Morphological, thermal, rheological, and mechanical properties of polypropylene-nanoclay composites prepared from masterbatch in a twin screw extruder
(6075-6086) Journal of Materials Science 46 #18 (2011)
Chafidz, Ali and Elleithyof King Saud University, Saudi Arabia melt blended a commercial homopolymer polypropylene with commercial nanoclay masterbatch at different concentrations of nanoclay using twin screw extruder (TSE).  The influence of three different concentrations (5, 10, and 15 wt%) of the nanoclay on the morphological, thermal, rheological, and mechanical properties was investigated.  The morphological analysis showed that the nanoclay was well distributed in the PP matrix as indicated by the SEM micrographs.  The DSC results showed that the presence of nanoclay in the PP matrix increased the degree of crystallinity of PP-nanoclay composites, which reached a maximum at 5 wt% of nanoclay concentration.  However, the melting temperature of the PP-nanoclay composites was not affected by the presence of nanoclay particles. In addition, rheological analysis showed that the melt response gradually changed from pseudo-liquid like to pseudo-solid like as the nanoclay concentration increased. Moreover, the storage modulus (G′) increased by increasing nanoclay content. Furthermore, tensile test results showed that the addition of nanoclay leads to a significant enhancement in the mechanical properties of the PP nanocomposites.  (RDC 6/27/2011)

Structure-orientation-properties relationships for polypropylene nanoclay composite films
(87-115) Journal of Plastic Film and Sheeting 27  #1-2 (2011)
Abstract
Tabatabaeiand Ajji of Ecole Polytechnique, Canada, studied the morphology, orientation, as well as the mechanical and barrier properties of monolayer and multilayer nanoclay filled polypropylene (PP) obtained from the film blowing process were investigated.  A significant alignment of nanoclay along the flow direction was observed from scanning electron microscopy images of the cross-section of the etched monolayer and trilayer films.  The crystalline structure formed in PP alone was such that the b-axis oriented in the normal and transverse directions (ND and TD, respectively) and the c-axis aligned in the machine direction (MD).  The addition of clay changed the orientation of the b-axis to ND, enhanced the a-axis orientation in MD, and also improved the c-axis alignment along MD.  Moreover, the 001 plane (normal to platelets plane) of the nanoclays lay into ND drastically. With the incorporation of the clay tactoid, the Young’s modulus was enhanced by 25—40%, the tensile strength remained almost unchanged, and the elongation at break along TD decreased by more than 70% for all the films. The permeability to oxygen and tear resistance along MD and TD were slightly reduced with the presence of nanoparticles and percentage of nanofiller studied. The haze of the nanocomposite films increased upon the presence of clay particles, except in the case of low clay contents of 1.5 and 2.5 wt%.  (RDC 6/27/2011)