Isoprene Rubber Research Articles

Relation of Water Vapor Permeability of Elastomers to Molecular Structure

Abstract This communication is a quantitative correlation of water vapor permeability of nonpolar elastomers with molecular structure. Permeability of physical blends and of composite layers of elastomers are also discussed. Permeability—Elastomer Structure.—Steric hindrance and unsaturation influence water vapor permeability of elastomers. The low permeability of isobutylene—isoprene (butyl) rubber is attributed to the presence of bulky methyl groups in its isobutylene component. The high unsaturation in isoprene and butadiene is blamed for the high permeability of natural rubber and styrene butadiene rubber. Hence, permeability should be correlated quantitatively with a factor which can evaluate and combine these two structural parameters. Defining the factors A and B to express the relative molar concentrations of unsaturated and steric groups in the average monomer unit of elastomers as (unsaturation) A=1+x/X (steric groups) B=1+y/Y

Butadiene and Isoprene Rubber in Giant Tire Treads

Abstract The lower abrasion found for IR in comparison with NR in an identical formulation could well be counterbalanced by proper modification of the formulation. In spite of the increased black level the heat build-up can still be kept within the limits set by the NR reference. Also, for ternary blends the reduced abrasion resistance of IR can be offset by increasing the black content, without sacrificing loss properties.

Effect of crystalline phase on the elasticity of rubbers

The dynamic mechanical properties of crystallizing divinyl and isoprene rubbers have been investigated over a wide temperature range. It is shown that the formation of a crystalline phase in the rubber leads to a regular increase in rebound resilience in the transition temperature range. The demonstrated relation between these quantities shows that the minimum elasticity can be used as a measure of the crystalline phase present in the polymer.

Hydrochlorination kinetics of natural and synthetic isoprene rubbers

Hydrochlorination kinetics of natural and synthetic isoprene rubbers

Graft Polymers from PVC and Rubber

Abstract 1. The authors investigate the graft copolymerization of vinyl chloride and butadiene-nitrile rubber by a chain transfer reaction, and also the combined mastication of PVC with various rubbers at elevated temperatures. 2. In physicomechanical properties Viniplasts produced on the basis of the products of graft copolymerization of vinyl chloride with butadiene-nitrile rubber, and also of the modification of PVC by butadiene, isoprene and natural rubbers are not superior to the corresponding characteristics of ordinary Viniplast. 3. In the combined mastication of PVC with Nairit and of PVC with butadiene-nitrile rubber at elevated temperatures compositions are produced which in respect of impact strength are 2 to 4 times superior to Viniplast from PVC. 4. It is suggested that the improvement in the physicomechanical properties in the combination of PVC with SKN-26 is connected with the formation of hydrogen bonds between the molecules of the polymers in question.

Crystallizability of SKI Vulcanizates by Adiabatic Stretching

Abstract Lithium isoprene rubber (SKI) which is very similar to natural rubber (NK) in structure and properties has been synthesized at the S. V. Lebedev VNIISK. During the development of the method of preparation and the investigation of the properties of SKI the necessity of studying the crystallizability of different samples of this new type of rubber became apparent. With this object in view we studied the conversion of work into heat during the adiabatic deformation of rubbers. It was shown that the conditions of preparation and of vulcanization determine whether SKI rubbers will crystallize on stretching or remain amorphous. This paper presents some of our data on the crystallizability of SKI rubber.

Determination of Isoprene Unit Structures in Polyisoprene Rubbers

Abstract Conditions were selected for simple and rapid determination of the percentage of 1,4, 3,4 and 1,2 units in synthetic isoprene rubbers from the curves of the rate of their oxidation by benzoyl hydroperoxide. The content of 1,4, 3,4 and 1,2 units in synthetic isoprene rubbers was determined by comparing the curves of the rate of their oxidation by benzoyl hydroperoxide with the curves of oxidation of model compounds, i.e. limonene and gutta percha.

Metal Oxides in Tetramethylthiuram Disulfide Vulcanization

Abstract Rubber is usually vulcanized with the aid of the so-called activators, metal oxides, zinc oxide being the one most often used. In vulcanization in the presence of MBT (mercaptobenzothiazole) or DPG (diphenylguanidine) as accelerators it was found that vulcanization activators have almost no effect on the rate of addition of sulfur to rubber, but have a significant influence on the rate and degree of crosslinking of the rubber molecules. Special interest attaches to studies of the action of metal oxides in vulcanization with tetramethylthiuram disulfide (TMTD), as it is known from actual practice that in the absence of zinc oxide this accelerator does not bring about vulcanization. Vulcanization with TMTD was studied on mixtures of natural rubber (extracted with cold acetone in a stream of nitrogen for 50 hours) and of synthetic isoprene rubber (SKI) masticated on microrolls, of the following compositions (in parts by weight).

Ski Rubber, Polyisoprene, Similar to Natural Rubber

Abstract Years of research at the S. V. Lebedev All-Union Scientific Research Institute for Synthetic Rubber have provided industry with a number of methods for making synthetic rubber from isoprene. Of all the known synthetic rubbers this comes closest to natural rubber in structure and properties; it is the best available substitute of natural rubber, possessing a high degree of elasticity and strength. The present article is a brief summary of the basic work on isoprene rubber done by the Scientific Research Institute of the Tire Industry. On the basis of this work recommendations were made for the development of the production of synthetic isoprene rubber and the substitution of isoprene rubber for natural rubber in the manufacture of heavy duty truck tires. By using different polymerization processes it is possible to produce isoprene rubbers whose chain structures are very similar, but whose molecular weights, and therefore physical and technological properties, are very different. The cis structure of the 1,4 polyisoprene chains is the basic structural element of the new isoprene polymer. Therefore these synthetic isoprene rubbers (SKI) obtained through catalytic polymerization when vulcanized show a crystalline structure when x-rayed in the stretched state. The x-ray photographs also show that the geometric distribution of interference spots in SKI rubbers corresponds to the distribution of interference spots in natural rubber, but that the relative intensities of the crystalline, liquid, and amorphous scatterings in the two rubbers are different (Figure 1).

Chemical Derivatives of Synthetic Isoprene Rubbers

Abstract Natural rubber was the subject of intensive investigation with respect to its chemical reactions and the preparation of commercially useful derivatives. General reviews in this field have been written by Fisher, Schidrowitz, Jones, Sibley, Memmler, Dawson and Schidrowitz, and Farmer. Before World War II several of these reaction products, such as rubber hydrochloride (Pliofilm), isomerized rubber (Pliolite), and chlorinated rubber (Parlon), had been marketed successfully. During the past five years drastic restriction of the commercial use of natural rubber for chemical derivatives prompted the study of synthetic rubbers for this purpose. Endres recently reported on chlorinated and cyclized synthetic lubbers, with special emphasis on GR-S as the starting material. This paper deals particularly with derivatives of polyisoprene and other isoprene-containing synthetic rubbers which behave chemically very much like natural rubber because of the similarity in structure. It is shown that GR-S and other butadiene-containing synthetic rubbers, under the same conditions, are either nonreactive or behave differently. Because of its similarity to the natural rubber product, isomerized synthetic polyisoprene has been designated Pliolite S-1. Chlorinated synthetic polyisoprene is referred to as Pliochlor.

Chemical derivatives of synthetic isoprene rubbers

Chemical derivatives of synthetic isoprene rubbers

Strength of Amorphous and of Crystallizing Rubberlike Polymers

Abstract The strengths of unloaded vulcanizates and the action of active fillers differ greatly according to the types of elastomers from which they are derived. These differences are not connected directly with the chemical compositions of the elastomers. Thus, for example, vulcanizates of natural rubber and synthetic isoprene rubber differ in strength in the ratio 10–15 to 1, whereas vulcanizates of Butyl rubber and of polychloroprene are very similar to natural rubber vulcanizates with respect to tensile strength. These differences in tensile strength cannot be ascribed directly to differences in structure of the chains, linear or branched; linear polymers of styrene and of methyl methacrylate “vulcanized” by small admixtures of butadiene-benzene or dimethacrylate-ethyleneglycol have, in the elastic state, tensile strengths which are just as low as those of unloaded vulcanizates of sodium-butadiene rubber or of isoprene rubber. The differences in tensile strength must, accordingly, be looked for in the different macroscopic properties of these polymers.

Observations on the Chemical Constitution and Physical Properties of Rubber

Abstract Some time ago we published the finding that the decrease in the iodine number of rubber on cyclisizing it electrically was accompanied by a marked loss of valuable colloid-chemical properties, and, moreover, that isoprene rubber originally characterized by a low iodine number improved in properties under the influence of the silent electric discharge, while the iodine number increased. These facts suggested that commercially less valuable grades of rubber might owe their inferiority to their essentially lower degree of unsaturation. Therefore the investigation was begun by comparing the known iodine numbers of the best grades of plantation rubber with those of the poorer grades. Pure rubber, as, for example, that prepared by Pummerer's method, is known to have an iodine number very near the theoretical (372.8). In the case of raw rubber each per cent of the rubber hydrocarbon present requires 3.728 units of the iodine number, so that naturally a lower value is to be expected as approximately four units must be subtracted for each per cent of impurity. If we suppose smoked sheets to contain 93% of rubber hydrocarbon, we can ascribe to it an iodine number of only about 347, provided that the impurities do not combine with any iodine, which, however, though not important, is not so. A sample of smoked sheet containing 3.2% of acetone-soluble material and 0.4% of mineral matter besides protein, etc., was found to have an iodine number of 348. Washed Congo rubber containing 5.9% of acetone-soluble material and 1.7% of mineral matter had an iodine number of 329. The iodine number of the acetone-soluble portion was 24, so that 5.9% of extract required approximately 1.4 units of the iodine number; hence the rubber hydrocarbon present had an iodine number of 327.6. If the components of the rubber insoluble in benzene were filtered off and the rubber precipitated twice with acetone and once with alcohol and then dried in a vacuum at 50° C. to constant weight, the iodine number rose to 351.4, thus closely approaching the theoretical value, considering the impurities still present. It is questionable whether or not one may attribute the less valuable properties of this wild rubber to its very slightly lower degree of unsaturation. For the present we shall restrict ourselves to the publication of our results in the following table, with the intention of returning to this question after a detailed examination of a greater amount of material.