Sulfur-coated asphalt pellets

A new composition is disclosed which comprises pellets of asphalt coated with a solid layer of sulfur. The sulfur shell provides a meltable container for the asphalt core while protecting it from contact with the atmosphere. The relative quantities of sulfur and asphalt in the pellets of the invention may be varied over a wide range to provide sulfur-to-asphalt ratios commonly used in both sulfur-asphalt-sand mixes and sulfur-extended asphalt binders. The advantages of pelletizing are virtual elimination of the danger of dealing with hot materials and significant reduction in energy costs associated with keeping asphalt and sulfur hot and pumpable. To produce an asphalt paving mix, the sulfur-coated asphalt pellets may simply be mixed with heated aggregate.U

Induced plasticization: a surface treatment technique for extending the environmental capability of solid propellant rocket motors

A concept is presented for extending the low temperature strain limit of rubber-based solid propellants by means of Induced plasticization. The concept is then extended for use as an inner bore treatment for solid propellant rocket motors. The process consists of exposing the cured propellant to a solution of a solvent (Freon-11) and a compatible plasticizing oil. The plasticizer, which alone cannot penetrate into the polymer, is transported by the Freon-11 which acts as a gentle swelling agent. Once the desired penetration depth has been achieved, the lower boiling solvent is removed by vacuum, leaving a plasticizer-rich layer capable of withstanding significantly greater strains without cracking. The ability to extend the environmental limits of solid propellants is first demonstrated in a series of laboratory scale tests which include: uniaxial tensile tests, a strain evaluation cylinder (analogue motor) cold soak-to-failure program, and 15-pound static motor firings. The laboratory and analytical procedures are then scaled-up and demonstrated on three full scale rocket motors. In addition to enhancing strain capability, the potential of the treatment for retarding the propagation of cracks is also demonstrated. Finally, a five-point criterion for a general, optimized treatment procedure for solid propellant rocket motors is presented

Induced plasticization: a surface treatment technique for extending the environmental capability of solid propellant rocket motors

A concept is presented for extending the low temperature strain limit of rubber-based solid propellants by means of Induced plasticization. The concept is then extended for use as an inner bore treatment for solid propellant rocket motors. The process consists of exposing the cured propellant to a solution of a solvent (Freon-11) and a compatible plasticizing oil. The plasticizer, which alone cannot penetrate into the polymer, is transported by the Freon-11 which acts as a gentle swelling agent. Once the desired penetration depth has been achieved, the lower boiling solvent is removed by vacuum, leaving a plasticizer-rich layer capable of withstanding significantly greater strains without cracking. The ability to extend the environmental limits of solid propellants is first demonstrated in a series of laboratory scale tests which include: uniaxial tensile tests, a strain evaluation cylinder (analogue motor) cold soak-to-failure program, and 15-pound static motor firings. The laboratory and analytical procedures are then scaled-up and demonstrated on three full scale rocket motors. In addition to enhancing strain capability, the potential of the treatment for retarding the propagation of cracks is also demonstrated. Finally, a five-point criterion for a general, optimized treatment procedure for solid propellant rocket motors is presented

Sulfur-coated asphalt pellets

A new composition is disclosed which comprises pellets of asphalt coated with a solid layer of sulfur. The sulfur shell provides a meltable container for the asphalt core while protecting it from contact with the atmosphere. The relative quantities of sulfur and asphalt in the pellets of the invention may be varied over a wide range to provide sulfur-to-asphalt ratios commonly used in both sulfur-asphalt-sand mixes and sulfur-extended asphalt binders. The advantages of pelletizing are virtual elimination of the danger of dealing with hot materials and significant reduction in energy costs associated with keeping asphalt and sulfur hot and pumpable. To produce an asphalt paving mix, the sulfur-coated asphalt pellets may simply be mixed with heated aggregate.U

Sulfur-coated asphalt pellets

A new composition is disclosed which comprises pellets of asphalt coated with a solid layer of sulfur. The sulfur shell provides a meltable container for the asphalt core while protecting it from contact with the atmosphere. The relative quantities of sulfur and asphalt in the pellets of the invention may be varied over a wide range to provide sulfur-to-asphalt ratios commonly used in both sulfur-asphalt-sand mixes and sulfur-extended asphalt binders. The advantages of pelletizing are virtual elimination of the danger of dealing with hot materials and significant reduction in energy costs associated with keeping asphalt and sulfur hot and pumpable. To produce an asphalt paving mix, the sulfur-coated asphalt pellets may simply be mixed with heated aggregate.U