What is different between spandex fabric and mechanical stretch fabric?

Stretchy clothing increases comfort, but do you know that the principle of the same stretch fabrics will be different due to the different needs?
Elastic yarns are divided into two categories:
1. Elastic fiber is generally called "OP" in Taiwan, "PU" in Japan, and it is called Lycra or Spandex in occidental countries. It is a rubber band-like fiber. Its advantages are high flexibility and high recoverability.
It can be used for functional sports fabrics, but the disadvantage is that the elasticity will be prone to aging and fracture over time, and the cost is also high.

2. High stretch yarn - the principle of it is to make the fiber spiral crimp to achieve the function of high stretch, so the stretch is higher than the inelastic fiber, generally called mechanical stretch, which can make the fabric have its own elasticity naturally. Although the stretch is not high as the elastic fiber, the cost is lower. It’s suitable for general clothing use. If there is a cost concerning in fabrics development, the high stretch yarn is also an option for designers to replace the elastic fibers.