The process has so far been restricted to spinning pure synthetic fibers, blends of synthetic fibers, or blends of synthetic with cotton fibers. Pure cotton can be processed only in combed form and usually still gives a low-strength product (with 50 - 70% of the strength of ring-spun yarn, which means that processing 100% cotton on two nozzle air-jet machines is not an industrial solution). Dirt in the fiber material acts as a disturbing factor. Almost all the yarn characteristics are improved by the use of longer and finer fibers. About 80 fibers at least are needed in the yarn cross-section.
The fibers should have:
- high strength;
- fairly high fiber-to-fiber friction;
- low bending stiffness;
- low resistance to twist; and
- only a small proportion of short fibers.