scholarly journals Enhancement of EPDM Crosslinked Elastic Properties by Association of Both Covalent and Ionic Networks

Polymers ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 3161
Author(s):  
Chloé Larrue ◽  
Véronique Bounor-Legaré ◽  
Philippe Cassagnau
Keyword(s):  
Metal Salts ◽  
Reversible Systems ◽  
Covalent Bonds ◽  
Long Period ◽  
Compression Set ◽  
Metallic Salts ◽  
Ionic Bonds ◽  
Physical And Chemical ◽  
Ethylene Propylene Diene Terpolymer ◽  
Physical Crosslinking

The objective of this study was to replace elastomer crosslinking based on chemical covalent bonds by reversible systems under processing. One way is based on ionic bonds creation, which allows a physical crosslinking while keeping the process reversibility. However, due to the weak elasticity recovery of such a physical network after a long period of compression, the combination of both physical and chemical networks was studied. In that frame, an ethylene-propylene-diene terpolymer grafted with maleic anhydride (EPDM-g-MA) was crosslinked with metal salts and/or dicumyl peroxide (DCP). Thus, the influence of these two types of crosslinking networks and their combination were studied in detail in terms of compression set. The second part of this work was focused on the influence of different metallic salts (KOH, ZnAc2) and the sensitivity to the water of the physical crosslinking network. Finally, the combination of ionic and covalent network allowed combining the processability and better mechanical properties in terms of recovery elasticity. KAc proved to be the best ionic candidate to avoid water degradation of the ionic network and then to preserve the elasticity recovery properties under aging.

First-Principles Study of Ag3Sn, AgZn3 and Ag5Zn8 Intermetallic Compounds

2021 ◽  
Vol 871 ◽  
pp. 254-263
Author(s):  
Zhan Cheng ◽  
Guan Xing Zhang ◽  
Wei Min Long ◽  
Svitlana Maksymova ◽  
Jian Xiu Liu
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Elastic Anisotropy ◽  
Constant Density ◽  
Mulliken Population ◽  
Covalent Bonds ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Anisotropy Index ◽  
Ionic Bonds

The first-principles calculations by CASTEP program based on the density functional theory is applied to calculate the cohesive energy, enthalpy of formation, elastic constant, density of states and Mulliken population of Ag3Sn、AgZn3 and Ag5Zn8. Furthermore, the elastic properties, bonding characteristics, and intrinsic connections of different phases are investigated. The results show that Ag3Sn、AgZn3 and Ag5Zn8 have stability structural, plasticity characteristics and different degrees of elastic anisotropy; Ag3Sn is the most stable structural, has the strongest alloying ability and the best plasticity. AgZn3 is the most unstable structure, has the worst plasticity; The strength of Ag5Zn8 is strongest, AgZn3 has the weakest strength, the largest shear resistance, and the highest hardness. Ag5Zn8 has the maximum Anisotropy index and Ag3Sn has the minimum Anisotropy index. Ag3Sn、AgZn3 and Ag5Zn8 are all have covalent bonds and ionic bonds, the ionic bonds decrease in the order Ag3Sn>Ag5Zn8>AgZn3 and covalent bonds decreases in the order Ag5Zn8>Ag3Sn>AgZn3.

scholarly journals GREEN SYNTHESIS OF PLANT-MEDIATED METAL NANOPARTICLES: THE ROLE OF POLYPHENOLS

2019 ◽  
pp. 75-84 ◽  
Author(s):  
LATIF MS ◽  
ABBAS S ◽  
KORMIN F ◽  
MUSTAFA MK
Keyword(s):  
Metal Nanoparticles ◽  
Biomedical Applications ◽  
Cost Effective ◽  
Metal Salts ◽  
Chemical Methods ◽  
Physical And Chemical ◽  
Labor Consuming ◽  
Day By Day ◽  
Biological Actions

The use of metal nanoparticles (MNPs) in various fields is increasing day-by-day leading to a genuine concern about the issues related to their environmental and biological safety. The major approaches for the synthesis of NPs include physical and chemical methods which are expensive and hazardous to health in addition to being toxic to the environment. This review highlights the potential of plant extracts to carry out the synthesis of MNPs with a special emphasis on the role of flavonoids in nanosynthesis. This green and clean approach have been actively utilized in recent years as an alternative to conventional hazardous approaches. It has proved as cost-effective, non-toxic, less time and labor consuming, efficient, and eco-friendly method for the synthesis of MNPs with specific biological actions. This review also focuses on the role of polyphenols, including the flavonoids as bioreductants of metal salts for the synthesis of NPs along with their biomedical applications. Various examples of the MNPs, along with their biological actions, have also been summarized.

Spectral Investigations Concerning the Degradation Degree of Romanian Historical Leather

2009 ◽  
Vol 415 ◽  
pp. 45-48 ◽  
Author(s):  
Maria Giurginca ◽  
Lucretia Miu
Keyword(s):  
Environmental Factors ◽  
Chemical Characteristics ◽  
Comprehensive Investigation ◽  
Spectral Techniques ◽  
Long Period ◽  
Physical And Chemical Characteristics ◽  
Historical Leather ◽  
Degradation Degree ◽  
Physical And Chemical

A comprehensive investigation has been made of a set of historical leather samples from the 17th – 20th centuries. For the investigation of the degradation degree spectral techniques in IR (MID and NIR) and UV-VIS have been used, and collateral Micro Hot Table (MHT) determination as well. Changes in the physical and chemical characteristics values of the leather issues due to the interaction with the environmental factors during a long period of time were used in order to identify the possible deterioration ways.

Alternatives to free molecular halogens as chemoselective reactants: Catalysis of organic reactions with reusable complexes of halogen metal salts

2012 ◽  
Vol 84 (3) ◽  
pp. 819-826 ◽  
Author(s):  
Laura I. Rossi ◽  
Manuel I. Velasco
Keyword(s):  
Organic Compounds ◽  
Organometallic Complexes ◽  
Organic Ligands ◽  
Organic Reactions ◽  
Metal Salts ◽  
Metallic Salts ◽  
Oxidation Of Organic Compounds ◽  
Reaction Media

Organometallic complexes of halogen metallic salts have been used as catalysts in different organic reactions, mainly the oxidation of organic compounds. Their use has not only allowed the reduction of the amounts of catalyst (since they can be reused) but also a lower generation of byproducts and wastes. The different reaction media developed through the research were analyzed by several green parameters, and the best results were obtained with complexes that have cyclodextrins as organic ligands. The proposed methodology is an alternative to use of molecular halogen as oxidant or catalyst when halogens are significant chemoselective reactants.

The Influence of Nanostructured Metal Oxides and Unsaturated Acids on Peroxide Cross-Linking of Ethylene-Octene Rubber

2012 ◽  
Vol 714 ◽  
pp. 271-276 ◽  
Author(s):  
Martyna Pingot ◽  
Tomasz Pingot ◽  
Magdalena Maciejewska ◽  
Marian Zaborski
Keyword(s):  
Metal Oxides ◽  
Sem Images ◽  
Covalent Bonds ◽  
Dispersion Degree ◽  
Link Density ◽  
Ionic Bonds ◽  
Density Analysis ◽  
Elastomer Composites ◽  
Nanostructured Metal Oxides ◽  
Nanostructured Metal

This paper deals with blends of ethylene-octene rubber (POE) with nanostructured metal oxides: magnesium oxide (MgO), calcium oxide (CaO), zinc oxide (ZnO) and unsaturated acids: itaconic acid (IA), sorbic acid (SA) and crotonic acid (CA), as co-agents. Dicumyl peroxide (DCP) was used as a vulcanizing agent. Elastomer composites were prepared in Brabender measuring mixer N50. Rheometric properties of rubber mixes and crosslink density of vulcanizates were measured. Mechanical properties of the samples were also investigated. Dispersion degree of coagents in elastomer matrix was studied by SEM images. Cross-link density analysis revealed that POE vulcanizates contained both ionic bonds and covalent bonds. The results showed that the nanostructured metal oxides and unsaturated acids used as co-agents can greatly improve the modulus at 100% of elongation and tensile strength of the vulcanizates.

scholarly journals First principle study of occupancy, bonding characteristics and alloying effect of Zr, Nb, V in bulk γ-Fe(C)

2020 ◽  
Vol 213 ◽  
pp. 01019
Author(s):  
Fei Liu ◽  
Shan Cong ◽  
Long Hao
Keyword(s):  
Solid Solution ◽  
Covalent Bond ◽  
Alloy Element ◽  
Chemical Bonds ◽  
Covalent Bonds ◽  
Binding Characteristics ◽  
Crystal Cell ◽  
Ionic Bonds ◽  
Crystal Cells ◽  
Bonding Characteristics

The total energy, binding characteristics, density of states, charge distribution and differential charge density of γ-Fe(C)-M crystal cells formed by solid solution of Zr, Nb and V in γ-Fe(C) were calculated by using the first-principles method. Thus, the mechanism of Zr, Nb, and V with γ-Fe(C) was investigated in this paper. The results show that Zr, Nb and V all preferentially replaced the Fe atoms which are at the top angle in γ-Fe(C). Crystal cell reaches its highest stability after V solid solution. Nb reaches after it, and Zr is relatively weak. In the γ-Fe(C)-Zr cell, Fe-Zr covalent bond and Zr-C ionic bond are the main chemical bonds. In the γ-Fe(C)-Nb and γ-Fe(C)-V cells, Fe-Nb and Fe-V covalent bonds are the main chemical bonds with a number of Nb-C and V-C ionic bonds. After solid solution, the electron cloud density around C atom changed little, while Fe atom changed obviously. The orbital electrons around Fe atoms in γFe(C)-V has maximal distribution, which means that the electrons delocalized most and most of the electrons are bonding. It is the main factor for the increase in the binding energy of crystal cell. The effects of Zr, Nb, V solution on austenitic stability are investigated by studying the influence of alloy element on γFe(C) electronic structure.

scholarly journals Demonstrating Bonds and Forces: From Nitrogen to Nanotubes

2013 ◽  
pp. 79-89
Keyword(s):  
Hydrogen Bonds ◽  
Covalent Bonds ◽  
Dipole Interactions ◽  
Ionic Bonds

In this exercise students will study chemical forces such as covalent bonds, ionic bonds, ion-dipole interactions and hydrogen bonds.

scholarly journals From Structure to Atoms: Compression/Tension Systems to a Molecular Tensegrity

Leonardo ◽  
2021 ◽  
pp. 1-11
Author(s):  
J. David Van Horn ◽  
Dayu Wang
Keyword(s):  
Subunit Structure ◽  
Particle Interactions ◽  
Covalent Bonds ◽  
Architectural Engineering ◽  
Macroscopic Structure ◽  
Ionic Bonds ◽  
Tension And Compression ◽  
Structural Analogy ◽  
Molecular Bonding ◽  
Tension Members

Abstract We reconsider macroscopic structure, including tensegrity structures, as ensembles of compression (C; repulsion) and tension (T; attraction) forces, and fit them to a triangular spectrum. Then, derivative structural analogy is made to the three classes of molecular bonding, as a bridge to microscopic structure. Basic molecular interactions and their “C/T” analogues are ionic bonds (with continuous compression/discontinuous tension), or metallic bonds (with both continuous tension and compression), or covalent bonds (with discontinuous compression/continuous tension—a tensegrity structure). The construction of tensegrity sculptures of particle interactions and the covalent molecules dihydrogen, methane, diborane, and benzene using tension and compression elements follows. We derived and utilized two properties in this analysis: 1) a “simplest tensegrity” subunit structure and 2) interpenetrating, discontinuous compressive members—tension members may also be discontinuous. This approach provides new artistic models for molecules and materials, and may inform future artistic, architectural, engineering and scientific endeavors.

Calculation of the BO3 triangle to BO4 tetrahedron ratio in borates

2002 ◽  
Vol 217 (5) ◽  
Author(s):  
E. Parthé
Keyword(s):  
Crystal Structures ◽  
Composition Range ◽  
Chemical Formula ◽  
Covalent Bonds ◽  
Oh Groups ◽  
Proper Number ◽  
Anion Complex ◽  
Ionic Bonds ◽  
Complex Forms ◽  
Covalently Bound

AbstractA bonding model, valid for alimited group of borates, is formulated which allows the ratio of triangularly to tetrahedrally coordinated B atoms to be calculated from the chemical formula. The anion complex, which is formed by covalently bound atoms, has non-directed ionic bonds with the surrounding cations. To complete its electron octet, each O atoms of the complex forms exactly two covalent bonds either with 2 B and/or with 1 B and 1 H atom, depending on the number of OH groups. The B atoms have no preference for either triangular or tetrahedral O coordination. However, a change of a B-O base triangle to an isoelectronic base tetrahedron decreases the number of O atoms which can be used for B-O-H bonds and increases the number of shared O atoms engaged in B-O-B bonds - and vice versa. The ratio of B-O triangles to tetrahedra is adjusted such that O atoms can form the proper number of B-O-B and/or B-O-H bonds. Using the model one can also prove that a borate with OH groups and all its dehydration products (independent whether they are crystallized or a glass) should have the same ratio of three- to four-coordinated B atoms. Under the presupposition that the bonding model is applicable, one can specify a simple mixture of base triangles and/or base tetrahedra with which it should be possible to construct an anion complex. The observed complex is either built up with this simple mixture or with a mixture of base polyhedra derived from the simple one by cross-substitution which does not change the triangle to tetrahedron ratio. The realization of the bonding model is in principle possible only within a restricted composition range in which lie one quarter of the known borates. The equation to calculate the triangle to tetrahedron ratio has been tested on all borates within this range. An agreement was found for 85 percent of the 222 investigated crystal structures.

Subplasticity in Australian soils. V. Factors involved and techniques of dispersion

Soil Research ◽  
1976 ◽  
Vol 14 (3) ◽  
pp. 273 ◽  
Author(s):  
K Norrish ◽  
KG Tiller
Keyword(s):  
New South ◽  
New South Wales ◽  
South Australia ◽  
Aggregate Stability ◽  
Clay Particles ◽  
South Wales ◽  
Montmorillonite Clays ◽  
Ionic Bonds ◽  
Almost All ◽  
Physical And Chemical

The subplastic soils studied were two from the Riverina area of New South Wales, two montmorillonite rich clays formed on basalt, from South Australia and Queensland, and a krasnozem from New South Wales. To assess the effectiveness of physical and chemical methods of dispersion, theoretical clay contents were calculated from the ratio of the CEC of the soil to that of separated clay. The composition of the clay from the soils showed little or no change with degree of dispersion. To disperse the soils without chemical pretreatment, a method of disaggregation was devised that involved vigorous shaking of a soil paste. Following this technique the Riverina soils and the krasnozem yielded almost all their clay. Lithium saturation was the only chemical treatment that aided dispersion of the montmorillonite clays, and this, together with the high tetrahedral lattice charge, suggests that aggregate stability is mainly due to a large electrostatic interaction between clay sheets. Any pretreatments involving the use of sodium hydroxide improved clay yields for the Riverina soils. The data indicated that the loss of subplasticity was accompanied by the solution of clay, suggesting that aggregate stability was due to non-ionic bonds between clay particles, possibly as the result of intergrowth of clay mineral crystals. Organic matter and/or free iron oxide was responsible for cementation of the krasnozem.

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