Characterizing the nanoclay induced constrained amorphous region in model segmented polyurethane–urea/clay nanocomposites and its implications on gas barrier properties

Abstract

There has been an increasing recognition of the fact that purely geometric factors associated with clay platelet dispersion in a polymer matrix cannot adequately explain the barrier properties of polymer/clay nanocomposites. The objective of the present work is to understand the nanoclay induced structural changes in a polyurethane-urea matrix and clay dispersion at different length scales using segment-specific characterization techniques and implications of the same in gas barrier properties using He, N2 and CO2 as probe molecules. Wide angle X-ray diffraction (WAXD) and positron annihilation life time spectroscopy (PALS) studies revealed nanoclay induced alterations in the chain packing of the amorphous soft segments of the polyurethane matrix at a molecular scale of a few Angstroms. The hard segment organization and the phase morphology of the nanocomposites, spanning length scales of several nanometers, were investigated by small angle X-ray scattering (SAXS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Furthermore, the presence of a constrained amorphous region surrounding the nanoclay was confirmed from AFM, WAXD and PALS results. Several pertinent structural variables from the gas transport point of view were deduced from these characterization techniques to understand the effect of the barrier properties in tandem with the clay dispersion morphology.

Micro and nanocomposites of polybutadienebased polyurethane liners with mineral fillers and nanoclay: thermal and mechanical properties

“…Nanoclay could be seen as dark coloured aggregates. The AFM micrograph showed that the clay agglomerates were broken into smaller tactoids, which are then intercalated/ exfoliated in HTPB [42,43].…”

Ablative Properties of Polyurethanes Reinforced with Organoclay

“…According to experimental results, a reduction in the segmental mobility of the chains near the surface of each lamina is observed due to the incorporation of organoclay. Therefore, the chain polymer rests immobilized, modifying significantly the physical properties .…”

α-ZrP Nanoreinforcement Overcomes the Trade-Off between Phosphoric Acid Dopability and Thermomechanical Properties: Nanocomposite HTPEM with Stable Fuel Cell Performance

“…38,39 This technique involves mapping the spatial variation of specific elements by rastering the electron beam over an area of interest. 38 From the EDS spectra, pertaining to the Zr elemental maps of the nanocomposites (Figure 3), it is observed that at 10% α-ZrP loading, the nanofiller distribution is uniform and homogenous with no evidence of agglomeration of the nanofiller. At higher loadings, agglomeration is evident with agglomerate sizes in the range 2−4 μm.…”