The combustion of a typical thermoplastic polymer, Polypropylene mixed with three additive fire retardants, magnesium hydroxide, aluminium hydroxide and antimony trioxide, was assessed in a cone calorimeter. It is found that the increased MS(OH)(2) content in Polypropylene, further increases the ignition time and reduces the heat release rate. its effect on smoke density is found to be somewhat different, when present at lower percentages it increases the smoke density of fire effluents.

descriptive and historical account with experimental evidence is provided for the production feasibility of micro- and nanofibrils from structured-fibres using existing technologies. Blends of 6.25% Polypropylene, 87.5% nylon 6 and 6.25% Polypropylene grafted with maleic anhydride as compatibilizer (N6/PP-g -MAH/PP) were spun into continuous filaments yarns using a melt spinning unit (pilot plant) at the speed of 2000 m/min. The yarn samples were drawn in a drawing unit with draw ratios of 1.3 and 2.6. Samples were treated with formic acid (98%) to dissolve the nylon component that forms the matrix of the bi-constituent filaments. Different analytical techniques including polarizing microscopy, scanning electron microscopy, FTIR spectroscopy, differential scanning calorimetry and wide angle X-ray diffraction were used to examine the filaments and fibrils. It is shown that by existing technology it is possible to produce polyblend filaments from two rather incompatible polymers, while the extraction of Polypropylene micro and nanofibrils is possible either by decantation or Soxhlet using formic acid as solvent for nylon 6. The extracted fibrils were partially crystalline having melting temperature close to neat Polypropylene. The fibrils have diameters less than one micrometer, down to less than 100 nm. By examining the fibrils, it was found that fibrils are partially crystalline with considerable molecular orientation.

Polypropylene-clay nanocomposites were prepared in solution and followed by a melt mixing process. The nanocomposites were prepared for 5% (by weight) organoclay with varying amounts of two oxidized Polypropylene waxes (OPPWs) as compatibilizer. The clay dispersion was analyzed by X-ray diffraction (XRD), transmission electron microscopy and melt rheology technique. The extent of intercalation in clay platelets was quantified by XRD analysis based on interactions between OPPW and clay layers. A maximum of ca.10% increase in clay basal spacing was observed. It was revealed that the degree of clay intercalation in solution technique varies by the polarity of OPPW. In subsequent melt mixing process, the clay dispersion was evaluated by XRD which correlated well with the variations of storage moduli at low frequency region and displayed a pseudo solid-like behaviour. The rheological measurements also showed higher dispersion of clay platelets in PP matrix in the presence of OPPW. The increase in storage moduli especially at low frequency region implied that there were stronger interactions between Cloisite® 15A organoclays and polymer chains when OPPW is present. The TEM images mainly suggested to com-patibilizing effect of OPPW in clay intercalation. In spite of low mechanical properties of OPPW, the DMTA showed the highest modulus of glassy region in nanocomposites with maximum OPPW content. These findings agreed well with each other in co-intercalation effect of OPPW in PP nanocomposites.

Observations are reported on isotactic Polypropylene in uniaxial tensile relaxation tests on specimens subjected to tension up to various maximum strains and retraction down to various stresses. Noticeable evolution of shapes of relaxation curves under retraction is revealed with stress at the beginning of relaxation process: with a decrease in this stress, relaxation diagrams characterized by a monotonic decay of stress with time (simple relaxation) become, first, non-monotonic (mixed relaxation), and, finally, monotonically increasing (inverse relaxation). A thorough investigation is performed on the effect of multi-cycle preloading (maximum strain per cycle, minimum stress per cycle, number of cycles, and strain rate) on transition from simple to mixed and to inverse relaxation. It is found that (1) intensity of mixed relaxation increases with maximum strain when this parameter remains below the yield strain and decreases in the post-yield region of deformations, (2) an increase in number of cycles under preloading leads to reduction of intensity of mixed relaxation and transition from mixed to inverse relaxation, (3) inverse relaxation diagrams of specimens subjected to the same preloading program with various strain rates can be superposed to construct a master-curve. A constitutive model is developed in cyclic viscoelastoplasticity of semi crystalline polymers. A polymer is thought of as two-phase continuum composed of amorphous and crystalline regions. Both phases were treated as viscoelastoplastic media whose response was governed by different kinetic equations for evolution of plastic strains and different kinematic equations for changes in relaxation rates and relaxation spectra driven by plastic flow. Good agreement is demonstrated between the experimental data in relaxation tests under retraction and the results of numerical simulation.