Search results for "MECHANICAL PROPERTIES"
showing 10 items of 199 documents
Ceramic/metal nanocomposites by lyophilization: Spark plasma sintering and hardness
2014
The present study is focused on the procedure of spray-drying and lyophilization techniques for the preparation of ceramic/metal nanocomposites. The results of the study at all stages are compared with those corresponding to powders conventionally dried by heating in furnace. Starting from aqueous solutions of metal salts and ceramic powders, the procedure follows with spray-drying, lyophilization, calcination of the resulting powders and subsequent Spark Plasma Sintering (SPS). X-ray diffraction analysis of the powders at different stages of the processing routes was used for phase indexing; further characterization was performed by Transmission Electron Microscopy and Energy Dispersive X-…
Effective antimicrobial materials based on low-density polyethylene (LDPE) with zinc oxide (ZnO) nanoparticles
2019
[EN] Effective antimicrobial polymeric nanocomposites were prepared with low density polyethylene (LDPE) and zinc oxide nanoparticles by melt compounding. These nanoparticles (~17 nm) obtained by the sol¿gel method, were used both as-synthesized and modified organically with oleic acid (Mod-ZnO). Young¿s modulus increased ~15 and 18% for LDPE/ZnO and LDPE/Mod-ZnO, respectively, compared to neat LDPE. When these composites were irradiated with white light, they showed an increase with nanoparticle incorporation, and the antimicrobial properties against E. coli were ~96¿99%. The release of the Zn cations was related to the antimicrobial properties. These nanocomposites are attractive for use …
The Engineering of Hot Carbon Nanotubes with a Focused Electron Beam
2004
Single-wall and multiwall carbon nanotubes at high temperature are irradiated with the focused electron beam in an electron microscope. Nanotubes can be tailored with monolayer precision, and new morphologies of nanotubes are created. Atoms from layers of multiwall tubes can be removed and the tubes can be bent by a predefined angle. Bundles of single-wall tubes are transformed locally to multiwall tubes with coherent transition between the two modifications.
Thermomechanical properties and thermal degradation kinetics of poly(methyl methacrylate) (PMMA) and polycarbonate (PC) filled with cerium-doped yttr…
2016
This paper reports on the thermomechanical properties and thermal degradation kinetics of poly(methyl methacrylate) (PMMA) and polycarbonate (PC) composites filled with cerium-doped yttrium aluminium garnet (Ce:YAG) at different contents ranging between 0.1 and 5 wt%, and prepared by melt compounding. The interaction between PMMA and the filler was much stronger than that between PC and the filler, and this resulted in a significant improvement in the dynamic mechanical properties of the PMMA composites. The presence of filler did not significantly increase the thermal stability of the PC, while an observable increase in the thermal stability was only observed at higher filler loadings for …
Orientation induced brittle – Ductile transition in a polyethylene/polyamide 6 blend
2014
Abstract Polyamide/polyolefin blends are of scientific and technological interest but, on the other hand, the different chemical nature of the two components makes them incompatible, resulting in unsatisfactory physical properties and making compatibilization necessary. In particular, although the two components are ductile, the binary blends can show brittle behaviour. It is also known that the effect of the elongational flow (and then of the induced orientation) on polymer blends is a decrease of elongation at break with increase of the degree of orientation. In this work, the effect of orientation on the mechanical properties of a low density polyethylene/polyamide 6 incompatible blend w…
Mechanical and rheological properties of polystyrene-block-polybutadiene-block-polystyrene copolymer reinforced with carbon nanotubes: effect of proc…
2017
Abstract Styrene-b-butadiene-b-styrene (SBS)-based nanocomposites filled with unmodified and –COOH functionalized carbon nanotubes (CNTs) have been formulated at different processing conditions in order to provide an understanding of the influence of the processing temperature and mixing speed on the nanofillers dispersion and on the overall properties of the nanocomposites. The evaluation of the nanocomposites’ mechanical and rheological behavior reveals that the effect of the processing speed on the final properties is almost negligible. Differently, the processing temperature influences strongly the mechanical and rheological properties of SBS-based nanocomposites. Indeed, for the nanoco…
Experimental assessment of the improved properties during aging of flax/glass hybrid composite laminates for marine applications
2018
The investigation for natural fibers composites in terms of performance, durability, and environmental impact for structural applications in marine environments is a relevant challenge in scientific and industrial field. On this context, the aim of this work is to assess the durability and mechanical stability in severe environment of epoxy/glass–flax hybrid composites. For the sake of comparison, also full flax and glass epoxy composites were investigated. All samples were exposed to salt–fog environmental conditions up to 60 aging days. Wettability behavior during time was compared with water uptake evolution to assess water sensitivity of hybrid composite configurations. Moreover, quasi-…
Material valorisation of amorphous polylactide. Influence of thermo-mechanical degradation on the morphology, segmental dynamics, thermal and mechani…
2012
[EN] This paper reports the effects of multiple mechanical recycling on the structure and properties of amorphous polylactide (PLA). The influence of the thermo-mechanical degradation induced by means of five successive injection cycles was initially addressed in terms of macroscopic mechanical properties and surface modification. A deeper inspection on the structure and morphology of PLA was associated to the thermal properties and viscoelastic behaviour. Although FT-IR analysis did not show significant changes in functional groups, a remarkable reduction in molar mass was found by viscometry. PLA remained amorphous throughout the reprocessing cycles, but the occurrence of a cold-crystalli…
Physical properties of virgin-recycled ABS blends: Effect of post-consumer content and of reprocessing cycles
2012
Abstract Virgin/post-consumer ABS (pc-ABS) blends were re-processed and re-formed up to three times. The effect of pc-ABS content and of reprocessing cycles on the physical properties of the prepared blends was evaluated by mechanical tests (tensile, flexural and impact tests) and by rheological and thermo-mechanical measurements. The processability of pc-ABS blends was not substantially different by that of virgin ABS up to two recycling steps even if the third one induced a slightly decrease of viscosity, more remarkable on increasing the pc-ABS content. The mechanical and thermo-mechanical properties of the samples worsened on increasing the level of pc-ABS and after each reprocessing op…
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 …