The homopolymer and butadiene copolymers of 1,1‐dihydroperfluorobutyl acrylate form a new class of vulcanizable elastomers with interesting and useful properties, of which solvent resistance is the most outstanding. The homopolymer (poly‐FBA), vulcanized by means of a polyfunctional amine in the presence of a reinforcing pigment, appears most promising because it offers the following unusual combination of desirable properties: (1) resistance to hydrocarbon solvents; (2) resistance to a variety of lubricants, hydraulic fluids, and similar high boiling liquids at temperatures up to 400°F.; (3) resistance to oxidation by ozone and fuming nitric acid; (4) fair stability and physical properties in air at elevated temperatures. It was shown that many of these properties depend upon compounding recipes and that further improvements can be anticipated.
Early in the investigation of butadiene-styrene copolymers as synthetic rubbers, this laboratory became interested in copolymers containing much more styrene than any of the American or German synthetics. This interest was soon directed to the resinous copolymers obtained when the styrene content is increased beyond the range in which rubberlike properties are observed at room temperature. The exploratory work, therefore, involved preparation and evaluation of butadiene-styrene copolymers containing from 65 to 98 per cent styrene. No description of similar polymers has been found. Konrad and Ludwig claimed the improvement of rubberlike properties of butadiene-styrene copolymers by increasing the styrene content from the normal range to “between about 47.5 and about 70 per cent”. The claims and examples of this patent emphasize the improvement of rubberlike properties, such as tensile, elongation, and rebound, at high temperatures. It is well known in this country, however, that increase in styrene content beyond a certain point, perhaps 50–55 per cent, is accompanied by a loss of overall balance of rubber characteristics. Therefore, the copolymers at the upper end of the range described by Konrad and Ludwig have definite limitations for rubber uses—for example, low rebound, high brittle point, shortness, etc. In the writers' laboratory useful resins have been prepared from dienes and vinyl aryl hydrocarbons in the range 5 to 20 per cent diene and 80 to 95 per cent vinyl aryl hydrocarbon. This paper describes the properties and certain uses of one of these copolymers containing approximately 15 parts of butadiene and 85 parts of styrene. This material possesses a combination of physical and chemical properties which permit its use in several applications where cyclized natural or synthetic rubbers are commonly employed. Cyclized natural rubber has been described by Bruson, Endres, and Thies and Clifford. Cyclized synthetic rubbers were described recently by Endres. One product of this type is made from a special synthetic rubber. The new 15 butadiene—85 styrene copolymer is now identified as Pliolite S-3, since it may be used in many Pliolite applications, often with distinct advantages over either the natural or synthetic rubber derivatives.
For several years work has been carried on here to evaluate a large number of diene polymers and copolymers as rubberlike materials. The writers have observed that changes in polymer composition which result in improved tensile strength and crack-growth resistance of the vulcanizate cause an increase in low temperature stiffness and a rise in brittle point. This generalization seems to apply to tensile values measured at elevated temperatures as well as to those at room temperature. For example, a butadiene copolymer of dichlorostyrene can be made which, as a tread type of vulcanizate, exhibits a tensile strength of over 1500 pounds per square inch at 93° C, in comparison with 800 to 1000 pounds per square inch for GR-S in the same test tread formula at the same temperature. The brittle point of the butadiene-dichlorostyrene rubber, however, is −35° C or higher. GR-S treads in the same test have brittle points between − 55° and −60° C. Probably of greater practical importance is the fact that the vulcanizate with the higher brittle point is stiffer at temperatures well above the brittle point. The purpose of this investigation was to determine to what extent the maximum tensile strength of tread stocks of several synthetic rubbers varies with the temperature difference between the brittle point and the tensile testing temperature of each rubber. These data can then be used to judge the validity and extent of the general observation that changes in copolymer composition which increase strength also raise the brittle point.
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