The Role of Nanoclay Partitioning on Microfibril Morphology Development in Polypropylene/Polyamide 6 Nanocomposite Fibers

The aim of the present work was to study the role of organically modified montmorillonite (OMT) partitioning on microfibrillar morphology development of polypropylene (PP)/polyamide 6 (PA6)/organoclay nanocomposite fibers by means of a rheological technique in conjunction with wide angle X-ray diffraction (WAXD) and scanning electron microscopy (SEM). Polypropylene (PP)/polyamide 6 (PA6) blend samples with the same blend ratio (65/35) and nanoorganoclay [Closite 30B (C30B)] content (3%) with and without PP grafted with maleic anhydride (PPgMAH) as a compatibilizer, were considered. All the samples were prepared by melt compounding in an internal mixer using two different methods; a direct method and a PA6 based master batch method. The nanocomposite samples were melt spun by using a single screw extruder equipped with a spinneret. The organoclay WAXD characteristic peak almost disappeared in the PA6/organoclay masterbatch and the master batch based nanocomposite samples, suggesting a highly intercalated and/or exfoliated morphology for these samples. This was evidenced by the melt linear viscoelastic results that showed a low frequency non-terminal storage modulus along with viscosity upturn for the samples prepared by both methods but to a much greater extent for the master batch prepared samples. The presence of compatibilizer was found to have a significant effect on reducing the PA6 particle size evaluated by SEM results for the samples prepared by both methods. Fibers with fibrillar morphology could hardly be produced from all the blend samples at a spinning temperature of 250 degrees C. However, fibers with well-defined fibrils could be obtained from these samples at 190 degrees C. This was explained in terms of the PA6 droplet size and hence the interfacial tension as well as melt strength of PA6 droplets. It was demonstrated that organoclay preferentially located in the PA6 phase in the master batch samples led to larger droplet size which assisted the microfibril formation in these samples compared to samples prepared by the direct method.