The State of Polydispersion of Hevea Latex. I

1946 ◽  
Vol 19 (1) ◽  
pp. 176-186
Author(s):  
J. H. E. Hessels
Keyword(s):  
Protein Content ◽  
Hevea Brasiliensis ◽  
The State ◽  
Rubber Content ◽  
Rubber Latex ◽  
Latex Particles ◽  
Rubber Particles ◽  
The Subject ◽  
Points Of View ◽  
Good Agreement

Abstract The rubber particles in the latex of Hevea brasiliensis are present in the form of a polydispersion, and their diameters lie within the range of 0.1 to 3 microns. The rubber hydrocarbon itself is composed of a mixture of macromolecules of different degrees of polymerization. Rubber latex is, therefore, a system which is at the same time both polydispersed and polymolecular. It is well known that the degree of dispersion of a substance governs to a great extent certain properties of the substance. Moreover, astonishing as it may seem, in the great number of investigations which have been made of the composition and properties of latex and crude rubber, almost no attention has been paid to the part which may be played by the dimensions of the latex particles. However, in an investigation concerned with the centrifugation of latex, Loomis and Stump have called attention to this possibility, and in a study of latex obtained by fractionation, and in which the majority of the latex particles were of large dimensions, McGavack came to the conclusion that the protein content is proportional to the surface area of the globules. This limited knowledge of the subject seemed to warrant a more thorough study of the problem, which is of fundamental importance both from the theoretical and practical points of view. The investigation as a whole divided itself into three essential parts: (1) separation of latex into fractions containing particles of different sizes, and measurement of the state of dispersion in these fractions, (2) a study of the relation of these fractions to the composition of the rubber, i.e., the relation between the content of nonrubber components and the size of the latex particles, and (3) a study of the changes in the properties of the rubber hydrocarbon with change in the size of the latex particles. The latex used in this investigation was ordinary latex, containing 38–40 per cent dry-rubber content and preserved with ammonia. For the most important points, a concentrated latex (creamed latex containing 60 per cent dry-rubber content) was also tested. These two latices were about two years old when the investigation was started, and they gave results which were in good agreement with each other. In the present paper, only the data obtained with the first of the two latices are presented.

Surface nanostructure of Hevea brasiliensis natural rubber latex particles

2011 ◽  
Vol 390 (1-3) ◽  
pp. 157-166 ◽  
Author(s):  
Kanjanee Nawamawat ◽  
Jitladda T. Sakdapipanich ◽  
Chee C. Ho ◽  
Yujie Ma ◽  
Jing Song ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Hevea Brasiliensis ◽  
Natural Rubber Latex ◽  
Rubber Latex ◽  
Latex Particles ◽  
Surface Nanostructure

Evaluation of Natural Rubber from Clones of Hevea Brasiliensis

2002 ◽  
Vol 75 (1) ◽  
pp. 171-177 ◽  
Author(s):  
Mariselma Ferreira ◽  
Rogério M. B. Moreno ◽  
Paulo S. Gonçalves ◽  
Luiz H. C. Mattoso
Keyword(s):  
Natural Rubber ◽  
Linear Correlation ◽  
Hevea Brasiliensis ◽  
Cold Season ◽  
The State ◽  
Rubber Content ◽  
Good Linear ◽  
Mooney Viscosity ◽  
In The Beginning ◽  
Good Linear Correlation

Abstract The latex and natural rubber from rubber trees [Hevea brasiliensis (Willd. exAdr. de Juss.) Muell. Arg.] from clones (RRIM 600, IAN 873, GT 1 and PB 252) recommended to the state of São Paulo, Brazil, were studied in three different tapping systems. The parameters studied were dry rubber content (DRC), percentages of ash and of nitrogen, Wallace Plasticity (P0) and Mooney Viscosity (VR). The rubber properties vary considerably as a function of clone type, tapping method and season of the year. DRC tends to decrease in the beginning of the dry, cold season (May and June), whereas both nitrogen % and ash % increase in the same period. A good linear correlation was obtained for P0 and VR. The highest P0 and VR were obtained for RRIM 600.

The Morphology of Rubber Latex Particles. A Critical Review

1946 ◽  
Vol 19 (1) ◽  
pp. 187-189
Author(s):  
Ernst A. Hauser
Keyword(s):  
Electron Microscopy ◽  
Chemical Composition ◽  
Critical Review ◽  
Light Microscope ◽  
Rubber Latex ◽  
Latex Particles ◽  
Synthetic Rubber ◽  
Hydrocarbon Polymers ◽  
The Subject ◽  
First Time

Abstract The morphology of the hydrocarbon particles of latices obtained from several rubber producing plants has in recent years again been the subject of studies applying the most modern tools of research. Lucas used for his studies an ultraviolet light microscope and later ultramicrocinematography. Quite recently Hendricks, Wildman, and McMurdie applied electron microscopy for the first time for this purpose. Since some of the deductions in regard to the form and structure of latex particles which have been drawn from these studies differ in several respects from conclusions based on micrugic and ultramicroscopic studies, some of which were reported twenty years ago, it seems advisable to clarify the picture. Such clarification is most important at present, because a better knowledge of the morphology of natural and synthetic rubber latex particles might offer a valuable aid in explaining some of the differences in the properties of these hydrocarbon polymers, which are not readily explainable on the basis of differences in chemical composition alone.

The Specific Gravity of Preserved Latex

1935 ◽  
Vol 8 (3) ◽  
pp. 448-455
Author(s):  
Edgar Rhodes
Keyword(s):  
Specific Gravity ◽  
Trade Association ◽  
Rubber Content ◽  
A Value ◽  
Straight Line ◽  
De Vries ◽  
The Subject ◽  
Rubber Phase ◽  
Content Range ◽  
Good Agreement

Abstract The Journal of the Rubber Research Institute of Malaya, 5, 234 (1934), contained a paper on the specific gravity of preserved latex written by the writer of this note. The paper has recently been made the subject of constructive comment by de Vries. As a result of the examination of 852 samples of preserved latex, a specific gravity/dry rubber content table was derived for preserved natural latices, and the dry rubber content range covered was wide enough to include natural unconcentrated latex in all the phases in which it is likely to be required by or become available to the commercial user. By the unavoidable expedient of extrapolation from the experimental results, a value of 0.902 was also derived for the specific gravity of the rubber phase in preserved latex. This value was in good agreement with the figure of 0.901 obtained by Scholtz and Klotz for “rubber” in fresh latex. On the other hand, de Vries, working with fresh latex had previously derived a value of 0.914 for the specific gravity of the rubber phase, and the specific gravity table used by the Rubber Trade Association of London for preserved latex gives on straight line extrapolation a value of 0.912. It seemed that the value indicated by the work of De Vries and that deduced from the table of the Rubber Trade Association were probably rather high, and certain experiments with centrifugal concentrated and centrifugal concentrate-skim mixtures were cited which provided some confirmatory evidence of this conclusion.

Problem aspects of mediation dispute resolution

2020 ◽  
pp. 215-233
Author(s):  
Saida Assanova ◽  
Serikkali Tynybekov ◽  
Arkhat Abikenov ◽  
Sarsengaly Aldashev ◽  
Gulyiya Mukaldyeva
Keyword(s):  
Dispute Resolution ◽  
Technical Progress ◽  
Legal Regulation ◽  
The State ◽  
Point Of View ◽  
Scientific Study ◽  
Foreign Countries ◽  
The Subject ◽  
Points Of View ◽  
The Republic

Legal features of dispute resolution in the order of mediation are of particular in-terest in connection with the relatively new and unexamined, from a scientific point of view, phenomenon of modernity, arising from increasing processes of globalization and internationalization of legal systems, as well as scientific and technical progress. This article is devoted to the scientific study of the international legal regulation of such phenomena as mediation on the example of the analysis of the legislation of foreign countries, and law of the Republic of Kazakhstan. This article presents various points of view of international and Kazakh scientists on the subject of dispute resolution in the mediation procedure. It was concluded that the mediation has a number of advantages, which satisfies the need of a person, society and the state to solve conflicts quickly and efficiently with minimal losses.

The Creaming of Hevea Latex by Colloids

1938 ◽  
Vol 11 (4) ◽  
pp. 608-623
Author(s):  
C. F. Vester
Keyword(s):  
Negative Charge ◽  
Dispersed Phase ◽  
Rubber Content ◽  
Rubber Latex ◽  
Ionogenic Groups ◽  
Rubber Particles ◽  
Dispersing Medium ◽  
Almost All ◽  
Short Time ◽  
Serum Components

Abstract Hevea latex is generally considered to be a suspension of rubber particles of various dimensions up to about 3 µ. The rubber hydrocarbon contains no “ionogenic groups,” and it is believed that part of the serum components imparts a negative charge to the rubber particles. Almost all latex imported into Europe is preserved by means of 0.5 to 0.7 per cent of ammonia. This ammonia plays a three-fold part: (1) it prevents premature souring of the latex; (2) it increases somewhat the charge on the particles; and (3) it attacks all types of serum components so that within a short time the “preserved” latex is hardly comparable with natural latex. As with all suspensions in which the dispersed phase is lighter than the dispersing medium, rubber latex exhibits the phenomena of creaming. The density of the rubber particles is approximately 0.914, that of the medium, 1.020. By means of creaming, it is possible to obtain a latex (1) which has a higher rubber content, whereby transportation space and cost are saved, and (2) which contains no components having a tendency to deposit a sediment. The natural creaming of latex, which is of no importance technically, was observed by Faraday as early as 1825.

The Concentration of Latex by Centrifugal Machines

1941 ◽  
Vol 14 (1) ◽  
pp. 160-175
Author(s):  
J. H. Piddlesden
Keyword(s):  
Research Work ◽  
Raw Material ◽  
New Materials ◽  
Rubber Content ◽  
Rubber Latex ◽  
Commercial Development ◽  
Shipping Cost ◽  
The Subject

Abstract Rubber latex has become a very important raw material and finds many applications, ranging from the proofing of fabrics and impregnation of paper to the manufacture of elastic threads, can-sealing compounds, adhesives, and upholstery. A large amount of research work has been carried out in the East with a view to supplying preserved latex suitable for these processes. The latex as it leaves the tree has an average dry rubber content of about 33 to 35 per cent, and is so unstable that it will coagulate within a few hours unless a preservative is added. Ammonia has been found to be a suitable preservative and, in spite of the continued search for new materials, it remains in general use. The problem of concentrating the latex to avoid the shipment of surplus water arose early. Three methods for carrying out this operation were developed, namely, centrifugal concentration, creaming by the addition of gums and mucilages, and evaporation. A fourth method, utilizing the phenomena of electrodialysis, has recently been the subject of commercial development. The advent of concentrated latex widened the field of latex applications, since the concentrated products found uses for which preserved field latex was not suitable. For many processes the properties and applications of the latex or concentrate are now perhaps more important that the question of shipping cost. Various types of product, described briefly below, are obtained from the different processes of concentration.

scholarly journals Total Solid Content and Compound Properties from Different Collection Time of Hevea brasiliensis Latex

2019 ◽  
Vol 22 (4) ◽  
pp. 104-108
Author(s):  
◽  
Andi Wijaya ◽  
Arief Rachmawan ◽  
Mochlisin Andriyanto
Keyword(s):  
Physical Properties ◽  
Hevea Brasiliensis ◽  
Total Solid ◽  
Solid Content ◽  
Rubber Content ◽  
Rubber Latex ◽  
Total Solid Content ◽  
Significant Difference ◽  
Collection Time

Abstract This study compared the total solid content and compound properties of Hevea rubber latex produced from material collected during different periods. Samples were collected from five trees, with the collection replicated three times with tapping task as replication. Observed parameters included total solid content, vulcanization characteristics, technical and physical properties. The results exhibited that the longer latex flowed, the more total solid content tended to decrease. Results indicate that compound of latex collected 20 minutes (C20), 60 minutes (C60), and 300 minutes (C300) after tapping qualified for SIR 20. Other parameters did not show a significant difference among the three tested compounds. Considering the products requiring high dry rubber content, it is suggested not to blend the late collection with main collected latex.

The working standard of the unit of power of electromagnetic waves in the frequency range from 37,5 to 220 GHz

2020 ◽  
pp. 53-58
Author(s):  
A. V. Koudelny ◽  
I. M. Malay ◽  
V. A. Perepelkin ◽  
I. P. Chirkov
Keyword(s):  
Microwave Power ◽  
Electromagnetic Waves ◽  
Primary Standard ◽  
The State ◽  
Frequency Range ◽  
Working Standard ◽  
Extended Frequency Range ◽  
Effective Efficiency ◽  
Extended Frequency ◽  
Good Agreement

The possibility of using bolometric converters of microwave power from the State primary standard of the unit of power of electromagnetic waves in waveguide and coaxial paths GET 167-2017, which has a frequency range from 37,5 to 78,33 GHz, in an extended frequency range up to 220 GHz, is shown. Studies of semiconductor bolometric converters of microwave power in an extended frequency range have confirmed good agreement and smooth frequency characteristics of the effective efficiency factor of the converters. Based on the research results, the State working standard of the unit of power of electromagnetic waves of 0,1–10 mW in the frequency range from 37,5 to 220 GHz 3.1.ZZT.0288.2018 was approved. The technical characteristics of the working standard of the unit of power of electromagnetic oscillations in an extended frequency range from 37,5 to 220 GHz are given.

ИЗМЕНЕНИЕ ПАРАДИГМЫ МЕТОДОЛОГИИ ЮРИСПРУДЕНЦИИ

2019 ◽  
Vol 13 ◽  
pp. 32-40
Author(s):  
Ю. М. Оборотов
Keyword(s):  
Legal Theory ◽  
Research Strategy ◽  
The State ◽  
New Paradigm ◽  
Methodological Question ◽  
Modern Development ◽  
Decisive Importance ◽  
The Subject ◽  
Methodological Approaches ◽  
The Law

В современной методологии юриспруденции происходит переход от изучения состо­яний ее объекта, которыми выступают право и государство, к постижению этого объек­та в его изменениях и превращениях. Две подсистемы методологии юриспруденции, подсистема обращенная к состоянию права и государства; и подсистема обращенная к изменениям права и государства, — получают свое отображение в концептуальной форме, методологических подходах, методах, специфических понятиях. Показательны перемены в содержании методологии юриспруденции, где определяю­щее значение имеют методологические подходы, определяющие стратегию исследова­тельских поисков во взаимосвязи юриспруденции с правом и государством. Среди наи­более характерных подходов антропологический, аксиологический, цивилизационный, синергетический и герменевтический — определяют плюралистичность современной методологии и свидетельствуют о становлении новой парадигмы методологии юриспру­денции.   In modern methodology of jurisprudence there is a transition from the study the states of its object to its comprehension in changes and transformations. Hence the two subsystems of methodology of jurisprudence: subsystem facing the states of the law and the state as well as their components and aspects; and subsystem facing the changes of the law and the state in general and their constituents. These subsystems of methodology of jurisprudence receive its reflection in conceptual form, methodological approaches, methods, specific concepts. Methodology of jurisprudence should not be restricted to the methodology of legal theory. In this regard, it is an important methodological question about subject of jurisprudence. It is proposed to consider the subject of jurisprudence as complex, covering both the law and the state in their specificity, interaction and integrity. Indicative changes in the content methodology of jurisprudence are the usage of decisive importance methodological approaches that govern research strategy searches in conjunction with the law and the state. Among the most characteristic of modern development approaches: anthropological, axiological, civilization, synergistic and hermeneutic. Modern methodology of jurisprudence is pluralistic in nature alleging various approaches to the law and the state. Marked approaches allow the formation of a new paradigm methodology of jurisprudence.

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