Crystallization and Morphology of Rubber

1995 ◽  
Vol 68 (3) ◽  
pp. 507-539 ◽  
Author(s):  
J. H. Magill
Keyword(s):  
Natural Rubber ◽  
Developmental Stages ◽  
Synthetic Polymers ◽  
Material Behavior ◽  
Science And Engineering ◽  
Good Science ◽  
Thermodynamics And Kinetics ◽  
Naturally Occurring ◽  
Scientists And Engineers ◽  
Resource Material

Abstract Naturally occurring materials like rubber predate the development of science and engineering as we know it today. Historically, rubber and more generally elastomers, known as a class of high polymers, are versatile and useful materials. Rubber is still an elastomer of choice for many engineering applications. After decades of R&D, scientists and engineers realized that technology needs good science. This position is nicely summarized in Figure 1. This scenario brings together four main items that are essential to create and to maintain quality industry(ies). In the case of rubber, particularly natural rubber, it is not only essential to understand these individual properties, but also to comprehend the important interrelationships that contribute to material behavior. In this respect, rubber has been an enabling resource material that has served as a paradigm amongst synthetic polymers in their developmental stages. In this article crystallization of natural rubber especially, is addressed in order to provide some perspective on items that relate to the relevant areas of the pyramid. This overview is far from exhaustive on the crystallization aspects of rubber, but hopefully it strikes a balance between thermodynamics and kinetics, since each discipline has contributed significantly to improve our understanding of polyisoprenes, and in a wider sense to crystallization and morphology that helps determine properties relevant to rubber and to polymers in general.

scholarly journals Metamaterials: The early years in the USA

2014 ◽  
Vol 1 ◽  
pp. 5 ◽  
Author(s):  
Richard W. Ziolkowski
Keyword(s):  
Early Years ◽  
Science And Engineering ◽  
Current Generation ◽  
Practical Applications ◽  
Artificial Materials ◽  
Naturally Occurring ◽  
Permittivity And Permeability ◽  
The Usa ◽  
Scientists And Engineers ◽  
Exotic Physics

Metamaterials are artificial materials formed by embedding highly subwavelength inclusions in a host medium, which yield homogenized permittivity and permeability values. By design they offer the promise of exotic physics responses not generally available with naturally occurring materials, as well as the ability to tailor their properties to specific applications. The initial years of discovery emphasized confirming many of their exotic properties and exploring their actual potential for science and engineering applications. These seed efforts have born the sweet fruit enjoyed by the current generation of metamaterials scientists and engineers. This review will emphasize the initial investigative forays in the USA that supported and encouraged the development of the metamaterials era and the subsequent recognition that they do have significant advantages for practical applications.

Extraction and identification of fillers and pigments from pyrolyzed rubber and tire samples

1996 ◽  
Vol 54 ◽  
pp. 174-175
Author(s):  
P. Sadhukhan ◽  
J. B. Zimmerman
Keyword(s):  
Zinc Oxide ◽  
Electron Microscope ◽  
Carbon Black ◽  
Natural Rubber ◽  
Transmission Electron Microscope ◽  
Rolling Resistance ◽  
Synthetic Polymers ◽  
Nitrogen Atmosphere ◽  
Transmission Electron ◽  
Curing Agents

Rubber stocks, specially tires, are composed of natural rubber and synthetic polymers and also of several compounding ingredients, such as carbon black, silica, zinc oxide etc. These are generally mixed and vulcanized with additional curing agents, mainly organic in nature, to achieve certain “designing properties” including wear, traction, rolling resistance and handling of tires. Considerable importance is, therefore, attached both by the manufacturers and their competitors to be able to extract, identify and characterize various types of fillers and pigments. Several analytical procedures have been in use to extract, preferentially, these fillers and pigments and subsequently identify and characterize them under a transmission electron microscope.Rubber stocks and tire sections are subjected to heat under nitrogen atmosphere to 550°C for one hour and then cooled under nitrogen to remove polymers, leaving behind carbon black, silica and zinc oxide and 650°C to eliminate carbon blacks, leaving only silica and zinc oxide.

Future Directions in International Science Education

1997 ◽  
Vol 3 (1) ◽  
pp. 233-239 ◽  
Author(s):  
Patrick Holmes
Keyword(s):  
Science Education ◽  
Engineering Education ◽  
Science And Engineering ◽  
Future Directions ◽  
International Dimension ◽  
The World ◽  
Scientists And Engineers ◽  
Science And Engineering Education

The international dimension of science and engineering education is of paramount importance and merits serious consideration of the coherent skill set that is required to allow scientists and engineers more readily to transport themselves and their work to other locations in the world. 

scholarly journals Material parametrization of natural rubber based compound and characterization of crack propagation under consideration of dissipative effects

2021 ◽  
Author(s):  
Dan Pornhagen ◽  
Konrad Schneider ◽  
Markus Stommel
Keyword(s):  
Energy Dissipation ◽  
Crack Propagation ◽  
Natural Rubber ◽  
Experimental Tests ◽  
Material Behavior ◽  
Prony Series ◽  
Material Forces ◽  
Cracking Behavior ◽  
Dissipative Effects

AbstractMost concepts to characterize crack propagation were developed for elastic materials. When applying these methods to elastomers, the question is how the inherent energy dissipation of the material affects the cracking behavior. This contribution presents a numerical analysis of crack growth in natural rubber taking energy dissipation due to the visco-elastic material behavior into account. For this purpose, experimental tests were first carried out under different load conditions to parameterize a Prony series as well as a Bergström–Boyce model with the results. The parameterized Prony series was then used to perform numerical investigations with respect to the cracking behavior. Using the FE-software system ANSYS and the concept of material forces, the influence and proportion of the dissipative components were discussed.

Characterizing the naturally occurring sacrificial bond within natural rubber

Polymer ◽  
2019 ◽  
Vol 161 ◽  
pp. 41-48 ◽  
Author(s):  
Xuan Fu ◽  
Cheng Huang ◽  
Yong Zhu ◽  
Guangsu Huang ◽  
Jinrong Wu
Keyword(s):  
Natural Rubber ◽  
Naturally Occurring

scholarly journals Post-Graduation Plans of International Science and Engineering Doctoral Students Attending U.S. Universities

2017 ◽  
Vol 7 (1) ◽  
pp. 1-21 ◽  
Author(s):  
Dorothy N. Ugwu ◽  
Maria Adamuti-Trache
Keyword(s):  
Doctoral Students ◽  
English Language ◽  
Academic Support ◽  
School Experiences ◽  
Science And Engineering ◽  
Integration Model ◽  
Model Study ◽  
Language Difficulties ◽  
Scientists And Engineers ◽  
Institutional Initiatives

This study examines the post-graduation plans of international science and engineering doctoral students at a public research-intensive university, and the extent to which graduate school experiences influence post-graduation plans. The study is grounded in Tinto’s Integration Model as well as Berry’s Acculturation Model. Study findings highlight the variety of challenges international doctoral students go through such as adapting to a new culture, experiencing English language difficulties, and cultural, social, and academic adjustment barriers. Using survey data collected in 2013-2014, this study reveals the complexity of factors that affect post-graduation plans and need for institutional initiatives to provide socio-cultural and academic support, and recommends changes in immigration policies to sustain the retention of talented international scientists and engineers upon degree completion.

Remote Teaching Laboratories in Science and Engineering

2011 ◽  
pp. 1749-1753 ◽  
Author(s):  
Dietmar Kennepohl
Keyword(s):  
New Technologies ◽  
Controlled Experiments ◽  
Science And Engineering ◽  
Science Courses ◽  
Laboratory Courses ◽  
Remote Laboratories ◽  
Excellent Method ◽  
Scientists And Engineers ◽  
Distance Educators ◽  
Viable Method

For scientists and engineers, the idea of remote controlled experiments is not a new. Remote control is often used when an experiment or instrument is physically inaccessible by virtue of location or danger. It is also an excellent method for sharing expensive equipment and facilities with other researchers. However, employment of remote laboratory access to deliver the practicum components of distance science courses is much more recent and certainly not as common. Historically, the complexity and technology involved has often dissuaded universal adoption of this method in regularly run laboratory courses. However with the increasing availability and robustness of new technologies, the use of remote laboratories is being explored by many distance educators in the sciences as a viable method of offering a first-class laboratory experience for the student.

scholarly journals Acetyl-CoA:4-Hydroxybutinylbithiophene O-Acetyltransferase Isoenzymes from Tagetes patula Seedlings

1987 ◽  
Vol 42 (7-8) ◽  
pp. 885-890 ◽  
Author(s):  
Gernot Metschulat ◽  
Rainer Sütfeld
Keyword(s):  
Coenzyme A ◽  
Developmental Stages ◽  
Complete Separation ◽  
Tagetes Patula ◽  
Acetyl Coa ◽  
Ph Optimum ◽  
Acyltransferase Activity ◽  
Enzyme Preparations ◽  
Naturally Occurring ◽  
Acyl Coenzyme A

Naturally-occurring hydroxybutinylbithiophene derivatives were acylated by enzyme preparations of Tagetes patula seedlings in the presence of distinct acyl-Coenzyme A esters. The O-acyltransferase activity could only be detected after almost complete separation of the enzyme from counter-currently acting esterases which were present in the same extracts. This was achieved by affinity chromatography on Cibachron Blue A. During this procedure, the O-acyl-transferase was split, yielding two active fractions. Both had a Mr of 37,000 (±5,000), equal isoelectric properties, a pH optimum of pH 7.0, and were considerably inhibited in the presence of free Coenzyme A. Small differences existed in their affinities for their thiophenic substrates (3,4-dihydroxybutinylbithiophene and 4-hydroxybutinylbithiophene, respectively), as well as for various acyl-CoA esters as cosubstrates. With the preferred cosubstrate, acetyl-CoA, acylation took place at the 4-position of the butinyl side chain of the molecules, forming the naturally- occurring 4-acetoxybutinylbithiophene and 3-OH,4-OAc-butinylbithiophene, respectively. From the other acyl-CoA esters employed, only propionyl-CoA was likewise converted, forming the corresponding O-propionyl esters. The reactions observed are suggested to be catalyzed by two acetyl-CoA: 4-hydroxybutinylbithiophene O-acetyltransferase isoenzymes which exhibit different affinities for particular substrates and cosubstrates. The activities of both the isoenzymes changed drastically if plant material from different developmental stages was used as enzyme source. Therefore, it may be suggested that these isoenzymes play an important regulatory role in the metabolism of naturally-occurring hydroxy- and acetoxybutinylbithiophenes and their derivatives.

scholarly journals An Integrated Geometric-Graph-Theoretic Approach to Representing Origami Structures and Their Corresponding Truss Frameworks

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Yao Chen ◽  
Pooya Sareh ◽  
Jiayi Yan ◽  
Arash S. Fallah ◽  
Jian Feng
Keyword(s):  
Mechanical Analysis ◽  
Geometric Graph ◽  
Theoretic Approach ◽  
Graph Products ◽  
Science And Engineering ◽  
Graph Theoretic ◽  
Graph Theoretic Approach ◽  
Repeated Unit ◽  
Unit Cells ◽  
Scientists And Engineers

Origami has provided various interesting applications in science and engineering. Appropriate representations and evaluation on crease patterns play an important role in developing an innovative origami structure with desired characteristics. However, this is generally a challenge encountered by scientists and engineers who introduce origami into various fields. As most practical origami structures contain repeated unit cells, graph products provide a suitable choice for the formation of crease patterns. Here, we will employ undirected and directed graph products as a tool for the representation of crease patterns and their corresponding truss frameworks of origami structures. Given that an origami crease pattern can be considered to be a set of directionless crease lines that satisfy the foldability condition, we demonstrate that the pattern can be exactly expressed by a specific graph product of independent graphs. It turns out that this integrated geometric-graph-theoretic method can be effectively implemented in the formation of different crease patterns and provide suitable numbering of nodes and elements. Furthermore, the presented method is useful for constructing the involved matrices and models of origami structures and thus enhances configuration processing for geometric, kinematic, or mechanical analysis on origami structures.

Differences in the Thinking-Writing Process

1972 ◽  
Vol 2 (1) ◽  
pp. 19-32 ◽  
Author(s):  
Gertrude Taylor Smith
Keyword(s):  
Writing Process ◽  
Behavioral Approach ◽  
Science And Engineering ◽  
Scientists And Engineers

This article presents differences between the thinking-writing experiences of outstanding mathematicians, scientists, and engineers (image thinkers) and those trained in the humanities (verbalizers). It advocates use of the behavioral approach and drill to teach mathematics-, science-, and engineering-oriented students to write. A few examples of recommended drills are included.

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