Hydrostatic pressure effects on 1/4 inch polypropylene line.

Abstract

The effects of hydrostatic pressure on the mechanical properties of 1/4 inch polypropylene line were investigated. The line was exposed to hydrostatic pressures of 5,000 and 10,000 psi for periods of 6, 12, and 24 hours, respectively. Upon completion of the pressurization period, the line was removed from the pressure vessel and its ultimate tensile strength recorded and compared to that of the line before pressurization. There was an increase in the tensile strength of the line as pressure increased and time progressed, with a maximum increase of 3.1 percent occurring after pressurization at 10,000 psi for 12 hours and at 5,000 psi for 24 hours. Secondly, there was no measurable difference in the relative elongation of the line after pressurization as compared to that before pressurization. The mode of failure was investigated by testing individual line fibers. Microscopic observation after failure showed no discernible difference between the mode of failure before and after pressurization. In each case, the fibers presented a somewhat jagged edge and the outer portions of the fiber appeared to have peeled back.