Spin finish oils have always played an important role in the processing of synthetic fibers.  This point is especially true for spandex considering that typical OPU levels are much higher for spandex than other fibers such as polyester or nylon.  Spandex finishes not only must provide lubrication to the fiber but must also be designed to help prevent inter-fiber sticking, controlled release from the bobbin, smooth unwinding tension, and antistatic protection.  The growing end-uses of spandex fiber make the type of spin finish used even more critical in today’s rapidly changing spandex market.  Goulston Technologies, Inc. has been supplying fiber lubricants for spandex nearly as long as the fiber has been in existence and knows very well how to design products to match the different needs of our customers and their market.  Rarely are two spandex processes or polymers exactly the same, so too spin finish formulations must change appropriately.  In general there are three classes of products which can typically be used based on the end use.  It is easy to see why selecting the right finish is crucial to ensuring that spandex fiber performs up to the expectations of the downstream end-user.

The following results compare some of the technical properties Goulston Technologies feels are important in choosing a spin finish for spandex.  The three types of spin finishes compared:

Friction control is the key reason for using a spin finish oil.  The first set of data compares the fiber to ceramic friction and unwinding tensions of the test samples.  Due to the wide ranging deniers and fiber tenacities, and deficiencies in commercial testing machines available, Goulston has specially designed its own test equipment.  Goulston’s test equipment is shown below.

Dynamic F/C Friction and Unwinding Tension

Notes:        Samples were prepared by application of 3% finish onto the 40d finish free yarn

µd was measured at 150 m/min against ceramic pins.

Draw ratio was set at 1:3. 

Unwinding tension measured in grams at 50 m/min unwinding speed. 

Aging was conducted for 3 days at 60ºC in the air forced oven

The above chart shows that the type of base lubricant used as well as the additives included is crucial in determining how the fiber responds to accelerated aging.  Low, controlled unwinding tension and friction are obviously important, but these can be affected by the amount of finish penetration into the fiber. For this reason, Goulston designs products so that the amount of finish penetration into the polymer is controlled.

Fiber-to-fiber friction is important for many reasons not the least of which is package formation during winding and unwinding of the fiber during downstream processes.  Shown below is the Goulston designed F/F Friction Test Equipment for Spandex.