One aspect of structure is the visual appearance, created solely by the peripheral layer of the yarn, and a second aspect is the internal and external make-up. Yarn structures are very variable. The differences are partly deliberately caused, depending on the intended use of the yarn, but for the most part they are predetermined by the means available. For example, it is difficult to produce a yarn equivalent to a ring-spun yarn by the new spinning processes – and the ring-spun yarn still represents the standard of comparison (Table 4).
The yarn structure is dependent primarily upon the raw material, spinning process, spinning unit, machine, machine settings, twist, etc. The structure can be open or closed; voluminous or compact; smooth or rough or hairy; soft or hard; round or flat; thin or thick, etc.
But yarn structure is not simply appearance. It has a greater or lesser influence on:
- insulating capacity;
- covering power;
- ability to resist wear, damage, strains, etc.;
- resistance to abrasion;
- ability to accept dye;
- tendency towards longitudinal bunching of fibers;
- wearing comfort, etc.