GR-S Emulsified with Rosin Soap

1947 ◽  
Vol 20 (1) ◽  
pp. 25-28
Author(s):  
G. R. Cuthbertson ◽  
W. S. Coe ◽  
J. L. Brady
Keyword(s):  
Natural Rubber ◽  
Fats And Oils ◽  
Synthetic Polymer ◽  
Polymerization Reaction ◽  
Rosin Soap ◽  
Double Bonds ◽  
Inhibiting Effect ◽  
Retarding Effect ◽  
Working Together

Abstract One of the most troublesome deficiencies of standard GR-S, in so far as product fabrication is concerned, is the inherent lack of tackiness or the incapability of laminated and spliced surfaces to flow and knit together easily. This was especially bothersome from 1942 to 1944, when the scarcity of natural rubber forced fabricators to use a synthetic polymer before they had developed satisfactory methods and equipment to compensate for its deficiencies. Early in 1942, in anticipation of a later scarcity of fats and oils suitable for making the soap used for emulsification, the several groups working on polymer development problems intensified their efforts to find emulsifying agents which could be made from noncritical domestic materials. Rosin was one of these. Early attempts to use it were unsuccessful, however, because the polymerization reaction was strongly retarded. Later the Hercules Powder Company and The B. F. Goodrich Company, working together, found that the retarding effect could be greatly reduced with the use of disproportionated rosin previously referred to as dehydrogenated rosin. (The treatment given to the rosin results in a molecular disproportionation of the hydrogen, with the elimination of the conjugated double bonds accountable for much of the inhibiting effect on the polymerization reaction.) This work made rosin available for use in the event of an actual scarcity of fats and oils of good quality.

Chlorination of Natural Rubber in Solution with Gaseous Chlorine

1953 ◽  
Vol 26 (4) ◽  
pp. 902-911 ◽  
Author(s):  
C. S. Ramakrishnan ◽  
D. Raghunath ◽  
J. B. Pande
Keyword(s):  
Double Bond ◽  
Natural Rubber ◽  
Cyclization Reaction ◽  
Double Bonds ◽  
Chlorine Atoms ◽  
Reaction Stage ◽  
Stage 1 ◽  
Additive Reaction

Abstract The chlorination of rubber solutions by gaseous chlorine was followed by isolating the partially chlorinated products and preparing their ozonides. The ozonides were hydrolyzed, and the acids and aldehydes formed on hydrolysis were determined. By a comparison with the amounts of acids and aldehydes obtained from ozonides of unreacted rubber, the amount of residual isoprenic double bonds present was found. The loss of double bonds attending the introduction of chlorine atoms into the molecule of rubber indicates four definite stages in chlorination : (1) initial substitutive attack by chlorine, with concomitant cyclization, resulting in a loss of one double bond between two isoprenic units, (2) substitution, (3) additive reaction, and (4) essentially substitution. Chlorination of aged rubber solutions differs from the above in that the cyclization reaction (stage 1) seems to be absent.

Mechanism of Rubber Vulcanization with Sulfur

1938 ◽  
Vol 11 (1) ◽  
pp. 107-130
Author(s):  
W. K. Lewis ◽  
Lombard Squires ◽  
Robert D. Nutting
Keyword(s):  
Natural Rubber ◽  
Temperature Coefficient ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Reaction Rate ◽  
Complex Behavior ◽  
Double Bonds ◽  
Irreversible Reaction ◽  
Sulfur Addition

Abstract THAT vulcanization of rubber with sulfur always involves a chemical reaction consisting in the addition of sulfur to the double bonds of the rubber molecule has been conclusively established (18, 28). The facts indicate that this addition of sulfur to rubber is an irreversible reaction (31). The temperature coefficient of the reaction is high, increasing about 2.65 fold per 10° C. at ordinary curing temperatures (31). Furthermore, the reaction is apparently exothermic (4, 24). It is noteworthy that catalysts are apparently necessary, since synthetic rubbers prepared from pure materials add sulfur slowly, if at all. The proteins and perhaps the resins in natural rubber undoubtedly serve as accelerators. The curves for combined sulfur vs. time of cure for typical mixes are shown in Figures 1 and 2. Figure 1 is taken from the data of Kratz and Flower (16); the composition and temperature of cure for this mix are shown in Cranor's Table I (9). Figure 2, curve 1, is from Table I of Eaton and Day (10), and curve 2 from data obtained in this laboratory (27, Table I). Superficial inspection of these curves shows extraordinary divergence of type. Figure 1 is a typical fadeaway curve, characteristic of most chemical reactions, where the reaction rate decreases with decreasing concentration of the reacting materials. Curve 1, Figure 2, is an entirely different type, where the rate of sulfur addition is constant until nearly 70 per cent of the initial sulfur has reacted. Curve 2, Figure 2, shows even more complex behavior. Again the rate is constant in the initial portions of the cure. However, following this period, the rate increases markedly but later falls off, approaching zero, to give an S-shaped eurve.

Statistical Lengths of Rubberlike Hydrocarbon Molecules

1943 ◽  
Vol 16 (3) ◽  
pp. 479-485
Author(s):  
Frederick T. Wall
Keyword(s):  
Natural Rubber ◽  
Physical Properties ◽  
Chemical Properties ◽  
Hydrocarbon Chain ◽  
Point Of View ◽  
Double Bonds ◽  
Gutta Percha ◽  
Cis And Trans ◽  
Trans Structure ◽  
And Chemical Properties

Abstract It has been known for some time that the pure hydrocarbons of balata (or gutta-percha) and natural rubber have the same chemical composition and chemical properties. Both balata and rubber appear to be polymers of isoprene, (C5H8)n, with the same degree of unsaturation. Their physical properties are sufficiently different, however, to make it clear that their structures must differ in some important respect. Since the molecules contain numerous double bonds, it has been suggested that rubber and balata are geometric isomers. Every fourth bond in a rubber or balata molecule is a double bond, so it follows that the possibilities for geometric isomerism are considerable. It was proposed by Meyer and Mark that natural rubber hydrocarbon has a structure for which the molecular chain is cis with respect to all of the double bonds. Balata (or gutta-percha) is then supposed to have a trans-structure throughout, this view having been verified by Fuller and Bunn. It is the purpose of the present paper to consider, from the point of view of recent theories of rubber elasticity, to what extent these structures explain the differences in physical properties. The method to be employed involves calculation of the root mean square lengths of the cis- and trans-structures, which, when compared to their maximum lengths, should give an indication of their extensibilities. In 1932 Eyring treated the problem of the average square length of a hydrocarbon chain. In the present paper a different derivation of Eyring's equation is given (for illustrative purposes), after which this derivation will be extended to the rubberlike molecules with double bonds.

Polymer-Modified Natural Rubber

1956 ◽  
Vol 29 (3) ◽  
pp. 706-717 ◽  
Author(s):  
F. M. Merrett ◽  
R. I. Wood
Keyword(s):  
Natural Rubber ◽  
Chemical Compounds ◽  
Synthetic Polymer ◽  
Technological Properties ◽  
Cooperative Program

Abstract Earlier efforts to prepare and examine rubber-synthetic polymer compositions have made virtually no attempt to determine the nature of the products, that is, whether they were simple mixtures or chemical compounds and, if the latter, of what type, and thus to rationalize, if only broadly, their physical and technological properties in terms of their basic structures. The work now described has had this object in mind, and represents a cooperative program of research, including chemical, physical, and technological aspects.

Structural Changes in Vulcanization of Buna-S

1946 ◽  
Vol 19 (3) ◽  
pp. 534-545
Author(s):  
Max H. Keck ◽  
La Verne E. Cheyney
Keyword(s):  
Natural Rubber ◽  
Chemical Reactions ◽  
Structural Changes ◽  
Double Bonds

Abstract In conclusion, the data presented here indicate that two types of chemical reactions take place during the vulcanization of Buna-S stocks of a specific type: (1) a combination with sulfur, which may or may not involve the double bonds in the polymer, and which may be similar in character to the primary vulcanization reaction of natural rubber; (2) a second reaction, presumably polymerization, which accompanies the first and is related to and possibly initiated by it, and which continues on over cure.

Halogenation of Ethylene Propylene Diene Rubbers

1971 ◽  
Vol 44 (4) ◽  
pp. 1025-1042 ◽  
Author(s):  
R. T. Morrissey
Keyword(s):  
Natural Rubber ◽  
Double Bonds ◽  
Optimum Amount ◽  
Ethylene Propylene ◽  
Rubber Compounds ◽  
Rubber Part ◽  
Curing Agents ◽  
Diene Rubbers ◽  
Curing Systems

Abstract The ethylene propylene diene rubbers (EPDM) have been modified by halogenation. The reaction has been considered as one mainly of addition to the double bonds of the diene portion of the rubber. Dehydrohalogenation may occur to varying degrees, depending on the conditions of the reaction and the diene present in the rubber. Part of the halogen is believed to be in the allylic position. The halogenated EPDM may be vulcanized by sulfur as well as many of the curing agents used for other halogen-containing polymers. Both types of curing systems can function in the same compound. Therefore, the halogenated EPDM rubbers can be covulcanized with the highly unsaturated elastomers such as natural rubber, cis polybutadiene, and the SBR rubbers. The excellent properties, resistance to ozone, and flexing, of the halogenated EPDM can be imparted to these elastomers using standard curing systems. Also, the uncured tack of halogenated EPDM can be improved by increasing amounts of natural rubber. In addition, other advantages are adhesion of these blends to other rubber compounds and metal. It has been shown that the cure compatibility properties of the halogenated EPDM can be varied as the halogen is increased in the rubber. Evidence has been presented which shows there is an optimum amount of halogen necessary for the best properties in mixtures with other elastomers.

Ozone and Sunlight Effect on Aging of Carbon Black Vulcanizates

1953 ◽  
Vol 26 (1) ◽  
pp. 127-135
Author(s):  
George E. Popp ◽  
Lynn Harbison
Keyword(s):  
Particle Size ◽  
Low Temperature ◽  
Carbon Black ◽  
Natural Rubber ◽  
Size Structure ◽  
Synthetic Polymer ◽  
Ozone Exposure ◽  
Polymer Compound ◽  
Type Particle ◽  
Weather Resistance

Abstract Carbon black, regardless of type, particle size, structure, and physical properties imparted, does not affect the rate or degree of checking or cracking in natural-rubber or low-temperature polymer compounds when subjected to weather or ozone exposure. Natural rubber will withstand much longer periods of exposure than the synthetic polymer studied. A pronounced degree of ozone and weather cracking and checking will result if no antioxidant is compounded into the synthetic polymer. An MAF black-synthetic polymer compound may be substantially improved in its resistance to ozone and weather resistance by selection and application of the proper antichecking ingredients.

Mineral Sulfide as Index of Disulfide Cross-Bonding

1947 ◽  
Vol 20 (3) ◽  
pp. 649-663 ◽  
Author(s):  
C. M. Hull ◽  
S. R. Olsen ◽  
Wesley G. France
Keyword(s):  
Natural Rubber ◽  
Cross Linking ◽  
Diallyl Disulfide ◽  
Double Bonds ◽  
Metal Soap ◽  
Sulfide Production ◽  
Sulfur Vulcanization

Abstract 1. The mechanism proposed by Armstrong, Little, and Doak to explain sulfur vulcanization in the presence of metal soap was investigated in polyprene and simpler systems from the viewpoint of the inorganic sulfide produced and, in the case of polyprenes, of the accompanying modulus. 2. Dodecanethiol was found to react with sulfur and zinc soap to produce inorganic sulfide equivalent to the oxidation of 80 to 100 per cent of the thiol to disulfide ; with excess thiol substantially quantitative conversion of sulfur or of zinc soap to inorganic sulfide can be obtained. 3. Several simple olefins were found to react readily with sulfur and zinc soap under vulcanizing conditions. The reaction is promoted by M.B.T. On the basis of the mechanism assumed, the inorganic sulfide formed is sufficient to indicate extensive conversion of the olefin to a substituted diallyl disulfide. 4. Assuming the validity of the proposed mechanism, inorganic sulfide production indicates substantial disulfide cross-linking between α-carbon atoms in conventional cures with natural rubber, and appreciable, though relatively less, cross-bonding of this type in the case of GR-S. The smaller extent of this type of cross-linking with GR-S is believed to result from greater tendency on the part of this elastomer to add the intermediate mercapto compound to double bonds, as proposed in the first paper of this series.

Natural and Synthetic Rubber. I. Products of the Destructive Distillation of Natural Rubber

1929 ◽  
Vol 2 (3) ◽  
pp. 441-451 ◽  
Author(s):  
Thomas Midgley ◽  
Albert L. Henne
Keyword(s):  
Experimental Data ◽  
Natural Rubber ◽  
Atmospheric Pressure ◽  
Experimental Results ◽  
Double Bonds ◽  
Synthetic Rubber ◽  
Single Bonds ◽  
Natural And Synthetic

Abstract Two hundred pounds of pale crepe rubber have been destructively-distilled at atmospheric pressure. The distillate was fractionated and its components identified from C5 to C10, as shown in the table. Assuming that the Staudinger formula is correct, that the single bonds furthest from the double bonds are the weaker spots and that the formation of six-carbon rings is favored, it has been shown that nearly all of the compounds actually isolated could be predicted. The experimental results, together with forthcoming experimental data, are expected to be used to throw light upon the formula of the rubber molecule.

The cyclization of natural rubber

1963 ◽  
Vol 273 (1354) ◽  
pp. 345-359 ◽  
Keyword(s):  
Natural Rubber ◽  
Stannic Chloride ◽  
Double Bonds ◽  
Perbenzoic Acid ◽  
Infra Red ◽  
Iodine Chloride ◽  
Series Of Experiments ◽  
Average Size ◽  
Kinetics Of ◽  
Reaction In Solution

Several methods of measuring the unsaturation remaining in natural rubber after cyclization have been compared. Approximate agreem ent was obtained with the reagents, perbenzoic acid, phenyl iododichloride and ozone; iodine chloride gave high values. Perbenzoicacid is considered the most satisfactory of these reagents. The unsaturation in some cyclized rubber samples was found to be below 20% of that in the original rubber. This value is inconsistent with a cyclized rubber structure of single rings each involving two isoprene units and supports instead a polycyclic structure. This structure is also supported by some degradation experiments. Infra-red spectroscopy shows that the double bonds remaining after cyclization are not of the original trialkyl-substituted type. Use has been made of measurements of total unsaturation by means of perbenzoic acid and of trialkyl-substituted double bonds by infra-red spectrometry to investigate the kinetics of the cyclization reaction in solution and catalyzed by stannic chloride. All the results were accurately fitted by theoretical equations derived for a reaction proceeding in stepwise fashion along the rubber chains. The average size of the polycyclic structures formed during cyclization was found to be independent of both rubber and catalyst concentrations but to be markedly dependent on the temperature, varying in a series of experiments from approximately one and a half condensed rings at 110 °C to six rings at 60 °C. The rate of the reaction was first order in the rubber and second order in the catalyst.

Sign in / Sign up

Export Citation Format

Share Document