Eveline Bischoff

The effects of ultrasound on organoclay dispersion in the PP matrix.

PP/MMT nanocomposites were prepared by solution intercalation using sonication and quiescent conditions, and the effects on the morphological, thermal and mechanical properties were evaluated by WAXD, TEM, DMA, TGA and DSC analyses. The present study aims to clarify the effects of ultrasound use on the organoclay surface with different amounts of organic modifiers and on the exfoliation processes. The sonication process decreased around of 200 nm the aspect ratio of C15A organoclay. Besides, the effectiveness of the ultrasound process was only achieved with the C15A system because there is a small energetic barrier between their layers (clay with larger d 001). The sonication process increased the exfoliation and distribution of the C15A platelets in the PP matrix, increasing by 5% its reinforcement capacity. However, for I44P system, the use of ultrasound did not show any significant effect on the morphology and consequently on the final properties of the PP matrix. The T(c) temperature and the thermal stability of the PP nanocomposites were increased, independent of the clay type or of the ultrasound use.

Morphological, thermo-mechanical, and thermal conductivity properties of halloysite nanotube-filled polypropylene nanocomposite foam

Studies about polypropylene nanocomposite foams are receiving attention because nanoparticles can change physical and mechanical properties, as well as improve foaming behavior in terms of homogeneous cell structure, cell density, and void fraction. In this research, the foaming behavior of polypropylene, polypropylene/long-chain branched polypropylene (LCBPP) 100/20 blend, and polypropylene/LCBPP/halloysite nanocomposites with 0.5 and 3 parts per hundred of resin (phr) is studied. The LCBPP was used to improve the rheological properties of polypropylene/LCBPP blend, namely the degree of strain-hardening. Transmission electron microscopy observation indicated that halloysite nanotube particles are well distributed in the matrix by aggregates. Subsequent foaming experiments were conducted using chemical blowing agent in injection-molding processing. Polypropylene foam exhibited high cell density and cell size as well as a collapsing effect, whereas the polypropylene/LCBPP blend showed a reduction of the void fraction and cell density compared to expanded polypropylene. Also, the blend showed reduction of the collapsing effect and increase of homogeneous cell size distribution. The introduction of a small amount of halloysite nanotube in the polypropylene/LCBPP blend improved the foaming behavior of the polypropylene, with a uniform cell structure distribution in the resultant foams. In addition, the cell density of the composite sample was higher than the polypropylene/LCBPP sample, having increased 82% and 136% for 0.5 and 3 phr of loaded halloysite nanotube, respectively. Furthermore, the presence of halloysite nanotube increased crystallization temperature (Tc) and slightly increased dynamic-mechanical properties measured by dynamic-mechanical thermal analysis. By increasing halloysite nanotube content to 3 phr, the insulating effect increased by 13% compared to polypropylene/LCBPP blend. For comparative purposes, the effect on foaming behavior of polypropylene/LCBPP was also investigated using talc microparticles.

Compounding sequence as a critical factor in the dispersion of OMMT/hydrocarbon resin/PP-g-MA/PP nanocomposites

AbstractThe properties of polyolefin nanocomposites strongly depend on the dispersion level of the nanoparticles, and the addition of dispersion agents has contributed to improvements in their performance. However, the mixing order of the components must be considered due to potential effects of each component alone. In this study, the morphology of the polypropylene nanocomposites was correlated to the preparation method, the use of hydrogenated hydrocarbon resin and the use of compatibilizing agents (PP-g-MA). The nanocomposites were prepared by intercalation of organoclay montmorillonite (OMMT) and PP-g-MA as compatibilizer with different maleic anhydride (MA) content in the molten state with either one-step or two-step mixing. A better distribution and dispersion of the OMMT platelets was achieved by using the two-step procedure. This improvement was observed to a significantly greater extent in samples with compatibilizing agents in the first mixing step. Additionally, the use of hydrogenated hydrocarbon resin showed improvement in morphology with lower MA content. These results point to the two-step method as a means to improve clay dispersion in the field of polyolefin nanocomposite processing.

Adsorption of ionic liquid onto halloysite nanotubes : thermal and mechanical properties of heterophasic PE-PP copolymer nanocomposites

The surface adsorption of inorganic clays with ionic liquids has attracted much attention due to improve the interaction of hydrophilic clay with the hydrophobic polymers. However, successful organic adsorption strongly depends on the characteristics of ionic liquid (anion, chain size and concentration), and the reaction conditions (as polarity of solvent). In this study, such factors were analyzed and correlated with morphology, thermal and mechanical properties of the nanocomposites. The heterophasic ethylene-propylene copolymer nanocomposites were prepared by melt intercalation method in a twin screw co-rotating extruder. The halloysite nanotubes (HNT) was used as filler – natural and modified with different ionic liquids. The results showed that a better distribution and dispersion of the nanoparticles was achieved in the samples with modified HNT (m-HNT) and was more significant when the ionic liquid adsorption was conducted in a less polar solvent. The thermal stability of the nanocomposites with m- HNT was higher compared to the neat CP. Additionally, the better balance in the mechanical properties was obtained by the use of the more hydrophobic ionic liquid and higher concentration with improve of 27% in the Young Modulus without loss in the impact properties at room temperature. These superior behaviors of ionic liquid adsorption products exhibit properties suitable for many industrial applications.