scholarly journals A New Ultra Fast Conduction Mechanism in Insulating Polymer Nanocomposites

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
M. Xu ◽  
G. C. Montanari ◽  
D. Fabiani ◽  
L. A. Dissado ◽  
A. Krivda
Keyword(s):  
Polymer Nanocomposites ◽  
Conduction Mechanism ◽  
Negative Charge ◽  
Polymer Chains ◽  
Electromechanical Properties ◽  
Electrical Field ◽  
Base Polymer ◽  
Insulating Polymers ◽  
Nanosilica Particles ◽  
First Time

A brand new phenomenon, namely, electrical conduction via soliton-like ultra fast space charge pulses, recently identified in unfilled cross-linked polyethylene, is shown for the first time to occur in insulating polymer nanocomposites and its characteristics correlated with the electromechanical properties of nanostructured materials. These charge pulses are observed to cross the insulation under low electrical field in epoxy-based nanocomposites containing nanosilica particles with relative weights of 1%, 5%, 10%, and 20% at speeds orders of magnitude higher than those expected for carriers in insulating polymers. The characteristics of mobility, magnitude and repetition rate for both positive and negative charge pulses are studied in relation to nanofiller concentration. The results show that the ultra fast charge pulses (packets) are affected significantly by the concentration of nanoparticles. An explanation is presented in terms of a new conduction mechanism where the mechanical properties of the polymer and movement of polymer chains play an important role in the injection and transport of charge in the form of pulses. Here, the charge transport is not controlled by traps. Instead, it is driven by the contribution of polarization and the resultant electromechanical compression, which is substantially affected by the introduction of nanoparticles into the base polymer.

scholarly journals Recent Advances in the Synthesis of Polymer-Grafted Low-K and High-K Nanoparticles for Dielectric and Electronic Applications

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2942
Author(s):  
Bhausaheb V. Tawade ◽  
Ikeoluwa E. Apata ◽  
Nihar Pradhan ◽  
Alamgir Karim ◽  
Dharmaraj Raghavan
Keyword(s):  
Energy Density ◽  
Polymer Nanocomposites ◽  
High Performance ◽  
Breakdown Strength ◽  
Polymer Nanocomposite ◽  
High Energy ◽  
Polymer Chains ◽  
High Energy Density ◽  
Grafted Nanoparticles ◽  
Grafting From

The synthesis of polymer-grafted nanoparticles (PGNPs) or hairy nanoparticles (HNPs) by tethering of polymer chains to the surface of nanoparticles is an important technique to obtain nanostructured hybrid materials that have been widely used in the formulation of advanced polymer nanocomposites. Ceramic-based polymer nanocomposites integrate key attributes of polymer and ceramic nanomaterial to improve the dielectric properties such as breakdown strength, energy density and dielectric loss. This review describes the ”grafting from” and ”grafting to” approaches commonly adopted to graft polymer chains on NPs pertaining to nano-dielectrics. The article also covers various surface initiated controlled radical polymerization techniques, along with templated approaches for grafting of polymer chains onto SiO2, TiO2, BaTiO3, and Al2O3 nanomaterials. As a look towards applications, an outlook on high-performance polymer nanocomposite capacitors for the design of high energy density pulsed power thin-film capacitors is also presented.

scholarly journals Interface and Interphase in Polymer Nanocomposites with Bare and Core-Shell Gold Nanoparticles

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 541 ◽  
Author(s):  
Albert J. Power ◽  
Ioannis N. Remediakis ◽  
Vagelis Harmandaris
Keyword(s):  
Polymer Nanocomposites ◽  
Polymer Matrix ◽  
Md Simulations ◽  
Polymer Chains ◽  
Core Shell ◽  
Wulff Construction ◽  
Density Profiles ◽  
Au Nps ◽  
Polymeric Chains ◽  
Terminal Dynamics

Metal nanoparticles are used to modify/enhance the properties of a polymer matrix for a broad range of applications in bio-nanotechnology. Here, we study the properties of polymer/gold nanoparticle (NP) nanocomposites through atomistic molecular dynamics, MD, simulations. We probe the structural, conformational and dynamical properties of polymer chains at the vicinity of a gold (Au) NP and a functionalized (core/shell) Au NP, and compare them against the behavior of bulk polyethylene (PE). The bare Au NPs were constructed via a systematic methodology starting from ab-initio calculations and an atomistic Wulff construction algorithm resulting in the crystal shape with the minimum surface energy. For the functionalized NPs the interactions between gold atoms and chemically adsorbed functional groups change their shape. As a model polymer matrix we consider polyethylene of different molecular lengths, from the oligomer to unentangled Rouse like systems. The PE/Au interaction is parametrized via DFT calculations. By computing the different properties the concept of the interface, and the interphase as well, in polymer nanocomposites with metal NPs are critically examined. Results concerning polymer density profiles, bond order parameter, segmental and terminal dynamics show clearly that the size of the interface/interphase, depends on the actual property under study. In addition, the anchored polymeric chains change the behavior/properties, and especially the chain density profile and the dynamics, of the polymer chain at the vicinity of the Au NP.

The reinforcing and characteristics of interphase as the polymer chains adsorbed on the nanoparticles in polymer nanocomposites

2017 ◽  
Vol 295 (10) ◽  
pp. 2001-2010 ◽  
Author(s):  
Nafiseh Nikfar ◽  
Milad Esfandiar ◽  
Mohammad Reza Shahnazari ◽  
Navid Mojtahedi ◽  
Yasser Zare
Keyword(s):  
Polymer Nanocomposites ◽  
Polymer Chains

scholarly journals The Position of Solid Carbon Dioxide in the Triboelectric Series

2019 ◽  
Vol 72 (8) ◽  
pp. 633 ◽  
Author(s):  
Jinyang Zhang ◽  
Simone Ciampi
Keyword(s):  
Carbon Dioxide ◽  
Negative Charge ◽  
Plastic Material ◽  
Indirect Evidence ◽  
Liquid Carbon ◽  
Solid Carbon Dioxide ◽  
Dry Ice ◽  
First Time ◽  
Charge Sign ◽  
Positively Charged

The process of releasing liquid carbon dioxide from a fire extinguisher is accompanied by a strong static charging of the plastic material making up the extinguisher discharge horn. Firefighters often report an electric shock when operating CO2 extinguishers, but the origin of this electrostatic hazard is largely unknown. Here, we begin to investigate this phenomenon, and test the hypothesis of plastic samples being tribocharged on contact with rapidly flowing solid CO2. Using Faraday pail measurements, we show that non-conductive polymers gain a net static charge when brought in and out of contact with dry ice (solid CO2). These measurements of charge sign and magnitude give indirect evidence helping to place solid CO2 for the first time on the triboelectric series. Polydimethylsiloxane (PDMS), polytetrafluoroethylene (PTFE), and polyvinyl chloride (PVC) samples acquire a negative charge when rubbed against dry ice, whereas poly(methyl methacrylate) (PMMA), glass, and nylon surfaces become positively charged. Therefore, we suggest the position of dry ice in the triboelectric series to be close to that of materials with stable cations and unstable anions, possibly locating it between PMMA and PVC.

scholarly journals Enhancement of microwave absorption bandwidth of MXene nanocomposites through macroscopic design

2020 ◽  
Vol 7 (8) ◽  
pp. 200456 ◽  
Author(s):  
Pritom J. Bora ◽  
T. R. Suresh Kumar ◽  
Daniel Q. Tan
Keyword(s):  
Microwave Absorption ◽  
Polymer Nanocomposites ◽  
Reflection Loss ◽  
The Other ◽  
Two Dimensional ◽  
Absorption Bandwidth ◽  
Hybrid Matrix ◽  
New Family ◽  
Two Dimensional Materials ◽  
First Time

MXene, the new family of two-dimensional materials having numerous nanoscale layers, is being considered as a novel microwave absorption material. However, MXene/functionalized MXene-loaded polymer nanocomposites exhibit narrow reflection loss (RL) bandwidth (RL less than or equal to −10 dB). In order to enhance the microwave absorption bandwidth of MXene hybrid-matrix materials, for the first time, macroscopic design approach is carried out for TiO 2 -Ti 3 C 2 T x MXene and Fe 3 O 4 @TiO 2 -Ti 3 C 2 T x MXene hybrids through simulation. The simulated results indicate that use of pyramidal meta structure of MXene can significantly tune the RL bandwidth. For optimized MXene hybrid-matrix materials pyramid pattern, the bandwidth enhances to 3–18 GHz. Experimental RL value well matched with the simulated RL. On the other hand, the optimized Fe 3 O 4 @TiO 2 -Ti 3 C 2 T x hybrid exhibits two specific absorption bandwidths (minimum RL value - −47 dB). Compared with other two-dimensional nanocomposites such as graphene or Fe 3 O 4 -graphene, MXene hybrid-matrix materials show better microwave absorption bandwidth in macroscopic pattern.

Cis-Trans Isomerization of Natural Rubber under the Influence of Organo-Aluminum Compounds and Titanium Tetrachloride

1959 ◽  
Vol 32 (4) ◽  
pp. 1036-1038 ◽  
Author(s):  
B. A. Dolgoplosk ◽  
E. N. Kropacheva ◽  
K. V. Nelson
Keyword(s):  
Natural Rubber ◽  
Ultraviolet Light ◽  
Titanium Tetrachloride ◽  
Chemical Properties ◽  
Regular Structure ◽  
Polymer Chains ◽  
Polymerization Process ◽  
Aluminum Compounds ◽  
Physical And Chemical ◽  
First Time

Abstract Ziegler catalysts have become of prime importance for synthesis of polymers with regular structure, particularly cis-polyisoprene. The disruption of the structure of the chain by the formation of trans units was, until now, connected only with the influence of the physical and chemical properties of the catalyst on the nature of the addition of the diene monomers during the polymerization process. In the present work it is shown that destruction of regularity of structure can be caused by isomerization of cis units in complete polymer chains into trans units under the influence of the compounds used for initiating the polymerization process. Attempts to isomerize natural rubber by means of ultraviolet light and iodine did not give the expected effect. Ferri established for the first time that under the influence of zinc chloride and titanium tetrachloride natural rubber undergoes changes accompanied by disappearence of crystallization on stretching as shown by x-ray structure analysis. On the basis of these results the authors presumed that under the influence of these agents isomerization of cis units to trans units occurs in the natural rubber chain. The isomerization of cis-1,4 units to trans units in polybutadiene by means of ultraviolet light in the presence of organic bromine or sulfur compounds was first accomplished and proved by Golub. The formation of trans units in natural rubber under similar conditions was not observed. The study of the isomerizing effect of TiCl4 and organo-aluminum compounds was conducted by us on solutions of milled natural rubber (NK) in benzene in sealed glass ampoules. The benzene used was dried and distilled over sodium. All work was conducted in an atmosphere of dry argon. Unsaturation and microstructure of the chain was determined on each sample. The study of microstructure of polyisoprenes was carried out by means of infrared spectra, the relative content of the different configurations of the polymer chain being determined by the absorption in the 800–1000 cm−1 region. The method previously developed by one of us was used for this purpose.

Development of a simple model to characterize the complex constrained polymer chains in polymer nanocomposites at the interphase of amorphous/semicrystalline ethylene vinyl acetate and nanosheets

2016 ◽  
Vol 51 (2) ◽  
pp. 179-186 ◽  
Author(s):  
Omid Yousefzade ◽  
Hamid Garmabi
Keyword(s):  
Simple Model ◽  
Polymer Nanocomposites ◽  
Vinyl Acetate ◽  
Volume Fraction ◽  
Expanded Graphite ◽  
Ethylene Vinyl Acetate ◽  
Analysis Data ◽  
Polymer Chains ◽  
Polymeric Nanocomposites ◽  
Dispersion State

A simple model was developed to characterize the constrained polymer chains at the interphase of amorphous/semicrystalline polymer nanocomposites based on ethylene vinyl acetate copolymer and some nanosheets such as expanded graphite, graphene and organo-modified montmorillonite. It was found that this method is a useful tool to describe the reinforcement efficiency of nanoparticles. Models were developed using dynamical mechanical thermal analysis data to identify the interphase properties. The volume fraction of constrained polymer chains shows power law relationship with filler content. Since the total volume fraction consists of the confined polymer chains at the surface of nanoparticles and in crystal lamellas, the contribution of nanosheet interphase was evaluated separately. Moreover, the thickness of constructed interphase between polymer chains and nanosheets were predicted using the filler characteristics in the polymer nanocomposites. This implies that the dispersion state of nanofiller in polymeric nanocomposites can be obtained by using this simple model.

The Role of Polymer-particle Interactions on the Viscoelastic Properties of Polymer Nanocomposites

2007 ◽  
Vol 1056 ◽  
Author(s):  
Alireza Sarvestani ◽  
Esmaiel Jabbari
Keyword(s):  
Polymer Nanocomposites ◽  
Volume Fraction ◽  
Molecular Model ◽  
Low Frequency ◽  
Maxwell Model ◽  
Equilibrium Structure ◽  
Polymer Chains ◽  
Spherical Particles ◽  
Filler Concentration ◽  
Adsorbed Polymer

ABSTRACTA molecular model is proposed for the dynamics of polymer chains in dilute polymer solutions containing well-dispersed spherical particles. In the presence of short range energetic affinity between the monomers and filler surface, the equilibrium structure of the adsorbed polymer layer is determined by a scaling theory. The viscoelastic response of the suspension is studied by a Maxwell model. It is shown that the solid-like properties of polymer nanocomposites in low frequency regimes could be attributed to the slowdown of the relaxation process of polymer chains. This process is controlled by the monomer-particle frictional interactions, density of the adsorbed polymer chains on the particles surface (controlled by monomer-particle adsorption energy), and volume fraction of the interfacial layer which can be enhanced by reduction of filler size or increasing the filler concentration.

Molecular insight into the Mullins effect: irreversible disentanglement of polymer chains revealed by molecular dynamics simulations

2017 ◽  
Vol 19 (29) ◽  
pp. 19468-19477 ◽  
Author(s):  
Chi Ma ◽  
Tuo Ji ◽  
Christopher G. Robertson ◽  
R. Rajeshbabu ◽  
Jiahua Zhu ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Molecular Model ◽  
Polymer Chains ◽  
Mullins Effect ◽  
Key Characteristics ◽  
Dynamics Simulations ◽  
First Time ◽  
Insight Into

For the first time, the key characteristics associated with the Mullins effect are captured by a molecular model.

Coupling Agents for Certain Types of Fluoroelastomers

1978 ◽  
Vol 51 (5) ◽  
pp. 897-906 ◽  
Author(s):  
J. W. Martin ◽  
T. V. Braswell ◽  
H. E. Green
Keyword(s):  
Molecular Weight ◽  
Coupling Agent ◽  
Coupling Agents ◽  
Low Molecular Weight ◽  
Mechanical And Thermal Properties ◽  
Effective Performance ◽  
Base Polymer ◽  
Service Conditions ◽  
Carbon Fillers ◽  
First Time

Abstract From the data presented in this paper, it is concluded that fillers can be coupled with certain types of fluoroelastomer base polymers. A useful coupling agent must have mechanical and thermal properties at least equivalent to the base polymer in order to provide an improvement in properties for the compound under extreme service conditions. For the particular case of peroxide-curable fluoroelastomers and carbon fillers, hydroxy-terminated low-molecular-weight polybutadienes with high 1,2-microstructure appear to be good coupling agents. Care must be exercised in selecting the peroxide level to obtain a high crosslink density of the coupling agent while retaining rubberlike properties of the compound. This type of polybutadienediol has a relatively high number of reactive vinyl groups (approximately 20 per molecule) and relatively high molecular weight. Based upon the hypotheses presented in this paper, that coupling between carbon black and fluoroelastomers has been demonstrated for the first time, both higher molecular weight and multifunctionality of the polybutadienediol are viewed as important characteristics for effective performance.

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