In this work, two types of zinc adipate β-nucleating agents, Adi-Zn(OH)2 (1:1) and Adi-ZnO (1:1), for polypropylene (PP) were prepared and their performances were evaluated and compared with commercial β-nucleating agent (named CNA). Results showed that Adi-Zn(OH)2 (1:1) was more effective in promoting PP to form β-crystals and improving the impact strength of PP in the range of nucleating agent addition (0–0.4 wt%). Based on these findings, the ratio of adipic acid to zinc hydroxide and the nonisothermal crystallization kinetics of the optimum ratio of adipic acid to zinc hydroxide were systematically studied; results showed that at 0.2 wt%, Adi-Zn(OH)2 (1:2), the nucleated PP displayed the highest impact strength, which was 2.6 times that of pure PP and 42% higher than that of CNA. Besides, Adi-Zn(OH)2 (1:2) could also afford to induce the formation of a high content of β-crystals and shorten the crystallization half time (t1/2) and accelerate the crystallization of PP.

Melt blending using a twin-screw extruder was used to prepare composites of polypropylene (PP)/organic rectorite (PR). The organic rectorite (OREC) was modified with dodecyl benzyl dimethyl ammonium bromide (1227). Wide-angle X-ray diffraction (WAXD) and transmission electron microscopy were used to investigate the dispersion of OREC in the composites. The d spacings of OREC in PR composites was greater than in OREC itself. The dispersion of OREC particles in the PP polymer matrix was fine and uniform when the clay content was small (2 wt.%). The rheology was characterized using a capillary rheometer. The processing behaviour of the PR system improved as the amount of OREC added increased. Non-isothermal crystallization kinetics were analysed using differential scanning calorimetry. It was shown that the addition of OREC had a heterogeneous nucleation effect on PP, and can accelerate the crystallization. However, only when fine dispersion was achieved, and at lower rates of temperature decrease, was the crystallinity greater. Wide-angle X-ray diffraction and polarized light microscopy were used to observe the crystalline form and crystallite size. The PP in the PR composites exhibited an a-monoclinic crystal form, as in pure PP, and in both cases a spherulite structure was observed. However, the smaller spherulite size in the PR systems indicated that addition of OREC can reduce the crystal size significantly, which might improve the ‘toughness’ of the PP. The mechanical properties (tensile and impact strength) improved when the amount of OREC added was appropriate. Dynamic mechanical analysis showed that the storage modulus (E′) and loss modulus (E″) of the nanocomposites were somewhat greater than those of pure PP when an appropriate amount of OREC was added. Finally, thermogravimetric analysis showed that the PR systems exhibited a greater thermal stability than was seen with pure PP.

The exposure to solar radiation (mainly due to the action of ultraviolet radiation) is one of the main causes for the premature failure of many polymeric materials, including the geotextiles. In this work, a nonwoven polypropylene geotextile (stabilized with a known amount of a hindered amine light stabilizer) was exposed to ultraviolet-aging tests, both in the laboratory (accelerated conditions) and outdoors (natural conditions). The damage occurred in the geotextile (caused by the ultraviolet-aging tests) was evaluated quantitatively (by monitoring changes in its mass per unit area, thickness, and tensile properties) and qualitatively (by scanning electron microscopy). The results, among other findings, showed that: (1) the ultraviolet-aging tests (both in the laboratory and outdoors) induced relevant damage in the polypropylene fibers of the geotextile (transverse cracks), leading to the deterioration of its tensile behavior, (2) the amount of degradation increased with the increase of the ultraviolet radiant energy, (3) the laboratory tests caused a faster deterioration of the polypropylene fibers than the outdoor tests, and (4) the degradation found by scanning electron microscopy in the polypropylene fibers correlated well with the deterioration occurred in the tensile behavior of the geotextile.

In this study, effects of surface modification of calcium carbonate (CaCO3) nanoparticles with a single-layer of stearic acid were investigated on dispersion in polypropylene (PP) matrix. Two kinds of CaCO3 nanoparticles (monolayer-coated and uncoated) were used to investigate this effect. All combinations were mixed in a co-rotating twin screw extruder and then were injection molded. After breaking the injection molded parts in liquid nitrogen, effect of surface modification of nanoparticles on their dispersion in the PP matrix was investigated using a field emission scanning electron microscope (FESEM). The results showed good agreement between the measurements made with the TGA analysis and the existing theories. The surface modification of calcium carbonate nanoparticles using a single layer of stearic acid also had an effective influence on improving distribution and dispersion of nanoparticles in the PP matrix.

A novel kind of solid amine-containing fibrous adsorbent (PP-GMA-TETA) was prepared through irradiation grafting copolymerization with glycidyl methacrylate (GMA) onto polypropylene (PP) fiber, followed by reacting with triethylenetetramine (TETA) to introduce primary and secondary amine groups on its surface. The effects of the reaction conditions, such as the TETA concentration, temperature, and reaction time on amination degree of PP-GMA-TETA, were investigated. Adsorption capacity of PP-GMA-TETA with 77.7% amination degree could reach 4.72 mmol/g. After adsorption, the spent fiber could be completely regenerated at 100 °C by steam for 20 min and its adsorption behavior kept almost constant within six recycles. The comparison of adsorption capacities of amine fibers aminated with various aminating agents also demonstrated that fibers with higher content of primary amine would obtain faster adsorption rates and higher adsorption capacities.

Nanocomposites with platelet reinforcements are emergent materials whose deformation mechanisms still need to be carefully investigated. In this study, we first present the studied class of nanocomposites (Polypropylene reinforced by Montmorillonite clay nanoplatelets). From uniaxial tensile tests, it is shown that some mechanical characteristics of the nanocomposite (Young's modulus, yield stress) significantly increase compared to the matrix even for very low volume fraction of reinforcements (maximum of 7% mass fraction for our tested specimen). The Ponte Castañeda and Willis [6] bound is adopted to account for the evolution of the elastic behavior of the material [7]. Adapting the Hill-type incremental method [13] allows the simulation of the non linear behaviour of the material. However, it is shown that this scheme requires careful choice of the aspect ratio, in the plastic domain, to provide good predictions of plasticity.

Nous présentons dans cet article une étude expérimentale de l'influence de la qualité de l'interface fibre/matrice sur le comportement en traction et en fluage jusqu'à rupture d'un polypropylène renforcé de 40 % en masse de fibres de verre courtes (soit 18,85 % de fraction volumique de fibres). Les essais de traction avec des taux de fibre de 20 et 30 % en masse montrent l'existence d'un plateau pour le matériau avec fibres non-traitées (absence d'ensimage) qui disparaît pour le taux de 40 % en masse. Également, ces essais de traction montrent, pour chaque type d'interface, l'existence de trois zones de comportement pour chaque matériau. La mesure de l'émission acoustique permet de quantifier les différents mécanismes d'endommagement et montre qu'il y a plus d'événements acoustiques pour le matériau avec fibres traitées. Des essais de fluage jusqu'à rupture sont entrepris avec la mesure de l'émission acoustique pour un taux de fibre de 40 % et montrent également plus d'événements acoustiques pour le matériau avec fibres traitées. Finalement on observe, à partir des résultats de l'émission acoustique, l'influence de la nature de la sollicitation sur les mécanismes d'endommagement et on constate qu'il y a plus d'événement lors des essais de fluage jusqu'à rupture.

The spherulitic and lamellar morphologies of melt crystallized isotactic polypropylene (iPP) have been investigated according to various crystallization temperatures and times. In this study, an appropriate chemical etching condition for the observation of iPP morphology by scanning electron microscopy (SEM) is determined. The optimum etchant formulation is 3 wt% potassium permanganate with the mixed solvent of sulfuric acid and phosphoric acid. The morphologies after etching reveal the microstructure of iPP clearly, such as the characterization of α/β spherulites and the different lamellar growth patterns.