Search results for " Mechanics of Materials"
showing 10 items of 110 documents
Novel strategic approach for the thermo- and photo- oxidative stabilization of polyolefin/clay nanocomposites
2017
Polyolefin/clay nanocomposites were prepared by melt mixing and their oxidative stability was studied under long-term thermo- and photo-oxidative test conditions in the absence and presence of a modified organo montmorillonite clay (OM-MMt) containing a chemically-bound hindered phenol antioxidant function, (AO)OM-Mt. It was found that nanocomposites based on both polyethylene (PE) and polyethylene-grafted-maleic anhydride (PEgMA) containing the (AO)OM-Mt gave a higher oxidative stability, along with better clay dispersion, compared to analogous PE or PEgMA-based nanocomposites containing an added (free) conventional antioxidant with a similar hindered phenol function (using the commercial …
Concentration-dependent anti-/pro-oxidant activity of natural phenolic compounds in bio-polyesters
2017
Abstract In this work, the potential of several naturally occurring phenolic compounds, such as Ferulic Acid (FA), Vanillic Acid (VA), Vitamin E (VE) and Quercetin (Q), as stabilizers against the photo-oxidative degradation of Polylactic acid (PLA) has been assessed. Specifically, PLA-based films containing different amounts of considered stabilizers have been formulated and their photo-stability under UVB exposure has been evaluated. The preliminary characterization of the formulated films shows that all used stabilizers exert plasticizing action, as probed by rheological analysis, due to their low molecular weight. Moreover, no significant modification of the PLA crystallinity has been no…
Thiophene pyrenyl derivatives for the supramolecular processability of single-walled carbon nanotubes in thin film heterojunction
2017
Abstract A major problem for the use of single-wall carbon nanotubes (SWCNTs) in electronic devices relates to their poor processability. Chemical modification inevitably introduces defects in the nanotube lattice, resulting in a loss of electronic properties. In this contest, we report on a supramolecular approach with the aim of increasing the dispersion of SWCNTs in solution and in organic semiconductor matrices by ensuring the optoelectronic properties. In particular, new pyrenyl derivatives of thiophene have been synthesized and used to improve the solubility of SWCNTs for electron transfer in thin film heterojunction with poly(3-hexylthiophene) (P3HT) as donor system. Photoinduced ele…
Use of Vegetation as Biomaterial for Controlling Measures of Human Impact on the Environment
2019
In a context of a climate change, bioengineering techniques and biomaterials are needed to reduce the human impact on the environment. Thus, in recent years, living materials have been used in environmental engineering applications. In the present paper, attention is restricted to the vegetation, and a brief review on its use as biomaterial in engineering control techniques is presented. The core of this review is a comprehensive overview of two important techniques using vegetation as living material for measures limiting the human impact both in extra-urban and in urban sites. In particular, the use of vegetation both as living material for soil erosion protection and river’s bank stabili…
Effects of aging in salt spray conditions on flax and flax/basalt reinforced composites: Wettability and dynamic mechanical properties
2016
Abstract In the last years, the industrial policies are more attentive to issues concerning sustainability, recycling and environmental care. Therefore, the use of natural fibres in composite materials has spread more and more. This paper deals with flax and basalt fibres within an epoxy matrix by investigating the wettability and the dynamic mechanical properties of the resulting composites, subjected to long-term aging tests in critical environmental conditions. The first laminate was constituted by stacking ten layers of bidirectional flax fabrics. The second one was produced by replacing two external flax layers with two layers of basalt mat, for each side of the laminate. Both laminate…
Experimental design of the bearing performances of flax fiber reinforced epoxy composites by a failure map
2018
Abstract This paper represents the first effort aimed to the investigation of the pin/hole contact stress and failure mechanisms of epoxy composites reinforced with woven flax fabrics, underwent to tensile bearing tests. In particular, the maximum loads and failure modes are evaluated at varying the laminate geometrical configuration. In order to optimize the use of polymer composites reinforced with flax fibers in structural applications, an experimental failure map, identifying main failure modes of mechanically fastened joints, is obtained as function of hole diameter, distance of the hole from the free edge of the laminate and laminate width. Moreover, a theoretical approach based on th…
Increasing the shear capacity of reinforced concrete beams using pretensioned stainless steel ribbons
2017
In this work, the second part of an experimental campaign investigating the efficiency of an alternative retrofitting method for increasing the flexural and/or shear capacity in reinforced concrete beams, based on the use of prestressed stainless steel ribbons and steel angles, is presented and analytically reproduced. This group of tests focuses on the ability of the adopted retrofitting method to improve the shear strength and ultimate deformation of reinforced concrete structural elements. As described in a companion paper, the adopted retrofitting method is alternative to traditional techniques of reinforced concrete retrofitting, being easy to install and usually reversible, and charac…
Not always what closes best opens better: mesoporous nanoparticles capped with organic gates
2019
ABSTRACT Four types of calcined MCM-41 silica nanoparticles, loaded with dyes and capped with different gating ensembles are prepared and characterized. N1 and N2 nanoparticles are loaded with rhodamine 6G and capped with bulky poly(ethylene glycol) derivatives bearing ester groups (1 and 2). N3-N4 nanoparticles are loaded with sulforhodamine B and capped with self-immolative derivatives bearing ester moieties. In the absence of esterase enzyme negligible cargo release from N1, N3 and N4 nanoparticles is observed whereas a remarkable release for N2 is obtained most likely due to the formation of an irregular coating on the outer surface of the nanoparticles. In contrast, a marked delivery i…
Influence of cation order on the dielectric properties of (1 – x)Pb(Sc 0:5 Nb 0:5 )O 3 -xPb(Yb 0:5 Nb 0:5 )O 3 ceramics
2020
Ceramic lead niobates and their solid solutions (1 - x)Pb(Sc0:5Nb0:5)O3 - xPb(Yb0:5Nb0:5)O3 were synthesized by solid state reactions from oxides. The structure of investigated samples was characterized by X-ray diffraction (XRD). Dielectric studies of the ceramics were performed by means of broadband dielectric spectroscopy at the temperature ranging from 600 K to 140 K. For all ceramic samples a diffuse phase transition as well as relaxor ferroelectric behavior were observed. © 2020 Barbara Garbarz-Glos et al., published by Sciendo 2020. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
Antiferromagnetism and p‐type conductivity of nonstoichiometric nickel oxide thin films
2020
Plasma‐enhanced atomic layer deposition was used to grow non‐stoichiometric nickel oxide thin films with low impurity content, high crystalline quality, and p‐type conductivity. Despite the non‐stoichiometry, the films retained the antiferromagnetic property of NiO.