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14. Simulation and experimental characterization of polymer/carbon nanotubes composites for strain sensor applications.

Author

De Vivo, B., Lamberti, P., Spinelli, G., Tucci, V., Vertuccio, L., and Vittoria, V.

Subjects
CARBON nanotubes, STRAIN sensors, TENSILE strength, COMPUTER simulation, MONTE Carlo method
Abstract

In this paper, a numerical model is presented in order to analyze the electrical characteristics of polymer composites filled by carbon nanotubes (CNTs) subject to tensile stress and investigate the possible usage of such materials as innovative sensors for small values of strain. The simulated mechano-electrical response of the nanocomposite is obtained through a multi-step approach which, through different modeling stages, provides a simple and effective tool for material analysis and design. In particular, at first, the morphological structures of the composites are numerically simulated by adopting a previously presented model based on a Monte Carlo procedure in which uniform distributions of the CNTs, approximated as of solid cylinders and ensuring some physical constraints, are dispersed inside a cubic volume representing the polymer matrix. Second, a geometrical analysis allows to obtain the percolation paths detected in the simulated structures. Suitable electrical networks composed by resistors and capacitors associated to the complex charge transport and polarization mechanisms occurring in the percolation paths are then identified. Finally, the variations of these circuit parameters, which are differently affected by the mechanical stresses applied to the composites, are considered to analyze the electromechanical characteristics of the composites and hence their performances as stress sensors. The proposed approach is used to investigate the impact on the electro-mechanical response of some physical properties of the base materials, such as the type of carbon nanotube, the height of energy barrier of polymer resin, as well as characteristics of the composite, i.e., the volume fraction of the filler. The tunneling effect between neighboring nanotubes is found to play a dominant role in determining the composite sensitivity to mechanical stresses. The simulation results are also compared with the experimental data obtained by performing stress tests on samples of a multi walled CNT filled composite based on poly (e-caprolactone), a polymer which is of interest for its biocompatibility. Model simulations and measured data show generally satisfactory agreement, confirming the effectiveness of the proposed approach to account for the impact of the interactions between CNTs and the insulating resin on the electromechanical response of the composite. [ABSTRACT FROM AUTHOR]

Published
2014
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30. Preparation, Characterization and Antibacterial Activity of Poly(epsilon-caprolactone) Electrospun Fibers Loaded with Amoxicillin for Controlled Release in Biomedical Applications

Author

Malagon Aviles, O., Cartuche Flores, L., Vittoria, V., Stanzione, M., Valarezo Valdez, B., and Tammaro, L.

Subjects
amoxicillin, antibacterial activity, caprolactone), nanofibers, poly(e, electrospinning
Abstract

Amoxicillin (AMOX) was successfully encapsulated at different concentrations into poly(caprolactone) (PCL) by the electrospinning technique, and mats of non-woven fibers were obtained and characterized in terms of morphology, in vitro release and antibacterial properties. The scanning electron microscopy evidenced the nanofibrous structure of the pristine PCL, composed of individual, uniform, and randomly oriented fibres with an average diameter ranging around 0.8 micron. The addition of amoxicillin at different concentrations (3, 5 and 7) did not evidence change in the fiber morphology. The release curves, for all samples, present mainly two stages: a first stage, quick as a burst, is followed by a second slow stage. The burst was analyzed as a function of amoxicillin concentration and thickness of the membranes, and values corresponding to absence of burst were individuated. In the second stage the release was found very slow extending up to months for the most concentrated sample. The antibacterial activity of the electrospun fibers was effective to inhibit in different proportions Staphylococcus aureus, Enterococcus faecalis and Escherichia coli. The properties of the filled membranes and their capability for local delivery of antibiotics make them suitable for biomedical applications.

Published
2012

37. Cure behavior and mechanical properties of structural self-healing epoxy resins

Author

Guadagno, L., Longo, P., Raimondo, M., Naddeo, C., Mariconda, A., Sorrentino, A., Vittoria, V., Iannuzzo, G., and Russo, S.

Abstract

Advances in the growing use of polymer composites in aerospace applications explore the possibility in the development of smart materials capable of self-repair. In this article, we have formulated and characterized a multifunctional autonomically healing composite inspired by the design of White et al. Microcapsules containing dicyclopentadiene (DCPD) and powders of Grubbs first generation catalyst were embedded in an epoxy formulation and both the epoxy precursor and the composite were cured up to the temperature of 120 °C that preserves the activity of the catalyst. The results on the cure behavior of an epoxy matrix for self-healing material and the influence of the components related to self-healing function on the dynamic-mechanical properties are investigated. The presence of catalyst powder causes a slight decrease in the elastic modulus value with respect to the epoxy matrix. At variance, a large recovery in this parameter is gained for the self-healing specimen, proving that well-distributed microcapsules contribute to improve the mechanical properties.

Published
2010
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48. Nanotechnologies for Multifunctional Materials

Author

Guadagno, Liberata, Gorrasi, G., Naddeo, Carlo, Tammaro, Loredana, Romeo, V., Bugatti, V., Raimondo, Marialuigia, Vertucci, L., Sorrentino, A., and Vittoria, V.

Published
2007

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