The Synthesis of Isocyanate-Modified Novolak Resins for Use in Natural and Synthetic Rubber

1980 ◽  
Vol 53 (2) ◽  
pp. 239-244 ◽  
Author(s):  
N. D. Ghatge ◽  
B. M. Shinde
Keyword(s):  
Tensile Strength ◽  
Synthetic Rubber ◽  
Natural And Synthetic

Abstract Resin-C and Resin-B give higher values for tensile strength, modulus, and hardness than all other resins.

Stress Relaxation of Natural and Synthetic Rubber Stocks

1944 ◽  
Vol 17 (3) ◽  
pp. 551-575 ◽  
Author(s):  
A. V. Tobolsky ◽  
I. B. Prettyman ◽  
J. H. Dillon
Keyword(s):  
Tensile Strength ◽  
Free Energy ◽  
Reaction Rate ◽  
Energy Of Activation ◽  
Effect Of Temperature ◽  
Rate Theory ◽  
Air Atmosphere ◽  
Synthetic Rubber ◽  
Commercial Nitrogen ◽  
Natural And Synthetic

Abstract 1. The complete decay of stress in the rubbers studied, held at constant elongation, appeared to involve the rupturing of a definite bond, either at some point along the molecular chain or at the cross-linking bond put in by vulcanization. In the case of a Hevea rubber gum stock the data could be fitted very well by ordinary reaction-rate theory, leading to the conclusion that the free energy of activation required for breaking the bond is 30.4 kcal. per mole of bonds. This result was found to be practically independent of the elongation, and of the presence of carbon black in a Hevea rubber tread stock. This is to be compared to a strength of about 90 kcal. per mole for the C—C bond. 2. In the case of other rubbers (Buna-S, Butaprene-N, Neoprene-GN, and Butyl) the activation free energy for breaking the bond did not vary by more than ±2.0 kcal. per mole from that of Hevea rubber. However, these differences were quite definite. For example, the relaxation of stress in GR-S was slower than in Hevea; a small difference in energy corresponding to a 2:1 ratio in the respective times of decay. 3. The effect of temperature on the relaxation of stress appeared to be of the general type characteristic of chemical reactions. By use of the ordinary formula for expressing rate of reaction in terms of energy of activation, one could predict very closely the behavior of the stress-log time curves at different temperatures. 4. Natural rubber and GR-S vulcanized with paraquinone dioxime and lead dioxide showed relaxation curves very similar to those of the sulfur vulcanized stocks. 5. Relaxation experiments in an ordinary air atmosphere and in an atmosphere of commercial nitrogen showed no appreciable differences. 6. Examination of stretched rubber bands in which the stress had decayed nearly completely (at 100° C) gave no evidences of gross oxidation, such as would make the rubber bands sticky or hard, or of surface deterioration. At higher temperatures, however, the rubber could be observed getting sticky, and then brittle. Specimens in which the stress had completely decayed showed very low tensile strength (by hand test). 7. Antioxidant added to a sulfur-stabilized Buna-S stock caused a definite retardation of the rate of relaxation. 8. Comparison of the results of these experiments with previously recorded observations in the literature indicated that the chemical reaction which ruptured the rubber structure and caused the decay of stress in these experiments (and concomitantly a lowering of tensile strength) was an oxidation of the rubber by small amounts of oxygen, the reaction rate being independent of the oxygen pressure in the range between that present in an ordinary air atmosphere and in a commercial nitrogen atmosphere. 9. The tests suggested a convenient and accurate laboratory method of determining the oxidizability of natural and synthetic rubber stock designed for service.

Vulcanization of Rubber with Synthetic Resins

1946 ◽  
Vol 19 (1) ◽  
pp. 86-99 ◽  
Author(s):  
A. J. Wildschut
Keyword(s):  
Tensile Strength ◽  
Magnesium Oxide ◽  
Sulfur Compounds ◽  
Chemical Bonds ◽  
Synthetic Resin ◽  
Gutta Percha ◽  
Synthetic Rubber ◽  
Synthetic Resins ◽  
Technical Properties ◽  
Natural And Synthetic

Abstract Natural and synthetic rubber can be vulcanized with several vulcanizing agents other than sulfur, though sulfur and sulfur compounds are the only agents of practical value. A combination of rubber and synthetic resin can be successful only when chemical bonds are formed. It has been found that this is the case with certain synthetic resins, and that natural and synthetic rubber can be vulcanized with these resins, without adding any other agent or filler, in much the same way as with sulfur. An example of these resins is the resol from pentaphene (p-t-amylphenol) and formaldehyde. Data are given for the technical properties of rubber-resin vulcanizates. Catalysis or a similar effect is produced by magnesium oxide, which increases the tensile strength, while hexamethylenetetramine prevents the reaction. Balata can be vulcanized with the same synthetic resins as rubber; with gutta-percha the effect of heating with rubber-vulcanizing resins is the same as with sulfur. The probable configuration of the rubber-resin vulcanizates consists of two systems of entangled thread-molecules, which are interlinked at a limited number of points by primary valence bonds.

Tensile Properties of Natural and Synthetic Rubbers at Elevated and Subnormal Temperatures

1950 ◽  
Vol 23 (2) ◽  
pp. 338-346 ◽  
Author(s):  
B. S. T. T. Boonstra
Keyword(s):  
Tensile Strength ◽  
High Temperature ◽  
Carbon Black ◽  
Natural Rubber ◽  
Tensile Properties ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
High Temperature Strength ◽  
Synthetic Rubber ◽  
Natural And Synthetic

Abstract It is necessary to determine the physical properties of rubbers at relatively high temperatures when products made from them are to be used at such temperatures in actual service. The term heat aging is used when the vulcanizate is tested at room temperature, exposed to elevated temperatures for given periods of time, and then tested again at room temperature. The term high-temperature strength is proposed for values obtained when the vulcanizates are tested at the actual higher service temperatures. Effective comparison of natural and synthetic rubbers is best obtained by determining tensile product values, which are the result of the combining of tensile strength and elongation values. In the evaluating of vulcanizates of tire compounds of various rubbers, another factor must be taken into account. Synthetic-rubber tires develop more heat in service than do natural-rubber tires, and the former therefore generally operate at higher temperatures than do the latter. Synthetic-rubber tires therefore require a greater high temperature strength than do natural rubber tires, but, as has been shown, synthetic rubbers actually have a lower high-temperature strength. The part played by carbon black with respect to the tensile properties of some synthetic rubbers is considered that of a substitute for crystallization in natural and other synthetic rubbers, which substitute does not, however, possess the same favorable features. Carbon black even in noncrystallizing rubbers does not increase strength; it merely shifts the optimum strength value to a higher temperature so that this temperature is in the room temperature range. The temperature coefficient of strength for Butyl and Neoprene rubbers is so large at room temperature that a few degrees' difference in temperature causes large changes in strength. The tensile strength and elongation at break of these two rubbers decrease sharply between 20 and 40° C.

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

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.

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

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.

NATURAL AND SYNTHETIC RUBBER. XI. CONSTITUENTS OF THE MILLED RUBBER HYDROCARBON

1932 ◽  
Vol 54 (8) ◽  
pp. 3381-3383 ◽  
Author(s):  
Thomas Midgley ◽  
Albert L. Henne ◽  
Mary W. Renoll
Keyword(s):  
Synthetic Rubber ◽  
Natural And Synthetic

Natural and Synthetic Rubber. XVI. The Structure of Polystyrene

1936 ◽  
Vol 58 (10) ◽  
pp. 1961-1963 ◽  
Author(s):  
Thomas Midgley ◽  
Albert L. Henne ◽  
Henry M. Leicester
Keyword(s):  
Synthetic Rubber ◽  
Natural And Synthetic
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