Publications by authors named "Davide Tranchida"

8 Publications

  • Page 1 of 1

Properties of Starve-Fed Extrusion on a Material Containing a VHMWPE Fraction.

Polymers (Basel) 2021 Mar 19;13(6). Epub 2021 Mar 19.

Institute of Polymer Extrusion and Compounding, Johannes Kepler University Linz, Altenberger Str. 69, 4040 Linz, Austria.

Single-screw extruders are usually operated with the screw fully filled (flood-fed mode) and not partially filled (starve-fed mode). These modes result in completely different processing characteristics, and although starve-fed mode has been shown to have significant advantages, such as improved mixing and melting performance, it is rarely used, and experimental studies are scarce. Here, we present extensive experimental research into starve-fed extrusion at feeding rates as low as 25%. We compared various operating parameters (e.g., residence time, pressure build-up, and melting performance) at various feeding rates and screw speeds. The results show a first insight into the performance of starve-fed extruders compared to flood-fed extruders. We explored starve-fed extrusion of a polyethylene material which contains a Very High Molecular Weight Polyethylene fraction (VHMWPE). VHMWPE offers several advantages in terms of mechanical properties, but its high viscosity renders common continuous melt processes, such as compression molding, ram extrusion and sintering, ineffective. This work shows that operating single-screw extruders in extreme starve-fed mode significantly increases residence time, melt temperature, and improves melting and that-in combination-this results in significant elongation of VHMWPE particles.
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http://dx.doi.org/10.3390/polym13060944DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8003239PMC
March 2021

Mechanical Behavior of Melt-Mixed 3D Hierarchical Graphene/Polypropylene Nanocomposites.

Polymers (Basel) 2020 Jun 8;12(6). Epub 2020 Jun 8.

Department of Industrial and Materials Science, Division of Engineering Materials, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.

The mechanical properties of novel low percolation melt-mixed 3D hierarchical graphene/polypropylene nanocomposites are analyzed in this study. The analysis spans a broad range of techniques and time scales, from impact to tensile, dynamic mechanical behavior, and creep. The applicability of the time-temperature superposition principle and its limitations in the construction of the master curve for the isotactic polypropylene (iPP)-based graphene nanocomposites has been verified and presented. The Williams-Landel-Ferry method has been used to evaluate the dynamics and also Cole-Cole curves were presented to verify the thermorheological character of the nanocomposites. Short term (quasi-static) tensile tests, creep, and impact strength measurements were used to evaluate the load transfer efficiency. A significant increase of Young's modulus with increasing filler content indicates reasonably good dispersion and adhesion between the iPP and the filler. The Young's modulus results were compared with predicted modulus values using Halpin-Tsai model. An increase in brittleness resulting in lower impact strength values has also been recorded.
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http://dx.doi.org/10.3390/polym12061309DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7361869PMC
June 2020

Melt-Mixed 3D Hierarchical Graphene/Polypropylene Nanocomposites with Low Electrical Percolation Threshold.

Nanomaterials (Basel) 2019 Dec 11;9(12). Epub 2019 Dec 11.

Department of Industrial and Materials Science, Engineering Materials, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.

Graphene-based materials are a family of carbonaceous structures that can be produced using a variety of processes either from graphite or other precursors. These materials are typically a few layered sheets of graphene in the form of platelets and maintain some of the properties of pristine graphene (such as two-dimensional platelet shape, aspect ratio, and graphitic bonding). In this work we present melt mixed graphene-based polypropylene systems with significantly reduced percolation threshold. Traditionally melt-mixed systems suffer from poor dispersion that leads to high electrical percolation values. In contrast in our work, graphene was added into an isotactic polypropylene matrix, achieving an electrical percolation threshold of ~1 wt.%. This indicates that the filler dispersion process has been highly efficient, something that leads to the suppression of the β phase that have a strong influence on the crystallization behavior and subsequent thermal and mechanical performance. The electrical percolation values obtained are comparable with reported solution mixed systems, despite the use of simple melt mixing protocols and the lack of any pre or post-treatment of the final compositions. The latter is of particular importance as the preparation method used in this work is industrially relevant and is readily scalable.
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http://dx.doi.org/10.3390/nano9121766DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6956219PMC
December 2019

Pushing the size limits in the replication of nanopores in anodized aluminum oxide via the layer-by-layer deposition of polyelectrolytes.

Langmuir 2012 Jul 20;28(26):10091-6. Epub 2012 Jun 20.

Department of Chemistry and Biology, Science & Technology, Physical Chemistry I, University of Siegen, Siegen, Germany.

We report on the successful replication of the smallest pores in anodized aluminum oxide (AAO) via the layer-by-layer (LBL) deposition of polyelectrolytes to date to yield free-standing, open nanotubes with inner and outer diameters (±2σ) down to 37 ± 4 and 52 ± 19 nm, respectively. This work is based on the fabrication of defined arrays of highly regular nanopores by anodic oxidation of aluminum. Pores with pore diameters between 53 ± 9 and 356 ± 14 nm and interpore distances between 110 ± 3 and 500 ± 17 nm were obtained using an optimized two-step anodization procedure. 3-(Ethoxydimethylsilyl)propylamine-coated pores were replicated by alternating LBL deposition of poly(styrenesulfonate) and poly(allylamine). The detrimental adsorption of polyelectrolyte on the top surface of the template that typically results in partial pore blocking was eliminated by controlling the surface energy of the top surface via deposition of an ultrathin gold layer. The thickness of the deposited LBL multilayer assembly at the pore orifice agreed to within the experimental error with the thicknesses measured by variable angle spectroscopic ellipsometry and atomic force microscopy (AFM) for layers assembled on flat substrates. The selective dissolution of the alumina template afforded free-standing, open polymer nanotubes that were stable without any cross-linking procedure. The nanotubes thus obtained possessed mean outer diameters as small as 52 nm, limited by the size of the AAO template.
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http://dx.doi.org/10.1021/la3017062DOI Listing
July 2012

Nanomechanical properties of advanced plasma polymerized coatings for mechanical data storage.

J Phys Chem B 2011 Apr 16;115(13):3385-91. Epub 2011 Mar 16.

Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.

In this paper we report on the unprecedented deformation behavior of stratified ultrathin polymer films. The mechanical behavior of layered nanoscale films composed of 8-12 nm thin plasma polymerized hexamethyldisiloxane (ppHMDSO) films on a 70 nm thick film of polystyrene was unveiled by atomic force microscopy nanoindentation. In particular, we observed transitions from the deformation of a thin plate under point load to an elastic contact of a paraboloid of revolution, followed by an elastic-plastic contact for polystyrene and finally an elastic contact for silicon. The different deformation modes were identified on the basis of force-penetration data and atomic force microscopy images of residual indents. A clear threshold was observed for the onset of plastic deformation of the films at loads larger than 2 μN. The measured force curves are in agreement with an elastic and elastic-plastic contact mechanics model, taking the amount of deformation and the geometry of the layer that presumably contributed more to the overall deformation into account. This study shows that the complex deformation behavior of advanced soft matter systems with nanoscale dimensions can be successfully unraveled.
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http://dx.doi.org/10.1021/jp112211cDOI Listing
April 2011

Binary self-assembled monolayers of alkanethiols on gold: deposition from solution versus microcontact printing and the study of surface nanobubbles.

Langmuir 2011 Feb 30;27(4):1353-8. Epub 2010 Nov 30.

Department of Physical Chemistry I, University of Siegen, Siegen, Germany.

The coadsorption of alkanethiols on noble metals has been recognized for a long time as a suitable means of affording surfaces with systematically varied wettability and other properties. In this article, we report on a comparative study of the composition of the mixed self-assembled monolayers (SAMs) obtained (i) by the coadsorption of octadecanethiol (ODT) and 16-mercaptohexadecanoic acid (MHDA) from ethanol and chloroform onto gold substrates and (ii) by microcontact printing using poly(dimethyl siloxane) (PDMS) stamps. SAMs prepared by coadsorption from solution showed a preferential adsorption of ODT for both solvents, but this trend was reversed in microcontact-printed SAMs when using chloroform as a solvent, as evidenced by contact angle and Fourier transform infrared (FTIR) spectroscopy measurements. An approximately linear relationship between the static contact angle and the degree of swelling with different solvents was observed, which suggests that the surface composition can be controlled by the interaction of the solvent and the PDMS elastomer. The altered preference is attributed to the different partitioning of the two thiols into solvent-swelled PDMS, as shown by (1)H NMR spectroscopy. Finally, molecularly mixed binary SAMs on ODT and MHDA on template-stripped gold were applied to study the effect of surface nanobubbles on wettability by atomic force microscopy (AFM). With a decreasing macroscopic contact angle measured through water, the nanoscopic contact angle was found to decrease as well.
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http://dx.doi.org/10.1021/la1039442DOI Listing
February 2011

Scanning Near-Field Ellipsometry Microscopy: imaging nanomaterials with resolution below the diffraction limit.

Nanoscale 2011 Jan 1;3(1):233-9. Epub 2010 Nov 1.

University of Twente, MESA+ Institute for Nanotechnology and Faculty of Science and Technology, Department of Materials Science and Technology of Polymers, P.O. Box 217, 7500 AE, Enschede, The Netherlands.

We introduce a simple Scanning Near-Field Ellipsometer Microscopy (SNEM) setup to address the rapidly increasing need for simple, routine optical imaging techniques with resolution well below the diffraction limit. Our setup is based on the combination of commercially available atomic force microscope (AFM) and ellipsometry equipment with gold-coated AFM tips to obtain near-field optical images with a demonstrated resolution below λ/10. AFM topographical data, obtained in contact mode, and near-field optical data were acquired simultaneously using a combined AFM-ellipsometer. The highly enhanced field due to lightning-rod effects and localized surface plasmons excited at the end of the gold-coated tip allowed us to resolve and identify metallic nanoparticles embedded in poly(methyl methacrylate) as well as microphases in microphase-separated block copolymer films.
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http://dx.doi.org/10.1039/c0nr00530dDOI Listing
January 2011

ORMOSIL thin films: tuning mechanical properties via a nanochemistry approach.

Langmuir 2006 Dec;22(26):11158-62

Istituto per lo Studio dei Materiali Nanostrutturati, CNR, via Ugo La Malfa 153, 90146 Palermo, Italy.

The mechanical properties (hardness and elastic modulus) of organically modified silicate thin films can be finely tuned by varying the degree of alkylation and thus the fraction of six- and four-membered siloxane rings in the organosilica matrix. This opens the way to large tunability of parameters that are of crucial practical importance for films that are finding increasing application in numerous fields ranging from microelectronics to chemical sensing.
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http://dx.doi.org/10.1021/la061520wDOI Listing
December 2006
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