reported in the examples the apparatus described above was charged with the applicable polymer pellets and the spin agent high pressure water was used to drive the pistons to generate a mixing pressure back pressure of approximately 2000 psig 13790 kpa gage the polymer and spin agent were then heated to the mixing temperature during which time the pistons were used to alternately establish a differential pressure u03b4p between the two cylinders so as to repeatedly force the polymer and spin agent through the mixing channel from one cylinder to the other to provide mixing and to effect formation of a spin fluid in the examples below the u03b4p values were all approximately 300 psi 2068 kpa the spin fluid temperature was then adjusted to the final spin temperature and held there for about 15 minutes or longer to equilibrate the temperature during which time mixing was continued in order to simulate a pressure letdown chamber the pressure of the spin fluid was reduced to a desired spinning pressure just prior to spinning this was accomplished by opening a valve between the spin cell and a much larger tank of high pressure water u201c the accumulator u201d held at the desired spinning pressure the spinneret orifice is opened as rapidly as possible after the opening of the valve between the spin cell and the accumulator the spinneret employed had an orifice with 30 mil diameter and a 30 mil length 30 mil 0 030 inches 0 0762 cm this generally takes about one second this is intended to simulate the letdown chamber effect that is used in larger scale spinning operations the resultant flash spun product was collected.