomposites were formed from low-density polyethylene, LDPE, and Organoclays over a wide range of processing temperatures. These composites show limited exfoliation, and hence, their X-ray analysis reveals a distinct peak corresponding to the interplatelet distances in the unexfoliated clay galleries. The degradation of the quaternary ammonium surfactant of the Organoclay in these systems was characterized by examining the change in the position of these peaks as a function of the melt processing temperature. Upon degradation, the mass of the surfactant within the clay galleries decreases, which causes the platelets to collapse and shifts the WAXS peak to lower d -spacings. The results of the WAXS analysis suggest that a significant portion of the surfactant is lost from the Organoclays when the melt processing temperature is increased from 180 to 200 °C or higher. The extent of surfactant degradation in these composites was determined to be independent of the Organoclay content. Organoclay degradation appears to limit the extent of exfoliation or dispersion in LDPE as revealed by stress–strain analyses of nanocomposites processed at different temperatures. The amount of surfactant lost during thermogravimetric analysis of various Organoclays indicates that surfactants with multiple alkyl tails have greater thermal stability than those with a single alkyl tail. A comparison of the mass of surfactant lost during melt processing of nanocomposites and during thermogravimetric analysis of Organoclays (in the absence of polymer) indicated that at a given time, a larger surfactant loss from the clay galleries occurs during extrusion than during the TGA experiment. This is attributed to the greater ease with which the degradation products (predominantly α-olefins) are solubilized in polyethylene for the composites as opposed to evaporated from the Organoclay during TGA.
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Organoclay degradation in melt processed polyethylene nanocomposites
Polymer, 2006Co-Authors: Rhutesh K. Shah, D. R. PaulAbstract:Melt processed nanocomposites were formed from low-density polyethylene, LDPE, and Organoclays over a wide range of processing temperatures. These composites show limited exfoliation, and hence, their X-ray analysis reveals a distinct peak corresponding to the interplatelet distances in the unexfoliated clay galleries. The degradation of the quaternary ammonium surfactant of the Organoclay in these systems was characterized by examining the change in the position of these peaks as a function of the melt processing temperature. Upon degradation, the mass of the surfactant within the clay galleries decreases, which causes the platelets to collapse and shifts the WAXS peak to lower d-spacings. The results of the WAXS analysis suggest that a significant portion of the surfactant is lost from the Organoclays when the melt processing temperature is increased from 180 to 200 °C or higher. The extent of surfactant degradation in these composites was determined to be independent of the Organoclay content. Organoclay degradation appears to limit the extent of exfoliation or dispersion in LDPE as revealed by stress-strain analyses of nanocomposites processed at different temperatures. The amount of surfactant lost during thermogravimetric analysis of various Organoclays indicates that surfactants with multiple alkyl tails have greater thermal stability than those with a single alkyl tail. A comparison of the mass of surfactant lost during melt processing of nanocomposites and during thermogravimetric analysis of Organoclays (in the absence of polymer) indicated that at a given time, a larger surfactant loss from the clay galleries occurs during extrusion than during the TGA experiment. This is attributed to the greater ease with which the degradation products (predominantly α-olefins) are solubilized in polyethylene for the composites as opposed to evaporated from the Organoclay during TGA. © 2006 Elsevier Ltd. All rights reserved.
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Surfactant degradation in melt processed polyethylene-Organoclay nanocomposites
AIChE Annual Meeting Conference Proceedings, 2005Co-Authors: Rhutesh K. Shah, D. R. PaulAbstract:Polymer-clay nanocomposites continue to generate much interest, owing to their potential for exceptional improvements in properties at lower filler concentrations as compared to their micro- and macro-composite counterparts. The key to achieving these benefits is exfoliating the clay into the polymer matrix to generate high aspect ratio particles. The first step in this direction is to make the hydrophilic smectite clay more organophilic using an ion exchange reaction between the naturally occurring alkali metal cations residing between aluminosilicate layers and alkyl ammonium surfactants to produce an "Organoclay". Unfortunately, the currently used alkyl ammonium surfactants have low thermal stability and are known to breakdown at the high temperatures required for melt processing most polymers. This could possibly affect the level of platelet exfoliation and interfacial bonding, which influence the physical and mechanical properties of the final nanocomposite. Since melt processing seems to be one of the most convenient and attractive methods of producing nanocomposites, the subject of Organoclay degradation during melt mixing has been the subject of recent attention in several laboratories. The objective of this study is to examine surfactant degradation in polyethylene- Organoclay nanocomposites prepared by melt processing. Since polyethylene has a low melting point, it was possible to conduct this examination over a wide range of temperatures (150°C to 240°C). Organoclay degradation was characterized using WAXD analysis and its effect on nanocomposite mechanical properties was determined by stress-strain analysis. Finally, the thermal stability of the three Organoclays with different alkyl contents (number of alkyl tails) are compared with each other by measuring the amount of surfactant lost during their thermogravimetric analysis (TGA). The surfactant degradation observed during TGA is also correlated to that seen in melt processed nanocomposites and a suitable degradation mechanism is proposed.
P J Yoon - One of the best experts on this subject based on the ideXlab platform.
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effect of Organoclay purity and degradation on nanocomposite performance part 1 surfactant degradation
Polymer, 2008Co-Authors: Dimitri M Khramov, Christopher W Bielawski, D L Hunter, P J Yoon, Donald R PaulAbstract:Abstract The alkylammonium surfactants used to form commercial Organoclays are known to begin to degrade at temperatures below the typical melt processing temperatures of some polymers. In this study, the thermal stability and degradation of various surfactants and their corresponding Organoclays were investigated. Several factors, such as surfactant type and excess surfactant in the Organoclay, that affect the thermal stability of surfactants on Organoclays are explored. Nuclear magnetic resonance (NMR) spectroscopy was used to analyze the decomposition products. Thermogravimetric analysis (TGA) was used as the primary method to characterize the thermal stability of these surfactants and Organoclays; the neat surfactants lose mass more rapidly, at a given temperature, than the corresponding Organoclay. Washing the Organoclay with methanol proved to be an effective way to remove the excess surfactant from the clay galleries. Such purification generally improves the thermal stability of the as-received Organoclays. Depending on the availability of residual halide anions in the Organoclay, the Organoclays decompose via either SN2 nucleophilic substitution or Hoffmann elimination pathways.
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polymer matrix degradation and color formation in melt processed nylon 6 clay nanocomposites
Polymer, 2003Co-Authors: T D Fornes, P J Yoon, Donald R PaulAbstract:Abstract Nylon 6 nanocomposites based on various quaternary alkyl ammonium Organoclays were prepared by melt processing using a twin screw extruder. Dilute solution viscosity techniques were used to evaluate the level of polymer molecular weight degradation experienced during nanocomposite compounding; whereas colorimeter techniques were used to document color formation. In general, a significant reduction in nylon 6 matrix molecular weight was observed, which is believed to stem, in part, from reaction(s) between the surfactant of the Organoclay and the polyamide chains. The level of degradation depends on both the type of nylon 6 material used and the surfactant chemistry in the Organoclay. For a given Organoclay, nanocomposites based on high molecular weight nylon 6 materials experience more matrix degradation, as well as color formation, than those based on low molecular weight materials; this is believed to arise from increased exposure of the Organoclay surface to the nylon 6 owing to increased platelet exfoliation. Different Organoclays lead to different levels of polymer degradation and color formation, depending upon the level of unsaturation present in the organic surfactant; the higher the number of double bonds the greater the degradation and the deeper the color formation. The primary mechanism of degradation is believed to be thermo-oxidative. Melt mixing of nylon 6 with model compounds, long-chain alkenes, shows that the same mode of degradation i.e. via double bonds can be replicated. In addition to unsaturation effects, the presence of hydroxyl–ethyl groups, opposed to methyl groups, in the Organoclay surfactant, results in more color. Isothermal thermogravimetric analysis (TGA) was conducted on the Organoclays to determine if thermal stability was a cause of molecular weight degradation; although, this relationship does not seem to exist, a direction correlation is observed between the Organoclay degradation and nanocomposite modulus, or indirectly level of exfoliation. Use of antioxidant was found to reduce the amount of molecular weight loss. All evidence suggests that morphology and physical properties of nanocomposites formed from nylon 6 are not measurably affected by the reactions that lead to molecular weight degradation or color formation.
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polycarbonate nanocomposites part 1 effect of Organoclay structure on morphology and properties
Polymer, 2003Co-Authors: P J Yoon, D L Hunter, Donald R PaulAbstract:Abstract Polycarbonate nanocomposites were prepared by melt processing from a series of Organoclays based on sodium montmorillonite exchanged with various amine surfactants. To explore the effects of matrix molecular weight on dispersion, an Organoclay was melt-mixed with a medium molecular weight polycarbonate (MMW-PC) and a high molecular weight polycarbonate (HMW-PC) using a twin screw extruder. The effects of surfactant chemical structure on the morphology and physical properties were explored for nanocomposites formed from HMW-PC. Wide angle X-ray scattering, transmission electron microscopy, and stress–strain behavior were employed to investigate the nanocomposite morphology and physical properties. The modulus enhancement is greater for nanocomposites formed from HMW-PC than MMW-PC. This trend is attributed to the higher shear stress generated during melt processing. A surfactant having both polyoxyethylene and octadecyl tails shows the most significant improvement in modulus with some of the clay platelets fully exfoliated. However, the nanocomposites formed from a range of other Organoclays contained both intercalated tactoids and collapsed clay particles with few, if any, exfoliated platelets.
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effect of Organoclay structure on nylon 6 nanocomposite morphology and properties
Polymer, 2002Co-Authors: T D Fornes, P J Yoon, D L Hunter, H Keskkula, Donald R PaulAbstract:Abstract A carefully selected series of organic amine salts were ion exchanged with sodium montmorillonite to form Organoclays varying in amine structure or exchange level relative to the clay. Each Organoclay was melt-mixed with a high molecular grade of nylon 6 (HMW) using a twin screw extruder; some Organoclays were also mixed with a low molecular grade of nylon 6 (LMW). Wide angle X-ray scattering, transmission electron microscopy, and stress–strain behavior were used to evaluate the effect of amine structure on nanocomposite morphology and physical properties. Three surfactant structural issues were found to significantly affect nanocomposite morphology and properties in the case of the HMW nylon 6: decreasing the number of long alkyl tails from two to one tallows, use of methyl rather than hydroxy-ethyl groups, and use of an equivalent amount of surfactant with the montmorillonite, as opposed to adding excess, lead to greater extents of silicate platelet exfoliation, increased moduli, higher yield strengths, and lower elongation at break. LMW nanocomposites exhibited similar surfactant structure-nanocomposite behavior. Overall, nanocomposites based on HMW nylon 6 exhibited higher extents of platelet exfoliation and better mechanical properties than nanocomposites formed from the LMW polyamide, regardless of the Organoclay used. This trend is attributed to the higher melt viscosity and consequently the higher shear stresses generated during melt processing.
Hongping He - One of the best experts on this subject based on the ideXlab platform.
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Changes in the morphology of Organoclays with HDTMA+ surfactant loading
Applied Clay Science, 2020Co-Authors: Hongping He, Peng Yuan, Ray L. Frost, Thor Bostrom, Loc Duong, Dan Yang, Yunfei Xi, J. Theo KloproggeAbstract:The detailed understanding of the interlayer structure of Organoclays is of importance in the design of Organoclay based materials and their industrial applications. In this study, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) have been used to provide new insights into the interlayer structure and morphology of HDTMA+/montmorillonite Organoclays. XRD patterns show that thermal treatment has an important effect on the stability of Organoclays, reflected by significant changes in the basal spacing. TEM and SEM micrographs demonstrate that the Organoclays with lower surfactant packing density are mainly composed of irregular layer stacking with a number of curved Organoclay layers, while those with higher surfactant packing density are mainly composed of regularly intercalated and flat layers. Variations of the interlayer distances exist in all Organoclays and are more pronounced in the Organoclays with lower surfactant packing density. This study demonstrates that not only the arrangement model of surfactant but also the morphology of Organoclay strongly depend on the surfactant packing density within the montmorillonite interlayer space
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changes in the surfaces of adsorbed para nitrophenol on hdtma Organoclay the xrd and tg study
Journal of Colloid and Interface Science, 2007Co-Authors: Qin Zhou, Hongping He, Ray L. Frost, Yunfei XiAbstract:Abstract Surfactant modified montmorillonitic clays synthesized by ion exchange using the hydrothermal reaction method have been compared using XRD and thermal analysis. X-ray diffraction (XRD) shows the changes in the surface properties of Organoclays through expansion with surfactant loading. A polynomial relationship exists between the basal spacing and the CEC loading described by the equation y = 0.3232 x 2 + 0.2052 x + 1.2834 with R 2 = 0.9955 . Different arrangements of the surfactant molecules in the Organoclays are inferred from the changes in basal spacings. para-Nitrophenol also causes the expansion of the montmorillonite clay and affects the arrangements of the surfactant molecules within the clay layers. Changes in the surfactant molecular arrangements were analyzed by thermogravimetry. Additional thermal decomposition steps were observed when para-nitrophenol is adsorbed on the Organoclay.
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FTIR investigation of CTAB-Al-montmorillonite complexes
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy, 2007Co-Authors: Weihong Xue, Jianxi Zhu, Hongping He, Peng YuanAbstract:In this study, CTAB-Al-montmorillonite complexes were synthesized by pre-modifying montmorillonite using different concentrations of surfactant (resulting in different surfactant loadings and basal spacings), then pillaring the Organoclays with hydroxy-Al cations. The resultant inorganic-organic montmorillonite complexes were characterized using FTIR, with a combination of XRD, TG and chemical analysis. This study indicates that the basal spacings of the CTAB-Al-montmorillonite complexes and the amounts of Al-contained pillars strongly depend on the surfactant loadings in the clay interlayer space, resulted from the mobility variation of the intercalated surfactants. During pillaring hydroxy-Al cations into clay interlayer space, part of the intercalated surfactants were removed, resulting in a decrease of the ordering of alkyl chains and the frequency shifts of Si(Al)-O, Si-O-Al and (M-O)Td stretching vibrations. The hydrophobicity of the CTAB-Al-montmorillonite complex also strongly depends on the surfactant loading whereas that of the CTAB-Al-montmorillonite complex is relative lower than that of the corresponding Organoclay, indicated by the frequency shift of the vibrations corresponding to the sorbed water and their contents estimated by TG curves. With the decrease of the sorbed water content, the frequency of the band of H-O-H bending (ν2) shifts to higher frequency while the O-H stretching vibration (ν1 and ν3) shifts to lower frequency, indicating that H2O is less hydrogen bonded. Meanwhile, the ordered conformations of the alkyl chains in CTAB-Al-montmorillonite complex decrease when compared with that of the corresponding Organoclay. © 2006 Elsevier B.V. All rights reserved.
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a novel Organoclay with antibacterial activity prepared from montmorillonite and chlorhexidini acetas
Journal of Colloid and Interface Science, 2006Co-Authors: Hongping He, Peng Yuan, Dan Yang, Weiping Shen, Ray L. FrostAbstract:A series of novel Organoclays with antibacterial activity were synthesized using Ca-montmorillonite and Chlorhexidini Acetas (CA) by ion-exchange. The resultant Organoclays were characterized using X-ray diffraction (XRD), high-resolution thermogravimetric analysis (HRTG) and Fourier transform infrared spectroscopy (FTIR). Their antibacterial activity was assayed by so-called halo method. In the Organoclay prepared at low CA concentration, CA ions within the clay interlayer adopt a lateral monolayer while a ‘kink’ state or a special state with partial overlapping of the intercalated CA in the Organoclays prepared at 1.0 – 4.0 CEC. HRTG analysis demonstrates that CA located outside the clay interlayer exists in all synthesised Organoclays, resulting from the complex molecular configuration of CA. The dramatic decrease of the surface adsorbed water and interlayer water is caused by the surface property transformation and the replacement of hydrated cations by cationic surfactant. These observations are supported by the results of FTIR. Antibacterial activity test against E. coli demonstrates that the antibacterial activity of the resultant Organoclays strongly depends on the content of CA. Meanwhile, the resultant Organoclay shows a long-term antibacterial activity that can last for at least one year. These novel Organoclays are of potential use in synthesis of Organoclay-based materials with antibacterial activity.
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Influence of cationic surfactant removal on the thermal stability of Organoclays
Journal of Colloid and Interface Science, 2005Co-Authors: Hongping He, Jannick Duchet, Jocelyne Galy, Jean-françois GérardAbstract:The microstructure, thermal stability, surface energy and swelling characteristics of two kinds of commercial Organoclays, before and after washing treatment with a mixture of H2O/ethanol, were investigated using X-ray diffraction (XRD), thermogravimetric analysis (TG/DTG), wettability measurement and swelling measurement. This study demonstrates that the external-surface physically adsorbed surfactant can be removed after washing treatment, resulting in an increase in thermal stability and a decrease in surface energy of the resultant Organoclays. Organoclays are difficult to be introduced into a solvent when their surface energies are lower than that of the solvent. On the other hand, the Organoclay with γOrganoclay < γsolvent is easier to be swollen and expandable by the solvent. The swelling and basal spacing measurements of the Organoclays introduced into organic media indicate that the swelling factor and the interlayer swelling are two independent parameters. Both the polar character of the solvent and the swelling capacity of clay have a prominent effect on the interlayer swelling of the Organoclays.