Monolayer Studies of Some Hydroxylated Polyolefin Rubbers

1958 ◽  
Vol 31 (3) ◽  
pp. 446-458
Author(s):  
W. R. Dean ◽  
V. Perera ◽  
J. Glazer
Keyword(s):  
Natural Rubber ◽  
Surface Reaction ◽  
Varying Thickness ◽  
Polar Groups ◽  
Gutta Percha ◽  
Styrene Copolymers ◽  
End Products ◽  
Balance Technique ◽  
Butadiene Styrene ◽  
Kinetic Features

Abstract The study of high polymer monolayers by the Langmuir balance technique has been almost wholly restricted to those polymers which contain polar groups, e.g., cellulose, proteins, polyacrylates, etc. Nonpolar polymers do not spread and so little attention has been paid to the hydrocarbon rubbers. Wall and Zelikoff have reported that natural rubber, gutta-percha, and butadienestyrene copolymers do not form stable monolayers on water, but that when these materials are modified chemically by thiocyanogen they form relatively thin films of varying thickness. Sivaramakrishnan and Rao have recently confirmed that natural rubber does not form a monolayer on water. However, they find that it spreads spontaneously on a subsolution of aqueous acidic potassium permanganate. We have investigated the surface reaction between certain polyolefins and aqueous permanganate ; the kinetic features of these reactions, discussed elsewhere, suggest that definite chemical end-products are formed on the surface. The purpose of this communication is to characterize the end-products obtained from natural rubber (cis-1,4-polyisoprene), gutta-percha (trans-1,4-polyisoprene), polybutadiene, and two butadiene-styrene copolymers of differing styrene content, when these react under controlled conditions at the surface of an acidic aqueous permanganate subsolution.

Flow Patterns in Elastomers and Their Carbon Black Compounds during Extrusion through Dies

1985 ◽  
Vol 58 (4) ◽  
pp. 815-829 ◽  
Author(s):  
Chin-Yuan Ma ◽  
James L. White ◽  
Frederick C. Weissert ◽  
Avraam I. Isayev ◽  
Nobuyuki Nakajima ◽  
...  
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Flow Patterns ◽  
Entrance Region ◽  
Evidence Based ◽  
Streamline Flow ◽  
Basic Study ◽  
Entrance Angle ◽  
Styrene Copolymers ◽  
Butadiene Styrene

Abstract A basic study of flow patterns in elastomers in the entrance region of a die has been carried out for various gum elastomers including emulsion and solution butadiene—styrene copolymers, polybutadiene, and natural rubber. All exhibit streamline flow into the entrance with the exception of a cold mastication degraded natural rubber which gave evidence of vortices in corners. A study of a die with a sharp diverging region showed dead spaces for all the elastomers. Carbon black compounds all exhibited converging streamline flow in a 180° entrance angle die and stagnant regions in the sharply diverging die. Evidence based on marker motions has been presented for slip in elastomer compounds in the entrance region.

Properties of Ebonite. XXXVII. Electrical Properties of Synthetic Rubber Ebonites

1949 ◽  
Vol 22 (4) ◽  
pp. 1084-1091
Author(s):  
D. G. Fisher ◽  
L. Mullins ◽  
J. R. Scott
Keyword(s):  
Natural Rubber ◽  
Power Factor ◽  
Power Loss ◽  
Ionic Conduction ◽  
Effect Of Temperature ◽  
Plastic Yield ◽  
Styrene Copolymers ◽  
Synthetic Rubber ◽  
High Dielectric ◽  
Butadiene Styrene

Abstract Experiments were carried out to explore the possibility of making good electrical ebonites from various types of synthetic rubber. The ebonites produced were tested for permittivity and power factor over wide ranges of temperature and frequency. Thioplasts (Thiokols AZ and FA) apparently do not produce hard ebonitelike vulcanizates by the normal procedure. Neoprenes (GN and I) give ebonites, but with such high dielectric power loss as to be unsuitable for use as high-frequency dielectrics; moreover, if the mix contains zinc oxide, the ebonite has a very hygroscopic and therefore electrically unsatisfactory surface. Butadiene copolymers containing polar groups (butadiene-acrylonitrile types and Thiokol RD) give ebonites with high power loss, hence are not suitable for making high-grade electrical ebonites. Polybutadiene (Buna-85) and butadiene-styrene copolymers (GR-S, Hycar-EP, Buna-S) are much nearer to natural rubber as far as the radio-frequency (100 to 2,500 kc. per sec.) power loss of their ebonites is concerned. The GR-S ebonite examined was not so good as natural rubber at room temperature, but was superior above about 50° C. Buna-85 and Hycar-EP were superior to natural rubber over the whole temperature range; indeed, the high-styrene copolymers, as represented by Hycar-EP and Buna-SS, appear to be the best type of synthetic rubber for making ebonite with low power loss, especially at high frequencies and temperatures. The effects of changing temperature and frequency on permittivity and power factor are discussed. Attention is drawn to the big effect of temperature on power factor; this was less with polybutadiene and butadiene-styrene ebonites than with natural rubber ebonite, in keeping with the greater heat resistance of the former as judged by plastic yield tests. Comparison of the effects of rising temperature and decreasing frequency shows that these produce broadly similar effects on power factor, as would be expected on theoretical grounds, but that rising temperature superposes a second effect (an increase), presumably due to increased ionic conduction.

Comparison of Natural and Synthetic Hard Rubbers

1947 ◽  
Vol 20 (1) ◽  
pp. 99-115
Author(s):  
G. G. Winspear ◽  
D. B. Hermann ◽  
F. S. Malm ◽  
A. R. Kemp
Keyword(s):  
Natural Rubber ◽  
Rapid Progress ◽  
Rubber Industry ◽  
Styrene Copolymers ◽  
Standard Procedures ◽  
Nitrile Rubbers ◽  
Normal Production ◽  
War Production ◽  
Short Time ◽  
Butadiene Styrene

Abstract The wartime replacement of natural rubber by synthetics required an unusual expenditure of effort by the hard rubber industry in a short time. At first, curtailment of normal production, coupled with War Production Board restrictions of formulations, mitigated the urgency for synthetic hard rubber research. It soon became evident, however, that a complete line of synthetic hard rubbers would be desirable. These materials could be fabricated with standard rubber processing equipment, and would offer physical and electrical equivalents for the various grades of natural hard rubber developed during nearly a century. A program was started in these laboratories with the realization that rapid progress might be difficult; research on the compounding of natural hard rubber over the years had failed to produce improvements in overall properties compared with the original “ebonites”. The latter, according to the accepted nomenclature, are simple mixtures of rubber with large proportions of sulfur vulcanized by heating until chemical saturation of the rubber is almost complete. The first approach to the problem was through a study of vulcanizing characteristics and through examination of the hard products resulting from the reaction of sulfur with butadiene-styrene copolymers. As the program progressed, the work was extended to cover the processing of GR-S for ebonite fabrication and the compounding of GR-S hard rubbers for specific applications. Studies also were conducted relating to the compounding and processing of hard nitrile rubbers, and new tests were developed to suplement standard procedures used in the physical evaluation of hard rubbers.

Low-Temperature Behavior of Butadiene-Styrene Copolymers. Effect of Compounding Variables

1950 ◽  
Vol 23 (4) ◽  
pp. 760-769
Author(s):  
R. D. Juve ◽  
J. W. Marsh
Keyword(s):  
Low Temperature ◽  
Natural Rubber ◽  
Compression Set ◽  
Similar Work ◽  
Styrene Copolymers ◽  
Synthetic Rubber ◽  
Low Temperature Flexibility ◽  
Extended Exposure ◽  
Butadiene Styrene ◽  
Elastic Characteristics

Abstract Synthetic rubbers and natural rubber increase in stiffness at low temperatures and tend to lose their elastic characteristics. This stiffening and hardening phenomenon occurs in varying degrees with various elastomers. Natural rubber and certain synthetic rubbers crystallize during extended exposure at low temperature, whereas other synthetic rubbers such as GR-S remain amorphous. In a general review of the low temperature properties of synthetic rubber, Liska has shown that decreased styrene in butadiene-styrene copolymers improves the flexibility at low temperature. The low temperature flexibility of vulcanized articles made from any particular rubber or synthetic rubber is influenced by the compounding ingredients admixed with the elastomer. This paper shows the results of some studies of the effect of these compounding ingredients on the low temperature serviceability of butadiene-styrene copolymers. Somewhat similar work on the effect of a large number of plasticizers in GR-S has been conducted at the Rubber Laboratory, Mare Island Naval Shipyard, with particular emphasis on compression set at low temperature.

Plastic Yield of Butadiene-Styrene and Isoprene-Styrene Ebonites

1951 ◽  
Vol 24 (2) ◽  
pp. 381-383 ◽  
Author(s):  
J. R. Scott
Keyword(s):  
Plastic Deformation ◽  
Natural Rubber ◽  
Elevated Temperatures ◽  
Styrene Copolymer ◽  
Heat Resistant ◽  
Plastic Yield ◽  
Styrene Copolymers ◽  
Styrene Content ◽  
Butadiene Styrene

Abstract In unloaded ebonites made from butadiene-styrene copolymers, the resistance to plastic deformation at elevated temperatures is better the higher the styrene content of the copolymer, at least up to 46 per cent. An isoprene-styrene copolymer ebonite has poorer plastic-yield resistance than a corresponding butadiene-styrene ebonite. All the styrene-containing copolymers, however give ebonites more heat-resistant than natural rubber ebonite, the best giving yield temperatures 30° C above the latter. To attain the best plastic-yield resistance in butadiene-styrene ebonites, the amount of sulfur added should correspond to more than 1 atom (e.g., 1.2 or even 1.4 atoms) per butadiene molecule.

The Brabender Plastograph in the Rubber Laboratory

1948 ◽  
Vol 21 (2) ◽  
pp. 531-538
Author(s):  
A. E. Juve ◽  
D. C. Hay
Keyword(s):  
Natural Rubber ◽  
Temperature Coefficient ◽  
Small Scale ◽  
Styrene Copolymers ◽  
Butadiene Styrene

Abstract With suitable modifications the Brabender plastograph can be used to advantage in studying, on a small scale, the factors which influence the changes in consistency of rubbers during their mastication. Typical results reported herein show that the temperature coefficient of the rate of breakdown for natural rubber is 1.47 and for GR-S, 1.36. The rate of softening of butadiene-styrene copolymers is shown to depend, among other factors, on the original consistency of the rubber and the type of modifier used in polymerization. The influence of commercial peptizing agents on the rate of softening of natural rubber, GR-S, and GR-I at 150° C is shown. The reproducibility of the mastication test was found to be good.

Mastication of Rubber. II. Interpolymerization of Natural Rubber and Neoprene on Cold Milling

1956 ◽  
Vol 29 (2) ◽  
pp. 427-437
Author(s):  
D. J. Angier ◽  
W. F. Watson
Keyword(s):  
Free Radicals ◽  
Natural Rubber ◽  
Small Molecules ◽  
The Other ◽  
Polymer Molecules ◽  
Commercially Important ◽  
The Individual ◽  
Cold Mill ◽  
General Method ◽  
Butadiene Styrene

Abstract The softening of elastomers on cold milling results from scission of the polymer molecules by the applied shearing forces. The ruptured chains are free radicals, which can undergo mutual combination, interaction with oxygen and various additives, and branching (grafting) on to other polymer molecules. A general method of producing graft and block interpolymers between elstomers is therefore indicated, namely, to cold-mill the polymers together in the absence of small molecules which can terminate the polymeric radicals in order that the radicals may cross-terminate or graft onto the polymer molecules of the other type. A survey of several pairs of the commercially important elastomers, natural rubber, butadiene-styrene, Neoprene, and butadiene-acrylonitrile, has shown that cold milling does effect interlinking. Detailed results for the rubber-Neoprene system are reported in this communication. Experimental verification of polymer interlinking was obtained from the solubility properties of the milled elastomers. Cold milling of Neoprene under nitrogen produces gel, whereas of natural rubber does not, but the milling of mixtures gives gels containing natural rubber. Also, the solubilities and precipitation of the milled mixtures cannot be accounted for by these properties of the individual polymers. Finally, Neoprene-natural rubber mixtures, after and not before cold-milling, can be cross-linked by magnesium oxide, with rubber bound into the vulcanizate.

Effect of Temperature on Ozone Cracking of Rubbers

1966 ◽  
Vol 39 (3) ◽  
pp. 643-650
Author(s):  
A. N. Gent ◽  
J. E. McGrath
Keyword(s):  
Polymer Chains ◽  
Effect Of Temperature ◽  
Ozone Molecule ◽  
Segmental Mobility ◽  
Network Chain ◽  
Styrene Copolymers ◽  
Rates Of Growth ◽  
Rate Controlling Step ◽  
Limiting Value ◽  
Butadiene Styrene

Abstract The rates of growth of single ozone cracks have been measured for vulcanizates of a series of butadiene—styrene copolymers, over a temperature range from − 5° C to 95° C. The rates appear to be determined by two mechanisms. At low temperatures, near the glass transition temperature, they are quantitatively related to the segmental mobility of the polymer. The principal rate-controlling step in this case is concluded to be movement of the polymer chains after scission to yield new surface. At high temperatures the rate approaches a limiting value of 10−3 cm/sec/mg of ozone/1. This is about 1/1000 of the maximum possible value when instantaneous reaction of one incident ozone molecule causes scission of one network chain.

The Dependence of Dielectric Properties on Crosslink Density of Rubbers

1978 ◽  
Vol 51 (1) ◽  
pp. 72-80 ◽  
Author(s):  
R. Bakule ◽  
A. Havránek
Keyword(s):  
Dielectric Properties ◽  
Natural Rubber ◽  
Crosslink Density ◽  
Unit Volume ◽  
Volume Distribution ◽  
Dicumyl Peroxide ◽  
Frequency Range ◽  
Polar Groups ◽  
Main Transition ◽  
Macroscopic Parameters

Abstract The dielectric properties of natural rubber, synthetic polyisoprene, andpolybutadiene samples crosslinked with sulfur and of natural rubber samplescrosslinked simultaneously with sulfur and dicumyl peroxide were studied. Inthe investigated systems, the number of polar groups in unit volume and thecrosslink density may be changed independently over relatively wide ranges.The measurements were performed in the frequency range from 101 to 105 Hzat various temperatures, and macroscopic parameters describing the dielectricproperties of the samples were evaluated. The position and intensity of thedielectric dispersion peak in the main transition zone is only slightly dependenton the crosslink density of the samples. These two values are mainly influencedby the amount of combined sulfur, or more generally, by the number and thedipole moments of polar groups in the sample. The influence of crosslink densityon the width of the absorption curve is very strong; the width increases withincreasing crosslink density. The possibility of explaining this effect in termsof the dependence of the free volume distribution function on crosslink densityis discussed.

Sign in / Sign up

Export Citation Format

Share Document