@article { ISI:000247943800001, title = {Influence of organic modification on mechanical properties of melt processed intercalated poly(methyl methacrylate)-organoclay nanocomposites}, journal = {Journal of Applied Polymer Science}, volume = {105}, number = {5}, year = {2007}, month = {SEP}, pages = {2433-2443}, publisher = {JOHN WILEY \& SONS INC}, type = {Article}, address = {111 RIVER ST, HOBOKEN, NJ 07030 USA}, abstract = {

The influence of organic modifiers on intercalation extent, structure, thermal and mechanical properties of poly(methyl methacrylate) (PMMA)-clay nanocomposites were studied. Two different organic modifiers with varying hydrophobicity (single tallow versus ditallow) were investigated. The nanocomposites were prepared from melt processing method and characterized using wide angle X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), and tensile tests. Mechanical properties such as tensile modulus (E), break stress (sigma(brk)), and 0\% break strain (epsilon(brk)) were determined for nanocomposites at various clay loadings. Extent of PMMA intercalation is sufficient and in the range 9-15 angstrom depending on organoclay and filler loading. Overall thermal stability of nanocomposites increases by 16-30 degrees C. The enhancement in T-g of nanocomposite is merely by 2-4 degrees C. With increase in clay loading, tensile modulus increases linearly while \% break strain decreases. Break stress is found to increase till 4 wt \% and further decreases at higher clay loadings. The overall improvement in thermal and mechanical properties was higher for the organoclay containing organic modifier with lower hydrophobicity and single tallow amine chemical structure. (c) 2007 Wiley Periodicals, Inc.

}, keywords = {mechanical properties, Nanocomposites, organoclay, structure, Thermal properties}, issn = {0021-8995}, doi = {10.1002/app.26192}, author = {Tiwari, Rajkiran R. and Natarajan, Upendra} } @article { ISI:000254004400057, title = {New poly(phenylene oxide)/polystyrene blend nanocomposites with clay: intercalation, thermal and mechanical properties}, journal = {Journal of Applied Polymer Science}, volume = {108}, number = {3}, year = {2008}, month = {MAY}, pages = {1818-1828}, publisher = {JOHN WILEY \& SONS INC}, address = {111 RIVER ST, HOBOKEN, NJ 07030 USA}, abstract = {

We present the first study and results on the preparation and characterization of montmorillonite clay filter based polymer blend nanocomposites of the miscible poly(phenylene oxide)/polystyrene blend. Intercalated nanocomposites, prepared by a melt-processing method with 2-6 wt \% commercially available organically modified sodium montmorillonite, have been characterized with wide-angle X-ray diffraction, transmission electron microscopy analysis, thermal analysis (thermogravimetric analysis and differential scanning calorimetry), and mechanical tensile tests. We show that nanocomposites can be successfully prepared in a batch mixer at temperatures much below the conditions conventionally used for this blend without organic degradation. Thermal stability is enhanced by nanoscale hybrid formation. The level of intercalation (change in the d-spacing) does not change with the clay loading. Better dispersion of clay in the blend matrix has been observed at a low level of clay content. The nanocomposites show improved tensile modulus (by 31\%) in comparison to the blend, whereas the tensile strength (stress at break) and elongation decrease in the presence of the filler with an increase in the clay loading. The Halpin-Tsai model is able to predict the modulus of the nanocomposites in very good agreement with the experimental data. (c) 2008 Wiley Periodicals, Inc.

}, keywords = {mechanical properties, Nanocomposites, organoclay, poly(phenylene oxide), Polystyrene, Thermal properties}, issn = {0021-8995}, doi = {10.1002/app.27743}, author = {Tiwari, Rajkiran R. and Khilar, Kartic C. and Natarajan, Upendra} } @article {46859, title = {Critical organic modifier aliphatic tail length for the formation of poly(methyl methacrylate)-montmorillonite nanocomposites}, journal = {Polymer Engineering and Science}, volume = {60}, year = {2020}, month = {JUL}, pages = {1604-1617}, type = {Article}, abstract = {

In this article, we report the influence of organic modifier structure (alkyl chain length C8-C20, single vs ditallow) and thereby, the effect of hydrophobicity on the structure, thermal and mechanical properties of poly(methyl methacrylate) (PMMA)-clay hybrids. Melt processed PMMA-clay hybrids were characterized using wide-angle X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. The organoclays having an alkyl chain length of more than 12 CH2 groups resulted in the formation of nanocomposites. The glass transition temperature (T-g) of PMMA increased in the presence of clay. The mean-field lattice model was used to predict the free energy for nanocomposite formation, which showed a reasonable match with the experimental results and provided a general guideline for the proper selection of polymer and organoclay (ie, organic modifier) to obtain nanocomposite. Tensile modulus showed maximum improvement of 58\% for the nanocomposites compared to 9\% improvement for the composites. Tensile modulus increased with increases in the alkyl chain length of the organic modifier and clay loading. The level of improvement for the tensile properties of nanocomposites prepared from primary and secondary ammonium-modified clay is the same as that obtained with the commercial organoclays.

}, keywords = {hybrid, mechanical properties, Montmorillonite, Nanocomposites, organoclay, poly(methyl methacrylate)}, issn = {0032-3888}, doi = {10.1002/pen.25405, Early Access Date = MAY 2020}, author = {Tiwari, Rajkiran R. and Natarajan, Upendra} }