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Clay Systems (clay + system)
Selected AbstractsMelt processing and characterization of multicomponent polymeric nanocomposites containing organoclayPOLYMER COMPOSITES, Issue 3 2007M. Letuchi Nylon 6 (Ny)/polypropylene (PP)/maleated polypropylene (PP- g -MA)/organoclay/wollastonite composites were prepared by melt processing. The polymers' composition was kept constant ([70PP/30Ny]/4PP- g -MA). Melt compounding was conducted using a twin-screw extruder in three different methods: (1) simultaneous incorporation of the components into the compounding equipment, (2) preparation of [Ny6/clay] concentrate, and then in a second step, mixing the other components with the concentrate, and (3) mixing of PP with wollastonite and clay followed by the addition of Ny6 and PP- g -MA in the second step. Injection-molded specimens were characterized in tension, scanning electron microscopy, X-ray diffraction (XRD), and differential scanning calorimetry. The sequence of component addition greatly influences the structure and properties of the composites. Enhanced mechanical properties were achieved when the two-step mixing procedure was used for the PP/Ny6/PP- g -MA/clay system (method 2) and also for the PP/Ny6/PP- g -MA/clay/wollastonite system (method 3). The XRD pattern of the PP/Ny6/PP- g -MA/clay nanocomposites produced by the two-step mixing method does not show a characteristic basal reflection of the pristine organoclay, indicating a predominately exfoliated structure of clay. POLYM. COMPOS., 28:417,424, 2007. © 2007 Society of Plastics Engineers [source] Kinetics of toluene sorption and desorption in Ca- and Cu-montmorillonites investigated with Fourier transform infrared spectroscopy under two different levels of humidityENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2004Yang-Hsin Shih Abstract Clays in soils or groundwater aquifer materials play roles in the sorption of organic pollutants. The intrinsic sorption kinetics of toluene in dry and humid clay films was investigated by tracking the change of infrared absorbance. Under the humid condition, similar toluene-sorbed intensities were found in Ca- and Cu-montmorillonites. However, a higher intensity of sorbed toluene was found in the Cu-form than in the Ca-form under the dry condition, which indicates a stronger interaction occurring in dry Cu-montmorillonite. The general time scale of sorption of toluene on clays is around 100 s. In both forms of montmorillonite, some portion of toluene was desorbed at an extremely slow rate under the dry condition. Some newly identified peaks were persistent against desorption from montmorillonites, suggesting the existence of irreversibly sorbed species and the possibility of toluene transformation occurring in clay systems. [source] Processing of transmission electron microscope images for quantification of the layer dispersion degree in polymer-clay nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2009Amir H. Navarchian Abstract Quantification of the layered silicates dispersion level is necessary to more accurately evaluate the performance in polymer/clay nanocomposites. In this article, a new approach is developed to quantify the degree of exfoliation, intercalation, and immiscibility of layered silicates in polymer matrix, based on bright-dark pixel measurement (BDPM) in transmission electron microscope (TEM) images. Several examples of exfoliated, intercalated, and immiscible composites with different polymer and clay systems were examined. The method is capable of estimating the percent contribution of all morphologies present in the image. Comparing with X-ray diffraction (XRD) evidences, it is indicated that as a rule of thumb, the exfoliated structure is dominant whenever the exfoliation percent calculated by BDPM methodology is over 65%, no matter what kind of clay or polymer matrix is used. The intercalated structure can be ascribed to the images with exfoliation level less than 65%, but with the intercalation degree over 28%. Application of this method can facilitate the modeling or correlation of various nanocomposite properties with respect to exfoliation degree. A quantified relation is also possible between XRD and TEM using this approach. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Mechanical and oxygen barrier properties of organoclay-polyethylene nanocomposite filmsPOLYMER ENGINEERING & SCIENCE, Issue 7 2007Yang Zhong An organically modified montmorillonite was compounded with ethylene vinyl acetate copolymer (EVA), low density polyethylene (LDPE), and high density polyethylene (HDPE) in a twin-screw extruder. The resulting organoclay-polyethylene nanocomposites were then blown into films. Tensile properties and oxygen permeability of these nanocomposite films were investigated to understand the effects of organoclay on different types of polyethylene. It was found that the clay enhancing effects are function of the matrix. The mechanical and oxygen barrier properties of clay/EVA systems increased with clay loading. Both the tensile modulus and oxygen barrier of EVA doubled at 5 wt% clay. Maleic anhydride grafted polyethylene (MAPE) usually is used as a compatibilizer for LDPE and HDPE-based nanocomposites. However, the MAPEs were found to weaken the oxygen barrier of the PEs, especially for HDPE. This is believed to be a result of less compactness caused by the large side groups and the increase in polarity of the MAPEs. Incorporating 5 wt% clay improves the oxygen barrier by 30% and the tensile modulus by 37% for the LDPE/MAPE system. Incorporation of clay does not enhance the properties of the HDPE-based systems, likely due to large domain structure and poor bonding. Halpin,Tsai equation and the tortuous path equation were used to model the tensile modulus and oxygen permeability of the clay/EVA nanocomposite films. POLYM. ENG. SCI., 47:1101,1107, 2007. © 2007 Society of Plastics Engineers [source] Mechanical and morphological properties of organic,inorganic, hybrid, clay-filled, and cyanate ester/siloxane toughened epoxy nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2007S. Nagendiran Abstract Organic,inorganic hybrids involving cyanate ester and hydroxyl-terminated polydimethylsiloxane (HTPDMS) modified diglycidyl ether of bisphenol A (DGEBA; epoxy resin) filled with organomodified clay [montmorillonite (MMT)] nanocomposites were prepared via in situ polymerization and compared with unfilled-clay macrocomposites. The epoxy-organomodified MMT clay nanocomposites were prepared by the homogeneous dispersion of various percentages (1,5%), and the resulting homogeneous epoxy/clay hybrids were modified with 10% HTPDMS and ,-aminopropyltriethoxysilane as a coupling agent in the presence of a tin catalyst. The siliconized epoxy/clay prepolymer was further modified separately with 10% of three different types of cyanate esters, namely, 4,4,-dicyanato-2,2,-diphenylpropane, 1,1,-bis(3-methyl-4-cyanatophenyl) cyclohexane, and 1,3-dicyanato benzene, and cured with diaminodiphenylmethane as a curing agent. The reactions during the curing process between the epoxy, siloxane, and cyanate were confirmed by Fourier transform infrared analysis. The results of dynamic mechanical analysis showed that the glass-transition temperatures of the clay-filled hybrid epoxy systems were lower than that of neat epoxy. The data obtained from mechanical studies implied that there was a significant improvement in the strength and modulus by the nanoscale reinforcement of organomodified MMT clay with the matrix resin. The morphologies of the siloxane-containing, hybrid epoxy/clay systems showed heterogeneous character due to the partial incompatibility of HTPDMS. The exfoliation of the organoclay was ascertained from X-ray diffraction patterns. The increase in the percentage of organomodified MMT clay up to 5 wt % led to a significant improvement in the mechanical properties and an insignificant decrease in the glass-transition temperature versus the unfilled-clay systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] | ||||||||||