scholarly journals Key Role of the Dispersion of Carbon Nanotubes (CNTs) within Epoxy Networks on their Ability to Release

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2530
Author(s):  
Maxime Pras ◽  
Jean-François Gérard ◽  
Luana Golanski ◽  
Guilhem Quintard ◽  
Jannick Duchet-Rumeau
Keyword(s):  
Polymer Matrix ◽  
Interfacial Strength ◽  
Advanced Materials ◽  
Mechanical Reinforcement ◽  
Rheological Analysis ◽  
Polymerization Kinetic ◽  
The Matrix ◽  
Dispersion State ◽  
The Relationship

Carbon nanotube (CNT)-reinforced nanocomposites represent a unique opportunity in terms of designing advanced materials with mechanical reinforcement and improvements in the electrical and thermal conductivities. However, the toxic effects of these composites on human health have been studied, and very soon, some regulations on CNTs and on composites based on CNTs will be enacted. That is why the release of CNTs during the nanocomposite lifecycle must be controlled. As the releasing depends on the interfacial strength that is stronger between CNTs and polymers compared to CNTs in a CNT agglomerate, two dispersion states—one poorly dispersed versus another well dispersed—are generated and finely described. So, the main aim of this study is to check if the CNT dispersion state has an influence on the CNT releasing potential in the nanocomposite. To well tailor and characterize the CNT dispersion state in the polymer matrix, electronic microscopies (SEM and TEM) and also rheological analysis are carried out to identify whether CNTs are isolated, in bundles, or in agglomerates. When the dispersion state is known and controlled, its influence on the polymerization kinetic and on mechanical properties is discussed. It appears clearly that in the case of a good dispersion state, strong interfaces are generated, linking the isolated nanotubes with the polymer, whereas the CNT cohesion in an agglomerate seems much more weak, and it does not provide any improvement to the polymer matrix. Raman spectroscopy is relevant to analyze the interfacial properties and allows the relationship with the releasing ability of nanocomposites; i.e., CNTs poorly dispersed in the matrix are more readily released when compared to well-dispersed nanocomposites. The tribological tests confirm from released particles granulometry and observations that a CNT dispersion state sufficiently achieved in the nanocomposite avoids single CNT releasing under those solicitations.

Filament Fragmentation Phenomena

1989 ◽  
Vol 170 ◽  
Author(s):  
Juan C. Figueroa ◽  
Linda S. Schadler ◽  
Campbell Laird
Keyword(s):  
Strain Energy ◽  
Stress Transfer ◽  
Fiber Surface ◽  
Yield Information ◽  
The Matrix ◽  
Two Parameters ◽  
The Relationship

AbstractThe effect of fiber surface treatments on the relationship between the tensile strength of a filament and the shear strength of its interphase is one of the central issues facing composite materials technologists today. We demonstrate here that analysis of fragmentation phenomena in monofilament composites can simultaneously yield information about these two parameters. Characterization of shear stress transfer zones in non-critical fragments has led us to the determination of interphase strength.A phenomenological treatment that highlights the role of the matrix in the fragmentation process is presented here. This analysis considers issues such as the strain energy exchange between a failing fiber and the matrix, as well as interphase relaxation due to the viscoelastic nature of the matrix. Our observations of the fragmentation phenomena in AU4/polycarbonate monofilament composites indicate that the fiber/matrix interaction in this system is governed by micromechanical locking.

EFFECT OF THE NANOFILLER SHAPE ON THE CONDUCTIVE NETWORK FORMATION OF POLYMER NANOCOMPOSITES VIA A COARSE-GRAINED SIMULATION

2018 ◽  
Vol 91 (4) ◽  
pp. 757-766 ◽  
Author(s):  
Fanzhu Li ◽  
Huan Zhang ◽  
Tiantian Li ◽  
Jun Liu ◽  
Yangyang Gao ◽  
...  
Keyword(s):  
Polymer Nanocomposites ◽  
Network Formation ◽  
Dynamics Simulation ◽  
Coarse Grained ◽  
Radius Of Gyration ◽  
Conductive Network ◽  
The Matrix ◽  
Dispersion State ◽  
Conductive Property ◽  
The Relationship

ABSTRACT It is very important to improve the electrical conductivity of polymer nanocomposites, which can widen their application. The effect of the nanofiller shape on the relationship between the nanofiller microstructure and the conductive probability of the nanofiller filled polymer nanocomposites (PNCs) has been investigated in detail by employing a coarse-grained molecular dynamics simulation. Four kinds of nanofiller shapes are considered: rod filler, Y filler, X filler, and sphere filler. First, the mean square radius of gyration gradually decreases from rod filler, Y filler, X filler, to sphere filler, which reflects the highest aspect ratio for rod filler. Meanwhile, the dispersion state of the nanofiller is relatively uniform in the matrix. The conductive probability (denoted by the formation probability of the conductive network) is adopted to stand for the conductive property. The results show that the conductive probability gradually decreases from rod filler, Y filler, X filler, to sphere filler, which is attributed to their gradually decreased size. In summary, the nanofiller shape affects the electric conductive property of PNCs.

scholarly journals Dynamics of matrix-free Ca2+ in cardiac mitochondria: two components of Ca2+ uptake and role of phosphate buffering

2012 ◽  
Vol 139 (6) ◽  
pp. 465-478 ◽  
Author(s):  
An-Chi Wei ◽  
Ting Liu ◽  
Raimond L. Winslow ◽  
Brian O'Rourke
Keyword(s):  
Mitochondrial Permeability Transition ◽  
High Capacity ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Cardiac Mitochondria ◽  
The Matrix ◽  
The Relationship ◽  
Matrix Free ◽  
Trigger Cell Death

Mitochondrial Ca2+ uptake is thought to provide an important signal to increase energy production to meet demand but, in excess, can also trigger cell death. The mechanisms defining the relationship between total Ca2+ uptake, changes in mitochondrial matrix free Ca2+, and the activation of the mitochondrial permeability transition pore (PTP) are not well understood. We quantitatively measure changes in [Ca2+]out and [Ca2+]mito during Ca2+ uptake in isolated cardiac mitochondria and identify two components of Ca2+ influx. [Ca2+]mito recordings revealed that the first, MCUmode1, required at least 1 µM Ru360 to be completely inhibited, and responded to small Ca2+ additions in the range of 0.1 to 2 µM with rapid and large changes in [Ca2+]mito. The second component, MCUmode2, was blocked by 100 nM Ru360 and was responsible for the bulk of total Ca2+ uptake for large Ca2+ additions in the range of 2 to 10 µM; however, it had little effect on steady-state [Ca2+]mito. MCUmode1 mediates changes in [Ca2+]mito of 10s of μM, even in the presence of 100 nM Ru360, indicating that there is a finite degree of Ca2+ buffering in the matrix associated with this pathway. In contrast, the much higher Ca2+ loads evoked by MCUmode2 activate a secondary dynamic Ca2+ buffering system consistent with calcium-phosphate complex formation. Increasing Pi potentiated [Ca2+]mito increases via MCUmode1 but suppressed [Ca2+]mito changes via MCUmode2. The results suggest that the role of MCUmode1 might be to modulate oxidative phosphorylation in response to intracellular Ca2+ signaling, whereas MCUmode2 and the dynamic high-capacity Ca2+ buffering system constitute a Ca2+ sink function. Interestingly, the trigger for PTP activation is unlikely to be [Ca2+]mito itself but rather a downstream byproduct of total mitochondrial Ca2+ loading.

Development of an Adhesion Test for Characterizing the Interface Fiber/Polymer Matrix

2012 ◽  
Vol 498 ◽  
pp. 210-218 ◽  
Author(s):  
Bouchra Hassoune-Rhabbour ◽  
Laurence Poussines ◽  
Valérie Nassiet
Keyword(s):  
Polymer Matrix ◽  
Composite Fiber ◽  
Matrix Interface ◽  
Pull Out ◽  
Structures And Properties ◽  
The Matrix ◽  
Fiber Matrix Interface ◽  
Fiber Matrix ◽  
Relationship Structures ◽  
The Relationship

There are several models on the relationship structures and properties of the composite fiber / matrix interface [1]. Including literature proposes the development of micromechanical tests suitable for assessing the shear strength of the interface fiber / polymer matrix. The first test which allowed to characterize the fiber / matrix interface is the pull-out test developed by Broutman [2]. It consists in extracting the fiber from the matrix that can be in block form, gout or disk of resin. To reduce the variation in results due to the geometries used, it was agreed to use a drop of resin with small dimensions. The test is to characterize the fiber / matrix interface of natural thermosetting or thermoplastic by determining the shear stress.

Studying the Relationship between the Strength and Stress-Related Characteristics of Concrete as a Conglomerate and the Properties of its Components

2021 ◽  
Vol 1022 ◽  
pp. 71-79
Author(s):  
Evgeniy M. Shcherban ◽  
Sergey A. Stelmakh ◽  
Aleksandr Sysoev ◽  
Andrei Chernil'nik
Keyword(s):  
Axial Compression ◽  
Experimental Tests ◽  
Cement Stone ◽  
Axial Tensile ◽  
Number Of Factors ◽  
Shrinkage And Creep ◽  
The Matrix ◽  
Load Action ◽  
The Relationship

The concrete conglomerate properties change over time and depend on a number of factors. When considering deformation under the effect of mechanical loads or changes in temperature and humidity, the mechanism of this process is based on three main provisions. Firstly, concrete is a composite material, the matrix of which is cement stone. Secondly, the elastic modulus and strength of the cement stone may be less or more than that of aggregate. Thirdly, the concrete destruction under axial compression occurs at the cement stone stresses exceeding its ultimate extensibility in the direction normal to the external load action. Considering the specifics of deformation under load in different periods and the role of stress-related characteristics in this process, it is advisable to outline ways to regulate them and thereby the main concrete properties in the desired direction. The importance and feasibility of this approach are determined by the need to develop techniques allowing control of properties such as elasticity, shrinkage, and creep. A series of experimental tests and a comparative analysis of the results have been performed. The effect of some aggregate rocks on certain strength and stress-related properties of the concrete conglomerate has been investigated. Limestone and sandstone have been taken as the rocks studied. The properties studied include impact, axial compression, and axial tensile strengths. According to the analysis, concrete prepared on crushed limestone has shown the best results concerning all the properties studied.

scholarly journals Hydrogels with Gigantic Thermopower for Low-grade Heat Harvesting

2021 ◽  
Author(s):  
Kuan Sun ◽  
Yongjie He ◽  
Qi Zhang ◽  
Hanlin Cheng ◽  
Yang Liu ◽  
...  
Keyword(s):  
Polymer Matrix ◽  
Large Scale ◽  
Great Promise ◽  
Physical Parameters ◽  
Low Grade ◽  
Te Material ◽  
Mobile Ions ◽  
Low Grade Heat ◽  
The Relationship

Abstract Harvesting energy from the environment to power the self-sustained systems has long been desired1,2. Ionic thermoelectric (i-TE) material with mobile ions as charge carriers has the advantage to generate large thermal voltages at low operating temperatures3-5. Recent works improved the thermopower substantially by modifying the polymer matrix of the i-TE hydrogels6-9. But the mobile ions have not been systematically studied in the context of i-TE hydrogels. This study highlights the role of ions in i-TE hydrogels employing a polyvinyl alcohol (PVA) polymer matrix and a number of ion providers, e.g. KOH, KNO3, KCl, KBr, NaI, KI, and CsI. The relationship between the intrinsic physical parameters of the ion and the thermoelectric performance is established, indicating electronegativity of the cation and the ability to influence the hydrogen bond by the anion are two crucial factors. Among these i-TE hydrogels, PVA/CsI hydrogel exhibits the largest ionic Seebeck coefficient, reaching 52.9 mV K-1, which is the greatest of all i-TE materials reported till date. In addition, PVA/NaI hydrogel exhibits excellent TE properties, with a record ZT value of 5.09 at room temperature. This flexible, inexpensive hydrogel that compatible with large-scale manufacturing shows great promise for low-grade thermal energy harvesting.

scholarly journals The use of image analysis for the interaction of 1,3,5-trisubstituted isocyanurates with oxidizer and different binders in composite materials

2006 ◽  
Vol 60 (3-4) ◽  
pp. 72-77
Author(s):  
Jasmina Dostanic ◽  
Mihela Barbu ◽  
Radmila Jancic-Heinemann ◽  
Tatjana Volkov-Husovic ◽  
Gordana Uscumlic ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Image Analysis ◽  
Polymer Matrix ◽  
Morphological Characteristics ◽  
Morphological Properties ◽  
Bonding Agents ◽  
Grain Color ◽  
The Matrix ◽  
Resin Binder

Composite propellants are non-homogenous propellants and comprise primarily crystalline oxidizer and metal fuels uniformly suspended in a resin binder. The strength of the bonds between the polymer matrix and the oxidizer determine the mechanical properties of composite propellants. In order to achieve good mechanical properties of the fuel, bonding agents are added to the mixture. The role of the bonding agents is to enable good interactions (interphase) between the polymer matrix and the oxidizer grains. The level of interconnection between the phases could be measured by using the surface obtained by cutting the composite material and observing the resulting surface. A problem in the visualization of such a material is to enable the visibility of the polymer matrix and the grains in the image as both phases are white. There are two possible ways to overcome this problem: to add a pigment into the matrix polymer and to color the matrix and make it different from the grain color. Another possibility is to find a solvent for one of the phases and to dissolve one of the phases in an appropriate solvent so that the remaining phase could be stained, photographed and analyzed using the image analysis program. The morphological characteristics of the image could be established and analyzed. The topic of this study was to establish the conditions of preparation of composite propellants containing ammonium per chlorate and HMX and RDX as oxidizers, and polymer of the polybutadiene type and 1,3,5-trisubstituted isocyanurates as bonding agents. The bonding phenomenon was investigated by optical microscopy. The established procedure of preparation will enable the visualization of the composite structure and the morphological characteristics of the surface will be obtained. From the morphological properties of the obtained composite, it will be possible to select a suitable polymer for the preparation of uniformly distributed composite propellant.

scholarly journals The role of interlayer adhesion in graphene oxide upon its reinforcement of nanocomposites

2016 ◽  
Vol 374 (2071) ◽  
pp. 20150283 ◽  
Author(s):  
Zheling Li ◽  
Ian A. Kinloch ◽  
Robert J. Young
Keyword(s):  
Graphene Oxide ◽  
Structural Integrity ◽  
Mechanical Reinforcement ◽  
Graphene Lattice ◽  
The Matrix ◽  
Observed Behaviour ◽  
Reinforcement Efficiency ◽  
Intrinsic Stiffness ◽  
High Degree

Graphene oxide (GO) has become a well-established reinforcement for polymer-based nanocomposites. It provides stronger interfacial interaction with the matrix when compared with that of graphene, but its intrinsic stiffness and strength are somewhat compromised because of the presence of functional groups damaging the graphene lattice and increasing its thickness, and its tendency to adopt a crumpled structure. Although the micromechanics of graphene reinforcement in nanocomposites has been studied widely, the corresponding micromechanics investigations on GO have not been undertaken in such detail. In this work, it is shown that the deformation micromechanics of GO can be followed using Raman spectroscopy and the observed behaviour can be analysed with continuum mechanics. Furthermore, it is shown that the reinforcement efficiency of GO is independent of its number of layers and stacking configurations, indicating that it is not necessary to ensure a high degree of exfoliation of GO in the polymer matrix. It also demonstrates the possibility of increasing the concentration of GO in nanocomposites without sacrificing mechanical reinforcement efficiency. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’.

The Study of the Morphology and Dielectric Properties of PVC + TiO2-Based Nanocomposites

2019 ◽  
Vol 201 (1) ◽  
pp. 178-182
Author(s):  
M. A. Ramazanov ◽  
A. M. Rahimli
Keyword(s):  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Dielectric Properties ◽  
Polymer Matrix ◽  
Chemical Structure ◽  
Sem Analysis ◽  
The Matrix ◽  
Agglomeration Of Nanoparticles ◽  
The Fourier Transform

In given work, PVC + TiO2-based nanocomposites were synthesized and their structure and dielectric properties were investigated. SEM analysis of samples was performed to determine the distribution of nanoparticles in the polymer matrix. It was pointed out that the nanoparticles play the role of structure nucleation centers when they are distributed in the polymer matrix in small quantities. As the concentration of particles increases, changes in the supramolecular structure of the polymer occurs, as well as the agglomeration of nanoparticles in the matrix, which leads to an increase in their size. The Fourier transform infrared spectroscopy (FTIR) measurements for pure polymer and nanocomposites were carried out. It has been determined that, as the concentration of TiO2 nanoparticles increases, there is no change in the chemical structure of the polymer and only decreases the intensity of the maxima of the spectra. It has been shown that polymer matrix is only physically interacted with the nanoparticles and does not form any chemical bond with nanoparticles. It has also been established that the increase in the percentage of TiO2 nanoparticles in the polymer has increased the dielectric permittivity of nanocomposites and it has started to decline at a certain concentration.

scholarly journals The Role of Investors and Financiers’ Support in Globalization of Pakistani Companies

2018 ◽  
pp. 39-55
Author(s):  
Jawaid Ahmed Qureshi ◽  
Muhammad Asif Qureshi ◽  
Amanat Ali Jalbani
Keyword(s):  
Bank Lending ◽  
Business Network ◽  
Second Stage ◽  
Corporate Globalization ◽  
The Matrix ◽  
Global Skills ◽  
Global Investors ◽  
Domestic Economies ◽  
The Relationship

In the regime of globalization, many companies around the world attempt to globalize their business network beyond domestic boundaries. The stimulus behind that is to nourish, avail opportunities, and earn profits by leveraging the global skills and resources. Such an extension of business can not only benefit them but also to the domestic economies, and overseas economies too in many respects. This study intensively examines the way investors and financers’ assist Pakistani companies to expand their business worldwide. When companies flourish their business ventures and even go global, investors feel confident in investing with them. Similarly, financers trust them and finance them at soft/discounted terms. This is a novel study in the matrix of Pakistan. One earlier research on this issue in some other country ascertained only about the role of bank lending in corporate globalization, while this probe also enlarges its scope by probing about the relationship among investors and globally expanding companies.           The research design of this study consists of sequential hybrid research approaches. At the first stage, a qualitative study was conducted to have basic acquaintance about the core theme of the investigation, corporate globalization and the role of investors and banks cum lending agencies to support Pakistani companies. At the second stage, quantitative study was conducted to test the hypotheses. The samples belong to the population of top-five export-oriented sectors in Pakistan since many of their companies have globalized their operations. The findings reveal evidence of trust and support by investors, banks, and lending entities to these companies.

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