Preparation and properties of aramid/layered silicate nanocomposites by solution intercalation technique

Polymer-clay nanocomposites were synthesized from aromatic polyamide and organoclay using the solution intercalation technique. Polyamide chains were produced through the reaction of 4,4'-oxydianiline (ODA) and isophthaloyl chloride (IPC) in N,N'-dimethyl acetamide, using stoichiometry yielding chains with carbonyl chloride end groups. The intercalation of sodium montmorillonite (Na-MMT) was carried out using p-phenylene diamine as a swelling agent through an ion exchange reaction. Different concentrations of organoclay were blended with the polyamide solution for complete dispersion of clay throughout the matrix. The resulting composite films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), mechanical testing, thermogravimetry (TGA), differential scanning calorimetry (DSC) and water absorption measurements. The XRD pattern and morphology of the nanocomposites revealed the formation of exfoliated and intercalated clay platelets in the matrix. The film containing a small amount of clay was semitransparent and had a tensile strength of the order of 70 MPa (relative to the 52 MPa of the pure aramid). Thermal decomposition temperatures were in the range of 300-450 degrees C and the weight of the samples remaining after heating to 900 degrees C was found to be roughly proportional to the clay loading. DSC showed a systematic increase in the glass transition temperature with increase in clay content. Water absorption of the pristine aramid film was rather high (5.7%), which reduced upon loading of organoclay. Copyright (C) 2008 John Wiley & Sons, Ltd.