Assignment of Effective Network Chains in Cured Rubbers Derived from Chemical Crosslinking, Entanglements, Polymer End Linking to Carbon Black and Filler Interaction: VII. Tensile Retraction Measurements

2006 ◽  
Vol 79 (2) ◽  
pp. 338-365
Author(s):  
William L. Hergenrother ◽  
J. D. Ulmer ◽  
Christopher G. Robertson
Keyword(s):  
Carbon Black ◽  
Volume Fraction ◽  
Polymer Network ◽  
Polymer Chains ◽  
Network Chain ◽  
End Groups ◽  
Individual Contributions ◽  
Cross Links ◽  
Effective Network ◽  
The Individual

Abstract The individual contributions to effective network chains from chemical cross-links and from trapped polymer chain entanglements were estimated for gum rubber compounds using Tensile Retraction (TR). In addition, the influences of carbon black and of polymers with functional end-groups, on the character of the polymer network in filled compounds were explored. The effective network chain contributions were established for gum vulcanizates through an entanglement model and an independent estimate of the polymer molecular weight between entanglements, Me. It was found that Me was related closely to the extrapolated γ intercepts obtained from the TR of cured gums. The gum compounds were used to further estimate the effects of fillers and functional end-groups on the total number of effective network chains. Comparing an α,ω-difunctional SBR with its non-functional counterpart enabled the assessment of the effects of functional end-groups. The comparison allowed for the determination of the probability, π, that a functional end group reacts with carbon black. The π was seen to increase as the volume fraction of filler increased, and π2 provided an estimate of the fraction of functional polymer chains that react with carbon black at both ends.

Hysteresis Contributions in Carbon Black-Filled Rubbers Containing Conventional and Tin End-Modified Polymers

1998 ◽  
Vol 71 (4) ◽  
pp. 637-667 ◽  
Author(s):  
J. D. Ulmer ◽  
W. L. Hergenrother ◽  
D. F. Lawson
Keyword(s):  
Carbon Black ◽  
Loss Modulus ◽  
Average Molecular Weight ◽  
Polymer Network ◽  
Linear Polymers ◽  
Network Chain ◽  
Modified Polymers ◽  
Rubber Compounds ◽  
Effective Network ◽  
Tan Δ

Abstract A methodology was developed to estimate individual hysteresis contributions arising from the carbon black network, polymer free chain ends and effective polymer network chains. The estimation technique was applied to rubber compounds formulated with linear polymers of varied number-average molecular weight (Mn) from each of three different series. The three series corresponded to polymers modified with either zero, one or two tin ends per chain. In general, the relative hysteresis contributions depend on strain amplitude and Mn. For unmodified polymers at strain amplitudes from 0.02 to 0.07, and with Mn in the neighborhood of 150 kg/mole, each of the three hysteresis sources contributes about one-third of the total tan δ. With respect to shear loss modulus (G″), the carbon black network contributes about 60%, while free chain ends and the effective polymer network chains each contribute about 20%. At the same Mn and strain conditions, tin end-modified polymers reduce G″ and tan δ by as much as 60%, in comparison to their unmodified counterparts. The benefit is achieved primarily through reductions of up to 85% in the carbon black network contribution to hysteresis. Since the hysteresis contribution from free chain ends is not reduced so much by tin end-modification, the greatest potential for additional tan δ benefits lies in further free chain end reduction. In addition, it was found that tin end-modification has no measurable effect on the hysteresis contribution from effective network chains. Further, the analysis showed that an ineffective polymer network chain provides approximately ten times the hysteresis and one-half the elasticity of an effective network chain, at the test conditions of the current study. In general, the quantitative results, and some qualitative results as well, will change with compound composition and with temperature. Consequently, the development of a methodology, one that allows estimation of individual hysteresis contributions from different sources, is a major component of the present study.

Dilute suspension of neutrally buoyant particles in viscoelastic turbulent channel flow

2019 ◽  
Vol 875 ◽  
pp. 286-320 ◽  
Author(s):  
Amir Esteghamatian ◽  
Tamer A. Zaki
Keyword(s):  
Channel Flow ◽  
Volume Fraction ◽  
Qualitative Difference ◽  
Turbulent Channel Flow ◽  
Polymer Chains ◽  
Spherical Particles ◽  
Lower Probability ◽  
Fluid Field ◽  
The Individual ◽  
Neutrally Buoyant

Direct numerical simulations of viscoelastic turbulent channel flow laden with neutrally buoyant spherical particles are performed. Two FENE-P viscoelastic and one Newtonian fluid are examined, and for each the particle-laden configuration is contrasted to a reference condition without seeding. The size of the particles is larger than the dissipation length scale, and their presence enhances drag in a manner that is intrinsically different in the viscoelastic and Newtonian flows. While the particles effectively suppress the turbulence activity, they significantly enhance the polymer stresses. The polymer chains are markedly stretched in the vicinity of the particles, altering the correlation between the turbulence and polymer work that is commonly observed in single-phase viscoelastic turbulence. At the lower elasticity, the particles enhance the cycle of hibernating and active turbulence and, in turn, their migration and volume-fraction profiles are qualitatively altered by the intermittency of the turbulence. Particle–fluid momentum transfer is investigated by estimating the local fluid field on a trimmed spherical shell around the individual particles. And by comparing the particle microstructures, a lower probability of particle alignment in the streamwise direction is observed in the viscoelastic configuration. This effect is attributed to a qualitative difference in the conditionally averaged velocity fields in the vicinity of the particles in the Newtonian and viscoelastic flows.

scholarly journals Side Chains and the Insufficient Lubrication of Water in Polyacrylamide Hydrogel—A New Insight

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1845 ◽  
Author(s):  
Lei ◽  
Zhou ◽  
Liu
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Polymer Network ◽  
Polymer Chains ◽  
Side Chain ◽  
Side Chains ◽  
Polyacrylamide Hydrogels ◽  
Young’S Moduli ◽  
Property Changes ◽  
Dynamics Simulations

Existing theories cannot predict the mechanical property changes of polyacrylamide hydrogels with different water content because of the absence of side chains. In this study, polyacrylamide hydrogels are prepared and tested to investigate the side chain effect on their mechanical properties. First, the comparison between the effective chain density and total chain density provides proof of the large amount of side chains in the polymer network of PAAm hydrogel. We propose a practical chain density fraction to measure the side chain fraction. Then, the abnormal Young’s moduli-polymer volume fraction relationship reveals that side chains affect the mechanical properties of hydrogel through the insufficient lubrication of water. Water confined in narrow space within a molecular-level size can bear shear force to provide extra deformation resistance. A constitutive mode considering the effect of the insufficient lubrication of water is proposed. Combining this constitutive model with experimental results, we find that this insufficient lubrication of water exists even in equilibrium PAAm hydrogel. Molecular dynamics simulations reveal that this insufficient lubrication of water comes from the constraint of polymer chains. It also demonstrates that when there is insufficient lubrication, the rearrangement of water molecules leads to the persistent energy dissipation in the Mullins effect of PAAm hydrogel.

Carbon Black Reinforcement in Pre-Swollen Rubbers

1966 ◽  
Vol 39 (5) ◽  
pp. 1553-1564 ◽  
Author(s):  
G. R. Cotten
Keyword(s):  
Carbon Black ◽  
Elevated Temperatures ◽  
Polymer Network ◽  
Radioactive Tracer ◽  
Polymer Chains ◽  
Additional Information ◽  
Bound Rubber ◽  
Black Surface ◽  
Swollen Vulcanizates ◽  
Mobile Adsorption

Abstract The mechanism of carbon black reinforcement was studied by examining stress-strain properties in SBR 1500 vulcanizates cured while swollen, then de-swollen. Carbon black-polymer attachments started contributing to the modulus of rubber at much higher elongations (ca. 300 per cent for a swelling ratio of 4.0) than in normally cured, unswollen specimens. The modulus in pre-swollen rubbers is considerably lower than in normal vulcanizates but it can be increased by heating the same specimens 30 minutes at 155° C in their de-swollen state. The observed increase in modulus of vulcanizates containing graphitized and regular carbon blacks after such a treatment was found to be related to carbon black “activity” and loading. Bound rubber does not seem to function as a distinct phase contributing to reinforcement, but it can be used as a measure of the number of attachments of carbon black and polymer. Additional information on the molecular mechanism of the phenomenon was obtained through radioactive tracer analysis. It was also found that regular vulcanizates can be softened by heating swollen samples at elevated temperatures (150-170° C). This softening was related to carbon black “activity” and was fully reversible: the original modulus could be recovered by additional heating of de-swollen vulcanizates for a further thirty minutes at 155° C. The above observations are discussed in terms of mobile adsorption of polymer chains on carbon black surface and the steric effect of fixing carbon black particles into an already extended polymer network.

A Handbook to Eddic Poetry: Myths and Legends of Early Scandinavia, ed. Carolyne Larrington, Judy Quinn, and Brittany Schorn. Cambridge: Cambridge University Press, 2016, xii, 413 pp., 12 b/w ill.

Mediaevistik ◽  
2018 ◽  
Vol 31 (1) ◽  
pp. 366-366
Author(s):  
Albrecht Classen
Keyword(s):  
Old Norse ◽  
Entire Volume ◽  
Cambridge University ◽  
Critical Studies ◽  
Individual Contributions ◽  
The Many ◽  
The Individual ◽  
Made In ◽  
Scandinavian Literature

Eddic poetry constitutes one of the most important genres in Old Norse or Scandinavian literature and has been studied since the earliest time of modern-day philology. The progress we have made in that field is impressive, considering the many excellent editions and translations, not to mention the countless critical studies in monographs and articles. Nevertheless, there is always a great need to revisit, to summarize, to review, and to digest the knowledge gained so far. The present handbook intends to address all those goals and does so, to spell it out right away, exceedingly well. But in contrast to traditional concepts, the individual contributions constitute fully developed critical article, each with a specialized topic elucidating it as comprehensively as possible, and concluding with a section of notes. Those are kept very brief, but the volume rounds it all off with an inclusive, comprehensive bibliography. And there is also a very useful index at the end. At the beginning, we find, following the table of contents, a list of the contributors, unfortunately without emails, a list of translations and abbreviations of the titles of Eddic poems in the Codex Regius and then elsewhere, and a very insightful and pleasant introduction by Carolyne Larrington. She briefly introduces the genre and then summarizes the essential points made by the individual authors. The entire volume is based on the Eddic Network established by the three editors in 2012, and on two workshops held at St. John’s College, Oxford in 2013 and 2014.

Employee Surveys and Sensing

2020 ◽  
Keyword(s):  
Organizational Performance ◽  
Employee Engagement ◽  
Computational Linguistics ◽  
Full Range ◽  
Organization Culture ◽  
Employee Survey ◽  
Passive Data ◽  
Individual Contributions ◽  
Action Taking ◽  
The Individual

This volume comprises 27 chapters focused on the design and execution of employee survey programs. These chapters reflect the latest advances in technology and analytics and a pervasive emphasis on driving organizational performance and effectiveness. The individual chapters represent the full range of survey-related topics, including design, administration, analysis, feedback, and action-taking. The latest methodological trends and capabilities are discussed including computational linguistics, applications of artificial intelligence, and the use of qualitative methods such as focus groups. Extending beyond traditional employee surveys, contributions include the role of passive data collection as an alternative or supplement in a comprehensive employee listening system. Unique contextual factors are discussed including the use of surveys in a unionized environment. Individual contributions also reflect increasing stakeholder concerns for the protection of privacy among other ethical considerations. Finally, significant clarifications to the literature are provided on the use of surveys for measuring organization culture, strategic climate, and employee engagement.

Knowledge First

2017 ◽  
Author(s):  
J. Adam Carter ◽  
Emma C. Gordon ◽  
Benjamin W. Jarvis
Keyword(s):  
Philosophy Of Mind ◽  
Theoretical Background ◽  
Contemporary Research ◽  
Timothy Williamson ◽  
Research Themes ◽  
New Directions ◽  
Individual Contributions ◽  
The Individual

In this introductory chapter, the volume’s editors provide a theoretical background to the volume’s topic and a brief overview of the papers included. The chapter is divided into five parts: Section 1 explains the main contours of the knowledge-first approach, as it was initially advanced by Timothy Williamson in Knowledge and its Limits. In Sections 2–3, some of the key philosophical motivations for the knowledge-first approach are reviewed, and several key contemporary research themes associated with this approach in epistemology, the philosophy of mind and elsewhere are outlined and briefly discussed. The volume’s papers are divided into two broad categories: foundational issues and applications and new directions. Section 4 discusses briefly the scope and aim of the volume as the editors have conceived it, and Section 5 offers an overview of each of the individual contributions in the volume.

scholarly journals Of Visions and Visionaries: Information and Communication Technologies (ICT) in China

2021 ◽  
Vol 50 (1) ◽  
pp. 3-11
Author(s):  
Barbara Schulte ◽  
Marina Svensson
Keyword(s):  
Information And Communication Technologies ◽  
Communication Technologies ◽  
Special Issue ◽  
Empirical Reality ◽  
Information And Communication ◽  
Individual Contributions ◽  
State Governance ◽  
Different Dimensions ◽  
Chinese State ◽  
The Individual

This special issue approaches information and communication technologies (ICT) visions and their realisation/implementation at various levels, among different actors and from various perspectives. Conceptually, we distinguish three different dimensions, even though those overlap in the individual contributions as well as in empirical reality – namely ideational, instrumental, and relational. The different contributions address both visions formulated by the Chinese state and by individual actors such as entrepreneurs. Even though the conditions for the use of ICT in China are deeply affected by state governance, this governance is in no way tantamount to one single government. As this issue’s contributions show, state attempts at building a stable cyber-governance are in need of allies and, depending on the allies’ visions and other, competitive visions, the outcomes of these dynamics are seldom truthful realisations of one original grand masterplan.

Investigate of Electrical Conductivity of Shape-Memory Polymer Filled with Carbon Black

2008 ◽  
Vol 47-50 ◽  
pp. 714-717 ◽  
Author(s):  
Xin Lan ◽  
Jin Song Leng ◽  
Yan Ju Liu ◽  
Shan Yi Du
Keyword(s):  
Electrical Conductivity ◽  
Carbon Black ◽  
Shape Memory ◽  
Shape Recovery ◽  
Volume Fraction ◽  
Shape Memory Polymer ◽  
Recovery Process ◽  
Thermomechanical Properties ◽  
Electrically Conductive ◽  
New System

A new system of thermoset styrene-based shape-memory polymer (SMP) filled with carbon black (CB) is investigated. To realize the electroactive stimuli of SMP, the electrical conductivity of SMP filled with various amounts of CB is characterized. The percolation threshold of electrically conductive SMP filled with CB is about 3% (volume fraction of CB), which is much lower than many other electrically conductive polymers. When applying a voltage of 30V, the shape recovery process of SMP/CB(10 vol%) can be realized in about 100s. In addition, the thermomechanical properties are also characterized by differential scanning calorimetery (DSC).

Research on Electrical Double Percolation of Carbon Black-Filled Cement-Based Composites

2011 ◽  
Vol 311-313 ◽  
pp. 201-204
Author(s):  
Hong Zhong Ru ◽  
Ran Ran Zhao
Keyword(s):  
Carbon Black ◽  
Cement Paste ◽  
Volume Fraction ◽  
Carbon Black Particle ◽  
Carbon Black Content ◽  
Percolation Behavior ◽  
Key Factor ◽  
Binder Ratio ◽  
Black Particle ◽  
Double Percolation

Electrical conductive carbon black-filled cement-based composites are significant as multifunctional structural materials. Double percolation in carbon black-filled cement-based composites involves both carbon black particle percolation and cement paste percolation, which has great effect on the resistivity of composites. Based on double percolation theory, the influences of sand-binder ratio and carbon black volume fraction on the resistivity of carbon black-filled cement-based composites are investigated. The results show that besides carbon black volume fraction, sand-binder ratio is a key factor affecting double percolation behavior in carbon black-filled cement-based composites. At a fixed carbon black content in overall mortar, with increasing sand-binder ratio, the cement paste percolation though aggregate phase increases due to high obstruction of aggregate but the carbon black particle percolation in cement paste decreases. This is because that the microstructure of aggregate is impenetrable so that the carbon black particles are limited in cement paste, that is, the carbon black content in paste is compacted and large amount of conductive paths are generated by lapped adjacent carbon black particles in paste. The double percolation in the electrical conduction in carbon black-filled cement-based composites is observed when the carbon black volume fraction is 7.5% and sand-binder ratio is 1.4, and its resistivity is only 3200 Ωcm, so that a sand-binder ratio of 1.4 and 7.5% carbon black volume fraction or more are recommended for attaining high conductivity with a compromise between workability and conductivity.

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