Search results for " Materiali"

Jean-Paul Sartre: cultura egemonica e cultura subalterna

2017

Scorrendo l’indice delle opere letterarie e teatrali di Jean-Paul Sartre, si po- trebbe ricavare l’impressione di trovarci dinanzi ad un autore che ha realizzato una vasta ed articolata produzione sezionabile in più parti. Di conseguenza si potrebbe desumere che ciascuna opera risulti slegata dalle altre, costituenti il complesso e ricco mosaico dell’uomo di cultura francese. In effetti, il Sartre scrittore e saggista o autore di opere teatrali non può essere disgiunto dal Sartre fi losofo.

In situ monitoring of moisture uptake of flax fiber reinforced composites under humid/dry conditions

2021

The use of green materials such as natural fiber-reinforced composites represents an increasingly stringent prerogative in the future planning of industrial and non-industrial production. The optimization of these materials is the main aim of the current research, focused on the evaluation of the behavior of flax fiber reinforced composites exposed to isothermal adsorption and desorption cycles, at varying the partial pressure of water vapor (P/P0). For this purpose, the moisture uptake and the morphology changes of the composite material and their constituents were in situ monitored through a measurement protocol, by using a dynamic vapor sorption (DVS) analysis, coupled with an environmen…

Effectiveness of sodium acetate treatment on the mechanical properties and morphology of natural fiber-reinforced composites

2021

This paper aims to investigate the ability of an eco-friendly and cheap treatment based on sodium acetate solutions to improve the mechanical properties of flax fiber-reinforced composites. Flax fibers were treated for 5 days (i.e., 120 h) at 25 °C with mildly alkaline solutions at 5%, 10% and 20% weight content of the sodium salt. Quasi-static tensile and flexural tests, Charpy impact tests and dynamical mechanical thermal (DMTA) tests were carried out to evaluate the mechanical properties of the resulting composites. Fourier transform infrared analysis (FTIR) was used to evaluate the chemical modification on the fibers surface due to the proposed treatment, whereas scanning electron micro…

Improving the mechanical properties of unidirectional flax fabrics reinforced epoxy composites by sodium bicarbonate treatment

2017

Despite their beneficial effects on the adhesion between natural fibers and polymeric matrices, chemical pretreatments have become less attractive since they are expensive and harmful to environment. The present paper deals with the effect of an eco-friendly and cost effective treatment, based on the use of a sodium bicarbonate solution, on the mechanical performances of flax reinforced epoxy composites. Materials and methods: A commercial epoxy resin and unidirectional flax fabrics (190 g/m2 areal density) were used as matrix and reinforcement, respectively. The fabrics were soaked in 5 and 10 wt% solutions of sodium bicarbonate for 5 days at 25°C, then dried at 105°C for 1 day. By using u…

Le strutture difensive delle colonie greche di Sicilia. Storia, tipologia, materiali

2010

Il presente Volume si propone di approfondire la conoscenza storica, tipologica e materica delle strutture difensive presenti nei maggiori siti archeologici siciliani di fondazione greca, premessa indispensabile per un qualsiasi tipo di intervento di recupero e fruizione. Il Volume affronta, innanzitutto, il tema della colonizzazione greca in Sicilia, in quanto la nascita delle fortificazioni è strettaente correlata alla necessità di difendersi dalle popolazioni indigene, e indaga sulle relazioni esistenti fra fortificazioni e tipologie insediative, soffermandosi, in seguito ad analizzare i vari subsistemi (fondazioni, muri, coronamenti, smaltimento delle acque) e componenti (porte e torri)…

Visco-elastic behavior through fractional calculus: an easier method for best fitting experimental results

2011

In capturing visco-elastic behavior, experimental tests play a fundamental rule, since they allow to build up theoretical constitutive laws very useful for simulating their own behavior. The main challenge is representing the visco-elastic materials through simple models, in order to spread their use. However, the wide used models for capturing both relaxation and creep tests are combinations of simple models as Maxwell and/or Kelvin, that depend on several parameters for fitting both creep and relaxation tests. This paper, following Nutting and Gemant idea of fitting experimental data through a power law function, aims at stressing the validity of fractional model. In fact, as soon as rela…

Mechanical properties of basalt fiber reinforced composites manufactured with different vacuum assisted impregnation techniques

2016

Abstract This work describes an experimental mechanical characterisation campaign on composites made out of a quasi-unidirectional basalt fabric. In order to evaluate the ability of commercial basalt fabrics and their composites to meet the potentials of basalt fibers, the work has used raw materials from commercial catalogs with no further modification. Two common manufacturing techniques for medium performance composites have been adopted: vacuum assisted resin infusion, and hand-impregnated vacuum bagging. Two panels, one for each technique, have been fabricated, able to provide a sufficient number of samples for a comprehensive stiffness and strength characterization through Tensile, Fl…

POSS Grafting on Polyethylene and Maleic Anhydride-Grafted Polyethylene by One-Step Reactive Melt Mixing

2018

This study reports the one-step reactive melt mixing preparation of organic-inorganic hybrid based on maleic anhydride-grafted polyethylene and 3-(2-aminoethyl)aminopropyl-heptaisobutyl substituted polyhedral oligomeric silsesquioxane, (NPOSS), as well as on low-density polyethylene and allyl-heptaisobutyl-POSS (1POSS) in dicumyl peroxide presence, which is believed to activate the unsaturation of the reactive functional group of POSS itself. The successful grafting of POSS molecules onto polymeric backbones was probed through rheological and spectroscopic analysis. Grafting of POSS molecules enhances their dispersion in the polymeric matrix as shown by morphological analysis. Moreover, the…

Sintesi di ossadiazoli fluorurati come nuovi Low molecular weight hydrogelators

2010

Perfluorocarbons–graphene oxide nanoplatforms as biocompatible oxygen reservoirs

2018

Abstract 3-Pentadecafluoroheptyl,5-perfluorophenyl-1,2,4-oxadiazole (FOX) molecules were attached onto a graphene oxide (GO) via a facile aromatic substitution in alkaline environment. This approach allows achieving high degree of functionalization under mild conditions. The covalent attachment of perfluoromoieties onto GO lamellae was confirmed by spectroscopic analyses. The performance of these nanoplatforms (GOF) as oxygen reservoirs was assessed at different concentrations and temperature. The results revealed that under physiologic conditions GO and FOX synergistically operate for increasing oxygen uptake and release, either from a thermodynamic and a kinetic point of view. Even at low…