Natural and Synthetic Rubber. XIII. The Molecular Weight of Sol Rubber

Abstract The reduction of isoprene by sodium in liquid ammonia was attempted to determine: (1) whether reduction would take place in preference to polymerization and (2) the location of the added hydrogen. Isoprene was added to sodium dissolved in liquid ammonia and a 60% yield of 2-methyl-2-butene resulted. No other volatile hydrocarbon was found. High molecular weight hydrocarbons were formed but were not investigated. It is thus shown: (1) that the predominant reaction proceeds in accordance with the equation C5C8+2Na+2NH3=C5C10+2NaNH2 and (2) that hydrogen adds to isoprene in the 1,4-position, in agreement with Thiele's theory. The hydrogen addition is similar to the bromination of isoprene at low temperature. If properly conducted the latter reaction stops after 2 atoms of bromine have been added to 1 molecule of isoprene; the resulting compound, 1,4-dibromo-2-methyl-2-butene, is characterized b the inactivity of its double bond toward bromine. Similarly, 2-methyl-2-butene obtained by reduction of isoprene is not reduced to isopentane by an excess of Na—NH3 reagent.

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Natural and Synthetic Rubber. XIII. The Molecular Weight of Sol Rubber

Rubber Chemistry and Technology ◽

10.5254/1.3548022 ◽

1934 ◽

Vol 7 (3) ◽

pp. 518-520

Author(s):

Thomas Midgley ◽

Albert L. Henne ◽

Alvin F. Shepard ◽

Mary W. Renoll

Keyword(s):

Molecular Weight ◽

Vulcanized Rubber ◽

Synthetic Rubber ◽

Natural And Synthetic

Abstract Partially vulcanized rubber has been fractionated into components in which rubber is combined with increasing amounts of sulfur. The analyses of these fractions concur to indicate a molecular weight of about 54,000 for the particular sample of rubber used. Specimens of varied origin can thus have their molecular weight measured by strictly orthodox chemical means.

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Resins Used in Rubber

Rubber Chemistry and Technology ◽

10.5254/1.3539653 ◽

1963 ◽

Vol 36 (5) ◽

pp. 1542-1570 ◽

Cited By ~ 8

Author(s):

Paul O. Powers

Keyword(s):

Molecular Weight ◽

Organic Substances ◽

Thermosetting Resins ◽

Average Value ◽

Synthetic Rubber ◽

Naturally Occurring ◽

Synthetic Resins ◽

Natural And Synthetic

Abstract Resinous materials have long been used to aid in the processing of rubber and to impart special properties to the vulcanized product. Resins have been described as various solid or semisolid organic substances. Originally, naturally occurring resins such as rosin were employed but with the advent of synthetic resins, many of these have been used with natural and synthetic rubber. In general the resins considered here are readily fusible and relatively low in molecular weight, the average value often being less than one thousand. However, thermosetting resins are also employed, usually being introduced into the rubber at a low stage of condensation. Resins are frequently added to assist in processing and often are considered as softeners although they are higher in molecular weight than most softeners and their efficiency as softeners is somewhat less. However, they do not soften the resulting vulcanizate and may even increase the hardness.

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Methods for sampling and further preparative procedures for raw, natural and synthetic rubber

10.3403/00311818u ◽

2015 ◽

Keyword(s):

Synthetic Rubber ◽

Natural And Synthetic

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Coactivation of Delayed-Action Vulcanization. Part I. Polymeric, Nonmigratory Cure Coactivators for Accelerated Sulfur Vulcanization

Rubber Chemistry and Technology ◽

10.5254/1.3536286 ◽

1989 ◽

Vol 62 (5) ◽

pp. 957-972

Author(s):

A. Y. Coran ◽

F. Ignatz-Hoover ◽

L. H. Davis

Keyword(s):

Molecular Weight ◽

Minimum Loss ◽

Synthetic Rubber ◽

Curing Characteristics ◽

Sulfur Vulcanization ◽

Delayed Action ◽

Very High ◽

Rubber Article

Abstract Rubbery vinylpyridine-butadiene copolymers, containing 20–65% by weight of vinylpyridine monomer units, are effective coactivators of vulcanization for TBBS-accelerated sulfur-vulcanized SBR. In addition to emulsion SBR, the new co-activator has been evaluated in copositions of solution SBR, BR, NR, and various blends. The co-activator is active in all of the compositions which contain butadiene-derived synthetic rubber. This includes blends such as SBR/BR, solution-SBR/BR, SBR/NR, BR/NR, SBR/BR/NR, etc. There is little or no activity in which NR is the only polymer. The most efficacious copolymers contain between 30 and 60% 2-vinylpyridine. The incorporation of such a copolymer into an unvulcanized butadiene-derived rubber mix can give a substantial increase in the rate of crosslink formation with only a minimum loss of scorch resistance. Since the polymeric coactivators are very high in molecular weight, it can be at least tentatively concluded that they will not migrate from one component stock to another in a built-up multi-stock rubber article, either before or during vulcanization. Since the curing characteristics of a vinylpyridine-copolymer-containing TBBS-accelerated stock can be similar to those of TBBS-accelerated NR, it might be concluded that the new additives will solve some of the problems in balancing the cures of adjacent NR and SBR stocks in a multicomponent cured rubber article.

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Alternative of bone china and porcelain as ceramic hand molds for rubber latex glove films formation via dipping process

REVIEWS ON ADVANCED MATERIALS SCIENCE ◽

10.1515/rams-2020-0042 ◽

2020 ◽

Vol 59 (1) ◽

pp. 523-537

Author(s):

Chaturaphat Tharasana ◽

Aniruj Wongaunjai ◽

Puwitoo Sornsanee ◽

Vichasharn Jitprarop ◽

Nuchnapa Tangboriboon

Keyword(s):

Thermal Expansion ◽

Flexural Strength ◽

Thermal Expansion Coefficient ◽

Expansion Coefficient ◽

Mold Surface ◽

Rubber Latex ◽

Latex Glove ◽

Bone China ◽

Synthetic Rubber ◽

Natural And Synthetic

AbstractIn general, the main compositions of porcelain and bone china composed of 54-65%wt silica (SiO2), 23-34% wt alumina (Al2O3) and 0.2-0.7%wt calcium oxide (CaO) suitable for preparation high quality ceramic products such as soft-hard porcelain products for teeth and bones, bioceramics, IC substrate and magneto-optoelectroceramics. The quality of ceramic hand mold is depended on raw material and its properties (pH, ionic strength, solid-liquid surface tension, particle size distribution, specific surface area, porosity, density, microstructure, weight ratio between solid and water, drying time, and firing temperatures). The suitable firing conditions for porcelain and bone china hand-mold preparation were firing at 1270°C for 10 h which resulted in superior working molds for making latex films from natural and synthetic rubber. The obtained fired porcelain hand molds at 1270°C for 10 h provided good chemical durability (10%NaOH, 5%HCl and 10%wtNaCl), low thermal expansion coefficient (5.8570 × 10−6 (°C−1)), good compressive (179.40 MPa) and good flexural strength (86 MPa). While thermal expansion coefficient, compressive and flexural strength of obtained fired bone china hand molds are equal to 6.9230 × 10−6 (°C−1), 128.40 and 73.70 MPa, respectively, good acid-base-salt resistance, a smooth mold surface, and easy hand mold fabrication. Both obtained porcelain and bone china hand molds are a low production cost, making them suitable for natural and synthetic rubber latex glove formation.

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Natural and Synthetic Rubber. IV. 4-Methyl-4-Octene by Isoprene Ethylation

Rubber Chemistry and Technology ◽

10.5254/1.3535508 ◽

1930 ◽

Vol 3 (3) ◽

pp. 483-484

Author(s):

Thomas Midgley ◽

Albert L. Henne

Keyword(s):

Double Bond ◽

Synthetic Rubber ◽

Double Bond System ◽

Bond System ◽

Usual Behavior ◽

Natural And Synthetic ◽

Long Chains

Abstract Isoprene has been ethylated; 4-methyl-4-octene was formed exclusively. The structure of this nonene is in agreement with the usual behavior of a conjugated double bond system. This type of addition is further evidence in favor of the hypothesis which regards the polymerization of isoprene to synthetic rubber as the formation of long chains of isoprene units linked together- by ordinary valences in the 1,4-position.

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