Search results for "Polymers."
showing 10 items of 3543 documents
Hybrid biocomposites based on polylactic acid and natural fillers from Chamaerops humilis dwarf palm and Posidonia oceanica leaves
2022
AbstractPlatelet-like and fibrous lignocellulosic fillers were achieved from the leaves of Chamaerops humilis (CHL) and Posidonia oceanica (POL) and used as a hybrid reinforcement for a polylactic acid (PLA) matrix at three different loading levels (from 5 to 20%). The materials were fully characterized from a morphological, physicochemical, mechanical, and dynamic-thermomechanical point of view. When compared to their counterpart containing either CHL or POL only, the resulting hybrid biocomposites showed the highest mechanical properties, with strengthening and stiffening effects respectively up to 120% and 50% higher than those expected from the linear combination of the two, and higher …
Electrospinning of α,β-poly(N-2-hydroxyethyl)-dl-aspartamide-graft-polylactic acid to produce a fibrillar scaffold
2010
Abstract α,β-Poly( N -2-hydroxyethyl)- dl -aspartamide grafted with polylactic acid (PHEA- g -PLA) is a biocompatible and biodegradable amphiphilic copolymer that has been already employed to prepare a drug delivery system. In this study we have prepared for the first time a fibrillar scaffold from PHEA- g -PLA by the electrospinning of a solution of this copolymer in a mixture of N , N -dimethyl formamide (DMF) and acetone (80:20 vol/vol). The average diameter and the morphology of electrospun fibers were detected by scanning electron microscopy. Chemical degradation studies in phosphate buffer solution pH 7.4 have been performed until 15 days in order to obtain a preliminary information a…
Asphalt mixtures improved with plastic additives: mix design and case study in an airport
La crescente domanda di prestazioni e le esigenze di salvaguardia dell’ecosistema spingono a sviluppare nuove tecnologie di lavorazione, a sperimentare l’impiego di nuovi materiali, a migliorare i metodi di progetto delle miscele. Il criterio seguito è quello di un impiego più razionale delle risorse e dell’utilizzo di tecniche a basso impatto ambientale. Per ragioni tecniche ed economiche stiamo assistendo al fenomeno di espansione nel mercato degli additivi, impiegati nella produzione di miscele bituminose per migliorarne le prestazioni e ridurre i costi. In generale, però riuscire a soddisfare tutti gli obiettivi con un unico prodotto è difficile, perché l’alta qualità richiede costi più…
On John Bates Clark's “Naive Productivity Ethics”: A Note
2023
Abstract This article explores in detail the reactions among American economists to John Bates Clark's famously controversial claim that the marginal productivity theory of factor pricing and distribution is necessarily just. The general debate around Clark's “naïve productivity ethics,” as George Stigler sharply called it, transcended the then existing distinctions within the discipline and involved figures of virtually all theoretical and ideological persuasions—from prolabor progressives such as Richard T. Ely to staunch conservatives such as Thomas Nixon Carver. Our reconstruction reveals that, contrary to several standard historical accounts, for American early twentieth-century margin…
ELECTROCHEMICAL FABRICATION OF METAL/OXIDE/CONDUCTING POLYMER JUNCTIONS FOR ELECTRONIC DEVICES
2014
Hidden Structural Features of Multicompartment Micelles Revealed by Cryogenic Transmission Electron Tomography
2014
The demand for ever more complex nanostructures in materials and soft matter nanoscience also requires sophisticated characterization tools for reliable visualization and interpretation of internal morphological features. Here, we address both aspects and present synthetic concepts for the compartmentalization of nanoparticle peripheries as well as their in situ tomographic characterization. We first form negatively charged spherical multicompartment micelles from ampholytic triblock terpolymers in aqueous media, followed by interpolyelectrolyte complex (IPEC) formation of the anionic corona with bis-hydrophilic cationic/neutral diblock copolymers. At a 1:1 stoichiometric ratio of anionic a…
Polyamide-Based Fibers Containing Microwave-Exfoliated Graphite Nanoplatelets
2016
Exfoliated Graphite NanoPlatelets (GNP) have been obtained from Graphite Intercalation Compounds (GIC) subjected to thermal and microwave treatments. Accurate morphological and structural characterization of obtained GNP, performed to compare the degree of exfoliation, show that microwave-treated GNP, exhibit well-exfoliated structure, without any reduction in dimensions compared with the native GIC, differently to the thermal-treated ones. Microwave-treated GNP have been introduced in polyamide (PA) through melt-mixing to obtain nanocomposite that has been subjected to elongational flow, with the aim to improve the nanofiller dispersion and induce GNP orientation along the fiber direction.…
Surface Coatings Based on Polysilsesquioxanes: Solution-Processible Smooth Hole-Injection Layers for Optoelectronic Applications
2009
Optoelectronic devices usually consist of a transparent conductive oxide (TCO) as one electrode. Interfacial engineering between the TCO electrode and the overlying organic layers is an important method for tuning device performance. We introduce poly(methylsilsesquioxane)-poly(N,N-di-4-methylphenylamino styrene) (PMSSQ-PTPA) as a potential hole-injection layer forming material. Spin-coating and thermally induced crosslinking resulted in an effective planarization of the anode interface. HOMO level (-5.6 eV) and hole mobility (1 × 10(-6) cm(2) · Vs(-1) ) of the film on ITO substrates were measured by cyclovoltammetry and time-of-flight measurement demonstrating the hole injection capabili…
From monolayer to multilayer N-channel polymeric field-effect transistors with precise conformational order
2012
Monolayer field-effect transistors based on a high-mobility n-type polymer are demonstrated. The accurate control of the long-range order by Langmuir-Schafer (LS) deposition yields dense polymer packing exhibiting good injection properties, relevant current on/off ratio and carrier mobility in a staggered configuration. Layer-by-layer LS film transistors of increasing thickness are fabricated and their performance compared to those of spin-coated films.
Electrophoretic flow behaviour and mobility of colloidal fluids and crystals.
2007
We report on measurements of the electrophoretic mobility mu of charged colloidal spheres in the deionized state, where the suspensions show fluid or crystalline order. In the fluid state, parabolic flow profiles are observed due to electro-osmotic solvent flow. In the crystalline state, complex flow profiles occur due to additional crystal cohesion. The mobility mu then may inferred from the flow velocity averaged over the complete cell cross section as performed in our home built super-heterodyne Doppler velocimeter. For two particle species of 68 and 122 nm diameter we measured mu as a function of particle concentration. Starting from a plateau value at low concentration, mu decreases ap…