Showing papers by "Cabot Corporation published in 1968"

Anomalous freezing point depression of swollen gels

Abstract: The anomalous freezing point depression, ΔT, of benzene-swollen vulcanizates has previously been attributed to the limitation of (benzene) crystallite size by the polymer network. This study was initiated to determine the benzene crystallite size in a number of rubber and benzene systems. A special low-temperature specimen holder was designed and constructed in the Cambridge Laboratories for running diffraction patterns at temperatures near −30°C. X-ray line broadening techniques were used to study a series of filled and unfilled vulcanizates of varying crosslink density. The results indicate that crystallite size is not depressed to the degree predicted by freezing-point measurements. Benzene crystallite sizes were similar in all rubber benzene systems, regardless of degree of crosslinking or benzene fraction, although carbon black loading appears to increase crystallite size. This effect may be attributed to lesser depth of penetration of the x-rays due to greater density as carbon black loading increases. Additional studies measuring the ΔT for solutions and similar vulcanizates of NR and SBR over a wide range of rubber concentrations showed that at the same rubber in benzene fraction, crosslinking increases ΔT but the addition of carbon black reduces ΔT. An explanation for the observed phenomena is advanced.

Bonding of Rubber to Carbon Black by Sulfur Vulcanization

Abstract: As an approach toward understanding the interaction of rubber with carbon black, we have studied the chemisorption of a model olefin (2-methyl-2-octene) on carbon black. Some olefin becomes chemisorbed on simply heating these two materials together, and can be distinguished from physically adsorbed material by its resistance to removal by solvents at room temperature. The presence of an MBTS accelerated sulfur curing system causes additional chemisorption. The amount of olefin chemisorbed can also be increased by the use of larger amounts of sulfur but is decreased by an increase in MBTS, owing to competitive chemisorption of the MBTS. Sulfur is also chemisorbed, to a somewhat greater extent than the olefin, but is desorbed more readily than the olefin, suggesting that these two components are chemisorbed separately. The chemisorbed olefin is believed to be highly mobile on the carbon black surface, and indeed its stability is ascribed primarily to a loss of translational entropy associated with ...

Preparation of tantalum metal

Abstract: THIS INVENTION RELATES TO AN IMPROVED METHOD OF PREPARING HIGH-PURITY TANTALUM METAL BY THE ALUMINO-THERIC REDUCTION OF TA2O5. BY ADDING SELECTED ALLOYING AGENTS TO THE ALUMINUM AND TANTALUM OXIDE, A MASSIVE METAL ALLOY READILY SEPARABLE FROM THE SLAG IS PRODUCED UPON REDUCTION OF THE MIXTURE. THE HIGH-PURITY TANTALUM METAL IS THEN RECOVERED BY HEATING THE ALLOY UNDER REDUCED PRESSURE TO A TEMPERATURE SUFFICIENT TO BOIL OFF THE ALLOYING METALS.

Metal surface treating process by use of lanthanum compounds

Abstract: METHOD FOR IMPROVING THE OXIDATION RESISTANCE OF IRON, NICKEL AND COBALT BASE ALLOYS CONTAINING CHROMIUM BY CONTACTING AN ALLOY OF THIS TYPE WITH A HEAT DECOMPOSABLE LANTHANUM COMPOUND AT ELEVATED TEMPERATURE.

Cobalt base oxidation resistant alloy

Abstract: A COBALT BASE, CHROMIUM-CONTAINING ALLOY HAVING MINOR AMOUNTS OF SILICON AND LANTHANUM CHARACTERIZED BY EXCELLENT OXIDATION RESISTANCE AT TEMPERATURES OF 1200*C. AND HIGHER. THE INCLUSION OF SMALL OF MANGANESE IN THE ALLOY FURTHER ENHANCES THE OXIDATION RESISTANCE OF THE ALLOY.

Reinforcement by carbon black considered as a rate process

Abstract: Following a survey of the behaviour of elastomers loaded with carbon black, a mechanism of reinforcement is proposed which is based upon theDannenberg's concept of “mobile absorption” or “molecular slippage” of elastomer macromolecules on the carbon black surface, and treats their motion as a rate process The behaviour of single molecular chains is described in detail