Styrene-butadiene rubber vulcanisate properties

Processing aid-80, a masterbatch in the form of pressed crumb consisting of an 80 20 blend of crosslinked to ordinary natural rubber. The correct proportions of vulcanised latex and field latex are blended, coagulated and the resulting crumb pressed into 100 lb bales. The use of PA 80 confers Superior Processing properties on any natural or styrene-butadiene rubber with which it may be mixed. See Superior Processing Rubber. 

High cis- 1,4-poly butadiene is manufactured on a large industrial scale and occupies a well-defined position in the elastomers market. It is employed mainly in the tyre industry, where it is blended with natural rubber and/or with styrene-butadiene rubber and applied in either sidewalls, threads or rims of tyres. It should be noted in this connection that natural rubber, in contrast to its synthetic counterpart, displays some physical properties that appear to be useful in the manufacture of tyres for heavy-duty machines. The fact is that some non-hydrocarbon substances appearing in natural rubber in small amounts (such as polypeptides) protect the high-dimensional tyre formed against collapsing prior to the vulcanisation process and thus enable a high-quality product to be obtained. 

The family consists of, in order of market volume, polybutadiene (or butadiene rubber, BR), solution styrene butadiene rubber (SSBR) and styrenic block copolymers (SBC). A further subdivision may be made into those polymers that require vulcanisation (BR, SSBR) and those that do not (SBC). The latter are also known as thermoplastic rubbers as they have rubbery properties below a certain temperature when they soften and may be processed like thermoplastics. 

STYRENE-BUTADIENE RUBBER/EPOXIDISED NATURAL RUBBER BLENDS THE EFFECT OF VULCANISATION SYSTEM ON BLENDS PROPERTIES... 

Studies on the vulcanisation of a black and oil filled styrene-butadiene rubber compound accelerated by a number of different sulphenamide and sulphenimide compounds were made using a conventional curemeter operated to normal ASTM standards. The vulcanisation reactions were also studied using different modelling software, CODESSA software for deriving quantitative structure-property relationships and MOPAC software for semiempirical molecular orbital calculations which together yielded excellent correlation to onset of cure and maximum cure... 

The cure and tensile properties of sulphur vulcanised styrene-butadiene rubber filled with a conventional furnace black or a fluorinated black have been determined. Compositions with the fluorinated black and normal curative levels exhibit retarded cure compared to corresponding ones with the furnace black. This is due to a reaction between the sulphenatnide accelerator and the fluorinated black. Notwithstanding, a fluoro-filled composition with no curatives substantially crosslinks when moulded at 150 deg.C. Thus, fluoro-black filled specimens have competing effects toward crosslinking. On the one hand, crosslinking is inhibited by reaction with the accelerator, while on the other, the fluoro-black itself can cause crosslinking. 2 refs. 

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