Morphology, mechanical, and thermal properties of aramid/layered silicate nanocomposite materials
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Ingo Lieberwirth Max Planck Institute for Polymer Research, 55128 Mainz, Germany
Zahoor Ahmad Department of Chemistry, Faculty of Science, Kuwait University, Safat-13060, Kuwait (Received 9 October 2007; accepted 8 February 2008)
Aramid-based nanocomposites were prepared by solution intercalation techniques using p-aminobenzoic acid-modified montmorillonite. Polyamide was synthesized by reacting 4,4⬘-oxydianiline with isophthaloyl chloride in dimethyl acetamide. To create chemical interactions between the two phases for better dispersion of organoclay, aramid chains were selectively amine end-capped. The influence of organically modified clay on the morphology was investigated by x-ray diffraction (XRD), polarized optical microscopy (POM), and transmission electron microscopy (TEM). Mechanical, thermal, and water uptake measurements were carried out to further verify other physical properties of the nanocomposites. Tensile strength, modulus, elongation at break, and toughness were improved relative to pure polymer with the addition of 6 wt% organoclay. Thermal-decomposition temperatures of the nanocomposites were in the range 300–450 °C. Water uptake of neat aramid film was rather high (5.7%) and decreased with augmenting organoclay. DSC exhibited increase in the glass transition temperature (118 °C) up to addition of 16 wt% of organoclay.
I. INTRODUCTION
Polymer–clay composites have received considerable interest in the last two decades.1 Swelling clays (smectite clays) are recognized for the development as nanocomposites due to their easier and cheaper availability, their capacity to intercalate many organic species,2–4 and the ease with which they may be surface-treated and dispersed, by various methods, in polymer matrices. Usually, the major component in such composite materials is the polymer, and clay loadings are typically of the order of a few percent by weight, providing a good dispersion. These small loadings are enough to obtain a significant improvement in such polymer properties as modulus, strength, heat and fire resistance, and liquid and gas barrier properties. These nanocomposites have found many applications in diverse fields, such as transportation, construction, electronics, and consumer goods. They offer outstanding combinations of stiffness, strength, and low
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2008.0301 2296
http://journals.cambridge.org
J. Mater. Res., Vol. 23, No. 9, Sep 2008 Downloaded: 14 Mar 2015
density that cannot be derived from their individual components. Suitable polymers and clay materials can be combined to produce strong, stiff, and tough materials capable of withstanding a wide range of temperature. The best candidates from the polymer side may be the aromatic polyamides because they have high tensile and impact strengths, stability at high temperatures, good abrasion resistance, and self-lubricating properties as bearings, and these make them an important class of engineering material. The aromatic polyamide
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