Search results for "polypropylene"
showing 10 items of 177 documents
Effect of processing temperature and mixing time on the properties of PP/GnP nanocomposites
2020
Abstract During processing of molten polymers the thermal and mechanical stress acting on the melt in presence of oxygen can induce degradation with a modification of the chemical structure of the polymers. This picture can become even more relevant if the melt is a multiphasic polymer system. In this last case, the effects of the degradation depend also on the presence of a second phase and on the interactions between the two phases. In this work, the effect of the processing conditions, temperature and time, have been considered in order to investigate the thermo-mechanical and thermo-oxidative degradation of nanocomposites made by polypropylene and different contents of graphene nanoplat…
Effect of the additive level and of the processing temperature on the re-building of post consumer pipes from polyethylene blends
2007
Abstract One of the main shortcomings of the mechanical recycling is that the properties of the secondary materials are generally sensibly inferior with respect to the virgin ones. This feature implies, for sure, that they cannot be used for the same technological application but also other uses of the secondary material are impossible. The aim of this work is to study the re-building of recycled post-consumer pipes, made of a blend of different polyethylenes, by re-processing in the presence of a nitroxyl compound as radical generator. The processing temperature and the additive concentration have been varied in order to study the effect of these parameters on the final properties. The mec…
Investigation on the Properties and on the Photo-Oxidation Behaviour of Polypropylene/Fumed Silica Nanocomposites
2021
This work investigates the effects of very small amounts of fumed silica on the morphology and on the rheological and mechanical behaviour of polypropylene nanocomposites and on their photo-oxidation behaviour. Polypropylene nanocomposites were prepared using a twin-screw corotating extruder with 0, 1 and 2 wt/wt% of SiO2. Morphological, mechanical, thermomechanical and rheological properties were examined. It was found that the viscosity of the matrix is reduced by the presence of the silica nanoparticles, suggesting a poor adhesion between the two phases and probably some lubricating effect. On the contrary, the mechanical and, in particular, the thermomechanical properties of the matrix …
Accelerated weathering of PP based nanocomposites: Effect of the presence of maleic anhydryde grafted polypropylene
2013
Polymer nanocomposites are currently a topic of great interest. The increasing importance they are gaining also in the standpoint of industrial applications, is giving concerns regarding their environmental stability and, in general, their behaviour in outdoor applications, under direct solar irradiation. Papers available in the literature have highlighted the different influences of different nanosized fillers, in particular clay-based nanofillers; however, few data are available regarding other nanosized fillers. Furthermore, the research on polymer nanocomposites has clearly pointed out that the use of compatibilizers is required to improve the mechanical performance and the dispersion o…
Photo-oxidation of polypropylene/graphene nanoplatelets composites
2019
Abstract The photo-oxidation behaviour of polymer nanocomposites depends not only on the photo-oxidation behaviour of the matrix, but also on the chemical composition, on the physical properties of the nanoparticles and on the possible interactions between the two phases. In the case of nanocomposites with carbonaceous particles, the main effect is a photo-stabilization due to the absorption of the UV energy and the radical scavenging action. In this work we investigated the effect of the presence of graphene nanoplatelets on the photo-oxidation behaviour of the polypropylene. The presence of the graphene nanoplatelets improves the photo-resistance of the polypropylene and this effect incre…
Accelerated laboratory weathering of polypropylene composites filled with synthetic silicon-based compounds
2019
Abstract Non-functionalized and n-alkyl functionalized polyhedral oligomeric silsesquioxanes (POSS), siloxane-silsesquioxane resins and the sol-gel silicas were for the first time examined as possible UV-stabilizers and/or antioxidants in polypropylene (PP). The obtained composites were subjected to the accelerated laboratory weathering tests. The influence of the weathering conditions on the structure and properties of the PP materials was evaluated on the basis of the results from Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) studies. It was found that weathering resistance of the PP materials was strongly de…
The Unique Versatility of the Double Metal Cyanide (DMC) Catalyst: Introducing Siloxane Segments to Polypropylene Oxide by Ring-Opening Copolymerizat…
2020
The combination of hydrophobic polydimethylsiloxane (PDMS) blocks with hydrophilic polyether segments plays a key role for silicone surfactants. Capitalizing on the double metal cyanide (DMC) catalyst, the direct (i.e., statistical) copolymerization of cyclic siloxanes and epoxides is shown to be feasible. The solvent-free one-pot copolymerization of hexamethylcyclotrisiloxane and propylene oxide results in the formation of gradient propylene oxide (PPO)-PDMS copolymers. Copolymers with up to 46% siloxane content with low dispersities (Ð < 1.2) are obtained in the molecular weight range of 2100-2900 g mol-1 . The polymerization kinetics are investigated by pressure monitoring and in situ 1 …
Effect of a new amido‐imidazolium compound as a clay modifier on properties of polypropylene composites
2021
Halloysite nanotubes (HNT) and montmorillonite (Mt) were modified by a novel, dicarboxylic fatty acid substituted amido-imidazolium chloride. It was found that the modification process of the clays by the imidazolium compound improved their dispersion in the polymer matrix, while HNT were a more beneficial filler of PP than Mt. PP/imidazolium modified HNT composites (PP/HNT-M) showed significant increase in thermo-oxidative stability, flexibility, and toughness, combined with a slight reduction in stiffness, as well as a lack of changes in crystallinity and strength, compared with neat PP. These effects were not observed for PP/Mt composites. The formation of strong interactions between the…
Process parameters of microsphere preparation based on propylene carbonate emulsion-precursors.
2020
This study aimed for a detailed understanding of the impact of different process parameters involved during celecoxib-loaded microsphere preparation based on propylene carbonate emulsion-precursors.Microspheres were prepared by a modified emulsification-solvent extraction method. Performed investigations included polymer solubility and viscosity, microsphere size, morphology and stability, propylene carbonate content as well as celecoxib solid state, content and release.Rough-walled round microspheres with sizes between 21 µm and 122 µm and an internal sponge-like structure filled with residual propylene carbonate (content between 1.9 ± 0.1% and 6.7 ± 0.5% w/w) were obtained. Encapsulation …
Grafting of Maleic Anhydride onto Isotactic Polypropylene in the Presence of Supercritical Carbon Dioxide as a Solvent and Swelling Fluid
2004
Grafting of maleic anhydride (MA) onto isotactic polypropylene (iPP) was carried out by thermal decomposition of dicumylperoxide (DCP) using supercritical carbon dioxide (scCO2) as a solvent and swelling fluid. Provided that the initial concentration of anhydride dissolved in scCO2 is higher than 1% w/w, the grafting occurs without significant molecular weight modification of the polymer, and with a proper selection of the operative conditions, a grafting level higher than 0.5% w/w with respect to the polymer mass was obtained. The amount of grafted MA was determined by FT-IR spectroscopy and polymer degradation was monitored by dynamic mechanical tests in the melt state. The effect of MA a…