Carbon Black Structure in Rubber

1963 ◽  
Vol 36 (1) ◽  
pp. 147-155 ◽  
Author(s):  
A. R. Payne ◽  
W. F. Watson
Keyword(s):  
Carbon Black ◽  
Dynamic Properties ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Organic Liquids ◽  
Carbon Blacks ◽  
Metal Soaps ◽  
Dispersing Medium ◽  
Structural Carbon ◽  
Filler Structure

Abstract Some of the properties of carbon blacks in rubber are ascribed to its “structure”. This paper presents results on the sinusoidal dynamic straining of rubber/carbon black vulcanizates over an amplitude range including strains less than 0.1% and suggests that an elucidation of structure effects and the nature of the structure underlying them is forthcoming from these results. The dynamic properties are profoundly modified by special processing. Heat treatment of stocks containing structural carbon blacks and particularly the use of N-methyl-N,4-dinitrosoaniline can greatly reduce structure effects. They are absent with attrited blacks. Similar results have been obtained with silica fillers, for which certain metal soaps virtually eliminate structure effects. Structure effects are shown to be not essentially related to the rubber network, including the type of rubber, but to be due to a physical, three-dimensional structure of the filler itself within the rubber; the rubber acts merely as a dispersing medium and a matrix to allow the filler structure to re-form after breakdown. These changes of the filler structure are often the major cause of hysteresis at low extensions. Mixtures of carbon black and organic liquids demonstrate the existence and properties of the physical carbon black structure in absence of rubber. The properties of the rubber have the structural effects of the filler superimposed upon them.

Strain-Dependent Dynamic Properties of Carbon-Black Reinforced Vulcanizates. II. Elastomer Blends

1975 ◽  
Vol 48 (1) ◽  
pp. 89-96 ◽  
Author(s):  
A. K. Sircar ◽  
T. G. Lamond
Keyword(s):  
Carbon Black ◽  
Dynamic Properties ◽  
Three Dimensional ◽  
Individual Characteristics ◽  
The Individual ◽  
Dispersing Medium ◽  
Polymeric Medium ◽  
Strain Dependent ◽  
Filler Structure ◽  
Predominant Effect

Abstract The three-dimensional aggregated structure of carbon black in elastomer blends behaves in a similar fashion to that of the individual elastomers. The elastomer seems to act merely as a dispersing medium. The properties of the rubber reflect the structural effects of the filler superimposed upon the elastomer itself. The elastomer molecules no doubt retain their individual characteristics of rotation of bonds which govern the stiffness of the molecule. However, the superimposed carbon-black network exerts the predominant effect, as far as the low-strain dynamic characteristics are concerned. The polymeric medium seems to influence this interaction by determining the magnitude of agglomeration and distribution of black in the phases, but does not have visible influence on the overall characteristics of the carbon-black networks. In this respect blends of two elastomers behave as a single elastomer. The importance of the present work is that the strain-dependent dynamic properties of blends of elastomers are very similar to those of single elastomers. In tires and antivibration applications, the strain imposed is usually less than 10%. More and more blends of elastomers are being used for these applications. The filler structure and its breakdown at these strains have an important contribution to hardness, modulus, and hysteresis of these compounds.

Low Strain Dynamic Properties of Filled Rubbers

1971 ◽  
Vol 44 (2) ◽  
pp. 440-478 ◽  
Author(s):  
A. R. Payne ◽  
R. E. Whittaker
Keyword(s):  
Carbon Black ◽  
Dynamic Properties ◽  
Fatigue Behavior ◽  
Van Der Waals ◽  
Three Dimensional ◽  
Solid Particles ◽  
Spherical Particles ◽  
Filled Rubber ◽  
Secondary Network ◽  
Filled Rubbers

Abstract Carbon black does not exist as single spherical particles but forms itself into a rodlike primary structure. These rodlike structures then form into an aggregated secondary network. This secondary network is believed to be held together by Van der Waals-London attraction forces. The decrease in shear modulus of filled rubber vulcanizates with strain is due almost certainly to these secondary forces. Special mixing techniques such as attrition of the carbon black, increased time of mixing, or the addition of chemical promoters which aim at dispersing the carbon black within the mix better are shown to decrease the value of G′0−G′∞. The absence of any modulus change with strain for unfilled vulcanizates and secondly the little change observed in values of G′0−G′∞ with increasing vulcanization of the rubber when containing the same amount of carbon black confirms that the decrease in modulus with strain amplitude is in no way associated with the gum phase of the filled vulcanizate. The similarity in behavior of carbon black filled rubbers with clay/water and clay/rubber systems indicates that the decrease in modulus with amplitude is due to the breakdown of the three dimensional filler aggregates. A number of rheological studies on clay systems has confirmed that clay particles form into rigid three dimensional structures when dispersed in a medium. Evidence for the aggregated filler structure to be held together by Van der Waals-London attraction forces comes from the reasonable agreement between the experimental values for the forces required to breakdown the carbon black aggregates in paraffin oil and the forces calculated from Van den Tempel's model for flocculated solid particles in a liquid. The successful application of a domain model to the hysteretical behavior exhibited by carbon black filled vulcanizates at low strains indicates that the carbon black structure breaks down under stress but reforms to the original state when the stress is removed. This conclusion is also supported by the similarity in behavior between filled rubbers and a dendritic crystal structure of PBNA in rubber. Under the optical microscope the PBNA is seen to break down and reform under a stress-strain cycle. The breakdown and reformation of this secondary aggregated carbon black structure increases the hysteresis in filled rubber vulcanizates. Other sources of hysteresis include viscoelasticity of the polymer, crystallization, stress-softening, and changes in network structure (e.g., breakage of weak crosslinks). These mechanisms have been discussed in depth in previous publications. Recent work has shown, however, that the strength of a rubber is dependent on the combined effect of the different hysteretical mechanisms. The breakdown and reformation of the carbon black structure at low strains in filler reinforced rubbers therefore not only affects the heat build up, transmissibility, and fatigue behavior but also influences the failure properties of the filled vulcanizate.

Interaction between Carbon Black and Polymer in Cured Elastomers

1951 ◽  
Vol 24 (3) ◽  
pp. 597-615
Author(s):  
R. S. Stearns ◽  
B. L. Johnson
Keyword(s):  
Molecular Weight ◽  
Carbon Black ◽  
Chemical Bonding ◽  
Physical Adsorption ◽  
Three Dimensional ◽  
Physical Property ◽  
Carbon Black Particle ◽  
Low Molecular Weight ◽  
Carbon Blacks ◽  
Black Particle

Abstract This research was initiated to determine whether the interaction at the interface between the surface of finely divided solids, such as carbon black, and cured elastomers is primarily physical or chemical in nature. Further, it was desired to correlate some physical property of the reinforced stock with the surface properties of the solid pigment. Through an examination of the thermodynamic changes accompanying the deformation of loaded stocks it is shown that physical adsorption of the van der Waals type occurring at the interface between pigment and polymer is inadequate to account for the experimental observations. However, if chemical bonding occurs at the interface between polymer and pigment, then the entropy of deformation of the stock may be correlated with the extent of this bonding. By a calorimetric method it was demonstrated that the surface of a carbon black particle contains sites that react with bromine to liberate the same amount of heat as low molecular-weight olefins. It is, therefore, proposed that a carbon black particle be considered as a disordered agglomerate of polymeric benzenoid type molecules which contain around their perimeters various functional groups. The existence of olefinic-type unsaturation on the surface of carbon blacks suggests strongly that, in the case of carbon blacks, the polymer and pigment are combined chemically through pigment-sulfur-polymer bonds into a continuous three-dimensional cross-linked matrix.

Structure of recombinant human lactoferrin expressed in Aspergillus awamori

1999 ◽  
Vol 55 (2) ◽  
pp. 403-407 ◽  
Author(s):  
Xiao-Lin Sun ◽  
Heather M. Baker ◽  
Steven C. Shewry ◽  
Geoffrey B. Jameson ◽  
Edward N. Baker
Keyword(s):  
Dynamic Properties ◽  
Release Kinetics ◽  
Three Dimensional ◽  
Strain Improvement ◽  
Human Lactoferrin ◽  
Aspergillus Awamori ◽  
Dimensional Structure ◽  
Iron Release ◽  
High Level ◽  
Chain Conformations

Human lactoferrin (hLf) has considerable potential as a therapeutic agent. Overexpression of hLf in the fungus Aspergillus awamori has resulted in the availability of very large quantities of this protein. Here, the three-dimensional structure of the recombinant hLf has been determined by X-ray crystallography at a resolution of 2.2 Å. The final model, comprising 5339 protein atoms (residues 1–691, 294 solvent molecules, two Fe3+and two CO_3^{2-} ions), gives an R factor of 0.181 (free R = 0.274) after refinement against 32231 reflections in the resolution range 10–2.2 Å. Superposition of the recombinant hLf structure onto the native milk hLf structure shows a very high level of correspondence; the main-chain atoms for the entire polypeptide can be superimposed with an r.m.s. deviation of only 0.3 Å and there are no significant differences in side-chain conformations or in the iron-binding sites. Dynamic properties, as measured by B-value distributions or iron-release kinetics, also agree closely. This shows that the structure of the protein is not affected by the mode of expression, the use of strain-improvement procedures or the changes in glycosylation due to the fungal system.

Filler-Elastomer Interactions. Part VIII. The Role of the Distance between Filler Aggregates in the Dynamic Properties of Filled Vulcanizates

1993 ◽  
Vol 66 (2) ◽  
pp. 178-195 ◽  
Author(s):  
Meng-Jiao Wang ◽  
Siegfried Wolff ◽  
Ewe-Hong Tan
Keyword(s):  
Gas Chromatography ◽  
Carbon Black ◽  
Inverse Gas Chromatography ◽  
Dynamic Properties ◽  
Random Packing ◽  
Attractive Potential ◽  
Carbon Blacks ◽  
Filled Rubber ◽  
Tan Δ

Abstract Based on the concepts of the occlusion of rubber and random packing of spheres whose volume is equivalent to that permeated by individual aggregates, an equation was deduced to estimate the distance between carbon-black aggregates in filled rubber. It was found that when the interaggregate distance reaches a critical point which is approximately identical for all carbon blacks investigated (furnace blacks), the elastic modulus measured at very low strain deviates from the modified Guth-Gold equation. Tan δ and resilience are mainly determined by the distance between aggregates. These phenomena are related to filler networking which is determined by the attractive potential and the distance between individual aggregates. Since the factor Sf, used to characterize the strength of secondary filler networks in hydrocarbon rubbers and measured by means of inverse gas chromatography, is approximately the same for all furnace blacks, the interaggregate distance seems to determine filler networking. A comparison of fillers with different Sf (graphitized vs. nongraphitized carbon blacks, carbon black vs. silica) shows that at the same interaggregate distance, a lower Sf leads to higher tan δ of the filled vulcanizates.

scholarly journals Cryo-EM structure of the bacterial actin AlfA reveals unique assembly and ATP-binding interactions and the absence of a conserved subdomain

2017 ◽  
Author(s):  
Gulsima Usluer ◽  
Frank Dimaio ◽  
Shunkai Yang ◽  
Jesse M. Hansen ◽  
Jessica K. Polka ◽  
...  
Keyword(s):  
Quaternary Structure ◽  
Dynamic Properties ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Atp Binding ◽  
Evolutionary Changes ◽  
Nucleotide Interactions ◽  
Evolutionary Variation ◽  
Domains Of Life ◽  
And Function

AbstractBacterial actins are an evolutionarily diverse family of ATP-dependent filaments built from protomers with a conserved structural fold. Actin-based segregation systems are encoded on many bacterial plasmids and function to partition plasmids into daughter cells. The bacterial actin AlfA segregates plasmids by a mechanism distinct from other partition systems, dependent on its unique dynamic properties. Here, we report the near-atomic resolution cryo-EM structure of the AlfA filament, which reveals a strikingly divergent filament architecture resulting from the loss of a subdomain conserved in all other actins and a novel mode of ATP binding. Its unusual assembly interfaces and nucleotide interactions provide insight into AlfA dynamics, and expand the range of evolutionary variation accessible to actin quaternary structure.Significance StatementActin filaments are dynamic cytoskeletal elements that assemble upon ATP binding. Actin homologs are present in all domains of life, and all share a similar three-dimensional structure of the assembling subunit, but evolutionary changes to subunit have generated many different actin filament structures. The filament structure of the bacterial actin AlfA, which positions plasmids - small, circular DNA molecules that encode important genes - to ensure that each daughter cell receives a copy at cell division. AlfA is different from all other actins in two critical ways: it binds to ATP in a unique way, and it is missing a quarter of the conserved structural core. These differences explain unusual AlfA assembly dynamics that underlie its ability to move plasmids.

Conformation of Ribosomes from Escherichia Coli

1974 ◽  
Vol 32 ◽  
pp. 210-211
Author(s):  
M. Boublik ◽  
W. Hellmann ◽  
F. Jenkins
Keyword(s):  
Binding Sites ◽  
Ribosomal Proteins ◽  
Fluorescent Dyes ◽  
Protein Biosynthesis ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Dimensional Structure ◽  
Complete Understanding ◽  
And Function

The present knowledge of the three-dimensional structure of ribosomes is far too limited to enable a complete understanding of the various roles which ribosomes play in protein biosynthesis. The spatial arrangement of proteins and ribonuclec acids in ribosomes can be analysed in many ways. Determination of binding sites for individual proteins on ribonuclec acid and locations of the mutual positions of proteins on the ribosome using labeling with fluorescent dyes, cross-linking reagents, neutron-diffraction or antibodies against ribosomal proteins seem to be most successful approaches. Structure and function of ribosomes can be correlated be depleting the complete ribosomes of some proteins to the functionally inactive core and by subsequent partial reconstitution in order to regain active ribosomal particles.

Three-Dimensional Reconstruction Using Stereo Pairs from Serial Thick Sections

1977 ◽  
Vol 35 ◽  
pp. 562-563
Author(s):  
Robert Glaeser ◽  
Thomas Bauer ◽  
David Grano
Keyword(s):  
Three Dimensional ◽  
Dimensional Structure ◽  
Serial Sections ◽  
Thin Sections ◽  
3 Dimensional ◽  
Transmission Electron ◽  
Freeze Dried ◽  
Dimensional Reconstruction ◽  
Stereo Imagery ◽  
Whole Mounts

In transmission electron microscopy, the 3-dimensional structure of an object is usually obtained in one of two ways. For objects which can be included in one specimen, as for example with elements included in freeze- dried whole mounts and examined with a high voltage microscope, stereo pairs can be obtained which exhibit the 3-D structure of the element. For objects which can not be included in one specimen, the 3-D shape is obtained by reconstruction from serial sections. However, without stereo imagery, only detail which remains constant within the thickness of the section can be used in the reconstruction; consequently, the choice is between a low resolution reconstruction using a few thick sections and a better resolution reconstruction using many thin sections, generally a tedious chore. This paper describes an approach to 3-D reconstruction which uses stereo images of serial thick sections to reconstruct an object including detail which changes within the depth of an individual thick section.

Electron Microscopy of Cytoplasmic Contractile Proteins

1978 ◽  
Vol 36 (3) ◽  
pp. 606-614 ◽  
Author(s):  
T.D. Pollard ◽  
P. Maupin
Keyword(s):  
Electron Microscopy ◽  
Actin Filaments ◽  
Three Dimensional ◽  
Uranyl Acetate ◽  
Contractile Proteins ◽  
Dimensional Structure ◽  
X Ray Diffraction ◽  
Cytoplasmic Matrix ◽  
Computer Image Processing ◽  
Nonmuscle Cells

In this paper we review some of the contributions that electron microscopy has made to the analysis of actin and myosin from nonmuscle cells. We place particular emphasis upon the limitations of the ultrastructural techniques used to study these cytoplasmic contractile proteins, because it is not widely recognized how difficult it is to preserve these elements of the cytoplasmic matrix for electron microscopy. The structure of actin filaments is well preserved for electron microscope observation by negative staining with uranyl acetate (Figure 1). In fact, to a resolution of about 3nm the three-dimensional structure of actin filaments determined by computer image processing of electron micrographs of negatively stained specimens (Moore et al., 1970) is indistinguishable from the structure revealed by X-ray diffraction of living muscle.

A New 1000kv Electron Microscope

1969 ◽  
Vol 27 ◽  
pp. 100-101
Author(s):  
J.L. Williams ◽  
K. Heathcote ◽  
E.J. Greer
Keyword(s):  
Electron Microscope ◽  
Direct Observation ◽  
High Voltage ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Specimen Thickness ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
Dynamic Experiments ◽  
Conventional Instrument

High Voltage Electron Microscope already offers exciting experimental possibilities to Biologists and Materials Scientists because the increased specimen thickness allows direct observation of three dimensional structure and dynamic experiments on effectively bulk specimens. This microscope is designed to give maximum accessibility and space in the specimen region for the special stages which are required. At the same time it provides an ease of operation similar to a conventional instrument.

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