and collected by conventional means the spinning rate is generally in the range of 100 to 1000 meters minute the as spun fibers are initially round the next step in processing the as spun or green fibers is stabilization the method and apparatus of u s pat no 4 576 810 are employed as knownin the art the as spun fibers are collected in the usual manner on a spinning spool or bobbin u s pat no 4 527 754 illustrates bobbins useful in this operation a finish such as a silicone oil finish may be applied to the as spun fibers prior to winding onto the bobbins the fibers on the bobbins are stabilized by heating in air or a mixture of oxygen and an inert gas the stabilization process is an exothermic oxidation reaction so care must be taken to prevent the reaction from proceeding too fast and too far generally the temperature of the reactiongas is increased in stages to a temperature between 200 u00b0 and 340 u00b0 c the rate at which the temperature is increased will depend on the concentration of the oxygen in the reaction gas and the rate at which the heat generated by the reaction can be transferred from the yarn.