The Role of Intermolecular Forces in the Mechanism of High Elastic Deformation. II. Relaxation Properties of Natural Rubber and Its Bromination Products

1951 ◽  
Vol 24 (1) ◽  
pp. 99-108
Author(s):  
B. Dogadkin ◽  
M. Reznikovskii˘
Keyword(s):  
Natural Rubber ◽  
Elastic Deformation ◽  
Intermolecular Forces ◽  
Relaxation Properties

Relaxation Processes in the Deformation of Unloaded Rubbers and the Influence of the Degree of Vulcanization

1951 ◽  
Vol 24 (4) ◽  
pp. 810-819
Author(s):  
B. A. Dogadkin ◽  
M. M. Reznikovskii˘
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Elastic Deformation ◽  
Relaxation Processes ◽  
Spatial Network ◽  
Relaxation Properties ◽  
Constant Rate ◽  
Different Temperatures ◽  
Kinetics Of

Abstract 1. It is shown that the process of stress relaxation at different initial elongations as well as the process of deformation at constant rate for unloaded rubbers at different temperatures (20–70° C) can be represented quantitatively by equations suggested in earlier works. Likewise the possibility of expanding the theories proposed for the kinetics of high-elastic deformation of spatial polymers is substantiated. 2. It is shown that the relaxation properties of soft unloaded vulcanizates of natural rubber and many synthetic rubbers do not undergo essential changes during vulcanization. 3. The conjecture is expressed that the invariability of the relaxation properties during vulcanization continues until the bonds of the spatial network are distributed sufficiently widely not to influence the activity or heat movement of the chain segments between them.

The Role of Intermolecular Forces in the Mechanism of High-Elastic Deformation. I. The Molecular Mechanism and an Equation for the Kinetics of High Elastic Deformation

1951 ◽  
Vol 24 (2) ◽  
pp. 336-343
Author(s):  
B. A. Dogadkin ◽  
G. M. Bartenev ◽  
M. M. Reznikovskii˘
Keyword(s):  
Molecular Structure ◽  
Molecular Mechanism ◽  
Elastic Deformation ◽  
Approximate Equation ◽  
Intermolecular Forces ◽  
Joint Application ◽  
Balanced Configurations ◽  
Kinetics Of ◽  
Constant Deformation

Abstract 1. The molecular mechanism of the relaxation of deformation of high-elastic polymers has been studied. 2. It is shown that the slow relaxation, which is typical of high-elastic polymers, may be best explained as a restoration process, which either partial or complete (depending on the degree of development of side chains in the molecular structure formed by the main valence chains) of the balanced configurations of the molecular chains. 3. It is shown that the rate of the relaxation process in this case is determined by the molecular activity of the particular polymer. 4. An approximate equation for the kinetics of high-elastic deformation which expresses qualitatively the mechanical properties of high-elastic polymers is proposed. 5. Hypotheses concerning the relation between the time of relaxation and the unbalanced stress are advanced. Equation (2) is derived as characteristic of this relation. 6. It is shown that the joint application of Equations (1) and (2) makes it possible to describe qualitatively the relaxation of stress at constant deformation.

Investigation of the Role of Intermolecular Forces in the Mechanism of High-Elastic Deformation. VII. The Effect of Molecular Interaction on the Fatigue Resistance of High Polymers Having Highly Developed Spatial Structures

1954 ◽  
Vol 27 (2) ◽  
pp. 363-373
Author(s):  
V. E. Gul ◽  
D. L. Fedyukin ◽  
B. A. Dogadkin
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Fatigue Resistance ◽  
Dibutyl Phthalate ◽  
Intermolecular Forces ◽  
Spatial Structures ◽  
Paraffin Oil ◽  
Degree Of Swelling ◽  
Natural Rubber Vulcanizates

Abstract It is shown experimentally that an irregular change of the fatigue resistance of loaded natural-rubber vulcanizates with increase of the degree of swelling in paraffin oil and in dibutyl phthalate is caused by the superposition of two processes: the increase of fatigue resistance, as a result of the reduction of mechanical losses, and the decrease of fatigue resistance due to the decrease of tensile strength proportional to the higher degree of swelling.

The Role of Intermolecular Forces in the Mechanism of High Elastic Deformation. III. Effect of Swelling on the Mechanical Properties of Vulcanized Rubber

1951 ◽  
Vol 24 (2) ◽  
pp. 344-353
Author(s):  
B. A. Dogadkin ◽  
V. Gul
Keyword(s):  
Elastic Deformation ◽  
Relative Elongation ◽  
Intermolecular Forces ◽  
Deformation Curves ◽  
Vulcanized Rubber ◽  
Maximum Value ◽  
Maximum Time ◽  
Gaseous Media ◽  
Mechanical Investigation

Abstract 1. The construction of an apparatus (elastometer) for the mechanical investigation of high elastic substances is described. This apparatus makes it possible to draw deformation curves and curves of the relaxation of stress atconstant temperature and in different gaseous media, and also to investigate the life at multiple deformations. The sensitivity of the apparatus is: ΔP=0.01 g., Δl=0.01 cm. 2. The molecular weight of the segments of the chains between the bonds of the spatial network of the vulcanizate, calculated by means of Flory's equation, increases with swelling, and approaches a certain maximum value. This is evidence of the rupture of the local intermolecular bonds on swelling. 3. The maximum time of relaxation, calculated according to the equation of Dogadkin, Bartenev, and Reznikovskil, as a consequence of swelling, generally does not change uniformly; it decreases with swelling of natural rubbers in benzene and chloroform in the initial stages, then increases, and finally decreases again in the last stages of swelling. 4. An increase of temperature displaces the minimum times of relaxation to lower degrees of swelling. 5. The increase of the maximum time of relaxation as a result of swelling causes a decrease of the life of the vulcanizate; a decrease of this factor is accompanied, at least within certain limits, by an increase of life. 6. Swelling causes a decrease of tensile strength and of the relative elongation of vulcanizates. 7. The changes recorded above in the equilibrium and kinetic characteristics of high elastic deformation are explained by the presence in the vulcanizate of different intermolecular bonds.

scholarly journals Influence of the Electrolyte Salt Concentration on DNA Detection with Graphene Transistors

Biosensors ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 24
Author(s):  
Agnes Purwidyantri ◽  
Telma Domingues ◽  
Jérôme Borme ◽  
Joana Rafaela Guerreiro ◽  
Andrey Ipatov ◽  
...  
Keyword(s):  
Phosphate Buffer ◽  
Species Interactions ◽  
Field Effect ◽  
Field Effect Transistors ◽  
Limit Of Detection ◽  
Debye Length ◽  
Intermolecular Forces ◽  
Single Layer Graphene ◽  
Dna Adsorption

Liquid-gated Graphene Field-Effect Transistors (GFET) are ultrasensitive bio-detection platforms carrying out the graphene’s exceptional intrinsic functionalities. Buffer and dilution factor are prevalent strategies towards the optimum performance of the GFETs. However, beyond the Debye length (λD), the role of the graphene-electrolytes’ ionic species interactions on the DNA behavior at the nanoscale interface is complicated. We studied the characteristics of the GFETs under different ionic strength, pH, and electrolyte type, e.g., phosphate buffer (PB), and phosphate buffer saline (PBS), in an automatic portable built-in system. The electrostatic gating and charge transfer phenomena were inferred from the field-effect measurements of the Dirac point position in single-layer graphene (SLG) transistors transfer curves. Results denote that λD is not the main factor governing the effective nanoscale screening environment. We observed that the longer λD was not the determining characteristic for sensitivity increment and limit of detection (LoD) as demonstrated by different types and ionic strengths of measuring buffers. In the DNA hybridization study, our findings show the role of the additional salts present in PBS, as compared to PB, in increasing graphene electron mobility, electrostatic shielding, intermolecular forces and DNA adsorption kinetics leading to an improved sensitivity.

scholarly journals Biocomposites of Epoxidized Natural Rubber/Poly(lactic acid) Modified with Natural Fillers (Part I)

2021 ◽  
Vol 22 (6) ◽  
pp. 3150
Author(s):  
Anna Masek ◽  
Stefan Cichosz ◽  
Małgorzata Piotrowska
Keyword(s):  
Tensile Strength ◽  
Lactic Acid ◽  
Natural Rubber ◽  
Epoxidized Natural Rubber ◽  
Poly Lactic Acid ◽  
Uv Aging ◽  
High Elasticity ◽  
Natural Fillers ◽  
Natural Additives

The study aimed to prepare sustainable and degradable elastic blends of epoxidized natural rubber (ENR) with poly(lactic acid) (PLA) that were reinforced with flax fiber (FF) and montmorillonite (MMT), simultaneously filling the gap in the literature regarding the PLA-containing polymer blends filled with natural additives. The performed study reveals that FF incorporation into ENR/PLA blend may cause a significant improvement in tensile strength from (10 ± 1) MPa for the reference material to (19 ± 2) MPa for the fibers-filled blend. Additionally, it was found that MMT employment in the role of the filler might contribute to ENR/PLA plasticization and considerably promote the blend elongation up to 600%. This proves the successful creation of the unique and eco-friendly PLA-containing polymer blend exhibiting high elasticity. Moreover, thanks to the performed accelerated thermo-oxidative and ultraviolet (UV) aging, it was established that MMT incorporation may delay the degradation of ENR/PLA blends under the abovementioned conditions. Additionally, mold tests revealed that plant-derived fiber addition might highly enhance the ENR/PLA blend’s biodeterioration potential enabling faster and more efficient growth of microorganisms. Therefore, materials presented in this research may become competitive and eco-friendly alternatives to commonly utilized petro-based polymeric products.

Role of Intermolecular Forces in Defining Material Properties of Protein Nanofibrils

Science ◽  
2007 ◽  
Vol 318 (5858) ◽  
pp. 1900-1903 ◽  
Author(s):  
T. P. Knowles ◽  
A. W. Fitzpatrick ◽  
S. Meehan ◽  
H. R. Mott ◽  
M. Vendruscolo ◽  
...  
Keyword(s):  
Material Properties ◽  
Intermolecular Forces

Radical Mechanisms in Saturated and Olefinic Systems. II. Disubstitutive Carbon-Carbon Cross-Linking by Tertiary Alkoxy Radicals in Isoprenic Olefins and Rubber

1951 ◽  
Vol 24 (4) ◽  
pp. 777-786
Author(s):  
E. H. Farmer ◽  
C. G. Moore
Keyword(s):  
Natural Rubber ◽  
Cross Linking ◽  
Chain Molecules ◽  
Alkoxy Radicals ◽  
Full Extent ◽  
Carbon Chains ◽  
Butyl Peroxide ◽  
High Degree ◽  
Vulcanization Process

Abstract The high degree of dehydrogenation effected by tert.-butoxy radicals at the α-methylenic groups of olefins enables these radicals to be used for the carbon-to-carbon cross-linking of unsaturated carbon chains, and especially of the polyisoprenic chains of natural rubber. Such cross-linking amounts to a vulcanization process in which the connecting links between chain molecules are just C—C bonds, which may be expected to have appropriate attributes. An examination has first been made of the cross-linking produced by tert.- butoxy radicals (from di-tert.-butyl peroxide) at 140° between the short iso-prenic chains in 1-methylcyclohexene, 4-methylhept-3-ene, 2,6-dimethylocta-2, 6-diene, and digeranyl. Cross-linking proceeds efficiently in each case, and the points of union in these isoprene units which become directly joined are not confined to original α-methylenic carbon atoms. Where the reagent radicals are in considerable deficit, e.g., one per two or three of the isoprene units present, those olefin molecules which are attacked become linked together mostly by single unions to form aggregates containing two, three or four molecules; but in the tetraisoprenic olefins the extent to which more than one union is formed between some of the directly linked molecules becomes appreciable. In natural rubber, cross-linking occurs smoothly and to nearly the full extent corresponding to the (in practice restricted) proportion of peroxidic reagent employed. Good vulcanizates can be so obtained in which the tensile stength is found to increase towards a maximum and then to decline rapidly as the degree of cross-linking steadily increases. Thus to obtain vulcanizates of the optimum physical characteristics, the degree of cross-linking must be suitably chosen. The role of the peroxidic reagent is almost entirely non-additive and non-degradative.

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