Harold M. Leeper

Role of the Elasticity of Rubber in the Controlled Administration of Drugs

Abstract The energy stored in an extended elastomeric reservoir can be usefully employed in the controlled delivery of drug solutions at constant rates of flow through a fixed resistance. The absol...

An Elastomeric Micrometering System for the Controlled Administration of Drugs

Abstract When drugs are infused, it is often necessary to minimize the volume of fluid delivered. Fluid delivery rates of 1 cm3/h or less are frequently desirable; however, the accurate metering of fluids at such low flow rates to the human body has been difficult to accomplish. The metering devices most commonly used to control flow rate from a constant-pressure source have been micrometer valves, clamped tubes, capillaries, and porous plugs. Each of these devices has specific disadvantages : micrometer valves are expensive and bulky, clamped tubes are not stable for long-term infusion and present a hazard of greatly fluctuating flow rates, capillary tubes are subject to particle blockage and are not adjustable, and porous plugs suffer from lack of adjustability. Recently a valve made of extruded silicone rubber rod with axial holes was reported to yield stable flow rates; it was adjusted by placement in a plastic clamp. A new low-infusion-rate metering system has been developed to overcome the above def...

Inflation of Thin-Walled Elastic Tubes

more economical sources of stored energy is in elastomers, which are deformed initially by external forces. For example, when rubber tubing of optimum dimensions and properties is inflated with a fluid, without any external constraints, there results a constant pressure acting upon the contained fluid, owing to the biaxial stresses-strains generated within the distended tubing walls. Fluid can be metered

Determination of Tensile Strength of Natural Rubber and GR-S. Effect of Specimen Size

Abstract Peirces equation, which relates observed tensile strength of textile fibers with their length, was found to be applicable to rubberlike material if specimen volume is used in place of specimen length. Experiments in which the tensile strengths of GR-S and natural rubber compositions were determined for a range of specimen volumes yielded results in close accord with theory. A tenfold increase in the volume of the material resulted in a decrease of 308 and 339 and of 204 pounds per square inch in the observed tensile strength of GR-S and comparable natural rubber stocks, respectively. The numerical magnitudes of the slopes of the straight lines obtained when tensile strengths were plotted against the logarithms of the relative specimen volumes are shown to bear direct relationships to the homogeneity of the stocks under test. The use of a dumbbell sample with a constricted center should result in a relatively simple means of measuring quantitatively the degree of homogeneity of rubber compositions.